Introduction

Riparian zones are the interfaces between river channel and upland terrestrial ecosystem and underpin key exchange of energy, inorganic and organic matter, and biota (Ballinger and Lake 2006; Hanser et al. 2010; Fu et al. 2016; de Mello et al. 2018; Lacko et al. 2018). These areas are among the most productive and biodiversity rich landscapes on the earth (Kardynal et al. 2009). Riparian zones are one of the fifteen globally recognized terrestrial biomes (Maraseni and Mitchel 2016). Although riparian zones comprise a relatively small area, but they support greater biodiversity than surrounding landscape (Naiman et al. 1993; Palmer and Bennett 2006; Glass and Floyd 2015). Riparian forests cover less than 2% of the total land surface in the American Southwest but are most biologically productive and ecologically important lands (Debano and Baker 1999; Lee and Rotenberry 2015). Hydrology is a major driver that regulates structural and functional aspects of riparian zones (Mitsch and Gosselink 2007; Ye et al. 2017).

Riparian zones differ from surrounding uplands in their soil and vegetative structure, topography, microclimate, moisture regimes, disturbance regimes, and productivity (Pettit and Naiman 2007). Thus, riparian zones are highly heterogeneous in time and space with complex biophysical structure (Naiman et al. 2005; Pettit and Naiman 2007). Riparian zones are affected by overbank flooding events and connect upland and aquatic ecosystem through surface and subsurface flow of water (Naiman et al. 2005; Vidon et al. 2010). Riparian zones are characterized by range of features like periodic flooding, sharp environmental gradients, topographic position, dendritic structure, high edge area, connectivity, and high biodiversity (Malanson 1993; Naiman et al. 1993; Forman 1995; Palmer and Bennett 2006; Fremier et al. 2015; Wang et al. 2018).

Riparian and floodplain forests are the vital components of the river ecosystem (Muller 1997). Riparian zones act as the ecological engineers that maintain and improve river health through providing multiple ecosystem functions (Singh and Singh 2019). They are recognized as the best management practices to maintain or improve stream condition by providing a buffer between waterways and agricultural fields (Dosskey et al. 2010; O’Toole et al. 2018). Riparian zones are recognized as the potential natural filters for sediments and nutrients between upland environments and streams (Vidon 2010; Ou et al. 2016; de Mello et al. 2017, 2018). Riparian ecosystems regulate river temperature through shading from solar insolation, stabilize streambanks, and provide habitat and food for a range of terrestrial and aquatic organisms (Naiman and Decamps 1997; Naiman et al. 2005; Vidon et al. 2010; Li et al. 2012; Guevara et al. 2015; Tonin et al. 2017; Garner et al. 2017). Riparian systems through infiltration of water enhance aquifer recharge and play an important great role in watershed (del Tanago et al. 2011).

Besides these important functions, riparian zones also deliver a range of ecosystem goods and services that support human well-being (Meli and Brancalion 2017; Wu et al. 2017; de Sosa et al. 2018a) such as forage to livestock (Fitch and Adams 1998), genetic resources and biota for ornamental uses (Capon et al. 2013), fuel wood (Shackleton et al. 2003), carbon sequestration (Hale et al. 2018), air quality regulation (Mander et al. 2005), flood regulation (Croke et al. 2017), pollination (Klein et al. 2007; Cole et al. 2015), recreation (Sharitz et al. 1992), and aesthetic value (Martin et al. 2012). Despite a multitude of ecosystem functions and services, riparian zones are among the most threatened ecosystems in the world due to human activities and natural disturbances (Casotti et al. 2015; Seena et al. 2017). Agricultural activities, urbanization, river flow alteration, overexploitation, climate change, pollution, and biological invasion are some of the major threats that degrade and deteriorate riparian zones (Nilsson and Berggren 2000; Groffmann et al. 2003; Dudgeon et al. 2006; Richardson et al. 2007; Poff et al. 2011; Capon et al. 2013; Ruwanza et al. 2013; Kuglerová et al. 2014;; Fu et al. 2016; Alemu et al. 2017; Modiba et al. 2017; Rosot et al. 2018). Globally, along many rivers, a large riparian zone either has been eliminated or is on the verge of degradation. A well-maintained riparian zone is critical for health and sustainability of ecological functions and services of rivers and streams (Fernández et al. 2014; Wu et al. 2017; Yang et al. 2018) which underpin the human well-being (Yang and Chen 2014; Morton et al. 2017). Maintenance of river health is a pressing need for sustainable development of human society (Meyer 1997; Pan et al. 2015) and it largely depends on the health of riparian zones. Therefore, conservation and management of riparian zones that play a key role in river health improvement is the need of hour.

Worldwide, many efforts have been implemented to manage riparian zones but many of them either failed or achieved little success due to lack of an integrated approach (González et al. 2017). Many approaches, projects and plans related to riparian management have been focused on implementing practices while ignoring other aspects such as making robust policy, assessing the condition of riparian zones, increasing people’s participation, strengthening of legislation and spreading awareness. Achieving the goals of riparian zones management in the era of changing environment needs an integrated approach combining the multiple strategies (Welsch et al. 2000). In this article, authors advocated an integrated approach for riparian zone management including multiple strategies like riparian condition assessment, policy framework, stakeholder’s participation, management practices, legislation and awareness based on global studies, for examples, Gouvernement du Québec (1987); Schultz et al. (1995), USDA (1997), Ball (2008), Burger et al. (2010), Miller et al. (2010), Chiramba et al. (2011), Miller et al. (2011), Sovell et al. (2000), Bourgeois et al. (2016), Clary et al. (2016), Hunter Jr. et al. (2017) and Meli and Brancalion (2017). This article also described the concepts, features, functions and threats of riparian zones.

Riparian zones: concepts and features

The word “riparian” is derived from Latin word riparius which denotes the land adjacent to the water body (Naiman and Decamps 1997; Sunil et al. 2010). Riparian zones are the transitional areas between the aquatic and the terrestrial environment (Betz et al. 2018). They encompass the space between flowing water at low levels and the highest water mark where vegetation is influenced by floods, elevated water tables, and soil type (González et al. 2017). Riparian zones comprise riverbed, banks, vegetation, adjacent land, and the floodplain (Maraseni and Mitchel 2016). For a river valley with a width less than 100 m, the entire floodplain is riparian zone and for all other rivers, a standard distance of 50 m on both sides is recommended as riparian zone (CEN 2004; Kujanová et al. 2018).

Biological, chemical, and physical interactions between terrestrial and aquatic ecosystems create a three dimensional riparian zone (Gregory et al. 1991; Kauffman et al. 1997). Riparian zones act as critical transition zones between river catchments and channels and mediate the flow of energy, biota, sediments and nutrients between these two environments (Naiman and Décamps 1997; Lake 2005; Naiman et al. 2005; Hale et al. 2014). Healthy riparian buffers are highly interactive with adjacent aquatic systems (Klemas, 2014). Riparian buffers are linear in nature (Qian et al. 2018). Topographic position, dendritic structure, high edge area, and connectivity through landscape make riparian habitats a distinctive landscape (Malanson 1993; Forman 1995; Palmer and Bennett 2006). A typical riparian zone with its distinguished features is represented in Fig. 1.

Fig. 1
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A typical riparian zone with its distinguished features

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A riparian corridor encompasses sharp environmental gradients, ecological processes and communities (Naiman et al. 1993). Width and functional attributes of a riparian zone are affected by stream size, stream position in drainage system, hydrology and geomorphology (Gregory et al. 1991; Naiman and Décamps 1997; Maruani and Amit-Cohen 2009). Hydrology is the powerful factor that regulates structural and functional aspects of riparian zones (Mitsch and Gosselink 2007; Ye et al. 2017). It also controls the water flow paths in riparian zones. Five main water flow characteristics are recognized as the important factors in shaping riparian plant communities; timing (season), duration, frequency, rate of change and magnitude (Nilsson and Svedmark 2002; New and Xie 2008).

Dosskey et al. (2010) highlighted several water flow paths in riparian zones such as (i) vertical flow of precipitation into riparian soil via plant roots (ii) lateral flow of streamwater through hyporheic zone (iii) overland and subsurface runoff from uplands (iv) surface and subsurface flow of flood water. Hyporheic zone is volume of sediments where stream water mixes with groundwater (Peralta-Maraver et al. 2018). On moving away from riverbank, the influence of river water and soil moisture decreases while the depth of water table increases.

