Threats to Big Cats in Southeast Asia
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Threats to Big Cats in Southeast Asia Madeleine McMillan Advisors: Dr. Stuart Pimm & Dr. Andrew Jacobson April 25, 2018 Masters project submitted in partial fulfillment of the requirements for the Master of Environmental Management degree in the Nicholas School of the Environment of Duke University 1 Abstract Southeast Asia is experiencing rapid rates of habitat conversion as homogenous oil palm plantations are replacing biodiverse areas. These oil palm plantations have exploded over recent decades, altering the landscape for species such as tigers, leopards, and clouded leopards who depend on large tracts of habitat for survival. To understand how to protect these big cats and their habitats, I examined 1) the current state of big cat habitat and habitat connectivity in Southeast Asia, 2) how oil palm plantation expansion would impact remaining habitat, 3) additional threats challenging big cats such as poaching, forest loss, and human population growth, and 4) the overlap between protected areas and threatened habitat. This study found that big cat habitat patches are already isolated from one another. While oil palm was not found to be the biggest threat to big cat connectivity, habitat in Malaysia would suffer most from the expansion of oil palm plantations. Overall, big cats are experiencing the greatest anthropogenic threats to their habitat in Malaysia, Myanmar, and eastern India with over half of the threatened habitat patches falling outside of protected areas. Introduction Southeast Asia is experiencing rapid rates of habitat conversion as homogenous oil palm plantations, agricultural expansions, and human developments replace biodiverse areas. Due to rising human populations, the landscape of Southeast Asia is increasingly under anthropogenic stresses and threats. Anthropogenic pressures destroy tracts of forest, and natural vegetation, eliminating the region’s wildlife (Sodhi et al. 2004). In Southeast Asia, big cats including tigers, Panthera tigris, leopards, Panthera pardus, and clouded leopards, Neofelis nebulosa, are under pressure due to habitat loss because they rely on sizable habitat patches for survival (Goodrich et al. 2015, Jacobson et al. 2016, Grassman et al. 2016). Tigers are the largest of these three cats and are listed as endangered by the IUCN Red List because observed populations have declined as much as 30% over the past 14 years and 2 occupy less than 6% of their historic range (Goodrich et al. 2015). Leopards have the widest distribution of any felid but are listed as vulnerable because they reside in approximately 25% of their historic range (Jacobson et al. 2016). Clouded leopards are the smallest of these three big cat species and are arboreal, spending much of their time in trees (Grassman et al. 2016). The clouded leopard’s conservation status is also vulnerable because they have lost an estimated 30% of their adult population over the past 20 years (Grassman et al. 2016). All three cats have experienced population declines due to poaching, habitat loss, and fragmentation, as well as additional human pressures (Goodrich et al. 2015, Grassman et al. 2016). One of the largest contributors to habitat loss in Southeast Asia is the rapidly increasing market for palm oil, a cheaply produced vegetable oil from the oil palm tree, Elaeis guineensis. This palm oil is found in processed foods, cosmetics, and cleaning supplies (Vijay et al. 2016). Oil palm plantations are replacing natural forests with homogenous rows of vegetation that support less biodiversity (Yue et al. 2015). Recent studies have found that replacing natural forests with oil palm plantations decreases the species richness and diversity for many mammals in Southeast Asia (Yue et al. 2015). Overall, oil palm plantations have been found to cause a decline in species diversity as animals do not occupy these unnatural forests for extended periods of time (Yue et al. 2015). Southeast Asia alone is responsible for over 80% of global palm oil production, largely from Malaysia and Indonesia (Bateman et al. 2010). Between 1999 and 2005, 59% of the natural forests in Malaysia were replaced with oil palm plantations, and this trend is only expected to continue (Bateman et al. 2010). Furthermore, the market for oil palm is poised to continue to expand, making the expansion of oil palm plantations one of the greatest threats to wildlife in Southeast Asia (Vijay et al. 2016). Due to the great threat oil palm poses to biodiversity and native forests, a recent study identified regions around the world that would be suitable for the expansion of oil palm plantations to evaluate the threat of future expansion of oil palm (Vijay et al. 2016). 3 In this study, I apply this new data on areas suitable for oil palm to examine how oil palm expansion would impact big cats in Southeast Asia by addressing the following questions: 1. What is the current state of tiger, leopard, and clouded leopard habitat and its connectivity? 2. How would habitat connectivity change if areas suitable for oil palm plantation expansion were developed? 