Keywords

1 Introduction

Wetlands are recognized as ecosystems of extreme importance to man and biodiversity. People derive many benefits from the goods and services provided by wetlands, while wetland systems are the “homes” of huge number of plants and animals and their habitats. Ramsar Convention defined the wetlands as areas of marsh, fen, peatland, or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, and fresh, brackish, or salt, including areas of marine water, the depth of which at low tide does not exceed six meters [1]. In Africa, wetland awareness has been paralleled by the need to develop mechanisms for tropical wetland management both to maintain the human benefits from wetlands and to secure their biodiversity into the future. In a review of the worldwide status of wetland biodiversity, Gopal and Junk [2] provided abundant evidence to support their statement that “wetlands are highly valuable, yet the most threatened ecosystems,” where little is known about “which factors regulate biodiversity and how.” Wetlands are composed of a number of physical, biological, and chemical components such as soils, water, plant, and animal species. Interaction among and within these components allows the wetland to perform many vital functions such as water storage; storm protection and flood mitigation; shoreline stabilization and erosion control; groundwater recharge and discharge; water purification through retention of nutrients, sediments; and pollutants; and stabilization of local climatic conditions, particularly rainfall and temperature [3, 4].

Macrophytes are conspicuous aquatic plants that dominate wetland, shallow lakes, and streams. They grow in or near water and can be emergent, submerge, or floating. They play a vital role in healthy ecosystems by serving as primary producers of oxygen through photosynthesis, providing a substrate for algae and shelter for fish and many invertebrates, and helping nutrient recycling and are potential to be used to treat the wastewater [3]. The natural lakes of Egypt have a unique combination of physical and chemical features. The chemical and hydro-physical characteristics of soils affect the diversity and structure of the vegetation of these lakes [5]. The rapid reduction of the biotic resources threatens the integrity of the global biosphere and its life-support systems [6]. Although representing only a very small portion of all the terrestrial landscapes on earth, the Mediterranean Basin is of a special significance because of its unique evolutionary and cultural history which makes it one of the richest biological regions outside the tropics [7]. The Mediterranean Basin integrates a large variety of ecosystems whose climates vary from humid, semi-humid, arid, to hyperarid. These ecosystems are under extreme and increasing pressure from direct human intervention like intense land use and land use change, desertification, and global change [8].

The aim of this chapter is to give the reader a background on the Egyptian Mediterranean lakes (Mariut, Edku, Burullus, Manzala, and Bardawil) in terms of landforms and morphometry, sediment and water characteristics, plant diversity and threatened species, conservation measures and goods, and services which they offer. After reading this chapter, the reader should understand the value of these wetlands as a hot spot for plant diversity and nature conservation. Also, this study will help decision makers to evaluate and valuate this ecosystem for biodiversity conservation.

2 Sites Description

2.1 Land Forms

The Mediterranean coast of Egypt extends for about 970 km, from Sallum (31° 34′ N, 25° 09′ E) in the west to Rafah in the east (34° 20′ N, 31° 25′ E). Along this coast, five natural lakes are extended: Mariut (western coast), Edku, Burullus, Manzala (Deltaic coast), and Bardawil (Sinai coast) (Fig. 1). They are separated from the sea by strips of sandbars that are very narrow in several places and are connected with the sea through narrow straits, which are either remnants of the mouths of old Deltaic branches or merely gaps in weak sections of the bars known as tidal inlets [9]. After the construction of Aswan High Dam, considerable changes have been observed in the morphology, water characteristics, and biotic composition of the Egyptian northern lakes [10]. Nowadays, these lakes are threatened by several factors such as continuous land reclamation, construction of roads along the north coast, touristic development, pollution, and coastal erosion. All these current or planned human activities will not only cause the loss of important unique wetland habitats but will also create new artificial ecosystems.

Fig. 1
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Location map of the five Mediterranean lakes of Egypt [1]

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2.2 Lakes Morphometry

Lake Manzala is the largest lake with an area of 1,200 km2, while Mariut (63 km2) is the smallest (Table 1). Lake Mariut is the deepest with an average depth of 1.2 m, while Lake Bardawil is the longest (75.0 km), and Manzala is the widest (49.0 km). Moreover, Bardawil is the most hypersaline, while the other lakes are brackish. Mariut is the only lake that has no natural connection with the Mediterranean Sea.

