How much soil is lost every year?
Panos Panagos and Cristiano Ballabio
European Commission’s Joint Research Centre, Directorate D – Sustainable Resources, Land Resources Unit, Ispra, Italy
Amount of soil lost by water erosion in 2012 at 250 × 250 m resolution for 202 countries (approx. 125 million km2). Image from Borrelli et al. 2017
Soil is home of thousands of organisms, targeted by hundreds of soil biology and ecology studies. Soil is not an infinite resource, therefore, as soil biologists/ecologists, the raw material behind all of your findings is eroding away. The link between soil erosion and biology/ecology is stronger than what you may expect. As soil erosion modelers, our work improves estimates of soil loss in order to clearly assess its effects on soil life and, eventually, to develop actions to control it.
The question is simple: how much soil is lost every year on Earth due to erosion? Human activity and changes in land use lead to increased soil loss, which in turn degrades nature's nutrient cycling system, diminishes land productivity and affects the capability of soil to act as a habitat. Furthermore, erosion is becoming more and more an issue due to intensive meteorological events associated to climate change. According to the Status of the World's Soil Resources, recently published by the Food and Agriculture Organization, soil erosion is the main threat to soil (and soil dwelling organisms) worldwide. Still, the precise amount of soil lost annually remains unclear.
So far, a reliable assessment of soil erosion at global scale was missing. In December 2017, this gap has been partially filled by our new study. The analysis, produced by a group of researchers led by the European Commission's Joint Research Centre, the University of Basel and the Centre for Ecology & Hydrology, was published in Nature Communications: An assessment of the global impact of 21st century land use change on soil erosion.
We have developed an unprecedentedly high resolution (250 × 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modeling and census data. The model result, an estimated 36 billion tons of soil eroded per year, is at least two times lower than previous annual soil erosion reference values.
As for biodiversity, we identified hotspots where erosion is more intense. The greatest amount of soil loss is estimated in Sub-Saharan Africa, South America and Southeast Asia. This means that some of the countries with less developed economies were estimated to experience the highest soil erosion rates. In particular, some of the largest and most intensively eroded regions are in African equatorial area (0.26 million km2, 3.2% of the region). Moreover, we calculated the spatial and temporal effects of land use change between 2001 and 2012. Our findings indicate a potential overall increase in global soil erosion mainly driven by cropland expansion (+0.22 million km2) and forest decline (−1.65 million km2).
Finally, we also evaluated the potential offset of the global application of conservation practices in agriculture. Our study estimated that, if applied correctly, conservation practices could save over a billion tons of soil per year. The highest reductions in soil loss due to conservation agriculture were estimated to occur in South America (16%), Oceania (15.4%) and North America (12.5%). The message is clear: soil erosion can be reduced if soil conservation practices are adopted in agriculture.
Overall, our research shows how soil erosion is a hot issue that requires actions to curb it, especially as it greatly affects developing countries. We hope that our work will promote the inclusion of soil erosion as one of the priorities in the environmental political agenda. This work will also help soil biologist and ecologists more aware of soil erosion and the impact it can have on their subject of study. Thus, we look forward to future studies integrating soil erosion modeling and soil biology and ecology. Indeed, another question arises: how do soil organisms affect the amount of soil eroded annually? It is up to soil biodiversity scientists to give an answer to that.