Introduction

Mangrove ecosystems are a group of trees and shrubs thriving in habitats shaped by tides, sharing similar morphological and physiological adaptations (Kathiresan and Bingham 2001). These coastal ecosystems hold significant economic, physical, and ecological value for humans (Bengen et al. 2022; Rahman et al. 2020a).

Indonesia has a large area of mangrove ecosystems, with the Ministry of Environment and Forestry (2021) reporting a coverage of 3.36 million ha, which constitutes 23.1% of the global total mangrove area and 59.8% of the area in Southeast Asia. The country also possesses a very high biodiversity of mangrove species (flora) as reported by Soemodihardjo et al. (1993) which found 157 species of mangrove consisting of 52 trees, 21 shrubs, 13 liana, seven palm, 14 grass, eight herbs, three parasites, 36 epiphytes, and three fern. Meanwhile, Kusmana (2014) stated that the number of mangrove species reached 158, consisting of 89 trees, five palms, 19 lianas, 44 herbs, and one fern.

Several studies on mangrove in Indonesia have been carried out in various places, specifically for flora and fauna diversity (Rahman et al. 2020a). Some other studies have been conducted on fauna biodiversity in Halmahera as a health bioindicator (Abubakar et al. 2022), Youtefa Bay Tourism Park, Papua (Sari et al. 2022), and in Indonesia (Zahdi 2022). However, these studies, though valuable, remain partial, and do not provide a comprehensive overview of mangrove ecosystems along the coastal areas of Indonesia.

The mangrove ecosystems in Indonesia have a high diversity of marine and terrestrial fauna distributed along the coastal areas (Yudha et al. 2021), but the types and numbers in the seven major regions, including Papua, Maluku Islands, Bali—Nusa Tenggara Islands, Sulawesi, Kalimantan, Java, and Sumatra (Arifanti et al. 2021), remain unknown. To address these gaps, detailed studies should be conducted in each of these regions to produce data that can be inventoried. Each region represents unique mangrove ecosystems found in coastal areas on the mainland and small islands. Several of these areas face degradation caused by timber extraction and land conversion into fishponds, settlements, and public infrastructure (Ilman et al. 2016; Rahman et al. 2020b) resulting in reduced mangrove area, density, and diversity (Rahman et al. 2019).

Management efforts have been undertaken in various regions, one of which is conservation. Information regarding how conservation strategies are implemented and their impact on the existence of mangrove flora and fauna biodiversity is still limited. Therefore, this study aimed to determine mangrove biodiversity and its conservation in Indonesia. The results are expected to become a scientific basis for the Indonesian government in achieving sustainable management based on biodiversity conservation.

Methods

Literature search and review

Literature searches on mangrove species distribution were conducted within 5 years, from September 2017 to January 2023. The collected literature were related to data on the structure and distribution of mangrove communities in seven major areas within Indonesia (Fig. 1). Each region was represented by 30 to 60 mangrove habitats from the mainland and small island coastal areas. The searches were carried out on Google Scholar, Science Direct, springer, and research gate databases with the keywords “mangrove community structure”, “mangrove identification”, “mangrove ecosystem conditions”, “mangrove vegetation”, “mangrove biodiversity”, “mangrove association” and “mangrove composition”. A total of 261 articles were collected, including two books providing insights into mangrove distribution in Indonesia. The total articles obtained are classified in each region based on the year published, namely 2001–2005, 2006–2010, 2011–2015, 2016–2020, and > 2020 (Fig. 2). Detailed information on some of the main articles published after > 2016 is presented in Table 1.

Fig. 1
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Seven major regions as representative of mangrove distribution in Indonesia

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Fig. 2
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Number of articles on mangrove diversity in 2001–2023 in Indonesia

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Table 1 Main references related to studies on mangrove diversity (2016–2023) by region in Indonesia
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Information about mangrove types in each literature was presented in the distribution table in each region and classified based on criteria (true or associate mangrove) and flora habitus (tree, shrubs, herbs, palm, epiphyte, lianas, fern, and parasites). According to Wang et al. (2010), true mangrove comprises halophytes (tolerant of high salt levels), while associates include glycophytes (only tolerates certain salt concentration levels).