Table 1 Morphometry of the five Egyptian northern lakes [11]
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2.3 Sediment and Water Characteristics

In the Mediterranean region of North Africa, increasing water usage presents a major threat to natural wetlands [12]. Fresh water availability is a most pressing issue affecting natural and semi-natural North African wetland lakes [13]. The northern lakes of Egypt are bodies of fresh, brackish, and saline water. These habitats are highly structured, and they can provide a gradient from extremely inundated to relatively mesic. The chemical and hydro-physical characteristics of soils affect the diversity and structure of the vegetation of these lakes [5, 14].

The physicochemical analysis of the sediments of these lakes showed that the pH values are in the alkaline side with a range of 7.3 (Burullus and Bardawil) and 7.6 (the other lakes), while salinity had the minimum value (2.0 mS cm−1) in Manzala but the maximum (6.6 mS cm−1) in Bardawil (Table 2). Sand ranges between 60.8% (Edku) and 79.6% (Mariut), silt between 12.9% (Mariut) and 21.9% (Burullus), and clay between 7.4% (Manzala) and 17.8 (Edku). In addition, organic matter ranges between 3.6% (Edku) and 6.9% (Mariut). Regarding the water characteristics, pH values are also in the alkaline side with a narrow range of variation (7.7–7.8), while salinity had a wide range of 2.9 mS cm−1 (Edku) and 48.1 mS cm−1 (Bardawil). Moreover, water temperature ranges between 17.8 °C (Bardawil) and 23.6 °C (Burullus), while transparency has a range of 25.3 cm in Edku and 63.0 cm in Bardawil.

Table 2 Sediment and water characters of the five Egyptian northern lakes [15]
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2.4 Prevailing Climate

The Mediterranean coast of Egypt belongs to the dry arid climatic zone of Koppen’s (1931) classification system [16]. According to the map of the world distribution, the northern Mediterranean part of the Nile Delta belongs to the arid region [17]. The climatic conditions are warm summer (20–30 °C) and mild winter (10–20 °C). The aridity index (P/PET, where P is the annual precipitation, and PET is the potential evapotranspiration) ranges between 0.03 and 0.2 at the north Delta (arid region) and less than 0.03 at the south (hyperarid region).

3 Prevailing Habitats

The Egyptian coastal lakes are characterized by 16 different habitats varied from one lake to another. The prevailing habitats varied between 8 in Mariut and Bardawil and 13 in Burullus. Shorelines, open water, and drains are the dominant habitats in all lakes, except Bardawil which has no connection with any drain. Sand formations (sheets, nebkhas, mobile dunes, calcareous, and siliceous-stabilized dunes) are well-represented habitats in Burullus and Bardawil.

4 Plant Diversity

4.1 Taxonomic Diversity

Four hundred and two species belonging to 248 genera and 68 families were recorded in the Egyptian coastal lakes (Table 3). Although the areas of these lakes (2,449 km2) contribute <0.003 of the total area of Egypt (one million km2), but they are inhabited by 19% of the whole Egyptian flora [18]. Thus, these lakes are important hot spots for the Egyptian flora, particularly the aquatic plants. Grasses have the highest contribution to the total flora (66 species and 40 genera), followed by composites (44 species and 35 genera), chenopods (38 species and 17 genera), legumes (32 species and 15 genera), and crucifers (27 species and 19 genera). According to Galal [10], 8 families (Gramineae, Compositae, Chenopodiaceae, Leguminosae, Cruciferae, Caryophyllaceae, Cyperaceae, and Polygonaceae) contributed nearly two-thirds of the total flora of these lakes. These families represent most of the floristic structure in the Mediterranean North African flora [19]. Burullus has 224 species, 149 genera, and 47 families; Mariut has 198 species, 148 genera, and 45 families; Manzala has 144 species, 107 genera, and 47 families; and Bardawil has 136 species, 109 genera, and 41 families, while Edku has 120 species, 100 genera, and 39 families (Table 3). The species to genus ratio for the flora of these lakes is 1.6, which is close to 1.9 recorded for the Nile Delta [20].Thus, the flora of these lakes goes below the average level of the Egyptian flora which has a ratio of 2.8. This means that the flora of the northern lakes is relatively richer than that of the Egyptian flora, as the region that has a certain number of species, each of which belongs to a different genus, is relatively more diverse than a region that has the same number of species but belongs to a few numbers of genera [21].

