How may deforestation rates and political instruments affect land use patterns and Carbon emissions in the semi-arid Chaco, Argentina?

Abstract

In the last decades, dry Chaco forests experienced both intensive deforestation and land use changes. The intensification of deforestation at the national level led to the enactment of the National Forest Law (N° 26.331) in 2007. However, after its implementation, deforestation continued at high rates in explicitly protected areas (Categories I and II) in the provinces of Salta, Chaco and Santiago del Estero. In this article we estimated carbon (C) emission due to deforestation in a portion of the Argentine semi-arid Chaco (around 11 M ha) along 12 land use scenarios. A spatial model (InVEST) was used to prospectively analyze land use in the next 20 years, considering 4 levels of Forest Law compliance (denominated Current, Permissive, Partial and Strict) and 3 deforestation rates based on 2009-2015 records (denominated Expansion, Deceleration and Acceleration). We simulated the deforestation and its subsequent replacement by productive land uses (croplands, pastures and silvopastoral systems) based on a supervised land use classification for the year 2015. The C contents in different compartments (above and belowground biomass, litter and soil) were obtained from previous studies, based on a simulation model (CENTURY). The level of Forest Law compliance did not define the cleared area, except for those scenarios that considered a Strict compliance. Thus, productive land uses increased between 0.9 and 3.5 M ha after 20 years, depending on the deforestation rate. The total C emission was estimated between 51 and 169 Tg, where the burning of biomass and the decomposition of the remaining organic material represented about 96% of the emissions. Carbon changes in the upper 20 cm of the soil, represented a very low proportion of total emission. Although these estimations were conservative, given that not all sources have been considered, the study area showed a high potential contribution to the C emission at national scale.