The exploration of fauna diversity was carried out within three years, from August 2020 to February 2023. The keywords used in the search included “fish diversity in mangrove”, “macrozoobenthos diversity”, “fauna in mangrove ecosystems”, as well as other keywords tailored to the objectives of the study. A total of 50 articles were collected including one book, and family classifications were grouped into two main categories: “fishes” and “macrozoobenthos”.

The same digital databases were also used to obtain data on the management of mangrove ecosystems in Indonesia. The keywords used were “mangrove ecosystem management”, “mangrove ecosystem conservation”, “mangrove management”, and “mangrove conservation”.

The literature review also focused on how mangrove conservation efforts were carried out and the impact on biodiversity in each region. Management practices that successfully preserved biodiversity will be reconstructed as a reference for other regions.

Result and discussions

Mangrove distribution

Indonesia has a very high diversity of mangrove flora, with the literature review results showing a total number of 240 species, consisting of 48 true and 192 associated mangrove (Fig. 3). The region with the most diverse flora was Java, with 180 species of 42 true and 138 associated mangrove. On the other hand, the region with the most minor diversity was the Maluku Islands, with 145 species of 36 true and 109 associated mangrove. These results can be attributed to the fact that mangrove exploration in Java was more intense than in eastern Indonesia, such as Papua and Maluku (Table 1). However, mangrove extent in Papua has greater potential for diversity than other regions with an area of 1.63 million hectares (50.37%), while Java has only 0.034 million hectares (1.06%) of the total mangrove area in Indonesia (MoEF 2021).

Fig. 3
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The number of mangrove species by type in the region of Indonesia

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The diversity in this study was greater than that of Soemodihardjo et al. (1993) and Kusmana (2014), stating that Indonesia has 157 and 202 mangrove species. The higher value was because the data analyzed in this study covered almost all regions in Indonesia, from the mainland to the coast of remote islands.

The diversity of mangrove flora habitus on the Indonesian coast consisted of 74 trees, 36 shrubs, 52 herbs, six palms, 43 epiphytes, 23 lianas, three ferns, and three parasites (Table 2). This category differed from the report of Soemodihardjo et al. (1993), who reported species such as 52 trees, 21 shrubs, 13 lianas, seven palms, 14 grasses, eight herbs, three parasites, 36 epiphytes, and three species of fern. In addition, Kusmana (2014) stated that the number of mangrove species in Indonesia had reached 157, consisting of 89 trees, five palms, 19 liana, 44 herbs, and one fern. The distribution of mangrove species by type and classification is presented in supplementary files.

Table 2 Distribution of mangrove species by region in Indonesia
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True mangrove

The diversity of true mangrove comprised 48 species consisting of 34 trees, two herbs, four shrubs, two lianas, three parasites, two ferns, and one palm. About 42 species were found in Papua and Java, 39 in Sulawesi and Kalimantan, 40 in the Bali-Nusa Tenggara, 38 in Sumatra, and 36 in the Maluku Islands region (Table 3). The herbaceous mangrove species included Acanthus ebracteatus and Acanthus ilicifolius, while the shrubs consisted of Aegialitis annulate, Kandelia candel, Scyphiphora hydrophyllacea, and the only palm-type species was Nypa fruticans.