Table 3 Taxonomic diversity of the recorded species in the five Egyptian northern lakes [10]
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A total of 189 species was confined to only one of the five lakes (Table 3). Lakes Bardawil, Mariut, and Burullus had the highest number of confined species. Sixty-seven species were confined to Bardawil (e.g., Ruppia cirrhosa), while 56 species were confined to Mariut (e.g., Arisarum vulgare), and 50 species were confined to Burullus (e.g., Amaranthus lividus).

4.2 Habit and Life Form

Along the coastal lakes, 203 species (50.5% of the total species) are annuals (e.g., Cakile maritima, Volutaria tubuliflora, and Erucaria hispanica), while 199 species (49.5% of the total species) are perennials (e.g., Phragmites australis, Tamarix nilotica, and Centropodia forsskaolii). Mariut contributed the highest number of annuals (119 species), while Burullus contributed the highest number of perennials (110 species). On the other hand, the lowest numbers of annuals (55 species) and perennials (65 species) were recorded in Edku. Moreover, 48 species are aquatic weeds (e.g., Echinochloa stagnina, Azolla filiculoides, and Nymphaea caerulea), while 170 species are terrestrial weeds (e.g., Malva parviflora, Cressa cretica, and Trigonella laciniata), 169 species are natural (e.g., Arthrocnemum macrostachyum, Suaeda vera, and Helianthemum stipulatum), and 15 species are escaped plants from cultivations (e.g., Anethum graveolens, Eruca sativa, and Hordeum vulgare). The highest number of aquatic weeds (35 species) is recorded in Manzala, while the highest numbers of terrestrial weeds (116 species) and escaped plants (12 species) were recorded in Burullus and Mariut, respectively. The highest number of aquatic plants in Manzala may be due to the excessive nutrient budget transported to the lake through the main drains [22]. Bardawil had the highest number of natural plants (104 species) associated with the lowest of aquatic (4 species) and terrestrial weeds (27 species).

Life form spectrum provides information, which may help in assessing the response of vegetation to variations in environmental factors [23]. The life form spectra of the recorded species in the coastal lakes (Fig. 2) indicate the predominance of therophytes (49% of the total recorded species), followed by geophytes–helophytes (14.7%) and chamaephytes (14.5%). Burullus contributed the highest number of phanerophytes (12 species), hemicryptophytes (19 species), geophytes–helophytes (40 species), and parasites (4 species). The highest number of chamaephytes, hydrophytes, and therophytes (34, 16, and 111 species, respectively) were recorded in Bardawil, Manzala, and Mariut. The highest number of therophytes in Mariut may be attributed to the heavy rainfall on the Western Mediterranean coast [1].

Fig. 2
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Life form spectrum of the total species recorded in the five lakes of North Egypt. Ph phanerophytes, Ch chamaephytes, GH geophytes–helophytes, H hemicryptophytes, HH hydrophytes, P parasites, and Th therophytes [10]

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4.3 Endemic and Near-Endemic Species

Five species are recorded in the coastal lakes as endemic taxa; these are Zygophyllum aegyptium (Burullus, Manzala, and Bardawil), Sinapis allionii (Mariut and Burullus), Sonchus macrocarpus (Burullus), and Astragalus camelorum and Bellevalia salah-eidii (Bardawil). In addition, three species are near-endemic taxa: Biarum olivieri and Iris mariae in Bardawil (Egypt and Palestine) and Carduncellus mareoticus in Mariut (Egypt and Libya).

