Peninsular Malaysian rain forests

eninsular Malaysian Rain Forests [IM0146] ecoregion, with 195 mammal species, has the second most mammal species in the Indo-Pacific, behind the Borneo Lowland Rain Forests [IM0102]. Yet most of the wide-ranging or top carnivore species lead a tenuous existence in these biologically outstanding forests. The tiger, Asian elephant, Sumatran rhinoceros, Malayan tapir, gaur, and clouded leopard all fall into this category. As in many other tropical forests in this region, habitat loss and poaching are the two primary reasons for the decline in these and other species.

Location and General Description

This ecoregion is made up of the lowland moist forests of peninsular Malaysia and the extreme southern part of Thailand. There are no clear seasons in peninsular Malaysia, and rainfall is plentiful year-round. Two monsoons punctuate the region. From October to March a northeastern monsoon brings extra rain to the eastern side of peninsular Malaysia. The southwest monsoon, which is more powerful, bathe the western side of peninsular Malaysia with rain from April to August. Based on the Köppen climate zone system, this ecoregion falls in the tropical wet climate zone (National Geographic Society 1999).

These majestic forests are dominated by the Dipterocarpaceae tree family, notably Anisoptera spp., Dipterocarpus spp., Dryobalanops spp., Hopea spp., and Shorea spp. (IUCN 1991). These forests contain a high diversity of tree species (an estimated 6,000 species), and dominant species are uncommon. The general characteristics of these forests are canopies of 24-36 m, with emergents reaching more than 45 m. Dipterocarpaceae is a dominant family in the emergent stratum (Whitmore 1984). In the richest forests, up to 80 percent of the emergent trees are dipterocarps. Of the dipterocarps, Dipterocarpus, Dryobalanops, and Shorea are the emergents, and Hopea and Vatica usually are found in the main canopy. Berseraceae and Sapotaceae are other common main canopy families (MacKinnon et al. 1996). The tallest tree species in these forests is not a dipterocarp but rather a legume. The Koompassia excelsa (known as tualang) can grow as tall as 76 m (250 feet) (Richards 1952). This tree is rarely felled when land is cleared because of its large size, hard wood, and huge buttresses. They are often laden with the wild honey-producing bees (Apis dorsata) and are therefore worth more money standing than being logged. Riverine forests are bordered by neram trees (Dipterocarpus oblongifolius), figs (Ficus racemosa), and kelat (Eugenia grandis) and are draped with numerous epiphytic orchids and ferns (Payne and Cubitt 1990). Below the canopy a layer of shade-tolerant species thrives. This layer includes many species from the Euphorbiaceae, Rubiaceae, Annonaceae, Lauraceae, and Myristicaceae families. Ground vegetation usually is sparse, mainly small trees, and herbs are uncommon.

This ecoregion also includes some karst limestone areas that are floristically rich. The limestone hills harbor more than 1,200 species of vascular plants, of which at least 129 are endemic to this habitat (IUCN 1991), most limited to one or a few isolated hills.

Biodiversity Features

Peninsular Malaysia shares many of its tremendous species diversity with Sumatra and Borneo. All three landmasses were once part of a single, larger landmass during the last ice age, when the sea level was more than 100 m lower than it is today. However, peninsular Malaysia retained a connection to Asian mainland, and the lowland forests have the greatest diversity of mammal species found in the Indo-Pacific region. Unfortunately for many of the wide-ranging or carnivorous species, survival in peninsular Malaysia is in doubt.

The tiger (Felis tigris) is peninsular Malaysia's largest predator. They exact estimate of the number of remaining tigers in peninsular Malaysia is not known, but estimates have ranged from 300 to 650 over the past decade. What is not in doubt is that Malaysia's tiger population is in danger of drifting toward extinction. As recent as the 1950s more than 3,000 tigers were estimated to live in Malaysia. However, poaching, habitat loss, and inadequate protection have drastically reduced the population. Taman Negara Nature Reserve remains one of the last refuges for the tiger and several other endangered species (Rabinowitz 1999). There are one Level I and two Level II TCUs in peninsular Malaysia that overlap this ecoregion (Dinerstein et al. 1997).

The Malayan tapir (Tapirus indicus) is the largest of the four living tapir species and only Old World representative. The population of the Malayan tapir has been drastically reduced, but they survive in protected areas. Tapirs can be seen in the Ampang Forest Reserve, and the largest surviving population probably lives around Taman Negara National Park (McClung 1997; Payne and Cubitt 1990). Peninsular Malaysia is also home to the world's smallest rhinoceros, the two-horned Sumatran rhinoceros (Didermocerus sumatrensis). It once ranged through much of southeast Asia, but today the entire population numbers about 500 individuals scattered in isolated populations from peninsular Malaysia to Sumatra and Borneo (McClung 1997). Populations of the rhinoceros survive at Sungai Dusun, Ulu Selama, and Endau-Rompin parks in peninsular Malaysia (Payne and Cubitt 1990).

Peninsular Malaysia's largest land animal, the Asian elephant (Elephas maximus), is also one of the most endangered. They range over vast tracts of land throughout peninsular Malaysia in search of food, and as habitat is destroyed the population has become fragmented and poached. The estimated population has varied widely from 600 to 6,000 elephants, demonstrating the poor knowledge of the actual status of this species in peninsular Malaysia (Sukumar 1989). The second largest mammal in these forests is wild cattle, the gaur (Bos gaurus), or seladang as it is known in Malaysia. Widespread poaching and habitat loss have drastically reduced gaur populations outside protected areas (Payne and Cubitt 1990).

Numerous other mammal species live in these forests and include squirrels, deer, otter, civet, primates, the rare sun bear (Ursus malayanus), the clouded leopard (Pardofelis nebulosa), and many bat species.

Birds species richness is also high, with more than 450 species attributed to the ecoregion. These include several pheasants: the crestless fireback pheasant (Lophura erythrophthalma), crested fireback (Lophura ignita), Malay peacock pheasant (Polyplectron malacense), great argus pheasant (Argusianus argus), and crested argus pheasant (Rheinardia ocellata). Hornbills, barbets, bulbuls, woodpeckers, pigeons, broadbills, and babblers are other highly speciose or characteristic groups.
Current Status

Most of these lowland forests have been converted to rice fields, rubber and oil palm plantations, and orchards, with the northwestern region being the most intensively cultivated (Cubitt and Payne and Cubitt 1990). Only about a fifth of the original forest cover now remains, scattered in fragments throughout the ecoregion. There are numerous protected areas that cover 3,875 km2 (3 percent) of this ecoregion (table 1). With the exception of Taman Negara, all are less than 500 km2, many less than 10 km2. None of the alluvial swamp forest in the ecoregion is protected in peninsular Malaysia (WWF and IUCN 1995).