Table 3 Distribution of true mangrove species by region in Indonesia
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A total of 25 true mangrove species were also found throughout the coastal areas (Table 3). In some areas, there were true mangrove, identified as new record species, including Avicennia rumphiana which was only found in Java, Kalimantan and Sumatra (Khaliza and Abdunnur 2022; Sulmartiwi et al. 2018; Wantoro et al. 2017). This species is an endemic mangrove in tropical regions, especially Malaysia, the Philippines, Indonesia, and Papua New Guinea (Dahdouh-Guebas 2023). Aglaia mackiana was only identified in Papua, according to the report by Pannell et al. (2020) on a mangrove expedition in the West Papua region. On the other hand, Sheue (2009) reported that Ceriops australis was newly identified in the region of Papua, Bali—Nusa Tenggara (Timor, Flores, Sumbawa), Java, and Sumatra (Pulau Bilinton). It is an endemic species in Australian waters (Huang et al. 2008), and the presence in the regions can be attributed to the spread of propagules carried by currents from Australia to Papua and further to Timor, Flores, Sumbawa, Java, and Sumatra. Moreover, it is closely related to South Pacific currents that enter Papua New Guinea (New Guinea Coastal Current/NGCC) (Kuroda 2000).

Different mangrove species dominated each region in Indonesia, for example, Java was dominated by Sonneratia alba (Donato et al 2011). Other cases of dominance included Kalimantan (Rhizophora spp., Avicennia spp., and Nypa fruticans) (Arifanti et al. 2019; Murdiyarso et al. 2015), Papua (Bruguiera gymnorrhiza and R. apiculata) (Murdiyarso et al. 2015), Sulawesi and Sumatra (Rhizophora mucronata and Rhizophora apiculata) (Murdiyarso et al. 2015). These differences were attributed to habitat characteristics such as bays, deltas, lagoons, open coasts, and estuary waters. Bay and estuary habitats were dominated by Rhizophora spp and Sonneratia spp. (Suyadi 2009; Lekitoo and Tambing 2018), while the Delta was dominated by Avicennia spp and Nypa fruticans (Sidik 2010; Rahman et al. 2017). Avicennia spp. and Sonneratia spp were predominant in the lagoon (Suryono 2012), while the open coast was dominated by Rhizophora spp. and Avicennia marina (Ulyah et al. 2022).

Diversity of mangrove fauna in Indonesia

The diversity of fauna in mangrove ecosystems can be classified into marine and terrestrial. This study classified fish, shrimp, macrozoobenthos, and other marine organisms as marine fauna, while birds, reptiles, mammals, and other species were considered terrestrial.

Mangrove marine fauna in Indonesia

The diversity of marine fauna in the mangrove ecosystems consisted of fish species and macrozoobenthos. The results showed 125 fish species from 47 families and 169 macrozoobenthos from 52 families. The macrozoobenthos consisted of 92 Gastropods, 24 Bivalves, 48 Crustaceans, two Polychaeta, and three species of Maxillopods (Table 4). The existence of marine fauna was closely related to the ecological function of mangrove as a provider of nutrients.

Table 4 The diversity of mangrove marine fauna in Indonesia
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According to Nordhaus et al. (2006), mangrove ecosystems provide nutrients to support marine biota’s life, such as fish, shrimp, crabs, shellfish, and others. The availability of these nutrients stems from the production of litter in the form of fallen leaves or fruit deposited in the sediments (Rahman et al. 2020c). Hulopi et al (2022) also stated that the presence of gastropods in mangrove ecosystems was closely related to the availability of food and the type of substrate in the habitat. As stated by Rahman et al (2020d), gastropods are perfectly associated with mangrove ecosystems in terms of spawning, nurturing, and foraging, while other biota, such as fish and shrimp, are partially associated. Partial associations are formed when the marine biota only uses mangrove ecosystems as a feeding ground or only as a spawning ground.