4.4 Threatened Species

According to the IUCN Red List categories [24], 13 threatened species were recorded in the Egyptian coastal lakes, 7 of which are endangered (Sinapis allionii in Mariut and Burullus, Nymphaea lotus in Edku and Manzala, Astragalus camelorum, Bellevalia salah-eidii, Biarum olivieri, and Salsola tetragona in Bardawil, and Nymphaea caerulea in Lake Manzala). Six species were rare (Juncus bufonius in Burullus and Manzala, Chlamydophora tridentata in Mariut, Iris mariae in Bardawil, and Clerodendrum acerbianum, Cynomorium coccineum, and Sonchus macrocarpus in Burullus).

5 Plant Communities

The Egyptian coastal lakes are characterized by 45 plant communities (Table 4). Halocnemum strobilaceum is a halophytic community that dominates the five lakes, while Sarcocornia fruticosa community is represented in all lakes except Manzala. The aquatic plants communities (e.g., Ceratophyllum demersum, Potamogeton pectinatus, and Typha domingensis) are common in all lakes except Bardawil due to its higher salinity [25]. It is of great interest to compare the vegetation groups in the northern lakes of Egypt with those of North Africa (CASSARINA sites). Reed and sedge beds of Phragmites, Typha, and Juncus are particularly important for stabilizing shore regions and providing habitats for nesting birds. These reed beds, which are wide spread in the Egyptian northern lakes (Mariut, Edku, Burullus and Manzala), were now effectively absent at Merja Zerga and Merja Bokka (Morocco) and Ichkeul and Korba (Tunisia) by the late 1990s [26]. In addition, the communities dominated by the sea grasses (Ruppia cirrhosa and Cymodocea nodosa) are restricted to Bardawil. Ruppia cirrhosa is probably the most common submerged aquatic plant in the more brackish lakes of Morocco and Tunisia [26]. This plant flourishes in Sidi Bourhaba and has become abundant in Ichkeul where it has replaced Potamogeton pectinatus since the 1980s [13].

Table 4 Community types of the five Egyptian northern lakes [1]
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Most of the species recorded in Bardawil are present in dominant communities in the desert dunes and wadis at the south and southeast of the lake [27]. This indicates that the flora of Bardawil may be more related to the southern desert flora than to the flora of the Mediterranean, and this may be attributed to the fact that Bardawil sediments were supplied by desert inland wadis like Wadi El-Arish [28]. Moreover, 31 communities are recorded in only 1 lake; 7 communities are exclusively recorded in Mariut (e.g., Atriplex halimus, Bromus rubens, and Volutaria tubiflora); and 7 are in Edku (e.g., Arundo donax, Bassia indica, and Rumex dentatus). The communities dominated by Salsola kali and Suaeda pruinosa were restricted to Lake Burullus, while Atriplex portulacoides, Azolla filiculoides, Ludwigia stolonifera, Ruppia maritima, and Scirpus maritimus communities are exclusively recorded in Manzala. Moreover, ten communities are common in Bardawil (e.g., Artemisia monosperma, Asparagus stipularis, Calligonum polygonoides, Cymodocea nodosa, and Thymelaea hirsuta).

6 Succession Trends

The decrease in moisture and changes in salinity and soil texture are the main operative factors in the successional process in the Egyptian Mediterranean lakes, depending on the regional and local conditions of topography and landforms (Fig. 3). The pioneer communities lead to the formation of submerged species (e.g., Ceratophyllum demersum). In the right part of the successional scheme, increasing salinity enhances the growth of the submerged species (Najas marina). Continuous decrease in moisture and building up of soil enhance the growth of terrestrial halophytic communities such as Arthrocnemum macrostachyum and then increase in aridity and formation of sand dunes lead to the formation of Lotus halophilus and Stipagrostis scoparia as a climax stage. This successional trend is more related to that of Bardawil [1]. On the other hand, the middle part of the scheme represents a succession closely related to that of the Deltaic lakes, which passes through the floating (e.g., Eichhornia crassipes) and emergent species (e.g., Phragmites australis) and ends by Tamarix nilotica as a climax stage. Moreover, coarser soil texture and decreased salinity may lead to the formation of Atriplex glauca and Juncus acutus communities from a halophytic community such as Sarcocornia fruticosa. Furthermore, increasing aridity may result in a community such as Thymelaea hirsuta as a climax stage (xerosere succession of the Mediterranean coast).

