The world's soils are rapidly deteriorating due to erosion, nutrient depletion, loss of organic carbon, soil sealing, and other threats, but this trend can be reversed as long as countries take the lead in promoting practices. sustainable management and the use of appropriate technologies, according to a new UN report released today.
The State of the World's Soil Resources, prepared by the FAO Intergovernmental Technical Group on Soils, brings together the work of some 200 soil scientists from 60 countries. Its publication coincides with World Soil Day -which is celebrated on December 4- and also with the closure of the UN's International Year of Soils 2015, an initiative that has served to raise awareness worldwide about the so-called “silent ally of humanity ”.
“Let us promote sustainable soil management based on adequate governance and rational investments. Together we can advance the cause of soils, which constitute a truly solid foundation for life, ”said UN Secretary-General Ban Ki-moon in a message on the occasion of World Soil Day.
Soils are of vital importance for the production of nutritious crops, filtering and cleaning tens of thousands of km3 of water each year. As an important store of carbon, soils also help regulate emissions of carbon dioxide and other greenhouse gases, thus being essential for regulating the climate.
However, the overwhelming conclusion of the report is that most of the world's soil resources are in poor or very poor condition and that conditions are worsening in many more cases than they are improving. In particular, 33 percent of the land is moderately to highly degraded due to erosion, salinization, compaction, acidification, and chemical contamination of soils.
“New losses of productive soils would seriously damage food production and food security, increasing food price volatility, and potentially plunging millions of people into hunger and poverty. But the report also offers evidence that this loss of resources and soil functions can be avoided, ”said FAO Director-General José Graziano da Silva.
In his foreword to the 650-page report, Graziano da Silva expressed the conviction that the content “will go a long way in galvanizing action at all levels towards more sustainable soil management,” adding that this was in line with the commitment of the international community to achieve the Sustainable Development Goals.
Impact of population growth, urbanization and climate change
Changes in the state of soils are driven mainly by population growth and economic growth, factors that are expected to persist in the coming decades.
The report points to the need to feed a world population that has grown today to about 7.3 billion people, and that more than 35 percent of the planet's ice-free land area has been used for agriculture. The result is that soils that have been cleared of natural vegetation for cultivation or grazing of livestock suffer strong increases in erosion and large losses of soil carbon, nutrients, and biodiversity.
Furthermore, urbanization is causing a high price to be paid. The rapid growth of cities and industries has degraded ever larger areas, with the contamination of soils with excess salt, acidity and heavy metals; compaction with heavy machinery; and permanently sealed under asphalt and cement.
Climate change - which is currently the focus of the UN COP21 conference in Paris - is an important additional reason for soil transformation, according to the report.
Higher temperatures and related extreme weather events, such as droughts, floods, and storms, impact soil quantity and fertility in a number of ways, including reducing moisture and depleting nutrient-rich topsoils. They also contribute to an increase in the rate of soil erosion and the retreat of coasts.
Achieve healthy soils
The report focuses on the top 10 threats to soil functions: erosion, loss of organic carbon, nutrient imbalance, soil acidification, pollution, waterlogging, soil compaction, sealing, salinization, and loss of soil biodiversity.
It is also explained that there is a general consensus on soil-related strategies that can, on the one hand, increase the food supply, and on the other, minimize harmful environmental impacts.
The proposed solution is one that focuses on sustainable soil management and requires the high involvement of stakeholders, ranging from governments to small farmers.
Erosion, for example, can be contained by reducing or eliminating tillage - digging, removing, and turning the soil - and using crop residues to protect the soil surface from the effects of rain and wind. . Similarly, nutrient-deficient soils can be restored and yields increased by returning crop residues and other organic materials to the soil, employing crop rotation with nitrogen-fixing crops, and making judicious use of nutrients. organic and mineral fertilizers.
The report identifies four priorities for action:
- Minimize further degradation of soils and restore the productivity of soils that are already degraded in regions where people are most vulnerable;
- Stabilize the world's reserves of soil organic matter, including both soil organic carbon and soil organisms;
- Stabilize or reduce world consumption of nitrogen and phosphorous fertilizers, in addition to increasing the use of fertilizers in nutrient-deficient regions; Y,
- Improve our knowledge about the state and trend of soil conditions.
- These actions need to be supported by well-targeted policies, including:
- Support for the development of soil information systems to monitor and forecast soil changes;
- Increased education and awareness in the field of soil, integrating it into formal education and study plans: from geology to geography and from biology to economics;
- Investment in research development and extension, to develop tests, disseminate sustainable soil management technologies and practices;
- Introduction of appropriate and effective regulation and incentives. This could include taxes that discourage harmful practices, such as the excessive use of fertilizers, herbicides, and pesticides. Zoning systems can be used to protect the best agricultural land from urban sprawl. Subsidies can encourage people to buy tools and other inputs that have a less damaging impact on soils, while certification of sustainable farming and ranching practices can lead to more commercially attractive and higher priced products;
- Support for the achievement of food security at the local, regional and international levels, taking into account the soil resources of the countries and their capacity to manage them sustainably.
Some of the main findings of the report:
Erosion removes 25 to 40 billion tonnes of topsoil each year, significantly reducing crop yields and the soil's ability to store and cycle carbon, nutrients, and water. Annual losses in cereal production due to erosion are estimated at 7.6 million tonnes. If no action is taken to reduce erosion, projections indicate a production reduction of more than 253 million tonnes by 2050. This loss of yield would be equivalent to removing 1.5 million square kilometers of agricultural land, or roughly all of the arable land in India.
Lack of soil nutrients is the greatest obstacle to improving food production and soil function in many degraded landscapes. All but three countries in Africa extract more nutrients from the soil each year than are returned through the use of fertilizers, crop residues, manure and other organic matter.
The accumulation of salts in the soil reduces the yield of crops and can completely eliminate agricultural production. Salinization caused by human activity affects some 760,000 square kilometers of land worldwide: an area larger than the entire arable area in Brazil.
Soil acidity is a serious obstacle to food production around the world. The most acidic arable layers in the world are found in areas of South America that have suffered from deforestation and intensive agriculture.