Diversity of terrestrial mangrove fauna in Indonesia

The diversity of terrestrial fauna in the mangrove ecosystems comprised 161 species, including 80 birds, 38 squamata, four crocodiles, six amphibians, 11 testudinate, and 21 mammals (Table 5). There were three species of decreasing aves classified as Least Concern (LC) according to the International Union for Conservation of Nature (IUCN), including Ardea cinerea, Ardea purpurea, and Halcyon cyanoventrism. Meanwhile, one species was classified as Near Threatened (NT), namely Anhinga melanogaster (BirdLife International 2016a, b). As stated in previous studies, mammal species including Lutra sumatrana, Macaca fascicularis, Macaca ochreata, and Nasalis larvatus had an Endangered (EN) status (Boonratana et al. 2021; Hansen et al. 2022; Sasaki et al. 2021), while Lutra perspicillata was in the Vulnerable Status (VU) (Khoo et al. 2021). Crocodylus siamensis and Tomistoma schlegeli were in the Critical Endangered (CR) and VU status, respectively (Bezuijen et al. 2012; 2014).

Table 5 Species of terrestrial mangrove fauna in Indonesia
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Biodiversity preservation through mangrove conservation strategies

Generally, the management of mangrove ecosystems in Indonesia predominantly focuses on conservation. Most conservation areas were integrated with ecotourism to increase community participation. Institutions or agencies entrusted with the mandate of conserving mangrove, include the Ministry of Environment and Forestry (MoEF), and the Ministry of Marine Affairs and Fisheries (MMAF). The mandate was outlined through the Presidential Regulation of the Republic of Indonesia Number 73 of 2012 concerning the national strategy for the management of mangrove ecosystems. This was further detailed in the ministerial regulations through various policies such as conservation and environment, rehabilitation, silvofishery, protected forests, and ecotourism. MMAF designates conservation areas as part of the coastal and small islands zoning plan (RZWP3K), while MoEF adopts the policy of the Directorate of Conservation Areas. The mandate aims to improve community welfare by conserving and rehabilitating mangrove ecosystems.

MMAF plays a crucial role in the protection, management, restoration, and utilization of mangrove ecosystems. These functions are carried out through the Regulation of the Minister of Marine Affairs and Fisheries in Indonesia No. 24 of 2016 concerning procedures for rehabilitating coastal areas and small islands. Meanwhile, MoEF has the function of formulating policies related to mangrove protection, establishing conservation areas, granting permits, supervising utilization by the community, and conducting investigations for further development. These functions are supported by Law No. 32 of 2009 concerning environmental protection and management, as well as MoEF Minister Regulation Number P.23 of 2021 concerning forest and land rehabilitation.

In 2010, the mangrove conservation areas in Indonesia reached 22%, or the equivalent of 758,472 ha (Sidik et al. 2018). The conservation efforts aimed to preserve and enhance ecosystem services such as mangrove biodiversity, potential carbon stocks, coastal protection, and the biodiversity of marine and terrestrial fauna (Sievers et al. 2023). The government initiates mangrove conservation through MoEF and MMAF by indulging various parties such as communities, non-governmental organizations, and the private sector. Efforts to conserve mangrove ecosystems and their fauna are supported by several regulations, including Law No. 5 of 1990 concerning the conservation of natural resources and their ecosystems, Government Regulation No. 68 of 1998 regarding nature reserves and conservation, as well as Minister of Environment Regulation No. P106 of 2018 concerning protected plant and animal species. The implementation and enforcement of these regulations have not been optimal in recent decades. This was reflected in the existence of several species included in the endangered category by the IUCN, as presented in Table 5.

Several unique faunas are protected in conservation areas and have become icons in ecotourism activities (Hadinata et al. 2020; Manihuruk et al. 2021). In each region, ecotourism-based conservation was implemented to maintain the unique diversity of fauna. According to previous studies, Crocodilus was protected in the regions of Papua, Kalimantan, Java, and Sumatra. The Halcyon sp. species were preserved in Papua and Java (Kusmana 2014); Anhinga sp. was protected in Kalimantan and Java (Kusmana 2014); while the proboscis monkey (Nasalis larvatus) was only found and conserved in the Kalimantan region (Kusmana 2014; Noorhidayah and Ma’ruf 2007; Sawitri et al. 2013; Widyastuti and Erianto 2017) (Table 6). Based on the results, ecotourism-based conservation and the protection of unique fauna were the main factors contributing to the high biodiversity in Indonesia. This action could also improve the economy of the community, triggering their active participation in managing the mangrove ecosystems (Wardhani 2011).