3. What are additional threats to big cat habitat, and what areas are under greatest anthropogenic pressures? 4. What does the overlap between big cat habitat and protected areas look like? And what is the overlap between threatened habitat patches and protected areas? Knowledge about the current state of habitat connectivity and the possible impacts from future threats provide a baseline for organizations to make informed decisions about the conservation of tigers, leopards, and clouded leopards in Southeast Asia so these big cats populations can be protected from further decline. Methods Study Area The study area includes Myanmar, Laos, Thailand, Cambodia, Peninsular Malaysia, Singapore, the Indian states of Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, and Tripura, and the Yunnan Province of China (Figure 1). This extent was selected as it represents a biologically similar region. 4 Figure 1: Study area including Myanmar, Laos, Vietnam, Thailand, Cambodia, Peninsular Malaysia, Singapore and the eastern region of India, and the Yunnan province of China. Within this region, I extracted the most updated extant habitat patches for tigers (Panthera 2015), leopards (Jacobson et al. 2016), and clouded leopards (IUCN 2016), excluding any habitat patch slivers less than 100 km2 because studies have found areas below this size are not suitable for supporting viable populations of the carnivores (Lynam et al. 2007). I overlapped all three big cat habitat patches to find the areas that support tigers, leopards, and tigers. In addition, I explored the extant habitat patch overlap with protected areas to calculate the percentage of habitat area comprised of designated protected areas (WDPA 2014, Li et al. 2016). Current State of Habitat Connectivity All analyses were conducted using ArcGIS 10.5.1 (ESRI 2001), using Asia North Albers Equal Area Conic projection and 330 x 330-meter grain size. This is appropriate because the 5 projection reduces shape and area distortion, and the grain size allows for a more rapid landscape-scale analysis. To address the first research question, I evaluated the current state of connectivity between habitat patches for tigers, leopards, and clouded leopards by conducting a subnetwork analysis. Subnetworks are groups of functionally connected habitat patches that an animal could possibly travel between given a maximum travel distance for the species. From behavior and tracking literature, I estimated distances that each species would be likely to travel. I found that tigers are likely to travel between 100 and 250 km under normal conditions (Singh et al. 2013), leopards are likely to travel between 80 and 225 km (Fattebert et al. 2013), and clouded leopards are likely to travel between 50 and 100 km (Giordano 2018). The tiger and leopard have been recorded traveling further distances, but these have been influenced by extreme conditions like chasing prey over long distances. I did not use the greatest travel distances recorded in the literature, rather I used conservative distances to prevent overestimation of connectivity. I buffered extant habitat patches for each species using the two different travel distances listed above for each species. If habitat patches were within the species’ maximum travel distance, these patches were considered functionally connected and grouped into a subnetwork. These initial subnetwork analyses only account for the maximum distance traveled by the species and do not incorporate features on the landscape that could also be impacting the animal’s ability to travel between patches. To incorporate these landscape features, I created three species-specific resistance layers including landcover (Globcover 2009), distance to roads (gRoads), and human population density (Asia Population Continental Dataset 2015). A resistance layer is a surface representing how easy or challenging it would be for an animal to move across the landscape. Each cell in the surface has a different cost value with higher values equating to a part of the landscape that would be more difficult to travel through. 6 I removed large bodies of water (WWF 2004) such as lakes from the landcover data because the cats would not be able to travel through them. Using information about each big cat species, I assigned cost values to different landcover types, different distances to roads, and different human population densities (A Tables 1-3). For instance, tigers prefer areas of dense, natural vegetation to more open areas and agricultural fields (Monirul et al 2007, Rabinowitz 1993). Tigers also tend to avoid human settlements and roads (Joshi et al 2013, Thatte et al. 2018). Using this information, I assigned cost values consistent with these preferences and combined all three landscape features giving landcover type a weight of 0.4, human population density a weight of 0.4, and distance to roads a weight of 0.2. Leopards also prefer areas of natural, dense vegetation (Hayward et al. 2016), but are a generalist species influenced less by human presence compared to the other big cats due to their high adaptability (Kshettry et al.