Riparian zones support rich biodiversity than their adjacent upland ecosystems. Various attributes such as proximity to water, structure and microclimate underpin the persistence of many wildlife species in riparian forests (National Research Council 2002; Viegas et al. 2014). Riparian vegetation is the integral component of the riparian zone. It is characterized by diversity of species of trees, woody shrubs, herbs/forbs, grasses, and sedges that differs structurally and floristically from other terrestrial vegetation due to influence of stream moisture, flood and soil attributes (Anderson 1993; Pert et al. 2010; Valero et al. 2014; Wang et al. 2018). River flow regime, groundwater, and morpho-dynamics significantly affect the life cycle of the riparian vegetation (Tabacchi et al. 1998; Wang et al. 2018).

Riparian zones as the ecological engineers: implications for river health improvement

It is an obvious question in the current scenario of global environmental changes that why should we manage riparian zones? The answer is simple that riparian zones play a significant role in river health improvement through a range of ecosystem functions. River health is a complex term encompassing various health indicators. River health indicators include the ecological status, water quality, hydrology, geomorphology, and availability of physical habitat (Maddock 1999). Ecological integrity, resilience and supporting of ecosystem structure, functions, and services are the characteristic features of the healthy rivers (Singh and Saxena 2018). River health protection is pivotal for the sustainable utilization of rivers to fulfill economic, social and domestic demands (Zhang et al. 2018). Maintaining the river health is a pressing need due to its giant role in ecosystem structure and functions, sustainable development and well-being of human society (Meyer 1997; Pan et al. 2015). Rivers are closely linked with human civilization (Gambino 2005; Braioni et al. 2017) culture and history (Pan et al. 2016). A healthy river ecosystem delivers a broad spectrum of ecosystem goods and services such as fish, freshwater, hydropower, soil and sand transportation, habitat for wildlife, nutrient cycling, opportunities for shipping and transportation, flood control, carbon dioxide fixation, water quality regulation, aesthetics and recreation (Limburg et al. 2002; Fisher and Turner 2008; Fisher et al. 2009; Yang and Chen 2014; Morton et al. 2017).

Riparian zones are recognized as the best management practices for river health improvement. Riparian zones act as the ecological engineers that improve river health through a stream of ecosystem functions (Fig. 2).

Fig. 2
figure 2

Riparian zones acting as the ecological engineers

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Healthy riparian zones preserve and sustain river health through delivering a stream of ecosystem functions (Naiman and Décamps 1997; Ryan et al. 2003; Fernandes et al. 2011). Riparian zones and associated vegetation provide ecological corridor, food and habitat to wildlife, moderate stream temperature, stabilize stream bank, buffer sediments and pollutants and enhances groundwater recharge (Hood and Naiman 2000; Pusey and Arthington 2003; del Tanago et al. 2011; Salemi et al. 2012; Asanok et al. 2017; Modiba et al. 2017).

Riparian zones stabilize streambank

Riverbanks are prone to water derived erosion. Riverbanks are the major sources of sediments and can supply over 50% of catchment sediment output (Lawler et al. 1999). The amount of sediment supplied by stream bank erosion is largely determined by numerous factors like topography, river morphology, riparian land-use, vegetation cover, bank material, weather cycles, and watershed area (Hagerty et al. 1981; Zaimes et al. 2004). Stream bank instability and resulting sediment load cause detrimental effects on water quality, aquatic organisms, human health, agricultural land, stream side infrastructure like bridges, and the overall ecological health of riparian and river ecosystems (ASCE 1998; Heartstill-Scalley and Aide 2003; Pollen and Simon 2005; Gomi et al. 2006; Botero-Acosta et al. 2017). Sediment load in stream paves the way for flooding (Zaimes et al. 2004).

Riparian vegetation helps in reducing the stream bank erosion (Vigiak et al. 2016). Root networks of riparian plants and trees enhance the apparent cohesion of soil and thereby bank stability through a blend of mechanical and hydrologic effects (Simon and Collison 2002; Pollen and Simon 2005). In mechanical effects, soil is reinforced by root system, while in hydrologic effects, riparian vegetation reduces soil moisture by canopy interception and evapotranspiration (Simon and Collison 2002). High speed of river flow in the channel causes streambank instability and thus increases sedimentation. Vegetation growing in the bank hinders the flow of the channel and reduces mean flow velocities and thereby affecting sediment erosion (Wilson et al. 2005; Pollen-Bankhead and Simon 2010). Herbaceous wet meadow riparian species including sedges (Carex spp.) and rushes (Juncus spp., Eleocharis spp.), are adapted to grow in riverbank environments with dense root networks that bind bank sediments (Nilsson et al. 1989; Micheli and Kirchner 2002). Some tree species like Willows (Salix species) and silver maple (Acer saccharinum L.), protect the stream bank due to their high density and deep rooting habits that increase soil resistance to fluid entrainment (Shields et al. 1995; Zaimes et al. 2004).

Riparian zones maintain river water quality

Riparian zones with dense vegetation sustain the stream water quality though filtering the sediments and nutrients such Nitrogen and Phosphorus (Goss et al. 2014; Connolly et al. 2015; de Sosa et al. 2018a). In a study at Georgia, Todd et al. (1983) found that forested buffer potentially removed 82% of waterborne nitrogen from agricultural runoff (Fennessy and Cronk 1997). Riparian zones particularly riparian soils are effective sink of heavy metals coming from river or upland areas through the process of sedimentation and adsorption and consequently maintain stream water quality (Pavlovic´ et al. 2016). Worldwide, much effort has been made through implementation of wastewater treatment plants, but these measures only reduce pollution from point sources (Hattermann et al. 2006). Pollution from diffuse sources like leaching from fertilized cropland and atmospheric deposition is not abated by these technological methods (Hattermann et al. 2006). Riparian zones play a significant role in reducing the diffuse pollution. Riparian zones reduce sediment load into streams through minimized erosion and floodplain deposition (Randhir and Ekness 2013; Nóbrega et al. 2020).

Riparian vegetation enhances water quality through physical, chemical and biological processes (Dosskey et al. 2010; O’Toole et al. 2018). In physical process, vegetation enhances hydraulic roughness, and thus decreasing surface flow and increasing infiltration rates which pave the way for increase in sediment and nutrient deposition in riparian zones (Naiman and Decamps 1997; O’Toole et al. 2018). Chemically, riparian vegetation alters redox potential and assists transformation of nutrients which in turn result in nutrient loss and nutrient release while through biological processes riparian zones diminish nutrient concentrations by assimilating them into plant biomass or by microbial immobilization (Naiman and Decamps 1997; Scalenghe et al. 2002; Tabacchi et al. 2000; Hoffmann et al. 2009; O’Toole et al. 2018).

Riparian zones regulate thermal regime of river

Thermal regime is crucial for ecological health of river (Kędra and Wiejaczka 2018). Most river organisms are ectothermic; therefore, water temperature influences their metabolic rates, growth, development, survival, and distribution (Allan and Castillo 2007; Kędra and Wiejaczka 2018). River temperature affects growth, survival and demographic features of the cold water adapted fish species such as salmonids (Jackson et al. 2018). Burton and Likens (1973) in their study found that stream temperatures reduced 4–5 °C about 50 m transitioning from non-forested to forested stream section (Goss et al. 2014). Riparian forest canopy regualtes river temperature dynamics through shading the river and reducing the incoming solar radiation (Nakamura and Yamada 2005; Garner et al. 2017). Geographical location, groundwater input, and composition, density and width determine the influence of riparian vegetation on stream temperature (Osborne and Kovacic 1993). Canopy shading through riparian vegetation also controls the intensive growth of aquatic macrophytes (Mander et al. 1997).

Riparian zones sustain food security of river organisms

Regulation of nutrient flux is one of the potential ecological values of the riparian forests (Gregory et al. 1991; Sterzynska et al. 2014). Riparian zones regulate dissolved organic carbon (DOC) input to rivers that affect the food web structure, control acid–base chemistry, and influence metal mobilization (Creed et al. 2008; Eglin et al. 2008; Kuglerová et al. 2014). Leaves of riparian trees undergo the decomposition in streams by fungi, bacteria and invertebrates (Cummins et al. 1989; Webster et al. 1999; Nisbet et al. 2015) and provide food for river organisms such as fish (Broadmeadow and Nisbet 2004). Organic carbon derived from leaf litter and decaying root biomass helps in denitrification in waterlogged soils and streams (Fortier et al. 2015). Terrestrial invertebrates falling into streams from the branches of riparian forests also provide food source for fish (Nakamura and Yamada 2005). During the period when streams become oligotrophic, terrestrial invertebrates can be used by fish as important and nutritious food source (Nakamura and Yamada 2005).