Table 6 Protected mangrove fauna species by region in Indonesia through ecotourism-based conservation
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In 2010–2020, about 78% of mangrove without a conservation status was found to be experiencing damage threat, triggering the degradation of Bruguiera hainesii and Heritera globosa with Critically Endangered (CE) and Endangered status, according to the IUCN (Duke et al. 2010; Sukardjo 2010). In the above-mentioned decade, the mangrove deforestation rate was estimated at 182,091 ha, with a deforestation rate of 18,209 ha per year (Arifanti et al. 2021). To address this, the Indonesian government increased its commitment to conservation and restoration programs. The President assigned the Peatland and Mangrove Restoration Agency (BRGM) to restore 600,000 mangrove ecosystems by 2020–2024. BRGM collaborates with MoEF and MMAF to carry out mangrove ecosystem restoration, resulting in the achievement of 52,853 ha restored area in 2021 (Ministry of Environment and Forestry 2021). The restoration target is aimed at achieving Sustainable Development Goals (SDGs), especially SDG 14 to increase marine biodiversity. However, the target has serious challenges, specifically related to the suitability of rehabilitation land (Sasmito et al. 2023). Despite these challenges, there is optimism that strong collaboration between stakeholders, specifically with the participation of the community will lead to successful mangrove restoration, resulting in increased protection of biodiversity.

According to Nurhati and Murdiyarso (2022), crucial steps that must be taken by both the government and other stakeholders in the mangrove conservation program include (1) Strengthening the regulatory, policy, and institutional framework; (2) Enhancing data and information management as well as the use of cutting-edge science and technology; (3) Increasing the role and capacity of the community as partners; (4) Law enforcement; (5) Encouraging funding mechanisms that support conservation as a profit rather than a cost center. Optimally implementing these steps will help maintain the biodiversity of the mangrove ecosystems in Indonesia and provide many benefits for the welfare of the community.

Conclusion

In conclusion, mangrove ecosystems in Indonesia were found to have high biodiversity, including mangrove species as well as marine and terrestrial fauna. This was attributed to the Indonesian government’s commitment expressed through conservation efforts. Conservation was carried out to preserve and improve ecosystem services including mangrove biodiversity, carbon stock potential, coastal protection, as well as the biodiversity of marine and terrestrial fauna. Based on the results, incredibly unique fauna included Crocodilus found in Papua, Kalimantan, Java, and Sumatra region, Halcyon sp in Papua and Java region, Anhinga sp in Kalimantan and Java region, as well as Nasalis larvatus in Kalimantan. However, in many unconserved mangrove areas, deforestation occurred in 2010–2020, triggering degradation evident in species such as Bruguiera hainesii and Heritera globosa with Critically Endangered (CE) and Endangered status. There were three species of declining aves classified as Least Concern (LC) according to the IUCN, including Ardea cinerea, Ardea purpurea, and Halcyon cyanoventrism, along with one species in the Near Threatened (NT) status, namely Anhinga melanogaster. Mammal species such as Lutra sumatrana, Macaca fascicularis, Macaca ochreata, and Nasalis larvatus were found to be in the Endangered (EN) status while Lutra perspicillata was in the Vulnerable status (VU). In addition, Crocodylus siamensis and Tomistoma schlegeli were classified as Critical Endangered (CR) and VU, respectively. Based on the results, the Indonesian government should continue to add mangrove conservation areas and optimize regulatory enforcement on the protection of unique and rare fauna, specifically those included in the IUCN Redlist Status.