Fig. 3
figure 3

Schematic representation of the presumed succession relationship between the plant communities in the Egyptian northern lakes [1]

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7 Goods and Services

In the these lakes, 283 species (70% of the total) offer at least one potential or actual good [11] with the following arrangement: 73% grazing (Adonis dentata and Avena barbata), 62% medicinal (Ammi visnaga and Artemisia monosperma), 24% human food (Anethum graveolens and Brassica rapa), 17% fuel (Thymelaea hirsute and Arthrocnemum macrostachyum), and 2% timber species (Tamarix nilotica). In addition, 241 species (60% of the total) have at least one aspect of the environmental services [11, 29, 30]: 34% sand controllers such as wind breaks, sand binders and hummock formers (Arthrocnemum macrostachyum and Retama raetam), 6% shaders (Salix tetrasperma and Tamarix nilotica), 6% weed controllers (Phyla nodiflora and Sphaeranthus suaveolens), 5% bank retainers (Arundo donax and Chenopodium ambrosioides), 2% nitrogen fixers (Argyrolobium uniflorum and Matthiola longipetala), and 2% are water purifiers (Eichhornia crassipes and Phragmites australis).

8 Carbon Sequestrations Potential

The coastal wetlands are among the most effective carbon sinks on the earth. Worldwide, these systems are among the most endangered and rapidly disappearing natural environments mostly owing to anthropogenic activities and unsustainable exploitation. In Egypt, the five Mediterranean lakes are threatened by several factors such as continuous land reclamation projects, construction of roads along the north coast, touristic development, pollution, and coastal erosion [15, 31]. Based on the area of these lakes, their carbon sequestration potential (CSP) ranged from 0.95 Gg C year−1 in Bardawil to 7.79 Gg C year−1 in Manzala (Table 5). Thus, it is necessary to protect these lakes, which currently suffer from lack of effective protection, for conserving their vital role in carbon sequestration process as well as other ecosystem goods and services.

Table 5 Sedimentation rate (SR), mean ± standard error of the carbon sequestration rate (CSR) and carbon sequestration potential (CSP) of the five Egyptian northern lakes
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9 Identified Threats

Erroneous policies for the disposal of sewage and industrial and agricultural wastes of Alexandria and Beheira Governorates seem to have no regard from the environmental viewpoint and led to severe deterioration of Lake Mariut, so it has become the most polluted wetland in the country. A sizable portion of the lake is heavily exploited for salt extraction from the salt pan at El-Max [10]. The continuous reduction in the area of Lake Burullus and its adjacent reed swamps and marshlands through substantial land reclamation poses the most serious threat to this wetland ecosystem. Vast area used to be part of this ecosystem but are now cultivated mainly with sugar beet, rice, broad beans, barley, and clover. Excess fertilizers and pesticides from these fields are bound to pour into the water of the lake, thus adding to the danger of the shrinking area of the lake. The shores of Burullus wetland, which protrudes the furthest, are subjected to long-term erosion, which is seen obviously at the Burullus inlet [32]. The average erosion rate is about 1 m year−1 [11]. This leads to the risk that all adjacent regions and even the Burullus area would be subjected to heavy erosion. In addition, the continuous inflow of domestic, agricultural, and industrial wastes of Gharbia and Dakahlia Governorates is the major source of pollution to the lake and its surroundings, especially along its eastern and southern peripheries [11].

El Salam Canal is a national project aiming at carrying the Nile water to North Sinai in order to allow agricultural development of about 92,000 ha south of Lake Manzala and 168,000 ha in North Sinai [33]. The isolation of sub-basins has resulted in limited water circulation and increased pollution, more significantly in the basins with drain discharges as the geographic dispersal of pollutants became more confined [33]. The polluted area is situated in the southeastern part of the lake at the mouth of Hadous drain; it has the highest total dissolved salts delivered into the lake [10]. This area also receives large amounts of drain water from Bahr El-Baqar drain, which transports partially treated sewage from eastern Cairo for about 170 km to the lake. The sandbar separating Lake Manzala from the Mediterranean Sea has been subjected to severe changes by the physical and man-made processes in the area. Furthermore, coastal changes along the Nile Delta have been recognized since the late nineteenth century, but it was dramatically accelerated after the construction of Aswan High Dam [33].

