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Clearance for agriculture or cattle ranching was the dominant land-cover change during the last two decades in the South American Dry Chaco. The Argentinean portion has been particularly affected, presenting greater deforestation rates than the continental and global averages. Little is known on the control factors of the location and the spatial clearance patterns. In this article we studied (a) deforestation dynamics in the Argentinean Dry Chaco and the factors determining land clearing locations for the last 25 years; (b) changes in the relative impact of those factors through time and space; and (c) the effect of regulations aimed to control the location and magnitude of land transformation. We also tested the “expansion of the agricultural frontier” hypothesis for the Argentinean Chaco. To identify the factors that defined agricultural expansion we used binomial logistic models that were fitted to a set of independent variables (bio-physical, infrastructure and political factors) that could eventually influence the distribution of new agricultural areas. Results indicate that the Forest Law devised by the Argentinean federal government to control the clearing process was insufficient to restrict both the area transformed per year and clearance locations. Agriculture is expanding over marginal areas and land clearing dynamics have been increasingly associated to the proximity to already cleared areas, defining a frontier—advancement pattern which gives the idea of a contagion process. According to our results, the relative importance of the anthropic factors associated to the agricultural expansion in the region increased through time. [ABSTRACT FROM AUTHOR]

The expression Forest Transition (FT) and Ecological Transition (ET) were coined to describe the recovery path of forested areas (or more general natural vegetation) after heavy conversion into croplands. FT/ET would be driven by two main socio-economic controls: a) agricultural intensification in the most productive areas and the simultaneous reduction of cropped area in the less suitable areas ( land-sparing ); and b) rural population migration from rural to urban areas. In the argentine portion of the Semiarid Chaco a rapid and extensive clearing for industrial agriculture and cattle ranching based on sown pastures is taking place. In this article we evaluated the occurrence, magnitude and localization of FT/ET in the argentine portion of the Semiarid Chaco during the 1977–2007 period using an approach based on remotely sensed data. From land cover maps we derived three diagnosis variables of FT/ET: (1) the area of natural vegetation at the end of the study period; (2) the rate of annual clearance (natural vegetation loss) for the whole period; and (3) the temporal change of the area of natural vegetation in the last portion of the study period. The diagnosis variables were combined to derive 12 classes (landscape types). We observed a systematic loss of the surface occupied by natural vegetation. Industrial agriculture grew in aggregated patches generating a homogenization of the landscape. In only a 4.8% of the study area we observed a pattern of change compatible with a FT/ET. In contrast, in a 34% of the study region (9.57 million ha) a clear negative trend in the cover of natural vegetation was observed during 1977–2007 period. The area that had a negative trend in the cover of natural vegetation was 7 times greater than the portion of the region experiencing positive trends. Such number indicates an imbalance in the landscape dynamics that would further reduce areas covered by natural vegetation. [ABSTRACT FROM AUTHOR]

The aim of this work was to characterize the spatial and temporal dynamics of the transformation of the natural cover in the Dry Chaco ecoregion from 1976 to 2012. Dry forests in this region have one of the highest deforestation rates in the world. We analyzed 44 Landsat scenes, including part of Argentina, Paraguay and Bolivia. The analysis was based on tracking individual transformed plots of the entire Dry Chaco region for over more than three decades using the same protocol. Until the end of 2012 15.8 million ha of the original habitats of the Chaco were transformed into croplands or pastures. Our study showed that the greater annual rates of transformation were observed in Paraguay, where deforestation increased dramatically in the last decade, reaching values higher than 4.0% in 2010, the highest historical value in the entire region. The size of the transformed plots increased significantly through the studied period both in Argentina and Paraguay, while in Bolivia decreased. At the landscape level, the use of several fragmentation indices showed the disruption of the continuity and connectivity of the original vegetation. The spatially explicit description of the dynamics of transformed areas is an indispensable tool for natural resources management, territorial planning and deforestation impacts assessment. The developed geo-database is available online at http://monitoreodesmonte.com.ar/ for further analyses and use. [ABSTRACT FROM AUTHOR]