Malaysia is a megadiverse country [1
] and is a part of the Southeast Asian biodiversity hotspot [2
]. The Malayan tiger, Panthera tigris jacksoni
, is endemic to Peninsular Malaysia and is threatened by habitat loss, in addition to poaching and the illegal trade of tiger parts, hunting of tiger prey, and retaliatory killings arising from human-wildlife conflicts [3
]. Following recent reports of a decline in Peninsular Malaysia’s tiger population, the Malayan tiger is now classified by the International Union for Conservation of Nature (IUCN) as a critically endangered species, i.e., a species facing an extremely high risk of extinction in the wild [3
]. Current estimates suggest a likely population of 250–340 adult tigers and an effective breeding population of 80–120 tigers, indicating a greater than 25% decline in one generation (equivalent to seven years) [3
]. Additionally, repeated population studies at a couple of sites indicate a 50 and 90% decline in tiger density estimates [3
Increasing human population, in addition to agricultural and infrastructure development, have resulted in the reduction of wildland extent, forcing tigers to survive in human-dominated landscapes [4
]. Asian countries have the highest population densities in forested areas and a long history of agricultural development [5
]. Southeast Asia has some of the highest deforestation rates globally [6
] and has a large proportion of cultivated/agricultural land under tree plantations [5
]. Peninsular Malaysia has a long history of land cover and land use change. Expanding agriculture, especially rubber (Hevea brasiliensis
) and oil palm (Elaeis guineensis
) plantations, has been historically responsible for forest reduction in the region [7
]. Rubber plantations in Peninsular Malaysia first appeared in the 1880s [11
] and expanded rapidly after a surge in rubber prices during 1905–1910 [12
]. Oil palm plantations appeared in Malaysia as early as 1917 [13
] and with a drop in rubber prices in the 1960s, commercial oil palm plantations started replacing those of rubber [12
]. By the 1940s, Peninsular Malaysia’s west coastal region was already heavily deforested. It had lost half of its original forest area by the late 1980s, while agricultural land had expanded from an estimated 21 to 35% of the land area between 1966 and 1982 [14
]. Agricultural expansion and oil palm production are considered significant threats to biodiversity and tiger habitat in Peninsular Malaysia [6
Historically, tigers inhabited all forest areas of Peninsular Malaysia [16
]. Currently, most breeding tiger populations are restricted to protected areas due to intensive human pressure [17
]. Rapidly growing economies and expanding markets have put greater pressure on the remaining tiger habitats [4
]. As a commitment to doubling wild tiger numbers by 2022, tiger-range countries adopted the Global Tiger Recovery Program (GTRP) [18
]. Under the GTRP, Malaysia’s National Tiger Recovery Program (NTRP) will focus on its National Tiger Recovery Priorities and the tiger recovery strategy described in its National Tiger Conservation Action Plan (NTCAP) [19
], which has identified the ‘net loss and gain of forests’ as an indicator for monitoring conservation actions, along with other indicators like tiger occupancy (presence or absence of species at sites within the study area), prey and tiger densities, and the use of corridors by tigers [20
]. While collecting data for most of these indicators is costly and time consuming, monitoring habitats using remotely sensed data may be achieved with minimal investments. Remote sensing is an effective tool for change assessment and the repeatable monitoring of large and remote tracts of land. Various remotely sensed datasets have been specifically generated to estimate the spatial extent of forest cover and forest loss from regional to global scales [21
]. Landsat’s 30 m spatial resolution allows mapping at a scale congruent with most human activity [25
]. The Landsat program also features the longest data archive suitable for multi-decadal regional change assessments [26
]. Remotely sensed forest and forest change products often use a biophysical forest definition, which includes forestry dynamics and plantation cycles in the quantification of forest and forest loss area [24
]. Natural forests and tree plantations offer a different suitability as tiger habitats. Plantations, like those of oil palm, have a uniform tree-age structure [13
], support fewer species than primary, logged, or disturbed forests [13
], or even degraded forests [29
], and provide poor habitat for tigers [30
]. Additionally, agricultural expansion also impacts tigers through access for poaching, disruption of connectivity for movement and dispersal, and by increasing human-tiger conflicts [15
]. Hence, it is important to separate natural forests from plantations when assessing forest dynamics in the context of tiger habitat.
Some studies providing forest loss estimates for Malaysia [10
] use national land use data compiled by the Food and Agriculture Organization of the United Nations (FAO) or other sources and do not distinguish between Peninsular Malaysia and Malaysian Borneo, which have very different land cover and land use change dynamics. This is partly due to the autonomy of states to make land and forest resource decisions [15
]. Previous studies providing forest loss estimates for Peninsular Malaysia [23
] do not focus on tiger habitat and only a recent study by [17
] assessed forest loss within the global priority tiger conservation landscapes (TCLs) across all tiger-range countries, identifying Malaysia’s Taman-Negara-Belum as a TCL with some of the highest forest loss during 2001–2014.