Riparian zones enhance groundwater recharge

Riparian zones play a vital role in maintaining hydrological conditions in watershed. Riparian vegetation facilitates the exchange between surface and groundwater (Tabacchi et al. 2000). Water via root hairs of vegetation enters into the soil and enriches the aquifer. Riparian vegetation enhances the infiltration capacity of soil and consequently water percolates to the aquifers. Riparian buffer enhances the evapotranspiration and rainfall interception while reduces runoff and overland flow (Alvarenga et al. 2017). The consequence of these effects enhances base flow/runoff relationship which suggests that riparian vegetation plays a key role in groundwater recharge (Alvarenga et al. 2017). Riparian ecosystems are flooded periodically due to their spatial position and connectivity with river channels and thus play a key role in water infiltration and aquifer recharge (del Tanago et al. 2011).

Leaf litter in riparian zones also plays an important role in groundwater recharge. Litter on the ground surface retains more water compared to bare soil and improves the infiltration into the soil (Le Maitre et al. 1999). Aquifer recharge in riparian zones sustains surface flow in rivers, maintains high water table and improves the width of productive riparian zone (Fitch and Ambrose 2003). Riparian trees not only have direct access to the stream water but also to the groundwater that flows either to or from the stream (Bren 1993). Soil water, groundwater, and river water are three major water sources for riparian vegetation (Si et al. 2014).

Riparian zones provide habitat to wildlife

Riparian biodiversity is an integral component of river health. Riparian zones harbor more species than their adjacent terrestrial upland areas. Natural riparian zones are among the most diverse, dynamic, and complex biophysical habitats on the terrestrial land of the planet (Naiman et al. 1993; Cabette et al. 2017). Landscape attributes of riparian forests such as proximity to water, nutrient availability, diverse vegetative structures, low light incidence and low temperature are important factors that support biodiversity (Brown 2000; National Research Council 2002; Sabo et al. 2005; Viegas et al. 2014; McClure et al. 2015; Cabette et al. 2017).

Riparian forests support rich biodiversity and act as corridors between forest habitats and populations (Fremier et al. 2015; de la Fuente et al. 2018). Riparian habitats provide home for a variety of organisms, ranging from plants to algae and insects to fish to migratory birds and resident animals (Webb and Leake 2006). They are recognized as the important sites for migratory and breeding birds (McClure et al. 2015). Species prefer riparian zones for migration, water, food, security, rest, cover, reproduction, nesting habitat, dispersal or movement between habitat patches (Gregory et al. 1991; O’Carroll 2004; Santos et al. 2011; Brost and Beier 2012; Fremier et al. 2015; Phoebus et al. 2017). Mosley et al. (2006) studied birds’ use of riparian zones in the boreal mixed wood forest of Ontario, Canada and found that birds used these areas extensively in breeding and fall migration periods. They also observed that during the breeding period, riparian zones had more insects than upland forests (Mosley et al. 2006). Riparian forests are also home of variety of invertebrates such as dung beetles and ground-foraging scavenging ants and butterfly (Gray et al. 2016; Cabette et al. 2017). Riparian vegetation is an important sanctuary for butterfly preservation in the Cerrado of Brazil especially during the dry periods characterized by water stress and limited resources (Cabette et al. 2017).

Major threats to riparian zones

In spite of the pivotal role in river health through a range of ecosystem functions, riparian zones are among the most threatened ecosystems in the world. Globally, riparian zones have extensively been degraded (Holmes et al. 2008). Riparian zones are affected by both human activities and natural disturbances (Fernandes et al. 2011; Casotti et al. 2015; Seena et al. 2017). In the current scenario, increasing degradation of riparian vegetation is a major risk to the quality and quantity of the drinkable water (Richit et al. 2017). Degradation of riparian vegetation severely affects not only water quality but also the biological diversity. Cabette et al. (2017) in their study found that the riparian forest removal severely affected the butterfly community. Worldwide, riparian ecosystems are under severe threats due to agricultural activities, urbanization, river flow alteration, overexploitation, climate change, pollution, and biological invasion (Patten 1998; Dudgeon et al. 2006; Poff et al. 2011; Modiba et al. 2017; Shen et al. 2017; Rosot et al. 2018).

Agricultural activities

Agricultural systems are not only the largest ecosystems of the Anthropocene but also among the major contributors causing the breaking of multiple planetary boundaries (Rockstrom et al. 2009; Steffen et al. 2015; DeClerck et al. 2016). Agricultural land expansion is responsible for more than 70% of the deforestation (Gibbs et al. 2010; Hosonuma et al. 2012; Wang and Qiu 2017). Agricultural development is clearing the riparian ecotones to make arable land and thereby reduction in riparian and river ecosystem services (Rheinhardt et al. 2012a; Truax et al. 2017). To prepare land for cultivation, riparian forests along farm streams have been cleared in many temperate agricultural landscapes (Fortier et al. 2015). Intensive agriculture is a major reason for vegetation degradation along the rivers and streams. During the past 200 years in North America about 90% of riparian habitats have been lost mainly due to intensified agricultural practices (Popotnik and Giuliano 2000; Deschenes et al. 2003). Intensive agricultural activities in riparian zones significantly alter the composition, diversity and richness of native species of riparian forests (Asanok et al. 2017). Intensive agriculture causes the excessive application of agrochemicals. Application of pesticides, herbicides, and fertilizers on agricultural fields threatens the ecological functions in riparian zones (Gregory et al. 1991; Nóbrega et al. 2020).

Riparian zones are one of the most preferred areas for grazing. Long-term unrestricted grazing is one of the most destructive forces to the river and riparian ecosystems as it reduces stream water quality, damages soil, degrades vegetation, enhances soil erosion, alters channel morphology, increases biological invasion and paves the way for biodiversity loss (Davis 1982; Kauffman and Krueger 1984; Trimble and Mendel 1995; Vidon et al. 2008; Miller et al. 2010; Hughes et al. 2016). Unrestricted cattle entry in riparian zones can alter or eliminate the vegetation. Livestock cause physical damage to riparian vegetation by rubbing, trampling, and browsing (Kauffman and Krueger 1984). Vegetation decrease due to overgrazing can adversely affect the hydrologic conditions in watershed and diminish stream flow (Armour et al. 1994). Livestock grazing causes soil compaction which increases runoff and consequently decreasing the water availability to plants (Kauffman and Krueger 1984). Increase runoff results in reduced entry of water in aquifers. Livestock grazing can also affect the riparian bird breeding behavior as evidenced by Hansen et al. (2019) in a study at riparian zones of northern Victoria, Australia. Hansen et al. (2019) explored that woodland bird breeding activity was declined in heavily and lightly grazed and degraded riparian sites compared to non-grazed sites.

Urbanization

Currently, more than half of the global population lives in urban areas (Ahmed et al. 2020). In the current scenario, urbanization is among the major drivers that are transforming landscapes worldwide (Ives et al. 2013). Urbanization directly impacts ecosystems by replacing vegetation with urban structures like buildings, roads, and indirectly by modifying vegetation composition and structure through fragmentation and degradation of ecosystems such as altered hydrology (McKinney 2002; Pennington et al. 2010). Urbanization has dual impacts on one hand, it threatens ecosystem structure and functions and on the other hand increasing the ecological demands on sustainable provision of ecosystem services (Song and Deng 2017; Peng et al. 2017).

Expansion of cities coupled with extensive infrastructure causes reduction and fragmentation of primary riparian forests (Zipperer et al. 2012; dos Anjos Santos et al. 2016; Asanok et al. 2017). Urbanization in riparian zones results in habitat fragmentation, degradation, and loss and consequently decline in biodiversity. Habitat degradation as a result of urbanization reduces the populations of various riparian animal species, for example riparian birds as evidenced by Rottenborn (1999). Rottenborn (1999) through a bird survey in the Santa Clara Valley of California, USA found that bird species richness and density were negatively related to number and proximity of bridges. Changes in hydrology due to urbanization cause riparian hydrologic drought by lowering water tables which alters soil, vegetation and microbial processes (Groffman et al. 2003). Urbanization is among the major factors causing the decline of riparian habitats in the United States (Groffman et al. 2003; Jones et al. 2010; McClure et al. 2015).

River flow alteration

The flow regime is a key factor that determines the structure and function of aquatic and riparian ecosystems of rivers (Poff et al. 2010). Cycles of floods and droughts (natural flow regime) are important features of rivers, but the alteration of this natural flow regime mainly by dam building, flood-control projects and other human activities raises questions to the biological evolution, conservation of living organisms and management of biodiversity (Lytle and Poff 2004). Riparian ecosystems have evolved in context of seasonal variability in natural flow regimes (Lytle and Poff 2004; Tonkin et al. 2018). River regulation through channelization and damming threatens riparian forest and their ecosystem services because riparian structure and processes are closely linked to fluvial regime (Poff et al. 1997; Nilsson and Berggren 2000; Nilsson et al. 2005; Kuglerová et al. 2014; Dixon et al. 2015). Damming significantly changes the shoreline vegetation though affecting not only the diversity and composition of plant communities but also the structural patterns (Wintle and Kirkpatrick 2007; New and Xie 2008). Riparian vegetation particularly shrubs and herbs are highly sensitive to change in hydrological regime (Ye et al. 2010).

