Abstract
The AraguaiaRiver Basincovers a considerable extent of Brazilian Savanna (locally called Cerrado) and part of Amazon Tropical Rainforest, embracing high biodiversity and a vast flooding area. This region has been converted to agricultural lands since 1970s, for the past four decades, leading to a fragmented landscape that holds one of the few large remaining blocks of Cerrado primary vegetation. Therefore, to assess the degree of preservation of this area a 2007 primary vegetation map was derived through Boolean operations using land use and land cover maps from 1975, 1985, 1996 and 2007, from digital classification of Landsat MSS and TM images. To evaluate the role of driving factors on the presence of pristine vegetation, a logistic regression analyses was performed. Tested factors were: distance from roads and cities, terrain slope, land tenure, soil fertility and flooding. We found statistical significant values (p nous lands, wetlands and areas with low fertility have positive influence on the presence and maintenance of these pristine areas. The occurrence of original vegetation in many cases is associated with environmental constraints that difficult or do not allow agricultural use. Analysis of physical and political factors, which may have direct or indirect influence on the conservation and degradation of native vegetation are very important for the comprehension of the dynamics of regional land use, and provide supporting information for a more efficient and sustainable regional landscape planning.
Highlights
The expansion of agricultural frontier in the tropics has been identified as one of the main drivers of deforestation (Alves et al, 2009; Geist & Lambin, 2001)
In Brazil, since 1980s, Savanna biome has been converted to agricultural lands at higher rates than those found for the Amazon, most of the attention to the consequences of land use and land cover change has been focused in Tropical Rain Forest ecosystems (Alves et al, 1999; Batistella & Moran, 2005; Cardille & Foley, 2003; Fearnside, 2006; Laurance et al, 2004; Mahar, 1989)
Previous studies in the Amazon region have shown that deforestation is more intense and concentrated near roads, with up to 90% of forest clearing occurring within a 20 km buffer from a road (Ballester et al, 2003; Ferreira 2001; Gils & Ugon, 2006; Kirby et al, 2006; Ludeke et al, 1990; Nepstad et al, 2001), suggesting their influence in the increase of land cover conversion
Summary
The expansion of agricultural frontier in the tropics has been identified as one of the main drivers of deforestation (Alves et al, 2009; Geist & Lambin, 2001). Forest clearance in Brazilian Amazon has been mainly concentrated at the deforestation arc (Ferreira et al, 2005), encompassing the south, east and west boundaries of the Tropical Rain Forest and a transition zone between this biome and the Cerrado. This transition zone includes about 600 hundred km of savannas located in the drainage basins of Tocantins and Araguaia Rivers. Due to its high biodiversity and vast flooding area, the alluvial zone of the Araguaia and the Bananal lowland regions were identified by the Brazilian Ministry of Environment as a priority area for conservation (MMA, 2010).
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