Lake Bardawil is the only wetland in the Mediterranean coast of Egypt that is not connected to any irrigation or drainage canals [25]. Furthermore, the population density around the lake is the smallest among all the other northern lakes of the country [34]. Consequently, it might be claimed that Bardawil is the nearest of all Egyptian wetlands to environmental virginity [25]. At present, oil pollution from sea-going ships and the refuge from fishing boats in the lake are the most serious sources of threat to the balance of the entire ecosystem [34]. El Salam Canal is part of the agricultural development of North Sinai and will draw a mixture of water from various sources west of the Suez Canal including Bahr El-Baqar drainage with all its load of pollutants (mostly sewage from eastern Cairo), fauna, flora, and microorganisms [25].

10 Conservation Measures

There are no conservation measures taken for Mariut and Edku Lakes and their adjacent marshlands, which remain entirely unprotected. A small area of about 35 km2 of Lake Manzala, including its connection with the Mediterranean Sea at Ashtum El-Gamil, has been declared as a protected area by the Prime Minister’s Decree Number 459 in 1988 [35]. After that, a project had been launched by the Egyptian Government in 1997–1999, with a financial support from the Global Environment Facility (GEF) to clean up the polluted water of Bahr El-Baqar drain which pours its drainage water into Lake Manzala in order to reduce its pollution and their adjacent Mediterranean shoreline.

In 1988, Lake Burullus was included as a Ramsar site according to Ramsar Convention which deals with wetlands of international importance as waterfowl habitat. After that, the entire area of this lake and most of its surrounding sandbar and marshland has been declared as a protected area by the Prime Minister’s Decree Number 1444 for 1998 [36]. Moreover, as Lake Bardawil falls on one of the major routes for bird migration in the world, thus its eastern sector, which includes the only natural outlet to the Mediterranean Sea at Zaranik, has been declared by the Prime Minister’s Decree Number 1429 as a protected area in 1985 [34], and in 1988 it was also included as a Ramsar site. Two management plans were prepared for each of Burullus [36] and Bardawil [34] lakes, but unfortunately, application of these needs to be enforced and financially supported.

11 Conclusion and Recommendations

  • About 402 plant species, categorized into 45 plant communities, were identified in the five Egyptian Mediterranean lakes. Five of these species are endemics, while three are near endemics (with Libya or Palestine).

  • Although the areas of these lakes (2,449 km2) contribute <0.003 of the total area of Egypt (one million km2), but they are inhabited by 19% of the whole Egyptian flora, In view of this, these wetlands could be considered as important hot spots for the Egyptian flora, particularly the aquatic plants.

  • Bardawil (67 species: e.g., Ruppia cirrhosa), Mariut (56 species: e.g., Arisarum vulgare), and Burullus (50 species: e.g., Amaranthus lividus) have the highest number of confined species.

  • According to the IUCN Red List categories, 13 plant species were threatened in the 5 Egyptian coastal lakes, 7 of which were evaluated as endangered species, while 6 were evaluated as rare species.

  • Seventy percent of the species (283 species) offer at least one potential or actual good (e.g., grazing, medicinal drugs, human food, fuel, and timber). In addition, 241 species (60% of the total) have at least one aspect of the environmental services (e.g., sand controllers, shaders, weed controllers, bank retainers, nitrogen fixers, and water purifiers).

  • The vegetation and sediment of these lakes are effective as carbon sinks; therefore, they play, in contribution with the other world wetlands, a vital role in mitigation of global warming.

  • Coordination between the stakeholders involved in the management of these lakes should be activated in order to apply the activities that enhance the biodiversity and productivity in these wetlands. The main stakeholders are association of fishermen societies, governorate administrations, general authority of development of fisheries resources, management team of Burullus, Ashtum El-Gamil and Zaranik protected areas, ministry of health, agency of north coast construction, coast guard, and police of water surfaces.

  • Mariut and Edku lakes should be added (fully or partially) to the net of the Egyptian protected areas in order to reduce the severe human impact upon them.

  • Evaluating their role in mitigating the thermal extremity, as the vegetated wetlands act as sinks for the absorption of CO2 (one of the gases responsible for the global warming).