The soil is losing its hold and is being carried away by increasingly heavy rainfall: The global soil loss due to runoff could increase drastically in the course of climate change and intensive soil management over the next 50 years, according to model calculations. Counter-steering is urgently needed, say the researchers. The study also shows in which parts of the world more intensive erosion is to be expected, which can help when planning regional countermeasures.
The soil forms a literal basis for the existence of humans and terrestrial ecosystems. Humans have already transformed the earth into an intensely cultivated planet: around 38 percent of the land surface is used for agriculture. Ultimately, around 95 percent of global food production depends on the ability of the soil to enable agricultural production and animal husbandry. But that foundation is at risk, according to a recent United Nations report on the state of global soil resources.
Many soils are therefore in a problematic state, which favors the removal of the valuable substance. Accordingly, unsustainable agricultural practices and deforestation and overgrazing are the main causes of human-induced soil erosion. This creates conditions that favor erosion by wind and above all by water. In principle, these factors have been gnawing at the substance of the soil since the beginning of agriculture. But in the meantime another factor has been added: Due to an increase in heavy rainfall in the course of climate change, the loss of soil due to runoff is increasing.
A look into the future
In light of current trends, how could the problem of soil erosion develop in the future? The researchers led by Pasquale Borrelli from the University of Basel have dealt with this question. On the basis of extensive data collections on current developments in agriculture in around 200 countries around the world and climate prognoses, they have made predictions about global soil erosion by water. In making their predictions, the researchers relied on possible future scenarios, as used by the IPCC. They outline possible developments in the 21st century – from rather optimistic to pessimistic.
As the scientists report, their model calculations show: In all scenarios, a sustained increase in the threat of water erosion can be assumed worldwide. This applies to all simulated climatic conditions and in almost all of the around 200 countries examined. Compared to 2015, the simulations predict an increase in water erosion of 30 percent to 66 percent by 2070, depending on the scenario.
The results suggest that climate change will be the main cause of the increase in soil erosion. But even unsustainable agriculture can have a strong negative impact against the background of current trends. If practices don’t change and global warming measures fail, the study estimates an additional annual soil loss of over 28 billion tons. That would be around two thirds more than the assumed soil loss of 43 billion tons for 2015, say the scientists.
Sustainable land management should help
These results are global assessments that are intended to provide an overall impression of the problem. It is clear, however, that agricultural and climatic developments will have very different effects in different parts of the world. The significance of the study therefore lies in the fact that the researchers have developed maps that provide detailed information on where, due to current trends, increasing soil losses can be expected. The tropical and subtropical countries with low and middle incomes are most susceptible to a sharp increase in erosion.
In order to make the soil more resilient to the increasing burden of precipitation, it is particularly important for these countries in the global south to promote the spread of sustainable agricultural practices, the authors say. “Soil erosion can be influenced by sustainable management and appropriate policy measures,” says Borrelli. “We hope that our prognoses will help us to understand the impending extent of erosion and enable policymakers to develop effective measures to limit the effects,” said the scientist.
Source: University of Basel, specialist article: PNAS, doi: 10.1073 / pnas.2001403117