River flow alteration paves the way for the invasion of exotic species in the riparian zones (Chen et al. 2017). Alteration in natural flood peaks can prevent the growth of indigenous riparian vegetation and allow establishment and proliferation of non-native trees (Stromberg et al. 2007; Poff et al. 2010). Flow regulation is one of the major reasons that extensively established exotic Tamarix in western North American riparian ecosystems (Everitt 1998; Shafroth et al. 2002). Riparian woodlands of the Alberta's St Mary River in Canada collapsed due to insufficient summer flows and rapid reductions in spring flow (Rood et al. 1995,2005). Lowered groundwater levels following river regulation reduce the reproduction of pioneers followed by a successive dieback of mature individuals (Stromberg et al. 1996; Nilsson and Berggren 2000). Lack of regeneration moves the succession toward older, less productive states, and consequently reduced riparian biodiversity (Nilsson and Dynesius 1994; Nilsson and Berggren 2000).

Overexploitation

Ecological systems are under huge pressure of overgrowing population and their associated demands of ecosystem goods and services (Etter et al. 2006). It is estimated that 60% of the global ecosystems are being used in unsustainable way (Millennium Ecosystem Assessment 2005; Pattison-Williams et al. 2017). Riparian zones are under severe threat of degradation due to huge pressure of overexploitation and utilization (Fu et al. 2016). Anthropogenic activities such as logging, surface water extraction, sand mining and groundwater pumping severely alter the riparian ecosystem structure, functioning and services (Poff et al. 1997; Nilsson and Berggren 2000; Allan and Castillo 2007; Kuglerová et al. 2014; Fu and Burgher 2015). Riparian forest along the Tarim River, China is among the most threatened riparian ecosystems of the world due to overexploitation of river basin natural resources such river water and riparian wood (Thevs et al. 2008; Lang et al. 2015). Groundwater abstraction can significantly affect growth of riparian plants as well as the species assemblage (Le Maitre et al. 1999). Phreatophytes (plants that use groundwater) are sensitive to alterations in the hydrogeological regime (Le Maitre et al. 1999). Logging activities in riparian forests is among the major threats to riparian ecosystem and their functions and services (Kuglerová et al. 2014). Deforestation of riparian buffers results deleterious effects on riverine ecosystems through facilitating invasion of exotic species and degrading allochthonous energy sources to aquatic organisms (Bunn and Arthington 2002; Ramírez et al. 2008). Timber harvesting increases sediment load, alters morphology, temperature, hydrology, and water quality of stream, and consequently affecting flora and fauna (Chizinski et al. 2010; Santiago et al. 2011).

Sand mining from river bed and floodplains is one of the deleterious threats to the riparian ecology. The quantity of sand mined from the alluvial reaches in the midlands and lowlands of the Muvattupuzha, Periyar and Chalakudy rivers (Kerala, India) amounts to 6.4 million ty−1, which is more than 58 times higher than the natural replenishments (0.11 million ty−1) (Sreebha and Padmalal 2011). Indiscriminate river sand and gravel mining deleteriously impacts the river ecosystem though erosion riverbank, lowering of ground water table, declining flora and faunal diversity and damaging riparian habitats (Poulin et al. 1994; Padmalal et al. 2008). Excessive sand mining from river ecosystem can pave the way for alteration in flow regime, groundwater, geomorphic units, channel dynamics, and sediment flow.

Climate change

According to a report of the IPCC, there is an estimate of about 1.4–6.4 °C increase in global temperature by 2100 (IPCC 2007; Mishra et al. 2013). Climate change is projected to cause an increase in frequency and severity of extreme weather events including more frequent and severe floods and more intense droughts (Easterling et al. 2000; Seavy et al. 2009). Although riparian restoration are recognized as effective strategy to enhance ecosystem resilience to climate change (Seavy et al. 2009) but at the same time, it is also true that riparian forests are highly vulnerable and responsive to climate-change induced flow regimes and land-use changes (Hoffman and Rohde 2011; Flanagan et al. 2015; Fernandes et al. 2016). Many climate change scenarios predict that rivers including riparian habitats will face extensive future pressures due to global warming and expansion of alien species (Hoffman and Rohde 2011). Rising temperature affects physiology, growth, phenology and geographical distribution of riparian flora and fauna (Perry et al. 2012). Under the scenarios of climate change, riparian ecosystems will be exposed to the rising air and surface water temperature, changes in the precipitation and altering river flows and consequently change in reproductive physiology, structure, functions and distribution of riparian biota (Arnell 2003; Palmer et al. 2008; Rosenzweig et al. 2008; Seavy et al. 2009; Perry et al. 2012; Capon et al. 2013).

Rivaes et al. (2013) predicted that extreme climatic change will fuel the vanishing of the pioneer and young succession stages of riparian forests of the Mediterranean rivers (Rivaes et al. 2013). Climate change can cause narrowing of riparian zones. According to Ström et al. (2011) climate-driven hydrologic changes are predicted to cause narrowing of riparian zones along the Vindel River in Northern Sweden by the end of the twenty-first century. Immigration of temperate species, loss of boreal species, expansion of existing population of exotic plants, drought stress during summer due to increased evaporation are examples of predicted changes in Boreal riverine ecosystems following increased temperature (Nilsson et al. 2013). It is predicted that drying and warming of riparian zone in temperate south-western Australia will cause removal of stenothermal animals and may facilitate establishment of invasive animal species characterized by a broader thermal range (Catford et al. 2013).

Pollution

Worldwide pollution is a major threat to sustainability of riparian zones (González et al. 2016). Riparian zones are highly sensitive to pesticide and heavy metal pollution. Pesticide accumulations potentially disturb microbial activity and nitrogen cycle in riparian sediments (Chen et al. 2019). Anthropogenic activities upstream or on adjacent uplands cause heavy metal pollution in riparian zones (Ye et al. 2019). Polluted sediments due to river flooding contribute to the heavy metal contamination in riparian soils (Bai et al. 2012; Zhang et al. 2017). Industrial discharge, sewage, and agricultural run-off are the major anthropogenic sources of heavy metal pollution in riparian soils (Bai et al. 2016; Ye et al. 2019). Mining activities in riparian ecosystems can cause accumulation of heavy metals in floodplain (Graf et al. 1991).

When the content of metals in riparian sediments goes beyond environmental quality standards, they become eco-toxic risks for the riparian organisms (Wang et al. 2015; Pavlović et al. 2019). Heavy metal accumulation in riparian soils can cause deleterious effects on richness and diversity of plant species. Schipper et al. (2011) investigated relation between the plant communities and soil heavy metal contamination in a lowland Rhine River floodplain. They found a significant decrease in plant species richness and diversity with the level of contamination. Metal pollution in streams can alter riparian food webs. High level of metal pollution in rivers can reduce prey availability to riparian web-building spiders (Paetzold et al. 2011; Kraus et al. 2014).

Biological invasion

Biological invasion refers to the arrival, survival, successful reproduction and dispersal of species in an ecosystem where the species did not occur earlier (Carlton 1989; Whitfield et al. 2002). Riparian forests are among the most vulnerable ecosystems to the biological invasion (Richardson et al. 2007; Sosa et al. 2018a, b, c). Some authors consider riparian zones “as heaven for exotic plant species” (Stohlgren et al. 1998; Michez et al. 2016). Changing nutrient levels and hydrology, low lying areas in landscape, flooding, propagules dispersal by moving water and contribution of stream banks as a reservoir for propagules of indigenous and exotic species make riparian zones highly susceptible to invasion of alien plants (Galatowitsch and Richardson 2005; Richardson et al. 2007; Beater et al. 2008; Vosse et al. 2008).

Presence of invasive species in riparian zones is an environmental problem that affects biodiversity, and threatens the ecological integrity of river ecosystems (Jiménez-Ruiz et al. 2016). Riparian zones of South Africa are vulnerable to the widespread invasion of Eucalyptus camaldulensi (Forsyth et al. 2004; Tererai et al. 2013;). All riparian ecosystems in the Southwest USA, are at risk for decline (Tellman et al. 1997) and the invasion of non-native species, mainly tamarisk (Tamarix ramosissima), posed a great concerns for sustainability and ecological health of these ecosystems (Webb and Leake 2006).

