How do climate and human land use affect soil erosion?

A study of soil depth in the United States determines how climate and human use affect soil erosion

Tom Vanwalleghem, a professor at the University of Córdoba (UCO) in Spain, who is part of the Agricultural Hydrology and Hydraulics research group of the ‘María de Maeztu’ Unit of Excellence in the Department of Agronomy (DAUCO), participated in the work. He was supported by researchers from the University of Wisconsin-Madison and the University of Oregon, both in the United States, as well as the University of Minas-Gerais in Brazil.

In recent times, concern for ‘soil health’ has gained ground among public priorities. Through its Soil Monitoring Act, the European Union has set itself the goal of achieving healthy soils in its member countries by 2050. This is no small challenge: while global climate change and human activity are accelerating soil deterioration, it is estimated that it takes around a thousand years to form 2.5 centimetres of soil. In other words, soil is eroding faster than it is formed, and this is an obvious problem given that this non-renewable natural resource is essential for life.

In this context, understanding the variations and dynamics that soil undergoes can help implement conservation measures that limit the loss of this resource. This is the objective of the aforementioned study carried out by researchers from Spain, Brazil and the USA.

The research team, led by Yakun Zhang, analyzed data collected between 1950 and 2018 in the 48 contiguous United States.

Vanwalleghem explains that the depth of the soil layer determines agricultural fertility and controls the hydrological cycle and biodiversity, hence “knowing the variability of its depth is important, as it allows us to adapt agricultural management, such as fertilization or irrigation, and design soil conservation measures adapted to each area.”

The new study investigated how climate and human land use affect soil erosion. (Photo: Amazings / NCYT)

The research is pioneering, as it is unusual for an erosion analysis to cover such a long period of time: 69 years, compared to traditional erosion studies that are limited in time to a couple of years, which makes it impossible to capture long-term evolution or the effect of extreme storms. This has made it possible to detect, for example, a significant loss of the top layer of soil in the Great Plains, where one of the most productive types of soil in the agricultural field predominates, such as Molisol; as well as in sloping areas and in general in crop areas.

The study analyzed spatial variability in soil using cutting-edge statistical methods, such as Generalized Additive Models (GAMs), and using big data techniques. In addition, the researchers analyzed a huge database of the depth of the so-called “A horizon” – the top layer of soil – and total depth, at 37,712 and 22,409 locations in the United States, respectively.

The breadth of this database, also studied over time, has made it possible to analyse the evolution of the soil over these 69 years, determining that the depth of the “horizon A” and the total depth of the soil are related to soil moisture and temperature, respectively.

The study is titled “Climate and land use changes explain variation in the A horizon and soil thickness in the United States.” And it has been published in the academic journal Communications Earth & Environment. (Source: UCO)