Researchers determined that within 20 years, the soy monoculture in the Semi-arid Chaco would release into the atmosphere an amount of carbon dioxide equivalent to 76% of the emissions from the combustion of the Argentine automotive tram system.
The forests of the Semi-arid Chaco, in the north of Argentina, suffer an annual deforestation rate three times higher than the world average. This happens as a consequence of the agricultural and livestock expansion in the region, a process that accelerated during the last two decades. These changes in land use, which have soy as the predominant crop, have negative consequences for the sustainability of agroecosystems. One of them is the emission of gases that contribute to climate change. Therefore, a study revealed that the intensification of these practices over the next 20 years would release into the atmosphere an amount of carbon dioxide equivalent to 76% of the emissions from the combustion of the transportation system in Argentina.
During the period 1976-2015, almost 11.5 million hectares of the Argentine Chaco forest were lost, which were replaced with pastures and agricultural crops. “The management carried out in the area causes a loss of soil carbon that is essential for its fertility and other ecosystem services. Furthermore, when the original forest cover is replaced, a large amount of carbon stored in the above-ground and underground biomass is released. This release of carbon in the form of carbon dioxide - or CO2- it intensifies global warming, since it is a greenhouse gas ”, pointed out Pablo Baldassini, professor in the Department of Quantitative Methods and Information Systems at the Faculty of Agronomy of the UBA.
"Soy cultivation occupies between 50 and 60% of the area sown in the region, and compared to the cultivation of corn or corn-wheat, it is the one that most imbalances the inputs and outputs of soil carbon. On the livestock activity side, we also observe that it has a negative impact on the carbon balance of soils, since high animal loads are used; that is, a large number of animals per hectare ”, he highlighted.
In his research, Baldassini projected the impact of the continuity of these transformation processes on carbon. “By means of a 20-year simulation we observe that if the deforestation rate of the 2009-2015 period continues, the carbon output of the system in the form of CO2 towards the atmosphere will represent values equivalent to 44% of the average emissions from 2000 to 2010 from the combustion of transportation in Argentina. This value can rise to 76% in case the deforestation rate doubles ”. These emissions would represent between 15% and 26% of those estimated for the entire Argentine Chaco in more than 100 years, between 1900 and 2005 ”.
What about soil carbon?
“The carbon stored in the soil is a key component of ecosystems, since it intervenes in the provision of different services such as carbon sequestration, climate regulation, erosion control and the maintenance of physical, biological and chemical properties of the floor. For this reason, it is essential that there is a positive balance between carbon inputs and outputs in the ecosystem ”, explained the researcher.
However, Baldassini pointed out that agricultural and livestock practices that increased its area reduced the carbon gain compared to the original forest. Along the same lines, he stated that, although the wheat-corn rotations or only corn showed similar carbon gains to those of the forest, they also determined a negative balance, since 45% of what it produces is harvested. “These lower carbon gains reduce soil organic carbon. We do not observe current agricultural management practices that allow maintaining their levels ”.
“If we want to reverse this situation, rotations and fertilizations should be better planned, in the case of crops. On the pasture side, it is possible to maintain and even increase the carbon of the system with a low or moderate load ”, indicated the teacher.