Browsing by Autor "Peter J. Ersts"

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Clearance and Fragmentation of Tropical Deciduous Forest in the Tierras Bajas, Santa Cruz, Bolivia
(Wiley, 2001) Marc K. Steininger; Compton J. Tucker; Peter J. Ersts; Timothy J. Killeen; Z. Villegas; Susanna B. Hecht
Abstract: The Tierras Bajas is an area of 20,000 km 2 of lowland deciduous forest in eastern Santa Cruz, Bolivia, that has undergone rapid change during the past two decades. As part of the largest remaining area of intact deciduous tropical forest in the world, it has been nominated a priority area for conservation by several environmental organizations. We quantified the spatial and temporal patterns of deforestation in the area by digital processing of high‐resolution satellite imagery from 1975 through 1998. The estimated rate of deforestation was among the highest in the world for such a limited area, ranging from 160 km 2 /year in the early1980s to almost 1200 km 2 /year in the late 1990s. Although most deforestation up to 1984 was in Bolivian peasant and Mennonite colonies, most deforestation after 1984 was in non‐Mennonite industrial soybean farms. The level of fragmentation of uncut forest, caused by the spatial patterns of deforestation, also differed among these broad land‐use types. Deforestation in planned and spontaneous peasant colonies was complex in shape, forming relatively large areas of edge‐affected forest, whereas that in Mennonite and other industrial farms was in large, rectangular increments, creating relatively less edge. But the distribution of these farms and the practice of initially clearing around the peripheries of properties resulted in the isolation of large areas of forest. In 1998 four‐fifths of the remaining forest were either within 1 km of a clearance edge or in isolated fragments of <50 km 2 . Compared with deforested areas, the areas of isolated and edge‐affected forest were disproportionately large during the early stages of frontier colonization. These results imply that if the fragmentation effects of deforestation are to be minimized, conservation planning must occur at the earliest stages of frontier development.
Tropical deforestation in the Bolivian Amazon
(Cambridge University Press, 2001) Marc K. Steininger; Compton J. Tucker; John Townshend; Timothy J. Killeen; Arthur Desch; Vivre Bell; Peter J. Ersts
The distributions of forest and deforestation throughout the tropics are poorly known despite their importance to regional biodiversity and global climate and biodiversity. Deforestation estimates based on surveys or sampling have large errors, and high-resolution, wall-to-wall mapping of tropical forests is necessary to assess the impacts of fragmentation. Landsat satellite images from the mid-1980s and early 1990s were thus used to map closed-canopy tropical forest extent and anthropogenic deforestation in an approximately 700 000 km 2 area of Amazonian Bolivia with precipitation >1000 mm yr −1 . Total potential forest cover extent, including tropical deciduous forest, was 448 700 km 2 , while the area of natural non-forest formations was 245 100 km 2 . The area deforested was 15 500 km 2 in the mid-1980s and 24 700 km 2 by the early 1990s. The rate of tropical deforestation in the forest zone of Bolivia with >1000 mm yr −1 precipitation below 1500 m elevation and north of 19° S, was 1529 km 2 yr −1 from 1985–1986 to 1992–1994. Our estimates of deforestation are significantly lower than those reported by the Food and Agriculture Organization of the United Nations (FAO). We document a spatially-concentrated ‘deforestation zone’ in Santa Cruz where >60% of the Bolivian deforestation has occurred. These results indicate that the rate of deforestation in Bolivia has been rapid despite a relatively small human population, and, as in Brazil, clearance has concentrated in the more deciduous forests.