Land degradation

Serious land degradation in Nauru after the depletion of the phosphate cover through mining

Land degradation is a process in which the value of a biophysical or biochemical environment is affected by a combination of natural or human-induced processes acting upon the land. It is viewed as any change or disturbance to the land perceived to be deleterious or undesirable. Natural hazards are excluded as a cause; however human activities can indirectly affect phenomena such as floods and bush fires.

Expert projections suggest that land degradation will be an important theme of the 21st century, impacting agricultural productivity, biodiversity loss, environmental change, and its effects on food security. It is estimated that up to 40% of the world's agricultural land is seriously degraded.

Scale

According to the Special Report on Climate Change and Land of the Intergovernmental Panel on Climate Change, "About a quarter of the Earth's ice-free land area is subject to human-induced degradation (medium confidence). Soil erosion from agricultural fields is estimated to be currently 11 to 20 times (no-tillage) to more than 100 times (conventional tillage) higher than the soil formation rate (medium confidence)."

The United Nations estimate that about 30% of land is degraded worldwide, and about 3.2 billion people reside in these degrading areas, giving a high rate of environmental pollution. About 12 million hectares of productive land—which roughly equals the size of Greece—is degraded every year. This happens because people exploit the land without protecting it. The United Nations Sustainable Development Goal 15 has a target to restore degraded land and soil and achieve a land degradation-neutral world by 2030.

Types

Potato field with soil erosion

In addition to the usual types of land degradation that have been known for centuries (water, wind and mechanical erosion, physical, chemical and biological degradation), four other types have emerged in the last 50 years:

• pollution, often chemical, due to agricultural, industrial, mining or commercial activities;
• loss of arable land due to urban construction, road building, land conversion, agricultural expansion, etc.;
• artificial radioactivity, sometimes accidental;
• land-use constraints associated with armed conflicts.

Overall, more than 36 types of land degradation can be assessed. All are induced or aggravated by human activities, e.g. soil erosion, soil contamination, soil acidification, sheet erosion, silting, aridification, salinization, urbanization, etc.

A problem with defining land degradation is that what one group of people might view as degradation, others might view as a benefit or opportunity. For example, planting crops at a location with heavy rainfall and steep slopes would create scientific and environmental concern regarding the risk of soil erosion by water, yet farmers could view the location as a favourable one for high crop yields.

Causes

The rate of global tree cover loss has approximately doubled since 2001, to an annual loss approaching an area the size of Italy.

Overgrazing by livestock can lead to land degradation.

Land degradation is mainly derived by numerous, complex, and interrelated anthropogenic and/or natural proximate and underlying causes. For example, in Ethiopia the country has been affected by chronic and ongoing land degradation processes and forms. The major proximate drivers are biophysical factors and unsustainable land management practices, while the underlying drivers are social, economic, and institutional factors.

Land degradation is a global problem largely related to the agricultural sector, general deforestation and climate change. Causes include:

• Land clearance, such as clearcutting, overlogging and deforestation
• Agricultural activities such as:
  • Activities that lead to depletion of soil nutrients through poor farming practices such as exposure of naked soil after crop harvesting;
  • Monocultures which destabilize the local ecosystem;
  • Poor livestock farming practices such as overgrazing (the grazing of natural pastures at stocking intensities above the livestock carrying capacity);
  • Inappropriate irrigation
• Climate change because it can "exacerbate land degradation, particularly in low-lying coastal areas, river deltas, drylands and in permafrost areas"

Soil erosion in a wheat field near Pullman, US

High population density is not always related to land degradation. Rather, it is the practices of the human population that can cause a landscape to become degraded.

Severe land degradation affects a significant portion of the Earth's arable lands, decreasing the wealth and economic development of nations. As the land resource base becomes less productive, food security is compromised and competition for dwindling resources increases, the seeds of famine and potential conflict are sown.