Given the history of land cover changes in Peninsular Malaysia and the role of plantations in land use conversion, it is important to assess the drivers of forest loss in the region and to quantify the role of plantation expansion. In this study, we assess recent forest dynamics in Peninsular Malaysia and considering the Malayan tiger as an example of Malaysia’s endangered and threatened megafauna, we specifically focus on forest dynamics within Malaysia’s tiger landscapes. The overarching goal for this study was to quantify the area of natural forest loss and conversion to plantations between 1988 and 2012 within Malaysia’s tiger habitat. The specific objectives of this study were: (1) to map Peninsular Malaysia’s natural forest in 1988 as a proxy for potential tiger habitat; (2) map and quantify natural forest loss between 1988 and 2012 in Peninsular Malaysia and its tiger habitat; and (3) quantify the proportion of the total forest and tiger habitat loss converted to plantations.
Sample-based area estimates provide a better estimation of loss area than simple map-based estimates [46
] and have been used to correct for the underestimation of forest loss [48
]. Error-adjustment increased the estimated areas of natural forest loss and tiger habitat loss for both pre-2000 and post-2000 periods. User’s and producer’s accuracies are not distributed uniformly, although the omission error is consistently high for both periods for natural forest and tiger habitat loss.
Based on our total estimated gross natural forest loss of 1.35 Mha, it is evident that deforestation continues to be a problem for Peninsular Malaysia’s forest. Our estimated forest loss area from 2000–2010 of 0.49 Mha is higher compared to the 0.44 Mha value reported by [23
]. This difference can be attributed to the improved spatial resolution of data used (250 m vs. 30 m in this study), and the implementation of the sample-based unbiased area estimation method. We observe an acceleration in forest loss from pre-2000 to post-2000, similar to previous reports across the humid tropics and in Asia [25
]. Our study adds to a recent study of global tiger habitat [17
] and provides a more extensive assessment of habitat loss within Peninsular Malaysia and the contribution of expanding plantations. However, we have only mapped forest loss within habitat and have not assessed the quality of the remaining habitat, which can be further affected by the fragmentation or creation of greater edge and increased access. Furthermore, the estimated conversion of natural forests and habitat to plantations in our study is limited by the plantation dataset used. Any undetected or cryptic plantations will result in an underestimation of the forest area converted to plantations over the study period. While any forest conversion to cryptic plantations is a concern for tiger habitat loss, the forest area converted to these plantations is of relatively low importance when compared with forest conversions to large industrial plantations like those of oil palm and rubber.
With 48% of all the natural forest lost during 1988–2012 converted to plantations by 2014, plantation expansion can be considered a major contributor to forest loss in Peninsular Malaysia. Large industrial plantations constitute more than half of the forest converted to plantations in both study periods. Contrary to claims by the Malaysian palm oil industry [50
], our results show that oil palm plantations have continued to expand at the expense of natural forest areas. Our analysis shows that approximately 242,000 ha of mapped forest loss between 1988 and 2012 were converted to industrial oil palm plantations by 2014. Additionally, we observe an increased conversion of both forest and habitat loss to plantations post-2000, primarily due to the observed increase of annual loss after 2006, especially within tiger habitat. The proportion of total loss converted to plantations has increased from 40 to 54% between the two periods, while the proportion of habitat loss converted to plantations has increased from 35 to 57%.
Although the conversion of forest and habitat to oil palm plantations has dominated throughout the study period, the proportion of conversions to large-scale rubber plantations has increased significantly post-2000. Mapped habitat loss converted to rubber plantations has increased by 96% between pre-2000 and post-2000, while conversions to oil palm plantations have only increased by about 14%, suggesting that rubber cultivation could be a developing threat for the forests and tiger habitat. Other reports also indicate substantial increases in the forest reserve area converted to rubber plantations between 2005 and 2012 [3
]. Latex-timber clones, rubber trees that can be used for both rubber and timber, are being propagated across the landscape as a means to expand timber plantations [15
]. Policies that allow for selectively logged forests under state jurisdiction to be converted to rubber tree plantations [15
] and aggressive plantation schemes by the government [3
] continue to endanger Malaysia’s forests and tiger habitat.
The observed increase in habitat loss under the cleared plantation class could probably be explained by delays in plantation establishment after forest clearing and that recently established plantations could look very similar to land cleared for other land-uses [52
]. It is important to note that our analysis focuses on forest loss area that is under plantation in the year 2014 and other intermediary land uses could exist before plantation establishment. Forest conversion has been shown to follow initial logging disturbance in Indonesia [27
]. In Peninsular Malaysia, oil palm plantations are usually established on degraded, previously logged forest or other existing plantations [31
]. Moreover, about 85% of the Malaysian tiger population inhabits forest reserves that have been predominantly assigned for selective logging [53
]. It is essential that the role of logging in deforestation and habitat loss in the region be further investigated.