The story of the human relationship with wetlands is a bleak one, and our relationship with tropical peat swamp forests is no different. Throughout the ages these peat-covered forests have been viewed as wastelands of unproductive, waterlogged soil ready to be drained, burned, and transformed into plots for agriculture and development. While we have hungrily consumed these peatlands in exchange for monoculture plantations, we have overlooked their importance to the global carbon cycle and as a cornucopia of biodiversity, including some of the world’s most unusual and important flora and fauna.
Christian Hinz
So what exactly is a tropical peat swamp forest?
Peat swamp forests cover between 30 to 40 million ha worldwide, around 70% of which are found within the small islands of Southeast (SE) Asia. The high concentration of peat swamp forests in SE Asia is due to the unique climatic conditions of the region. While the area is subject to high precipitation, SE Asia lacks the strong seasonality in rainfall common in many other tropical areas. This creates wetter conditions throughout the year with precipitation consistently higher than evapotranspiration. These wet, soggy conditions slow down the rate of decomposition, causing organic matter to accumulate.
Peat swamp forests have low primary productivity with nutrient-deficient, acidic peat soils with a typical pH between 3 and 4.5. They share many similarities with northern raised bogs, however, the peat is formed by woody organic material rather than the Sphagnum mosses typical of northern peatlands. This peat forms in waterlogged, anoxic conditions, with the organic matter content ranging from 90-98%. It can accumulate at a rate of more than 2 mm each year and most of these systems develop on elevated peat domes with peat measuring anywhere between 0.5 mm to 10 m in depth. As peat accumulates above the surrounding area it no longer receives water and nutrient inputs from ground or surface inflows, relying solely on precipitation for nutrient and water input. These wetlands face the paradox of being both high and wet, with gravity continually draining water into the surrounding ecosystems. Despite this challenge, continuous rain allows them to develop, and the peat domes act as giant sponges, storing water above the surrounding systems.
Flora
Despite the difficult growing conditions, the ecology of tropical peat swamp forests supports the highest floral diversity of all global peatland types. Approximately 1524 plant species are found in Southeast Asian tropical peat swamp forests, 172 of which are endemic. Many plant species have evolved special adaptations to survive in the waterlogged conditions of peat domes including forming buttressed and stilt roots, pneumatophores, and superficial root mats (Meer 2013). These adaptations are an important contribution to water storage, reducing the rate at which surface water runoff leaves the system. This slowing down of runoff is also an important resource for flood control in surrounding zones (Meer 2013).
Approximately 1524 plant species are found in Southeast Asian tropical peat swamp forests, 172 of which are endemic.
Licuala paludosa, Bill Baker, iNaturalist 2012
Much of the vegetation found in peat swamp forests is important to the local and global economy, with more than 200 plant species used by local people for material, medicine, and food (Meer 2013). One tree of local importance is the golden licuala (Licuala paludosa) a species of palm locally popular for its ethnobotanical uses as well as its use in traditional cuisines (Meer 2013; Tekula 2017). Swamp kapur (Dryobalanops rappa) an endemic Bornean tree species, is commonly used for timber (Meer 2013). It is an emergent tree species with a unique life history thought to aid in its success in the soft, wet soils it grows in. As adults, this species exhibits buttressed roots. However, they also exhibit vegetative sprouting from some of their decumbent shoots, allowing for rapid growth as juveniles (Yamada and Suzuki 2004). One of the most valuable tree species found in tropical peat swamp forests is ramin (Gonystylus bancanus), a slow-growing, critically endangered tree species that is used in the production of furniture, dowels, and other construction materials. Because of its popularity it has been overexploited by the timber industry and is now listed on the IUCN Red List as Critically Endangered and under CITES Appendix II (Meer 2013). Not only is this species important to the economy, but it is also an essential component of the ecosystem, providing habitat for many rare and endangered arboreal species.
A number of unique non-woody species can also be found within SE Asian peat swamp forests. These include herbaceous species like Bakong ayer (Hanguana malayana), a perennial rhizomatous herb that can grow both terrestrially and aquatically and up to 2 m in height. This herb provides important habitat for aquatic invertebrates as well as waterfowl (Meer 2013). Other important herbaceous species include Bemban (Donax canniformis) and pandan (Pandanus vinaceus) which are used for handicrafts, fishing materials, and as traditional medicine (Meer 2013). Fern species are also used in local communities, including giant swordfern (Nephrolepis biserrata), locally known as Paku kubok, and swamp vine fern (Stenochlaena palustris), locally known as Paku midin, both of which are used as vegetables (Meer 2013).
