Soil Degradation

Primary reference(s)

FAO, 2020. FAO Soils Portal Key definitions. Food and Agricultural Organization of the United Nations (FAO). Accessed 19 October 2020.

Additional scientific description

Soil degradation consists of biological, chemical and physical degradation. Currently, about 33% of world soils are moderately to highly degraded. Forty percent of these degraded soils are located in Africa and most of the rest are in areas that are afflicted by poverty and food insecurity. The strong relationship between soil health and food security calls for strategic and immediate actions, especially at the local level, to reverse soil degradation in order to increase food production and alleviate food insecurity in the areas where it is most needed and in the context of climate change (FAO, 2015).

Soil is an essential component of ‘land’ and ‘ecosystems’ that both are broader concepts encompassing vegetation, water and climate in the case of land, and in addition to those three aspects, also social and economic considerations in the case of ecosystems. Degraded soils have a health status such that they do not provide the normal goods and services of the particular soil in its ecosystem (FAO, 2020a).

Soil degradation is the decline in soil condition caused by its improper use or poor management, usually for agricultural, industrial or urban purposes. It is a serious environmental issue. Soils are a fundamental natural resource and are the basis for all terrestrial life. Avoiding soil degradation is crucial to our well-being (NSW Department of Planning, Industry and Environment, 2019).

Soil degradation is the physical, chemical and biological decline in soil quality. It can be the loss of organic matter, decline in soil fertility, and structural condition, erosion, adverse changes in salinity, acidity or alkalinity, and the effects of toxic chemicals, pollutants or excessive flooding. Soil degradation can involve: water erosion (includes sheet, rill and gully erosion); wind erosion; salinity (includes dryland, irrigation and urban salinity); loss of organic matter; fertility decline; soil acidity or alkalinity; structure decline (includes soil compaction and surface sealing); mass movement; and soil contamination (NSW Department of Planning, Industry and Environment, 2019).

Metrics and numeric limits

12 million hectares of agricultural soils are lost globally through soil degradation every year. Soils with soil organic matter content lower than 0.8% are unproductive and often abandoned. Agroforestry systems can reduce soil erosion by as much as 100 times in steep slopes. Growing Faidherbia albida in association with millet (Pennisetum glaucum) increased grain yields by 50% in Burkina Faso and Senegal. In Honduras the adoption of soil conservation practices tripled or quadrupled maize yields for 1200 families (FAO, 2015).

Examples of drivers, outcomes and risk management

The United Nations Environment Assembly during the Third Session in 2017 acknowledged that soils, which contain the second largest active carbon stock (the first being the oceans), are an essential element for climate change mitigation and resilience, and that land pollution leads to a reduction in soil biological activity and is therefore a factor contributing to the reduction of its capacity to act as a carbon sink (UNEP, 2018).

Agroecology is part of the Strategic Framework of the Food and Agricultural Organization of the United Nations (FAO), in particular the Strategic Objectives of making agriculture, forestry and fisheries more productive and sustainable, increasing the resilience of livelihoods and reducing rural poverty (FAO, 2015).

The agroecological approach starts by restoring soil life in order to re-establish and/or enhance the multiple soil-based biological processes. This requires (FAO, 2015):

• Increasing and monitoring soil organic matter: Soil organic matter is considered the most common deficiency in degraded soils and the main indicator for soil quality. Practical, accessible indicators can support local decisions and larger landscape monitoring and analyses for district level implementation.
• Facilitating and monitoring of soil biodiversity: Soil biological communities are directly responsible for multiple ecosystem functions.
• Building on local farmers’ knowledge: Participatory scientific approaches to soil ecosystem management, such as Farmer Field Schools, are of great importance to inform farmers’ knowledge with researchers’ scientific principles in order better locally adapt agroecological systems.

The FAO and its Global Soil Partnership launched a new programme to boost soil productivity and reduce soil degradation for greater food and nutrition security in Africa. The Afrisoils programme aims to increase soil productivity in 47 African countries by 30% and reduce soil degradation by 25% in the next ten years (FAO, 2018).