Managing riparian zones through integrated approach

Current scenario of riparian zone management

Worldwide, many efforts have been executed to manage riparian zones. Many riparian zone management projects and plans have either failed or partially succeed due to numerous reasons. Riparian zone management is frequently executed without an accurate assessment of their condition and ecosystem services (Novoa et al. 2018). It has been found that recommendations and guidance about riparian zone management are generally started without assessing their status and ecosystem services and consequently diverged from target and provide little benefits (de Sosa et al. 2018a). Understanding of spatial extent of various processes such as flooding, erosion, sedimentation, geomorphic channel processes, fire, insects and wind disturbances, variation in light, soil and topography supports riparian management (Lee et al. 2004). Riparian management decisions should be based on the knowledge of geomorphic setting and the most valuable ecosystem functions of riparian zones (Allan 2004). Establishing buffer zones without considering local hydrological and soil conditions will not be efficient (Mander et al. 2017). Riparian health assessment following management works is essential for the success of riparian management plans (Burger et al. 2010). According to Burger et al. (2010) despite a voluminous investment in Australia and elsewhere, there have been little efforts to assess the changes in riparian condition following restoration works. It is essential to assess the riparian condition both prior and after the implementation of management plan.

Lack of nature-based sustainable practices hampers the path of integrated management of riparian zones in the changing environment. A suite of sustainable practices paves the way for successful riparian zone management. Practices should be adopted according to the problems of area. One practice cannot be executed at all places. “One size fits all” approach to riparian management is not effective because riparian zones functions vary with geography of the area (Quinn et al. 2001; Strayer et al. 2003; Allan 2004). For example, the management practice for a riparian zone dominated by intensive agriculture should be different than the riparian zone under the threat of urbanization. Many riparian forest management guidelines usually focused on the protection of stream water quality while ignoring the protection of other services such as diversity of native flora and fauna and organic matter flux into the aquatic systems and consequently degradation of ecological services of riparian forests (Broadmeadow and Nisbet 2004; Palik et al. 2012).

Poorly planned or poorly applied forest management practices threaten the ecological services of riparian forests (Palik et al. 2012). Poorly designed plans and policies cannot go longer on the path of riparian zone management. Generally, policy-makers ignore the views and opinions of local people while framing a policy. Frequently it was found that many management plans did not achieve their targets due to lack of coordination, collaboration and participation among different stakeholders. Moreover, a single policy is framed and executed to the whole river basin keeping the local problems aside. It has been found that management practices have been poorly implemented under the weak legislation and guidelines. Most of the time, people are not aware about the role of riparian zones in their local environment. Moreover, all people are not aware about different acts and guidelines of government for riparian zone management.

Integrated management of riparian zones

Management of riparian zones through integrative approach is the need of hour. Social, economic, and political interests along with biological considerations pose a complexity to riparian management, and thus needs an integrated approach (Welsch et al. 2000). Integrated management is characterized by several features like collaboration, quest of long-term goals, dissemination and use of information, and modification of actions based on monitoring of progress (Welsch et al. 2000). González et al. (2017) stressed on the management framework addressing technical–ecological, socio-economic, and legal issues. Integration of technical, environmental, economic, and social dimensions is necessary for effective management of riparian zones.

González et al. (2017) proposed a framework for an integrated conservation strategy including education, inventory, protection, sustainable management and restoration. In this framework, education included the outreach activities, citizen science, and engaging local communities. Inventory helps in assessing the health, status, condition and extent of riparian zones using different techniques like remote sensing by aerial photographs or LiDAR imagery, and photogrammetry, traditional photointerpretation. Riparian zones can be conserved through protection by implementing legislation or incentive schemes like payment for ecosystem services (PES). Sustainable management approach is important for riparian zone conservation through satisfying economic, societal, and environmental needs. In restoration approach defining clear goals, choosing among multiple techniques and evaluation are strategies for riparian zone conservation. González et al. (2017) advocated the inclusion of these activities in an integrative manner. Including social values can reduce legal, political and jurisdictional battles arising from exclusion of concerned citizens from the management process (Welsch et al. 2000). Inclusion of human dimension is increasingly important component for developing management, planning of riparian zones, minimizing conflicts, and facilitating a dialogue between people and decision makers (Welsch et al. 2000).

Integrated management of riparian zones can be linked with river ecosystems and human society as shown in Fig. 3.

Fig. 3
figure 3

Linking integrated management of riparian zones to river health and human well-being

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Managing riparian zones through integrated approach can be helpful not only for improving structure and functions of riparian zones but also for river health improvement and supporting human well-being. For example, payment for ecosystem services approach to manage riparian zones ecosystem services can be beneficial for river health, riparian health and human well-being. In this approach, riparian farmers can be encouraged to adopt sustainable practices of food production on getting financial rewards in return (Singh and Singh 2019). Riparian farmers can be inspired to adopt agroforestry which is a sustainable agricultural practice. Adoption of agroforestry in riparian fields can improve riparian health though increasing forest cover and river health by buffering sediment and nutrients (Hain 2014). This practice can also enhance human well-being by diversifying livelihood and increasing farmers’ income.

Considering the above-mentioned recommendations and suggestions for integrated management of riparian zones, authors framed an integrated approach based on various dimensions including (i) riparian condition assessment (ii) policy framework (iii) stakeholder’s participation (iv) management practices (v) legislation, and (vi) awareness (Fig. 4).

Fig. 4
figure 4

Different dimensions of integrated riparian zone management

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The above-mentioned different dimensions for riparian management are interlinked. For example, riparian condition assessment is necessary for making a policy and plan. Riparian condition assessment provides foundations to frame policy based on current status of riparian condition including structure and composition of streamside vegetation (Fig. 5).

Fig. 5
figure 5

Interrelationship between different dimensions of riparian zone management

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Policy framework guides the framing of different rules and regulations for riparian zone management. Legislation is required for effective implementation of management practices through providing restrictions to follow. Increasing awareness can help not only in implementation of management practices but also in assessing the riparian condition. Stakeholders’ participation is important for every aspect of management including riparian condition assessment, framing the policy, implementing legislation, increasing awareness and executing management practices. Stakeholders’ participation can support monitoring, policy and planning for ecosystem management including river basins (Gallego-Ayala and Juízo 2014; Villasenor et al. 2016; Verbrugge et al. 2017). Stakeholders’ participation is advocated in development of policy documents and decision making for natural resources management including water resources (Pahl-Wostl 2008; Blackstock et al. 2012; Gallego-Ayala and Juízo 2014). In the following sections, every dimension of integrated management of riparian zone is described.

Riparian condition assessment

The assessment of riparian condition is perquisite for making, implementing and tracking the riparian management projects. Quantification of riparian quality is basic step to identify river reaches for restoration or conservation purposes (Fernández et al. 2014). Riparian quality denotes to the several aspects of riparian plant communities in terms of extension, structure, composition and naturalness (Fernández et al. 2014). Riparian quality is high when riparian vegetation consists of forested areas. On the other hand, riparian quality is low when land is lacking woody vegetation along river corridors.

Riparian condition assessment is helpful not only prior to implementation of management plan but also after implementation to assess the changes under different management regimes. Burger et al. (2010) assessed the changes in soil and vegetation properties in riparian zones, following livestock removal and replanting, adjacent to tributary streams in one of south-eastern Australia’s main agricultural regions. Assessing riparian condition after execution of management practices paves the way not only for design and implementation of restoration and monitoring projects but also for future ecological studies (Burger et al. 2010). Hale et al. (2018) assessed changes in structural vegetation and soil properties following livestock exclusion and replanting in lowland streams in the Murray-Darling Basin (MDB), south-eastern Australia. The US federal law mandates riparian monitoring for federal land management agencies to achieve sustainable resource management (Booth et al. 2007). Ferreira et al. (2005) assessed the changes in riparian woods over space and time in three river basins belonging to the Tagus fluvial system (Portugal).

Riparian vegetation is an important indicator for assessing the riparian condition (Macfarlane et al. 2017). Worldwide various indicators such as riparian zone width, streambed width, longitudinal continuity, vegetation overhang, and bank stability have been used to assess the condition of riparian zones (Ferreira et al. 2005; Akasheh et al. 2008; Johansen et al. 2010). Measurement of riparian buffer width and biomass is important to assess the success of buffer conservation and restoration (Klemas 2014; Yang et al. 2018). Rheinhardt et al. (2012b) used biomass and proximity of biomass to channel to develop an indicator of riparian condition.

