Natural Denudation Versus Anthropogenically Accelerated Erosion in Central Brazil: A Confrontation of Time and Space Scales

Land degradation resulting from increased continental surface erosion is a worldwide and systemic phenomenon due to unsustainable human activities. Already fragile, the intertropical zone is likely to be further affected by climate change like increased aridity, an aggravating factor of soil erosion and land degradation. A major challenge is thus to provide the necessary knowledge to not only deepen our understanding of the Earth's system and its critical thresholds but also to help achieving sustainability. Understanding the factors that control the properties and processes of the critical zone, and especially what will be its responses to ongoing climate and land use changes, requires multidisciplinary efforts to tackle time scales that are compatible with morphogenesis and soil development as well as environmental disturbances of anthropogenic origin. Due to its prominent ecological importance, the Brazilian Cerrado biome is an ideal natural laboratory were to gauge the consequences of recent and intense agricultural activities on continental surface erosion. We focused on the region of Brasilia where our approach allows confronting the temporal scales of long-lived and stable cosmogenic nuclides with that of short-lived radioactive isotopes, through a comparison of natural and anthropogenically disturbed land surfaces. Our results indicate that long-term, background denudation rates are lower than 10 mm Kyr(-1) whereas recent erosion rates due to human activities may reach rates at least 160 times higher, exceeding by far the sustainability of the soil resource.

Automated summary

Land degradation from continental surface erosion is a global issue caused by unsustainable human activities. The intertropical zone, which is already fragile, will likely be further impacted by climate change, leading to increased aridity and exacerbating soil erosion and land degradation. It is crucial to understand the factors that control the critical zone, including its responses to climate and land use changes, in order to achieve sustainability. The Brazilian Cerrado biome provides an ideal natural laboratory for studying the consequences of intense agricultural activities on continental surface erosion, and our findings indicate that human-induced erosion rates greatly exceed sustainable levels.