Biodivers Conserv (2010) 19:393–409 DOI 10.1007/s10531-008-9510-5 O R I G I NA L P AP E R
Loss of biodiversity and ecosystem functioning in Indo-Malayan peat swamp forests Catherine M. Yule
Received: 4 May 2008 / Accepted: 20 October 2008 / Published online: 5 November 2008 © Springer Science+Business Media B.V. 2008
Abstract The tropical peat swamp forests of Indonesia and Malaysia are unusual ecosystems that are rich in endemic species of Xora, fauna and microbes despite their extreme acidic, anaerobic, nutrient poor conditions. They are an important refuge for many endangered species including orang utans. Ecosystem functioning is unusual: microbial decomposition is inhibited because the leaves are sclerophyllous and toxic to deter herbivory in the nutrient poor environment, yet bacteria are abundant and active in the surface layers of the peat, where they respire DOC leached from newly fallen leaves. The bacteria are subsequently consumed by aquatic invertebrates that are eaten by Wsh, and bacterially respired CO2 is assimilated by algae, so bacteria are thus vital to carbon and nutrient cycling. Peat swamp forests are highly sensitive to the impacts of logging, drainage and Wre, due to the interdependence of the vegetation with the peat substrate, which relies on the maintenance of adequate water, canopy cover and leaf litter inputs. Even minor disturbances can increase the likelihood of Wre, which is the major cause of CO2 emissions from regional peat swamp forests and which impact ecosystems worldwide by contributing to climate change. Indo-Malayan peat swamps aVect the hydrology of surrounding ecosystems due to their large water storage capacity which slows the passage of Xoodwaters in wet seasons and maintains stream base Xows during dry seasons. These forests are of global importance yet they are inadequately protected and vanishing rapidly, particularly due to agricultural conversion to oil palm, logging, drainage and annual Wres. Keywords Bacteria · Biodiversity · Carbon sequestration · Hydrology · Indonesia · Malaysia · Microbial communities · Peat Wres · Tropical forests Abbreviations DOC Dissolved organic carbon UNDP United Nations Development Programme IUCN International Union for Conservation of Nature
C. M. Yule (&) School of Science, Monash University, Sunway Campus, Jalan Lagoon Selatan, 46150 Bandar Sunway, Selangor, Malaysia e-mail:
[email protected]
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Biodivers Conserv (2010) 19:393–409
Introduction The global centre of biodiversity of tropical peat swamp forests lies in the Indo-Malayan region where these unique habitats impact the functioning of ecosystems far beyond their borders through their inXuence on climate and hydrology. These forests support a biological resource of global importance, yet on a daily basis they are being rapidly degraded and destroyed. Their ecology has received little attention: most research has focused on biodiversity (e.g. Anderson 1963, who also looked at vegetation structure; LatiV et al. 2005; Ng et al. 1994; Ng and Ibrahim 2001; Beamish et al. 2003; Prentice and Aikanathan 1989; Wells and Yule 2008), carbon storage (e.g. Maltby and Immirzi 1993; Sorensen 1993; Page et al. 2004; Chimner and Ewel 2005; Jauhiainen et al. 2005; Rydin and Jeglum 2006; Hooijer et al. 2006; Takashi et al. 2007) and agricultural conversion (e.g. Coulter 1957; Kanapathy 1975; Andriesse 1988; Vijarnsorn 1996). Relatively few studies have been published in peer-reviewed journals—most are reported in symposia and workshops (e.g. Aminuddin 1992; Maltby et al. 1996; Chin and Havmoller 1999; Rieley and Page 2002; LatiV et al. 2005). This paper reviews our knowledge of the present state of Indo-Malayan peat swamp forests and examines what is known of the impacts of logging, Wre and agricultural conversion on biodiversity and ecosystem functioning. The tropical peat swamp forests of the Indo-Malayan region are unusual ecosystems and they diVer dramatically from north temperate and boreal peat lands which are dominated by Sphagnum spp., grasses, sedges and shrubs. Trees in the peat swamp forests can grow to over 70 m high (Peter Ashton, personal communication), despite the extreme conditions of low pH (2.9–4), low nutrients and anaerobic, unstable, spongy substrate of peat that may be 20 m deep or more. The forest Xoor is Xooded during wet seasons, but even during dry seasons the peat remains waterlogged, with pools in amongst the trees (Fig. 1). Streams and rivers only Xow out of these forests, so the sole nutrient inputs are from rainfall, dust and marine aerosols, otherwise river inXow would create nutrient rich, freshwater swamps. Peat swamp forests support a diverse Xora and fauna with many endemic and endangered species. Unfortunately our knowledge of their Xora and fauna is far from complete and these forests are vanishing before we know what we are losing.
Regional distribution and conservation status Most of the world’s tropical peatlands (about 62%) are found in the Indo-Malayan region (80% in Indonesia, 11% in Malaysia, 6% in Papua New Guinea, with small pockets and remnants in Brunei, Viet Nam, the Philippines and Thailand: Rieley et al. 1996; Page et al. 2006). These peat swamp formations are geologically recent, mostly
