Land Degradation, Desertification, and Forest Loss

Land degradation is the decline in the biological or economic productivity of land caused by human activity and climate, desertification is its form in dry regions, and forest loss is the reduction in forest area through clearing and degradation; together, they threaten food production, water supplies, biodiversity and climate stability. In brief: the UN Convention to Combat Desertification (UNCCD) estimates that up to 40% of the world’s land is degraded, and that the lives of billions of people are affected. The world’s forests cover about 4.06 billion hectares (31% of the land area), and deforestation continues at about 10 million hectares a year, partly offset by new growth and planting, giving a net loss of around 5 million hectares a year in the 2010s.

Sustainable land management is central to the Sustainable Development Goals, in particular the target of “land degradation neutrality” by 2030. This guide explains the main causes and consequences of land degradation and forest loss, examples from around the world, restoration and policy responses, compares the processes in a table, works through calculations, outlines the history and corrects common mistakes.

What is land degradation and what causes it?

Land degradation covers several processes: soil erosion by water and wind, loss of nutrients and organic matter, compaction, salinization and waterlogging from poor irrigation, pollution, loss of vegetation cover and the loss of biodiversity. The direct causes include unsustainable farming (overcultivation, no crop rotation, plowing steep slopes), overgrazing, deforestation, mining and construction, urban expansion over fertile land and water mismanagement. Underlying drivers are population growth, poverty, insecure land rights, market pressures and weak policies, while climate change and extreme weather make land more vulnerable. The Aral Sea is an example of large-scale degradation caused by water diversion. Degradation reduces yields and income, increases costs for fertilizer and irrigation, and can lead to hunger and displacement of people. Since degraded soil stores less carbon, it also adds to climate change.

What is desertification?

The UNCCD defines desertification as land degradation in arid, semi-arid and dry sub-humid areas, caused by climate variability and human activities. It does not mean the advance of existing deserts, but the creation of desert-like conditions where the land loses its productive capacity. Drylands cover about 40% of the land surface and are home to roughly a third of the world’s people, many of them poor and dependent on farming and herding. According to UNCCD, around 12 million hectares of productive land are lost each year to drought and desertification. Regions at risk include the Sahel, Central Asia, northern China, the Middle East, parts of the Mediterranean, southern Africa and Australia. Responses include the “Great Green Wall” initiative of the African Union to restore land across the Sahel, which began in 2007 and has aimed to restore 100 million hectares, though progress has been slower than planned.

How and why are forests lost?

According to the FAO’s Global Forest Resources Assessment, forests cover 4.06 billion hectares, about 31% of the land. The area of deforestation (conversion of forest to other uses) was around 10 million hectares per year in 2015–2020, and the net loss, after taking into account regrowth and plantations, was about 4.7 million hectares per year in 2010–2020. Loss has been highest in Africa and South America. The main driver is agriculture: about 90% of deforestation is linked to the expansion of cropland and grazing, with cattle ranching, soybeans and oil palm leading. Other causes are logging, fuelwood and charcoal, mining, infrastructure and fires, including peat fires in Indonesia. Forest degradation, a decline in the quality of forest without complete clearance, from selective logging, fires and fragmentation, is also widespread.

Consequences include loss of biodiversity, reduced carbon storage and release of emissions, soil erosion and landslides, changes in rainfall and local climate, loss of livelihoods for forest-dependent people (including many Indigenous groups), and increased risk of floods and of diseases that jump from wildlife to people. Contrasts can be striking: on the island of Hispaniola, Haiti has lost most of its forest, while the Dominican Republic has retained a much larger forest cover, though causes include both policy and poverty.

What can be done?

• Sustainable land management: crop rotation, cover crops, agroforestry, terraces, no-till, planned grazing and water-saving irrigation.
• Restoration: large programs such as the restoration of the Loess Plateau in China (starting in 1994), which stopped severe erosion and raised farmers’ incomes, and the Bonn Challenge, which aims to restore 350 million hectares of degraded land by 2030. Farmer-managed natural regeneration in Niger has re-greened millions of hectares.
• Protecting forests: protected areas, secure land rights for Indigenous and local communities, enforcement against illegal logging, supply-chain rules (such as the EU regulation on deforestation-free products) and payments for forest protection (REDD+).
• Land use planning: directing development to already degraded land and keeping fertile soil and forests intact.
• Monitoring: satellites, such as Landsat and Sentinel, and systems like Global Forest Watch give near real-time information on forest loss.
• Policy goals: SDG target 15.3 aims for a “land degradation-neutral world” by 2030, which means that any loss of healthy land is balanced by restoration elsewhere.

The processes compared

Worked example: areas, rates and neutrality

The values are approximate or hypothetical and illustrate common calculations.

1. Forest share: forests cover 4.06 billion hectares of a land area of about 13.0 billion hectares. The share is 4.06 ÷ 13.0 = 31%.
2. Net forest loss: if deforestation is 10 million hectares a year and new forest growth (natural expansion and planting) adds 5.3 million, the net loss is 10 − 5.3 = 4.7 million hectares a year.
3. Loss over a decade: 4.7 million × 10 = 47 million hectares, an area larger than Sweden (about 45 million hectares) and 47 ÷ 4,060 = 1.2% of the world’s forest.
4. Degraded land: if 40% of 13.0 billion hectares of land is degraded, the area is 0.40 × 13.0 = 5.2 billion hectares. To restore 350 million hectares, as the Bonn Challenge aims, is 350 ÷ 5,200 = 6.7% of this area.
5. Land degradation neutrality: in a country, 800,000 hectares are degraded in a decade, and 500,000 hectares are restored. The net change is 500,000 − 800,000 = −300,000 hectares, so the country is not neutral. It would need to restore a further 300,000 hectares or avoid losing the same amount.
6. Carbon in restored land: restoring 100,000 hectares of degraded land with trees that store 4 tonnes of carbon per hectare per year captures 100,000 × 4 = 400,000 tonnes of carbon a year, or 400,000 × 3.67 = about 1.47 million tonnes of CO₂.

How has the response developed?

The Dust Bowl of the 1930s in the United States led to the first national soil conservation programs. The severe drought in the Sahel in the late 1960s and early 1970s, which caused famine, brought desertification to world attention, and the UN held a Conference on Desertification in 1977. At the Rio Earth Summit in 1992, countries agreed to negotiate a convention, and the UNCCD was adopted in 1994 and entered into force in 1996. Concern about forest loss, especially in the Amazon, grew from the 1970s and 1980s, and policy tools such as REDD+ were developed in the 2000s. In 2021, over 140 countries pledged at COP26 to end and reverse forest loss by 2030, and the UN Decade on Ecosystem Restoration runs from 2021 to 2030. The use of satellites has made monitoring much more accurate.

Which mistakes are common?

Mistake 1: Thinking that net forest loss equals deforestation

Net loss subtracts forest growth and planting. The gross loss from clearing is larger, and newly grown forests rarely have the same biodiversity as old ones.

Mistake 2: Equating land degradation with desertification

Degradation occurs everywhere, including humid regions. Desertification is the form that occurs in drylands.

Mistake 3: Assuming that cleared forest can easily be restored

Natural forests take decades or centuries to recover, and restoration needs suitable soil, water and protection from renewed clearance.

Mistake 4: Blaming only local farmers

Much forest loss is driven by distant markets, investors and policies, so solutions must include supply chains and governments.