While the Amazon, with its meteoric conversion of forest to farmland, has received a great deal of media coverage, it is unfortunately not the only case of massive degradation of ecosystems. The Uruguayan pampas, for example, have seen a major expansion in agriculture over the last 30 years, particularly of soya.
Researchers from the LSCE and their Uruguayan and Brazilian partners took sediment cores from two reservoir lakes downstream of two agricultural catchment areas feeding the Rio Negro river (Uruguay). The analyses, carried out on the Doséo platform at the CEA’s List Institute, trace the sediment inputs to these lakes, and hence the loss of thickness of the soils from which they originate. This reduces the water and CO2 storage capacity of these soils. In addition, a change in their physical properties threatens their fertility. Inputs are then used, often phosphate- and nitrogen-based, which further impoverish the soil. It’s a vicious circle.
Two periods of acceleration have been identified: the first in the mid-1990s, when eucalyptus and pine plantation programmes were launched. The second, and more significant, came after 2000, with the expansion of soya cultivation. In the space of just a few years, human activities have led to a spectacular and widespread transformation of Uruguay’s ecosystems, linked not only to political choices but also to local and regional economic crises and pressure from national and international investors on production choices.
In addition to the direct consequences for biodiversity and soil and water contamination, this agricultural expansion is directly affecting the sedimentary cascade, which in turn is threatening the sustainability of soil and water resources.
Contacts LSCE: Anthony Foucher, Pierre-Alexis Chaboche & Olivier Evrard