Fragmentation of Asia’s remaining wildlands: implications for Asian elephant conservation

Habitat loss and fragmentation are main causes for Asian elephant population declines. We mapped wildlands – large, unfragmented and undeveloped areas – asking: (1) Where are the largest wildlands that constitute elephant habitats? (2) What proportion of these wildlands is protected? (3) What is their potential for elephant conservation? Our study demonstrates that wildlands constitute only 51% of the Asian elephant range. Myanmar has the largest wildland (~170,000 km2), followed by Thailand and India. In Principal Components Analysis (PCA), the first two components explained 73% of the variation in fragmentation among ranges. We identified three fragmentation clusters from the PCA. Cluster A contains large ranges with unfragmented wildlands; cluster B includes ranges with well-developed transportation networks and large human populations; and cluster C contains ranges with severely fragmented wildlands. In cluster A, we identified four ranges with elephant populations >1000 animals: ARYO, MYUC, BNMH and BITE. Together with ranges that support >1000 elephants in cluster B, these A ranges have great potential for long-term elephant conservation. We propose that fragmentation clusters and population size can be used to identify different elephant monitoring and management zones. All correspondence to: Peter Leimgruber, Conservation & Research Center, 1500 Remount Road, Front Royal, VA 22630 USA. Tel: +1–540–635–6559; Fax: +1–540–635–6506; E-mail: [email protected]. Animal Conservation (2003) 6, 347–359 © 2003 The Zoological Society of London DOI:10.1017/S1367943003003421 Printed in the United Kingdom must also be large enough so that natural disturbances do not reduce their area below the minimum required to maintain viable populations (Pickett & Thompson, 1978). To map wildlands for Asian elephant conservation, we combined global land-cover data with development data, under the following assumptions: (a) Long-term elephant conservation requires large wildlands (Sukumar, 1989). All major natural vegetation types (e.g., forest, shrubland/savanna, grassland) are potentially wildlands and can be mapped using satellite data. (b) Elephants live in a variety of wildland habitats, including grasslands, shrublands/savannas and forests (McKay, 1973; Seidensticker, 1984). (c) Irrigated grasslands are under intensive agricultural use and thus are not wildlands. (d) Frequent fires are an indicator of increased human activity. Because of differences in natural fire regimes, we expect no fires in some ecosystems (most tropical forests), and a few fires each year in others (grasslands, shrublands, savannas). Even in fireadapted systems, fire frequencies should not exceed one or two a year. (e) Roads and transportation network structures are indicators of human development and fragment wildlands. (f) The smaller and more fragmented a wildland area, the less suitable it is for elephants. Areas smaller than the minimal home range reported for an Asian elephant herd are not likely to support elephant populations in the long term. Data sources and mapping Based on our mapping assumptions we combined data layers from eight different sources to create two products: (1) a map delineating remaining unfragmented wildlands inside and outside elephant ranges; (2) a map showing current protection status of these wildlands (Table 1; Fig. 1). Each hierarchical mapping step corresponded to one or several of our assumptions. Details on mapping procedures and data sources are listed in Appendix 1. (a) Extracting potential wildlands. We used the 1 km resolution Global Land Cover Characterization (GLCC) map to extract potential wildlands (Appendix 1(a)). We created three wildland categories by reducing the original GLCC land-cover classes into: forest, shrubland/savanna and grassland (Appendix 2, Fig. 1). (b) Removing irrigated grasslands from wildlands. Distinguishing grasslands from croplands using satellite imagery is difficult because of similarities in spectral reflectances. We used global irrigation data to exclude areas with >0% irrigation from our grassland category, assuming these areas are agricultural. 348 P. LEIMGRUBER ET AL. Potential wildlands = Forest savanna, brushland, grassland & crop/natural vegetation mosaic Potential wildlands minus area of crop/natural vegetation that are irrigated Potential wildlands minus -forest areas with fires -savannas and brushlands with ≥2 fires grasslands with ≥ 3 fires Potential wildlands minus areas within 1 km of roads Potential wildlands minus area ≤ 110 km3 km Digital map of irrigated areas Global landcover characterization Protected and remaining wildlands in elephant ranges Protected area Geographic range of asian elephant Remaining wildlands in elephant ranges Remaining wildlands World fire web daily fires 2000–1 Digital chart of the world roads