Monitoring of stream flow is an important step in assessing effects of management practices in riparian zones (Welsch et al. 2000). Water depth in river is affected by alteration in river flow regimes. The river flow is the key driver that affects the survival of riparian vegetation (Vesipa et al. 2017). River flow fluctuations affect riparian vegetation at any stage of plant life, from the seed dispersal and germination stages to the seedling development and adult phase (Vesipa et al. 2017). Flooding and water level fluctuations result in landscape disturbances that paves the way for a variety of habitats for plants (New and Xie 2008). Thus assessment and monitoring of river flow is an important part of riparian zone management.

González et al. (2017) advocated various techniques to assess riparian condition such as remote sensing, LiDAR (Light Detection and Ranging) imagery, photogrammetry, and traditional photointerpretation. Image-based riparian assessment potentially assesses various aspects of riparian zones such as width, invasive species, reduction of spatial extent, and shifts in vegetation pattern in flooding (Apan et al. 2002; Arroyo et al. 2010; Džubáková et al. 2015; Michez et al. 2016; González et al. 2017). Geographic information systems (GIS) and remote sensing (RS) are potential techniques for characterization, analysis, and monitoring of riparian landscapes (Novoa et al. 2018). RS plays a significant role in riparian zone mapping and monitoring due its wide coverage and ability to map inaccessible areas (Johansen et al. 2010). Akasheh et al. (2008) mapped in detail the riparian vegetation in the Middle Rio Grande River Basin of New Mexico using high-resolution multi-spectral airborne remote sensing. High-resolution airborne RS is a powerful tool for mapping riparian vegetation and provides an extensive indication of riparian zone health and condition (Akasheh et al. 2008).

Tompalski et al. (2017) characterized the streams and riparian zones in northern Vancouver Island, British Columbia, Canada using airborne laser scanning (ALS) data. Wasser et al. (2015) used LiDAR data to quantify land use effects on forested riparian buffer vegetation structure in Spring Creek watershed of central Pennsylvania, USA. Yang et al. (2018) used unmanned aircraft vehicles (UAVs) and normalized difference vegetation index (NDVI) to assess the changes in biomass and riparian buffer width in the terminal reservoir under the impact of the South-to-North Water Diversion Project in China. Rigge et al. (2013) used NDVI in the assessment of the effect of Off-Stream Watering Points (OWSPs) on riparian vegetation in rangelands of along the Bad River in Western South Dakota.

Worldwide, several indices and protocols have been developed for assessing health and condition of riparian zones. Rapid Appraisal of Riparian Condition (RARC), QBR index (“qualitat del bosc de ribera”), Tropical Rapid Appraisal of Riparian Condition (TRAC), and Proper Functioning Condition (PFC) assessment are some of the prominent indices to assess the condition of riparian zones. Jansen et al. (2005) used Rapid Appraisal of Riparian Condition (RARC) index to assess the ecological condition of riparian habitats in three areas of Australia including on the Murrumbidgee River, in Gippsland, and in the Goulburn Broken catchment. RARC index comprises of five sub-indices each with a number of indicators: (1) habitat continuity and extent (HABITAT) (2) vegetation cover and structural complexity (COVER) (3) dominance of natives versus exotics (NATIVES) (4) standing dead trees, hollows, fallen logs and leaf litter (DEBRIS) and (5) Indicative features (FEATURES). Munné et al. (2003) assessed ecological quality of riparian habitat of river basins in Catalonia, Spain through using QBR index. The QBR index (“qualitat del bosc de ribera”) is a simple method that evaluates riparian habitat quality (Sirombra and Mesa 2012). QBR index consists of four components of riparian habitat; (1) total riparian vegetation cover (2) cover structure (3) cover quality, and (4) channel alterations (Munné et al. 2003).

The Tropical Rapid Appraisal of Riparian Condition (TRAC) is a visual assessment of riparian zone using various indicators of condition (Dixon et al. 2006). TRAC comprises four condition sub-indices: (1) plant cover (2) regeneration (3) weeds, (4) erosion. It also includes an index of pressure. TRAC was specially developed to assess riparian zone condition in wet–dry savanna environments of tropical Australia in a rapid and cost effective manner (Dixon et al. 2005; Johansen et al. 2007). Johansen et al. (2007) assessed the riparian zone condition along the Daly River of Australia using a modified version of the TRAC comprising twenty three indicators with five sub-indices; (1) vegetation cover and leaf litter (2) regeneration of native plants (3) weediness (4) bank stability, and (5) disturbance/pressures.

Proper functioning condition (PFC) assessment protocol provides a consistent approach for assessing the physical functioning of riparian zones based on hydrologic, vegetative, and geomorphic attributes relative to the potential of the stream being assessed (Dickard et al. 2015). According to Dickard et al. (2015), a lotic riparian zone is considered to be in PFC, or “functioning properly,” when adequate vegetation, landform, or woody material is present to: (a) dissipate stream energy associated with high water flow, thereby reducing erosion and improving water quality (b) capture sediment and aid floodplain development (c) improve floodwater retention and ground-water recharge (d) develop root masses that stabilize streambanks against erosion, and (e) maintain channel characteristics. PFC assessment is helpful in assessing how well the physical processes of riparian systems are working (Booth et al. 2007).

Policy framework

Framing an appropriate policy paves the way for sustainable management of forest ecosystems including riparian zones. A good policy is the foundation on which the plan of riparian zone management builds. Decision making and policy design faces dual challenge of improving human well-being and ensuring sustainable use of natural resources (Guerry et al. 2015; Grizzetti et al. 2016). The policy for protection and management of riparian zones needs a multidimensional approach. Framing policies according to the socio-economic, cultural, institutional, and ecological context of country is an urgent need to foster the local solutions for riparian ecosystem restoration (Meli and Brancalion 2017). In the Oregon State of the United States, policy for protection of riparian zones is very diverse. It depends on the ownership (federal, state or private), land use (agriculture, rural or urban, forest) and stream attributes that help in formulating the standards for riparian land-management practices (Boisjolie et al. 2017). Ecosystem services are getting a rising traction as policy shaping framework (Scott et al. 2018). Policy to manage riparian zone also needs a high coverage of river length. For example, Chesapeake Bay Program on the east coast of the USA set an ambitious goal of greening 3216 km of streams with riparian forest buffers (Buckley et al. 2012).

Stakeholders’ participation

Stakeholders are those who are affected by, or can affect, a decision (Freeman 1984; Reed 2008). Stakeholders’ participation is pivotal in decision-making and addressing the environmental problems (Reed 2008). Stakeholders play a key role in the implementation, development, and assessment of BMPs (Tumpach et al. 2018). In riparian management, various stakeholders can be a part of like farmers cultivating fields near river, people living in riparian settlements, policy and decision makers, scientists and other local people obtaining livelihood from riparian ecosystems. For effective riparian management, it is needed to integrate the human dimensions information early in the planning process (Welsch et al. 2000). People’s values, attitudes, beliefs, knowledge, and expectations are as important for riparian management which can be unearthed by in-depth interviews of individuals (Welsch et al. 2000).

Community-based natural resource management (CBNRM) aims long-term sustainability through comprehensive stakeholder participation in decision-making (Mountjoy et al. 2016). It includes full participation of communities and resource users in decision-making process and incorporation of local institutions, customary practices, and knowledge systems in management, regulatory and enforcement processes (Barrett et al. 2001; Armitage 2005). The Rio Agenda 21 states that effective implementation of sustainable development will be function on the degree of commitment and genuine involvement of all social groups and the public at decision-making (Rafika et al. 2016). The European Union Water Framework Directive (EU WFD, 2000) advocates and encourages active involvement of the public and all interested parties in decision-making processes for river basin management plans in the European Union (Parés et al. 2015; Feichtinger and Pregernig 2016; Euler and Held 2018).

Active participation of various stakeholders is the need of hour for riparian zone management. Stakeholder’s participation enhances the success rate of riparian management plan. Diverse knowledge of various stakeholders strengthens the strategy of riparian zone management. There is an urgent need to make a common platform where various stakeholders can discuss issues related to riparian zone and river health. Worldwide there are several examples where active involvement of stakeholders played a key role in managing the riparian zones. The Parrett project in Somerset, England successfully managed and restored the floodplain of the Parrett catchment through stakeholder involvement and teamwork (Ball 2008). In this project, a partnership was formed between local authorities, stakeholder organizations, and landowner groups to create temporary flood storage areas, new wetland habitat, and woodland (Ball 2008).

Management practices

Worldwide, a range of practices have been advocated to manage the riparian zones. Authors introduced various sustainable practices to manage riparian zones such as riparian buffer strips, streambank fencing, rotational grazing, off-stream watering points, alternate shade structures, and payment for ecosystem services based on literature review (Table 1).

