Environmental Conservation 35 (2): 93–103 © 2008 Foundation for Environmental Conservation doi:10.1017/S0376892908004864 Deforestation dynamics in a fragmented region of southern Amazonia: evaluation and future scenarios FERNANDA MICHALSKI 1,2 ∗ ,CARLOS A. PERES 1 AND IAIN R. LAKE 1 1 Centre for Ecology, Evolution and Conservation, School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK 2 Instituto Pr´ o-Carn´ ıvoros, CP 10, Atibaia, SP, 12940-970, Brazil Date submitted: 22 August 2007; Date accepted: 26 May 2008 SUMMARY The ‘arc of deforestation’ of southern Amazonia has one of the highest deforestation rates documented anywhere in the world. Landscape changes in a poorly studied but strategically important region in the Brazilian Amazon were studied using biennial Landsat TM/ETM+ images from 1984 to 2004. Deforestation rate for the period 1984–2004 was 2.47% yr -1 in the 7295 km 2 study area, but decreased to 1.99% and 2.15% in 2000–2002 and 2002–2004, respectively. Landscape structure changes were characterized by smaller forest patches that were further apart, but increasingly complex in shape. Deforestation was mainly driven by cattle ranching, which in turn was affected by distance to roads, with forest cover increasing at greater distances from roads. A multi-layer perceptron was used to develop future scenarios based on Markov Chain analysis. Based on current land use, forest cover in the region will decline from 42% in 2004 to 21% by 2016. Results indicate a critical threshold at 51% of forest cover in which landscape structure and connectivity changes abruptly. This suggests that the region requires greater efforts in environmental law enforcement, land-use planning and education programmes to maintain the remaining forest cover near this threshold. Keywords: Alta Floresta, Amazon, deforestation, land-cover change, geographical information system, Mato Grosso INTRODUCTION Deforestation causing landscape change and loss of wildlife habitat is considered to be the most serious threat to global biodiversity (Sala et al. 2000). Deforestation has profound consequences for climate change (Meir et al. 2006; Gullison et al. 2007), biogeochemical cycles (Davidson & Artaxo 2004), and biodiversity in tropical, temperate and boreal regions (Gurd et al. 2001; Laurance et al. 2002a; Schmiegelow & M¨ onkk¨ oen 2002; Peres & Michalski 2006). Despite its importance, accurate estimates of deforestation rates are not available for most countries in the humid tropics (Grainger ∗ Correspondence: Dr Fernanda Michalski Fax: +55 51 3332 0762 e-mail: fmichalski@procarnivoros.org.br 1993), or the deforestation statistics from different sources are inconsistent (Hansen & DeFries 2004). The Brazilian Amazon, which encompasses two-thirds of the Amazon basin, is the most extensive region of remaining tropical forest within a single country. However, annual deforestation rates have accelerated in recent years from 1.4 Mha in 1990 to 1.8 Mha in 1996, > 2.3 Mha in 2002 and > 2.7 Mha in 2004 (INPE [Instituto Nacional de Pesquisas Espaciais] 2008). This process continues to date with 0.7 Mha of forest cleared in August–December 2007 (INPE 2008). Since the 1970s, large-scale deforestation has been concentrated in the more accessible eastern, southern and south-western parts of the Amazon basin (Skole & Tucker 1993; Ferraz et al. 2005; INPE 2008) often generating a highly fragmented forest landscape containing forest remnants of varying size, shape, degree of connectivity and multiple disturbance regimes (Peres & Michalski 2006). Forest loss along this section of the Amazonian ‘arc of deforestation’ creates several types of landscape structure, ranging from the typical fish-bone pattern, in which small properties are regularly distributed along roads, to those dominated by sizeable remnants within extensive cattle ranches (Oliveira- Filho & Metzger 2006). Amazonian deforestation is likely to continue with further expansion of the cattle and soybean industries and other agricultural frontiers, so that 40% of the forest cover is likely to be converted by 2050 (Soares-Filho et al. 2006). Different landscape patterns can influence the dynamics of populations, but the ecological consequences can differ depending on the pattern imposed on the landscape (Trani & Giles 1999). When a formerly continuous forest is isolated, the number of species will shift from its original equilibrium. This is affected by the area reduction in remaining forest patches and the distance to continuous forest or between patches (Laurance et al. 2002a). Declines in species diversity and abundance are usually related to the size of forest remnants and their degree of isolation (MacArthur & Wilson 1967; Diamond 1976; Simberloff 1976; Terborgh 1976). The larger the remaining forest area, the higher the original number of species remaining and the lower the rate of subsequent extinctions (Terborgh & Winter 1980). Quantifiable changes in landscape structure, including land cover, remain an important aspect of landscape ecology because of their relationship with ecological processes (Turner 1989). Over the past decades, several metrics and indices have been developed to describe landscape configuration and composition (for example O’Neill et al. 1988; McGarigal &