Nepenthes bicalcarata, Marcel Silvius, iNaturalist 2014
Carnivorous plants like the fanged pitcher plant (Nepenthes bicalcarata) also make their home in the nutrient-poor soils of peat swamp forests. Although they are found in different taxonomical orders, the fanged pitcher plant shares many similarities with the pitcher plants found in other wetlands across the globe. Following its convergent evolution with other pitcher plants, this species obtains nitrogen and other nutrients from digested insects and insect fecal matter captured within its modified leaves. The fanged pitcher plant is a terrestrial climber and can reach 15 m in height. It also serves as a home for a species of ants, Camponotus schmitzi, it shares a mutualistic relationship with. The fanged pitcher plant is listed as vulnerable on the IUCN Red List and under CITES Appendix II due to overharvesting for horticulture.
Fauna
Despite the assumption that Southeast Asian peat swamp forests are barren wastelands, a diverse collection of animals reside there, including over 123 mammal species, 75 reptiles, 27 amphibians, and 219 species of fish (Posa et al). Of the 268 bird species found in SE Asian peat swamp forests 27% of them are considered globally threatened (Meer 2013). This includes the Hook-billed Bulbul (Setornis criniger), an endemic songbird listed as vulnerable on the IUCN Red List. More than 5 species of hornbill also reside within tropical peat swamp forests, all of which serve important ecological roles as seed dispersers for various tree species. Some of the tree species relying on hornbill seed dispersal are valued edibles in the local and global economy (Nakashima et al. 2007; Meer 2013). The Wrinkled Hornbill (Rhabdotorrhinus corrugatus), a large, relatively long-lived, species with a diet rich in drupes and figs, is listed as endangered on the IUCN Red List. Another hornbill species, the Black Hornbill (Anthracoceros malayanus) is an important seed disperser for durian (Durio graveolens), a tree that produces fruit with a global market value of USD 17.6 billion in 2018. There is growing demand for this fruit for its potential health benefits and its global market value is expected to increase to 28.6 billion by 2025. The Black Hornbill is listed as vulnerable on the IUCN Red List.
Anthracoceros malayanus, Luke Mackin, iNaturalist 2016
Of the 219 fish species recorded in peat swamp forests, at least 80 are endemic and 31 species are restricted to single locations (Posa et al. 2011; Meer 2013). Some of these rare blackwater fish species include Betta fish, a threatened species commonly known as fighting fish and exploited for use in home aquariums. At least 3 species of these Betta fish , B. miniopinna, B. persephone, and B. spilotogena are threatened by a decrease in habitat area and quality and are listed on the IUCN Red List as endangered or critically endangered. Other fish species found in these tropical peat swamp forests include the vulnerable Bihunichthys monopteroides, a spineless eel, Encheloclarias, a genus of endangered, air-breathing catfish, and Parosphromenus, a genus of labyrinth fish of conservation concern (Meer 2013). For many of these fish species, little is known or being researched. This lack of knowledge is of growing concern as habitat quality and area continue to be reduced and as some of these species continue to be exploited for both local cuisine and global trade.
While there are no endemic mammals, anthropogenic pressures on surrounding rainforests have made peat swamp forests a refuge for a substantial number of species, including many of which are vulnerable, endangered, and critically endangered. 51% of the mammal species found in peat swamp forests are considered to fall into one of these threat categories according to the IUCN Red List. Endangered felids that utilize tropical peat swamp forests include the flat-headed cat (Prionailurus planiceps), the Sunda clouded leopard (Neofelis diardi), the Sumatran tiger (Panthera tigris sumatrae), and the marbled cat (Pardofelis marmorata) (Posa et al. 2011). Threatened primates are also found in Southeast Asian peat swamp forests including proboscis monkeys (Nasalis larvatus), Bornean banded langers (Presbytis chrysomelas), Siberut Macaques (Macaca siberu), and Kloss’s Gibbons (Hylobates klossii). Some of the most notable mammalian species relying on this ecosystem are the orangutans. This includes the Sumatran (Pongo abelii) and Bornean (Pongo pygmaeus) orangutan who requires high-quality peat swamp forests and lowland alluvial forests for habitat. The Tapanuli orangutan (Pongo tapanuliensis) once roamed peat swamp forests also, but have now been restricted to approximately 2.7% and 5.0% of their historical range. These large primates are listed as critically endangered on the IUCN red list with a population trend in decline.
Pongo abelii, laiet17, iNaturalist, 2015
Anthropogenic Threats
Despite the rare and threatened species that rely on tropical peat swamp forests, the vital role it plays in the carbon cycle, and the unique hydrology of these wetlands, a complexity of anthropogenic threats are encroaching on these systems. Logging, fire, poaching, and land conversion are the largest direct threats, while deforestation in surrounding rainforests amplifies the impact. Peat swamp forests require a balance between their vegetation and hydrology and an upset in this balance can and is having devastating results with local and global consequences.
