Critical soil degradation: a "serious danger to human well-being"

Credit: Gellinger / Pixabay - License: CC0

According to the first comprehensive global assessment of soil degradation and restoration published by IPBES, soils are now in critical condition, with serious consequences for biodiversity, climate change and the stability of our societies.

Every year, 12 million hectares of soil are lost in the world: polluted, degraded, leached, artificialized, waterproofed ... They can no longer fulfill their ecological role essential for biodiversity , climate and humanity. Indeed, soils are the key environments for cultivating, for sheltering biodiversity and for storing atmospheric carbon. In addition, they provide, including under forest cover , several ecosystem services such as water purification, energy supply and other essential contributions to the people.

Today, less than a quarter of the Earth's surface still escapes the substantial impacts of human activity - by 2050, IPBES experts estimate that this figure will have fallen to less than 10%.

Once again, the report is alarming: "critical" levels of degradation have been achieved in many parts of the world according to the IPBES report, which is a reference in this field and which will soon be published in full: it brings together more 100 experts in 45 countries; relies on more than 3,000 sources of scientific, governmental, indigenous and local knowledge; has been improved by more than 7,300 comments from 200 external evaluators, and has been peer reviewed.

The Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services ( IPBES ) is the equivalent of the IPCC for biodiversity. IPBES has 129 Member States.

According to this report, the aggravation of soil degradation caused by human activities affects the welfare of 2/5 of humanity , or at least 3.2 billion people, also leading to the extinction of species and intensifying climate change. It is also an important factor of massive human migration and increased conflict.

" The degradation of the Earth's surface by human activities is pushing the planet towards a massive sixth extinction of species, " said Professor Robert Scholes (South Africa), chair of the evaluation with Dr. Luca Montanarella (Italy), who " Avoiding, reducing and reversing this problem, and restoring degraded lands, is an urgent priority to protect biodiversity and vital ecosystem services for all life on Earth and to ensure human well-being ".

" The wetlands have been particularly affected, " said Dr. Montanarella. " We have seen 87% losses in wetlands since the beginning of the modern era - with 54% losses since 1900 ". The loss of biodiversity is expected to reach 38 to 46% by 2050.

In the natural state, 80% of the land mass biomass is contained in soils. Earthworms alone represent 1 to 4 t / ha. Today, intensively cultivated soils do not contain more than 200 kg of biomass per hectare and even only 50 kg / ha.

Land degradation exacerbates climate change

The IPBES report finds that soil degradation is a major contributor to climate change , with deforestation alone contributing about 10% of all anthropogenic greenhouse gas emissions. Another important factor of climate change is the release of carbon previously stored in the soil. Thus, soil degradation between 2000 and 2009 resulted in the emission of 3.6 to 4.4 billion tonnes of CO2 per year, which is about 10% of current global CO2 emissions .

"Without urgent action," says the report, 36 gigatonnes of carbon from land - particularly in sub-Saharan Africa - will be released into the atmosphere, equivalent to 20 years of global transportation emissions! Major processes include deforestation and forest degradation, dewatering and burning of peatlands, and declining carbon content in many soils and pastures under cultivation due to excessive disturbance and insufficient return of organic matter to the soil .

Finally, the economic cost is enormous : around 10% of the global annual gross product in 2010 through the loss of biodiversity and ecosystem services.

Why are soils degrading?

No need to invoke any curse, it is still the unsustainable pressure of human activities coupled with rampant demography, which defile our support of life. The overconsumption society as a model of development is materialized by the rapid expansion, the unsustainable management of cultivated land and the multiplication of pastures for livestock farming. In addition, extraction of natural and mineral resources and urbanization generally result in even higher levels of land degradation irreversibly.

For example, in 2014, more than 1.5 billion hectares of natural ecosystems were converted into cultivated land whose biodiversity is very poor as evidenced by the disappearance of birds from the French countryside . To date, the main drivers of biodiversity loss are: agriculture followed by forestry, infrastructure installation, urban sprawl and climate change.

Cultivated land and pastures now cover more than a third of the earth's surface, with recent clearing of native habitats, including forests, grasslands and wetlands, concentrated in some of the world's most the planet.

What options for soil restoration?

While the report makes a dramatic assessment of the situation, he notes that there are successful examples of land restoration in all ecosystems, and that many proven traditional and modern practices and techniques can avoid or reverse degradation.

In cropland, for example, some of these include reduced soil loss and improved soil health, the use of salt-tolerant crops, conservation agriculture and integrated cropping systems. , breeding and forestry.
In pastures where traditional grazing is practiced, the maintenance of appropriate fire regimes and the reestablishment or development of local livestock management practices and institutions have proven effective.
Successful interventions in wetlands included control of pollution sources, management of wetlands in the landscape, and reforestation of wetlands damaged by drainage.
In urban areas, urban planning, the replanting of native species, the development of green infrastructure such as parks and waterways, the remediation of contaminated and impervious soils (under asphalt), the treatment of wastewater and re-entry. 

What should encourage soil restoration is that the costs involved are much lower than the benefits gained. On average, the benefits of restoration are 10 times higher than the costs (estimated for nine different biomes ) and, for regions such as Asia and Africa, the cost of inaction to land degradation is at least three times the cost of action, says the report.

2050: the "nightmare scenario"

The report's projections are part of the "nightmare scenario": " about 4 billion people will be living in arid zones ," said Professor Scholes. " By then, it is likely that land degradation, coupled with the interrelated problems of climate change, will have forced 50-700 million people to emigrate." Declining land productivity also makes societies more vulnerable to climate change. social instability - especially in arid areas, where years of extremely low rainfall have been associated with a 45% increase in violent conflict. "In 2010, 2.7 billion people were already living in arid areas.

Mr. Montanarella added: " By 2050, the combination of land degradation and climate change is expected to reduce global agricultural yields by 10 percent on average and by 50 percent in some regions. much of the degradation will occur in Central and South America, sub-Saharan Africa, and Asia, where there is still the most suitable land for agriculture. "

Finally, the growing demand for food and biofuels is likely to lead to a steady increase in nutrient and chemical inputs to cultivated areas and a shift towards industrialized animal production systems. Therefore, the use of pesticides and fertilizers is expected to double by 2050.

Unless humanity finally realizes the urgency of a dietary transition to diets that favor more vegetables and less animal protein , while reducing food waste .

" Land degradation, biodiversity loss and climate change are three different faces of the same central challenge: the increasingly dangerous impact of our choices on the health of our natural environment." We can not afford to tackle in isolation to any of these three threats - each deserves the highest political priority and must be addressed together, "said Sir Robert Watson, Chair of IPBES.

Source: https://www.notre-planete.info/actualites/522-degradation-sols-biodiversite-changement-climatique-conflits

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