Save Our Soils: Finding ways to stop erosion

FAO hosts global symposium to catalyze efforts to reduce depletion of a non-renewable resource

15 May, 2019, Rome - Wind, rain and industrial farming techniques accelerates soil erosion and can be mitigated before the world faces calamitous losses in terms of agricultural yields and critical ecosystem functions.

"The negative impacts of soil erosion are ever more evident and the need to work jointly ever more urgent," FAO Deputy Director-General, Climate and Natural Resources, Maria Helena Semedo, said today while opening a three-day symposium focusing on enhancing how the world measures and manages soil erosion as well as its economic costs.

"We have solutions," she said. "Preventing soil erosion through education, advocacy and concrete actions in the field are the best way to maintain healthy soils and help achieve the Sustainable Development Goals."

Today the equivalent of one soccer pitch of soil is eroded every five seconds, and the planet is on a path that could lead to the degradation of more than 90 percent of all the Earth's soils by 2050, Semedo said. Erosion, triggered by intensive agriculture, tillage, mono-cropping, overgrazing, urban sprawl, deforestation and industrial and mining activities, all contribute to accelerating soil erosion, which can  result in crop yield losses of up to 50 percent, she added.

As organic carbon particles are the most vulnerable to being washed or blown away, erosion also reduces soil's potential to help mitigate and adapt to climate change, triggering a "vicious cycle" in which extreme weather events and soil erosion reinforce each other, Semedo said.

The Global Symposium on Soil Erosion is co-organized by FAO, the Global Soil Partnership, the Intergovernmental Technical Panel on Soils, the UN Convention to Combat Desertification and a joint programme run by FAO with the International Atomic Energy Association to develop uses for nuclear techniques for food and agriculture.

Amid 20 sessions and more than 100 presentations, speakers include scientists, academic experts, farmers, government officials and even an astronaut describing soil erosion from space.

The greatest challenge

FAO launched Soil erosion: the greatest challenge for sustainable soil management, at the symposium.

The 100-page book, with Dan Pennock, professor at Canada's University of Saskatchewan as its lead author, takes stock of the current state of knowledge regarding soil erosion. More research has been published on the topic in the past three years than in the entire 20th century.

While knowledge of how soil erosion occurs and how to control it is  firmly established, more research is needed on how to measure soil loss rates and budget for measures to reduce them - remain under debate. Indeed, there is disagreement over whether erosion turns soil into a source or sink for carbon emissions, as well as rival formulas to assess the relationship between the size of raindrop splashes and the likelihood that they detach soil particles and remove them from the landscape.

Still, evidence is clear that soil erosion rates on conventionally ploughed agricultural land or intensively grazed pasturelands are notably greater than erosion under native vegetation - and much higher than soil formation rates - implying that we are depleting a non-renewable resource.

Vegetation cover - including shrubs, trees, resistant grasses, cover crops and stubble -can reduce wind erosion by more than 80 percent and also enhance water absorption capacity,  mitigating soil compaction and impeding the creation of rills and gulleys that impede agricultural work. Reduced or no-till practices are also effective, especially in drier regions.

For many farmers, erosion-control measures take a long time to bear fruit. Indeed, terracing, a capital-intensive and highly effective approach practiced for thousands of years, today is prone to failure due to poor management and design as well as abandonment, which is widespread in almost all regions where they are found, making natural solutions a logical tool for soil governance.

At the same time, many of erosion's impacts occur far from the source, as demonstrated by agrochemical runoff that can pollute and eutrophize water sources downstream, which further raises the importance of considering soil erosion control as an issue warranting tangible public support.

Among the planned outcomes of the symposium are the identification of "global hotspots" warranting priority actions in soil management, a data base on the best erosion control practices, and more consensus on how to carry out cost-benefit analyses of prospective interventions to prevent, remediate and mitigate soil erosion.

Photo: ©Carey Marks/ University of Plymouth
Erosion in Tanzania.