Table 1 Examples of practices for riparian zone management
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Riparian buffer strips (RBS)

Riparian buffer strips are vegetated strips of land extending alongside the watercourse and farmers are not allowed to cropping usually through agri-environment agreement (Stutter et al. 2012; McVittie et al. 2015). The retention of riparian buffer strips is important for protection, conservation and management of freshwater ecosystems including rivers and lakes. Riparian buffer strips is an agroforestry practice in Europe in which strips of perennial vegetation (trees/shrubs) natural or planted between croplands/pastures and water sources such as streams, lakes, wetlands, and ponds to protect water quality (Mosquera-Losada et al. 2018). Creating riparian reserve strips is among the best management practices (BMPs) to reduce the impacts of forest harvesting on watersheds (Yeung et al. 2017). Worldwide it is recognized that healthy riparian buffers deliver a range of services to their adjacent waterways (Correll 2005). It is recognized that the practice of leaving forested buffer strips along stream or river was first implemented in the United States in the late 1960s (Calhoun 1988; Brosofske et al. 1997; Lee et al. 2004).

Retention and maintenance of RBS is a sustainable and ecological strategy to control the entry of agricultural runoff into watercourses, conserve biodiversity and habitats, stabilize stream bank, regulate flood, regulate river temperature, mitigate climate, regulate water retention and infiltration, and provide recreation (Osborne and Kovacic 1993; Tabachi et al. 2000; Vowell 2001; Soman et al. 2007; Ramilan et al. 2010; Choi et al. 2012; Cardinali et al. 2014; McVittie et al. 2015; Mackay et al. 2016; Alemu et al. 2017; Richit et al. 2017; Chellaiah and Yule 2018; Jackson et al. 2018). In Indiana and North Carolina, USA it was observed that agricultural headwater streams with herbaceous riparian buffers were richer in fish diversity, macro-invertebrate abundance and macro-invertebrate diversity than streams without riparian buffers (Whitworth and Martin 1990; Smiley Jr et al. 2011).

Success of riparian afforestation or tree buffer establishment plans largely depends on the selection of trees adapted to local environment (Smaill et al. 2011; Truax et al. 2017). Fast growing woody trees are recommended for plantation in riparian zones. For example, fast-growing hybrid poplars (Populus. spp.) have ability to restore some forest attributes within a decade (Boothroyd-Roberts et al. 2013; Fortier et al. 2015). Multi-zones of riparian vegetation including a narrow grass strips and wider woody vegetation are more effective (Correll 2005). Multi-species riparian buffer strip (MSRBS) system is a potential tool that reduces soil erosion, filters pollutants, stabilizes stream banks, provides wildlife habitat, provides wood and enhances aesthetic value of agro-system (Schultz et al. 1995). Schultz et al. (1995) found that on creating MSRBS along the Central Iowa stream in USA riparian health was improved including soil stabilization and reduction in non-point source (NPS) pollutants. A general, multi-purpose, riparian buffer design comprises of a strip of grass, shrubs, and trees between the normal bank-full water level and crop field (Anbumozhi et al. 2005). Both grass and woodland have their important role in river health improvement. For example, woodland controls sediments by helping to slow water flows and grass has potential to trap and fix sediment deposits (Broadmeadow and Nisbet 2004).

Dimensions of buffer zone significantly affect the ability of riparian buffer zones to provide ecological services. (Mander et al. 1997; Syversen 2005; Bourgeois et al. 2016). Width of riparian buffer strip is important for its effectiveness. Generally, wider riparian buffer strips more effectively remove nutrients than narrow one (Mayer et al. 2006; Hénault-Ethier et al. 2017). Viegas et al. (2014) found that dung beetle richness was greater in fragments with the widest riparian zone than in those with a thinner riparian zone during spring and summer. Phillips (1989) suggested that a range of riparian width is more effective than a single value. Keller et al. (1993) recommend at least 100-m wide riparian buffer to provide some nesting habitat for area-sensitive species. Phillips (1989) suggests a range of 15–80 m for lower Tar River basin North Carolina.

Streambank fencing

Fencing is one of the recognized BMPs to prevent cattle entry in riparian zone and stream to enhance riparian health and water quality (Mostaghimi et al. 2001; Miller et al. 2010). Stream-bank fencing is a potential strategy to protect river ecosystems and their associated riparian zones from cattle grazing (Miller et al. 2014). Fencing helps to keep livestock away from streambanks and thus improves streambank stability and facilitates the establishment of vegetative buffer (Line et al. 2000; Feld et al. 2018). Fencing livestock from riparian zones improves water quality through reducing fecal matter deposition in water ways and riparian zones (Wilcock et al. 2009). Bragina et al. (2017) found that cattle exclusion using fencing reduced the level of fecal indicator bacteria (FIB) such as Escherichia coli (E. coli) in stream sediment reservoirs of northeast Ireland. Miller et al. (2010) assessed the influence of streambank fencing on riparian health and water quality of the Lower Little Bow River in Southern Alberta, Canada. They found that riparian health including vegetation, soil, and hydrologic features was improved by streambank fencing.

Rotational grazing

Worldwide rotational grazing system is getting huge attention in context of conservation and management of agro-ecosystems and riparian zones. It is widely mentioned that continuous season-long grazing degrades riparian zones (Rigge et al. 2014). Rotational grazing system is based on the approach of setting grazing and non-grazing (rest) periods to achieve increasing production through enhanced growth of vegetation and increased forage-harvest efficiency of grazing livestock (Briske et al. 2008; Roche et al. 2015). Rotational grazing systems are often prompted to cut undesirable selective grazing by livestock across multiple scales (Bailey and Brown 2011).

Rotational grazing improves distribution, increases uniformity of defoliation across species and communities and allows regrowth (Bailey and Brown 2011). Riparian habitats have extensively degraded in Wisconsin, USA through the continuously grazing and thereby Managed Intensive Rotational Grazing (MIRG) has been recommended to protect and restore stream ecosystems in Wisconsin (Undersander et al. 1992; Chapman and Ribic 2002). Sovell et al. (2000) in their study at Minnesota, USA found that water quality parameters such as coliform and turbidity was higher at continuously grazed than rotationally grazed sites. They also found that streambank health was much better at the rotationally grazed site than at the continuously grazed site.

Off-stream watering points (OSWPs)

Cattle use riparian zones mainly for water and cooling and, therefore, providing alternative water away from streams reduces the time cattle spend near streams (Franklin et al. 2009). Impacts of cattle in riparian zones can be reduced by providing alternative off-stream watering points (OSWPs). Provision of OSWPs is an effective and alternative watering source for cattle which reduces cattle impacts on the riparian zone and increases stream water quality (Olson et al. 2011; Brueggen-Boman 2012; Rawluk 2013; Malan et al. 2018). Off-stream watering is recognized as the best management practice that reduces cattle activity at the river, increases streambank stability, prevents river pollution, enhances riparian health, and improves soil and vegetative properties (Fielding et al. 2005; Miller et al. 2011). In a study at Alberta, Canada, Miller et al. (2011) found that implementation of OSWPs resulted in a range of benefits including reduction in river pollution and improvement in soil and vegetative properties in riparian zones. In Alberta, off-stream watering without fencing is recommended to protect riparian zones (Fitch and Adams 1998; Miller et al. 2011).

Most important benefit of OSWPs is reduction in time the livestock spend in riparian zones (Franklin et al. 2009). Godwin and Miner (1996) in their study at Tualatin river basin outside of Portland, Oregon observed that four cows spent averaged 60 min in riparian zone without off-stream watering while on giving the option of off-stream water, the total time was reduced to an average of 15 min. Franklin et al. (2009) in a study at Piedmont of Georgia, USA found that providing cattle with water troughs reduced the amount of time cattle spent in riparian zones by 63% when the temperature and humidity index (THI) ranged between 62 and 72.

Alternate shade structures

Cattle spend time in riparian zones for forage, water and shade availability (Bailey 2005; Kamp et al. 2013). Riparian zones have cool environment than their adjacent upland landscapes. Trees in riparian zones provide natural shade to the cattle. Livestock enhance their movement in riparian zones for getting this natural shade. An alternate method of cooling can reduce the time spent by livestock in streamside areas (Agouridis et al. 2005). Providing alternative shade structures is a best management practice that reduces time spent by cattle in riparian zone, encourages cattle to graze underutilized pastures, thereby reducing soil erosion and improving water quality (Clary et al. 2016). Alternate shade sources improve the riparian environment (Rigge et al. 2014). Clary et al. (2016) reported in their study that on average, cattle spent 30% less time within the riparian zone on providing an alternative shade pavilion. Providing alternate shade structures can also be integrated with off-stream watering points.

