Do subtropical seasonal forests in the Gran Chaco, Argentina, have a future?

Abstract

While much information is available about tropical and temperate ecosystems, there is a remarkably little information as to land cover and land use changes in the subtropical biomes of the world. Here, we quantify changes in the spatial patterns of land cover types at the southern edge of the seasonally dry, subtropical Chaco forest of South America during the second half of the 20th century using a vegetation map printed in 1969 and a Landsat TM based digital map produced 30 years later. Results show a massive contraction of forest; ca. 1.2 million ha of original lowland and mountain subtropical dry forests and woodlands, 85% of the total, have been cleared in only 30 years. This loss of Chaco forests of 2.2% year1 is consistent with or even exceeds, global trends. Forest vegetation now persists as fragments where there was formerly continuous cover. Most of undisturbed Chaco forest has now been converted to pasture or is undergoing secondary succession. Today, these new vegetation types, resulting mainly from agricultural expansion, have increased 10-fold in cover and now represent the commonest land cover types. The increased intensity of agricultural usage, possibly triggered by an increase in annual rainfall during the last decades, has been accompanied by changes in agricultural practices and a relative decline in the rural population.