Logging and Fire
Typical logging practices in Southeast Asian peat swamp forests have altered forest structure and composition, making logged areas virtually uninhabitable. Logging exposes peat through tree removal and the creation of canals for floating logs changes the hydrological conditions of the wetland (Posa et al. 2011). The peat substrate of peat swamp forests is highly flammable when dry, making them the most vulnerable forest type to fire (Posa et al. 2011). Logging, in combination with El Niño events, puts peat swamp forests at further risk of being damaged by fire. Because of the peat substrate, fire is able to burn both above and below the surface and smolder underground for several months. Underground fires destroy seed banks and vegetation structures that would have otherwise survived an above ground fire, causing lasting damage to the ecosystem (Posa et al. 2011). The spread of these fires can also be unpredictable, leading to collapse of overlying material away from the initial burn area. Furthermore, once an area has been burned it has a high probability of being burnt again. The impact of fires in these wetlands are also far reaching, creating shading effects that limit the ability for plants to photosynthesize and can reduce equatorial rainfall (Corlett 2014).
Land Conversion and Poaching
Globalization has recently driven large scale land conversion for the production of crude palm oil and pulpwood (Meer 2013). Peat swamp forests are being drained at a rapid rate and replaced with monocrops of Acacias (Acacia mangium and A. crassicarpa) and African palm (Elaeis guineensis) (Posa et al. 2011; Meer 2013). This draining not only reduces wildlife habitat and threatens plant communities but also has a global impact on climate change as stored carbon is released into the atmosphere in the form of CO2. The alteration in hydrology also effects the runoff patterns and hydrology of surrounding areas, resulting in a direct effect on local populations through water shortages (Meer 2013).
Poaching has played a further role on threatening wildlife species found in the diminishing area of peat swamp forests. New access roads, sometimes referred to as ecological trails, developed for logging practices or other harvests have increased the ease of access for poachers, making them the single greatest reason for wildlife decline (Meer 2013).
Get Involved
Southeast Asian tropical peat swamp forests support a rich community of plant and animal life found nowhere else on earth. The plants of peat swamp forests provide important local and global resources including food, medicine, and building materials. The wildlife found in these wetlands provide important ecological functions and also provide food for local communities. As humans continue to log, drain, and pillage these wetlands the resources and ecosystem services they provide too diminish. Without an urgent change in management and an increase in conservation plans not only will rare and critical species be lost, but so too will the resources and hydrological functions provided by these wetlands that are essential for local and global communities.
Want to get involved in protecting these unique ecosystems? Here are a few actions you can take to protect peat swamp forests.
Be informed. Read about peat swamp forests and the plants and animals found there. Learn about the palm industry and how agriculture impacts these wetlands. Follow podcasts and news from non-profits like Mongabay, Greenpeace, and the Nature Conservancy.
Use less palm. Help reduce the demand for palm (and other unsustainable oils) by limiting the amount we consume.
Choose more-sustainable palm. While there is no such thing as truly sustainable palm, we can still make smart choices when buying products. Support companies that have committed to sourcing and using deforestation- and conversion-free palm. Look for Rainforest Alliance and Palm Oil Innovation Group (POIG) certified products.
Demand change. We can hold big corporations like Mondelez International (the parent company of Cadbury) and Nabisco (the parent company of Oreo) accountable for their environmental destruction. Boycott. Call them out on Social Media. Write a letter to the editor. Tell these companies we want deforestation-free palm and more sustainable solutions.
Donate. Give time and money to non-profits that work to address deforestation, habitat loss, and conservation. Check out the Orangutan Foundation International, Wetlands International, and the IUCN Commission on Ecosystem Management.
Speak up. Our voices matter, and so do those of the researchers, non-profits, and activists working to protect tropical peat swamp forests, biodiversity, and indigenous way of life in Southeast Asia. Amplify their voices on social media by sharing their posts. Be a part of the conversation by commenting and sharing your own thoughts and concerns through your own social feed. Encourage friends and family to learn about peat swamp forests and other important ecosystems.
References
Corlett RT (2014) The ecology of tropical East Asia. Oxford University Press, Oxford
Meer PV (2013) Tropical peat swamp forests of Sarawak: Sustainable use and biodiversity conservation in a changing environment. Wageningen University and Research, Wageningen
Nakashima Y, Lagan P, Kitayama K (2007) A study of fruit-frugivore interactions in two species of durian (Durio, Bombacaceae) in Sabah, Malaysia. Biotropica 40(2):255-258. doi:10.1111/j.1744-7429.2007.00335.x
Posa MC, Wijedasa LS, Corlett R (2011) Biodiversity and conservation of tropical peat swamp forests. BioScience 61:49-57. doi:10.1525/bio.2011.61.1.10
Tekula S (2017) Palm of the week: Licuala paludosa, or "golden licuala". https://merwinconservancy.org/2017/05/palm-of-the-week-licuala-paludosa-or-golden-licuala/. Accessed 10 April 2019
Yamada T, Suzuki E (2004) Ecological role of vegetative sprouting in the regeneration of Dryobalanops rappa, an emergent species in a Bornean tropical wetland forest. Journal of Tropical Ecology 20(4):377-384. doi:10.1017/s0266467404001300