Climate change and land degradation

According to the Special Report on Climate Change and Land of the Intergovernmental Panel on Climate Change (IPCC) climate change is one of the causes of land degradation. The report state that: "Climate change exacerbates land degradation, particularly in low-lying coastal areas, river deltas, drylands and in permafrost areas (high confidence). Over the period 1961–2013, the annual area of drylands in drought has increased, on average by slightly more than 1% per year, with large inter-annual variability. In 2015, about 500 (380–620) million people lived within areas which experienced desertification between the year 1980s and 2000s. The highest numbers of people affected are in South and East Asia, the circum Sahara region including North Africa, and the Middle East including the Arabian Peninsula (low confidence). Other dryland regions have also experienced desertification. People living in already degraded or desertified areas are increasingly negatively affected by climate change (high confidence)." Additionally, it is reported that 74% of the poor are directly affected by land degradation globally.

Significant land degradation from seawater inundation, particularly in river deltas and on low-lying islands, is a potential hazard that was identified in a 2007 IPCC report.

As a result of sea-level rise from climate change, salinity levels can reach levels where agriculture becomes impossible in very low-lying areas.

In 2009 the European Investment Bank agreed to invest up to $45 million in the Land Degradation Neutrality Fund (LDN Fund). Launched at UNCCD COP 13 in 2017, the LDN Fund invests in projects that generate environmental benefits, socio-economic benefits, and financial returns for investors. The Fund was initially capitalized at US$100 million and is expected to grow to US$300 million.

In the 2022 IPCC report, land degradation is responding more directly to climate change as all types of erosion and SOM declines (soil focus) are increasing. Other land degradation pressures are also being caused by human pressures like managed ecosystems. These systems include human run croplands and pastures.

Consequences

Land degradation takes many forms and affects water and land resources. It can diminish the natural capacity of the land to store and filter water leading to water scarcity.

The results of land degradation are significant and complex. They include lower crop yields, less diverse ecosystems, more vulnerability to natural disasters like floods and droughts, people losing their homes, less food available, and economic problems. Degraded land also releases greenhouse gases, making climate change worse.

Further possible impacts include:

1. A temporary or permanent decline in the productive capacity of the land. This can be seen through a loss of biomass, a loss of actual productivity or in potential productivity, or a loss or change in vegetative cover and soil nutrients.
2. Loss of biodiversity: A loss of range of species or ecosystem complexity as a decline in the environmental quality.
3. Increased vulnerability of the environment or people to destruction or crisis.

Sensitivity and resilience

Sensitivity and resilience are measures of the vulnerability of a landscape to degradation. These two factors combine to explain the degree of vulnerability. Sensitivity is the degree to which a land system undergoes change due to natural forces, human intervention or a combination of both. Resilience is the ability of a landscape to absorb change, without significantly altering the relationship between the relative importance and numbers of individuals and species that compose the community. It also refers to the ability of the region to return to its original state after being changed in some way. The resilience of a landscape can be increased or decreased through human interaction based upon different methods of land-use management. Land that is degraded becomes less resilient than undegraded land, which can lead to even further degradation through shocks to the landscape.

Prevention

Sustainable land management

Further information: Land management

Actions to halt land degradation can be broadly classified as prevention, mitigation, and restoration interventions.

Sustainable land management has been proven in reversing land degradation. It also ensures water security by increasing soil moisture availability, decreasing surface runoff, decreasing soil erosion, leading to an increased infiltration, and decreased flood discharge.

Public awareness and education

Increasing public awareness about the importance of land conservation, sustainable land management, and the consequences of land degradation is vital for fostering behavioral change and mobilizing support for action. Education, outreach campaigns, and knowledge-sharing platforms can empower individuals, communities, and stakeholders to adopt more sustainable practices and become stewards of the land.

See also

• Environmental impact of irrigation
• Land improvement
• Land reclamation
• Sustainable agriculture
• Economics of Land Degradation Initiative
• Desertification
• Population growth
• Soil § Degradation
• Tillage erosion