Payments for ecosystem services (PES)

In PES scheme, ecosystem services beneficiary offers financial incentives to the ecosystem service provider (Sangha et al. 2018). Payments for ecosystem services are incentives given to farmers and landowners to provide an ecological service (Taffarello et al. 2017). It is based on the principle ‘you get what you pay for’ for positive effects from the flow of ecosystem services (Wunder 2007; Leimona et al. 2015). Worldwide, payments for ecosystem services have become a well-known method to combat environmental problems (Kemkes et al. 2010). PES is an effective policy instrument to minimize negative impacts of human activities, reduce deforestation, stop biodiversity loss, manage natural resources and protect environment (Garrastazú et al. 2015; Leimona et al. 2015; Alarcon et al. 2017; Da Ponte et al. 2017). PES programs not only assist land management agencies and non-governmental organizations (NGOs) for success in their conservation goals but also diversify the farmer’s income (Hansen et al. 2018).

Using PES scheme we can encourage farmers having their crop fields near rivers to adopt sustainable agricultural practices to enhance the river and riparian health. A pilot project was completed in the Lake Naivasha basin, Kenya where 974 farmers were encouraged to adopt various land management practices for enhancing downstream water quality and quantity with a financial incentive of USD 20,000 (Chiramba et al. 2011; Wanjala et al. 2018). Under this project, farmers managed riparian zones through various practices such as agroforestry, cover cropping, grass strips, and integrated pest management (Chiramba et al. 2011; Wanjala et al. 2018).

Legislation

Environmental legislation is pivotal for implementation of a plan and policy. In many countries, riparian forests are protected by legislation due to their significant ecological role (da Silva et al. 2017). Water Framework Directive of the European Union (WFD) stresses on the sustainable river management regarding hydro-morphology and biodiversity (Bączyk et al. 2018). The objective of WFD is to restore the riparian health in European Union (EU) through encouraging sustainable utilization of the ecosystem services delivered by waterways (Antunes et al. 2009; Collins et al. 2007; Gouldson et al. 2008; Euler and Heldt 2018). EU legislation encouraged stakeholders participation especially farmers for sustainable management of riparian zones (de Sosa et al. 2018b). In USA, riparian zones and wetlands are protected by the Clean Water Act through regulating use and modification of floodplains and wetlands (Dwire et al. 2017). The Clean Water Act regulates the streamside development in the United States (Lee and Rotenberry 2015). According to the forest management guidelines in most North American jurisdictions, there is restriction on harvesting trees along the rivers and streams that leaves behind riparian buffer zones (Lee et al. 2004; Phoebus et al. 2017). Guidelines for multispecies riparian buffer installation have been developed by the United States Department of Agriculture (USDA) Natural Resources Conservation Service to reduce nonpoint source pollution (USDA 1997; Bourgeois et al. 2016).

Brazil is among the countries that have most advanced legislation for helping the restoration of riparian ecosystems (Meli and Brancalion 2017). The Brazilian Forest Law protects riparian forest through prescription of riparian buffer width according to the river width (Nunes et al. 2015; da Silva et al. 2017). Areas of permanent protection (APPs) are legally required set-asides suggested by Brazilian Forest Code (Brasil 2012) that include riparian and stream headwater zones in addition to other fragile landscape features with the aim of maintaining hydrological functions, soil stabilization and landscape connectivity (Zimbres et al. 2018). The Government of Canada took a strong decision to conserve the river and riparian ecosystems from agricultural practices. Since 1987, agricultural practices such as soil tillage, fertilization, and pesticide have been banned in a riparian zone of at least three meter wide along streams adjacent to agricultural fields in Quebec, Eastern Canada (Gouvernement du Québec 1987; Bourgeois et al. 2016).

Awareness

Awareness of local people is a pressing need for the conservation and management of the riparian zones. Environmental awareness is the awareness to the environmental issues and active involvement in environmental organizations (Altin et al. 2014; Mei et al. 2016). Lack of environmental awareness in the era of environmental problems such as urbanization, climate change, industrialization, deforestation and biodiversity loss is a major obstruction that delays the achievements of policy maker’s efforts to combat the environmental issues (Keles 2012; Mei et al. 2016). Strengthening of public awareness plays a significant role in environmental protection and biological conservation and social media can play a crucial role in this context (Steel et al. 2005; Jefferson et al. 2015; Wu et al. 2018).

In the era of global crisis, education is the most influential tool to implement sustainable development principles and ideas (Nasibulina 2015). Environmental education is a potential tool to combat environmental problems of protection and conservation (Palmer 1998; Potter 2009; Otto and Pensini 2017). The importance of environmental education has been widely accepted in the era of environmental problems (Jia-nan 2012). Environmental education aims to promote environmental awareness in society and instills enduring behavior in people (Ors 2012). A lack of understanding of functions and services of riparian zones is common among people. Riparian zones are the small natural features (SNFs) with large ecological importance. Hunter Jr. et al. (2017) stresses on the role of education for the conservation of SNFs. Informing people about the functions and importance of underappreciated, unrecognized features can be a key foundation for their conservation (Hunter Jr. et al. 2017). Several environmental education programs such as field trips, trekking, camping and adventurous activities develop relations with nature, improve sensitivity towards the nature and establish social relations (Palmberg and Kuru 2000; Uzun and Keles 2012).

Conclusion and recommendations

Riparian zones are the important transitional zones between aquatic system and upland terrestrial system. They are small natural features but deliver a range of ecosystem functions and services of high value. Despite their small area, they support river health through a multitude of ecosystem functions. Riparian zones function as the ecological engineers and deliver several ecosystem functions like riverbank stabilization, pollutants buffering, food and habitat provision to organisms, groundwater recharge and regulation of river temperature. Riparian zones also underpin human well-being by providing numerous ecosystem goods and services such as livestock forage, genetic resources, herbal medicines, ornamental resources, fuel wood, carbon sequestration, flood regulation, pollination, recreation and aesthetic value. Riparian zones, though improve river health but their own health is at the high risk. Riparian zones are among the most threatened ecosystems of the world mainly due to agricultural activities, urbanization, river flow alteration, overexploitation, climate change, pollution, and biological invasion.

Riparian zone management is the need of hour to improve river health. In the era of global environmental changes, riparian zones can be managed using an integrated approach comprising of several dimensions such as riparian condition assessment, policy framework, stakeholders’ participation, management practices, legislation and awareness. Various management practices such as riparian buffer strips, streambank fencing, rotational grazing, off-stream watering points, alternate shade structures and payment for ecosystem services have been advocated as sustainable practices for riparian zone. Assessment of riparian condition is required not only before the execution of project but also after the implementation. There is a need to strengthen the environmental legislation to protect and manage the riparian ecosystems. Local people and various other stakeholders play a significant role in policy making and management. Last but not the least, without public awareness, we cannot hope much from the practices, policies, stakeholders’ participation and legislations. Therefore, public awareness should be increased for spreading the message of different aspects of riparian management.

The necessity for managing riparian zones in the changing global environment is an ongoing issue. The changing climate is now a reality and overgrowing population needs plenty of food production and houses for living and consequently urbanization, agricultural intensification and riparian zone degradation. Authors suggest following recommendations for integrated management of riparian zones to sustain the river health in the current scenario of environmental changes.

  1. 1.

    Managing riparian zones in the time of global environmental changes needs an integrated approach combining socio-economic, technological, and legislative issues.

  2. 2.

    Farmers should be financially supported to adopt the sustainable agricultural practices to produce food while improving watershed and maintaining agro-ecosystem biodiversity.

  3. 3.

    The study about ecosystem functions and services will play a key role in riparian zone management.

  4. 4.

    All the stakeholders should be a part of riparian zone management programs according to their abilities.

  5. 5.

    River flow regime is the master deriver of river as well as riparian health. It is the need of hour to maintain the flow in river throughout year.

  6. 6.

    Management practices should be applied after proper assessment of structure, functions, and services of riparian zones.

  7. 7.

    Continuous assessment of riparian health with multiple indicators like riparian structure, composition, water quality, river flow regime, and soil quality can help to identify and prioritize the target areas for riparian protection and management.

  8. 8.

    There is an urgent need for coordination and cooperation between different agencies and bodies involved in riparian restoration, conservation and management.

  9. 9.

    Environmental education and awareness should be promoted to makes the riparian zone management a people’s movement.

  10. 10.

    An integration of traditional knowledge, technology and nature based solutions would be a good option for riparian zone management.