Land Degradation and Desertification -
Land provides the principal basis of human well-being and livelihood. Soil supports tremendous biodiversity and provides ecosystem services like food production, carbon sequestration, decomposition of organic matter and biogeochemical cycling (like carbon, nitrogen, oxygen, phosphorous etc). It helps in water infiltration into the groundwater aquifers and plays an important role in hydrological cycling. Soil is a massive carbon sink and thus, plays an important role in the climate system.
The pressures on global land resources are tremendous in the present times. Rapid population growth and rising consumption levels are placing greater demands on the world’s land-based natural capital.
Major pressures on land include:
Changes in Land Use - Conversion of natural ecosystems like forests to other uses like agriculture expansion, urbanisation, mining etc.
Land Use Intensification - To meet the food demands of increasing human population and consumption, land use intensification in agriculture has happened.
Unsustainable Land Use Practices - In the form of over-application of chemical fertilisers; over-irrigation by groundwater to meet the food security demands of the human population.
Land Degradation is defined as a persistent reduction in the capacity of land to support biodiversity, ecosystem services and human needs. The process of land degradation is gradual. The significant symptoms of land degradation are long-term reduction or loss in biological productivity, ecological integrity or value to humans.
Desertification is land degradation in arid and semi-arid areas caused by human activities and climatic changes. Desertification is therefore, the deterioration of land in arid, semi-arid and dry sub-humid regions (also called dryland) of the world due to climatic variations and human activities.
It occurs slowly, as different areas of degraded land spread and merge, rather than through advancing deserts. It is a slowly but progressing ‘skin disease’ over the planet.
Major Types of Land Degradation -
Soil Erosion - Loss of top cover of the soil either by the action of wind, water or gravity.
Soil Salinisation - Saline and alkaline encrustations consisting of sodium, potassium and magnesium salts appear on the top layers of the soil through capillary action.
Soil Acidification - Excessive build-up of hydrogen or aluminium cations in soil due to long-term rainfall or acid deposition due to mining activities.
Soil Pollution - Presence of chemicals in soils that are either out of place or higher than normal concentrations.
Land degradation is a problem that affects all regions, not only the drylands and developing countries. Drylands are more vulnerable to natural and human destruction due to the small water containment in soil.
One-fifth of the world’s population is threatened by the impacts of global desertification. Its effects can be seen all over the world, in Asia, Africa, Latin America, throughout North America, and along the Mediterranean. Cultivable land per person is shrinking throughout the world, threatening food security, particularly in poor rural areas, and triggering humanitarian and economic crises.
Causes of Land Degradation
Major causes of land degradation include both natural and human-induced causes. These include the following:
Climate Change - Climate change acts as a threat multiplier for land degradation in the following ways:
Global warming has resulted in an increased frequency, intensity and duration of heat waves globally. In dryland areas, heat waves increase evapotranspiration and decrease precipitation, thus contributing to desertification. These areas include Sub-Saharan Africa, the Mediterranean, parts of East and Central Asia and Australia.
Extreme heat events and moisture stresses can trigger wildfires thus causing land degradation. Future climatic variability can cause wildfires even in tropical rainforest biomes.
Climate change has increased the frequency and intensity of droughts in regions like north-eastern Brazil, Patagonia, most of Africa, north-eastern China and the Mediterranean. Droughts act as a trigger for desertification.
Deforestation - With an increased demand for land for multiple purposes, the incidence of deforestation has increased. Forests actively prevent soil erosion, which has been considered the biggest cause of land degradation.
Overgrazing by Cattle - On marginal lands, rainfall is just barely enough to enable land to produce more vegetation than a desert. In such regions, even light grazing by cattle can be too much grazing which causes soil erosion.
Prolonged Droughts - Long droughts are one of the major reasons for land degradation globally. That’s why land degradation is most pervasive in the arid, semi-arid and dry sub-humid regions of the world which receive lesser rainfall (less than 100cm) and are drought-prone regions of the world. Such lands are called marginal lands where rainfall is insufficient to support crops over the long term.
Human Abuse of Lands - The atmosphere is continuously warming due to uncontrolled emission of industrial fumes and carbon dioxide which ultimately bring about climatic changes locally. Forests that control and moderate the climate are being abolished at an alarmingly fast rate. Marginal lands have been cultivated to such an extent that they have lost their fertility. Grasslands have been grazed to death and the mismanagement of farmlands has converted them into either dust bowls or saline wastes.
Wrong Agricultural process - A few examples of bad farming practices include:
Over-irrigation in arid and semi-arid areas causes soil salinisation. When irrigation water evaporates, it leaves behind salt residue. In drier regions like arid and semi-arid regions of the world, the evaporation rates are high and rainfall is insufficient to leach down the soluble salts. Therefore, these regions are more susceptible to soil salinisation-induced land degradation.
Excessive use of chemicals like chemical fertilisers, pesticides etc. which can chemically poison the soil.
Disposal of Industrial Wastes on Land - Improper disposal of toxic chemicals from industries can contaminate the soil. This is one of the major causes of land degradation due to human activities worldwide.
Consequences of Land Degradation and Desertification -
Degraded lands offer little economic value or biological productivity. More than 1.5 billion people in the world depend on degrading land, and 74% of them are poor. More than 160 countries have declared they are affected by desertification. Major consequences of land degradation and desertification are felt both across natural and human systems.
The impacts of land degradation and desertification on natural systems are -
Climate Change - Land acts both as a carbon sink and a carbon source. It is a carbon sink as it absorbs carbon dioxide during photosynthesis. However, when the decomposition of dead organic matter takes place in soils, land emits greenhouse gases.
Climate change exacerbates land degradation. Degraded lands have a compromised ability to support vegetative growth and therefore, reduced ability to act as a carbon sink. Between 2000 and 2009, land degradation was responsible for annual global emissions of 3.6 - 4.4 billion tons of carbon dioxide.
Biodiversity Loss and Loss of Ecosystem Services - land degradation makes soil less fertile. This reduces the vegetative cover over the soil. In turn, the floral and faunal species diversity also declines.
Any decline in biological diversity negatively affects ecosystem services as well. For example, degraded soils have poor water infiltration through them which reduces the recharge of groundwater aquifers. Similarly, the carbon sequestration capacity of such soils declines considerably. This exacerbates the existing climate change.
As per Land Degradation and Restoration Assessment by IPBES (June 2018), land degradation has already had a pronounced impact on ecosystem functions worldwide amounting to a 5% reduction in total global net primary productivity. It costs more than 10% of the annual global gross product in loss of biodiversity and ecosystem services.
The impact of land degradation and desertification on human systems are-
Threats to Food Security and Livelihood Loss - Land degradation is potent to disrupt agricultural food production and threaten food security. As per the UN, by 2050, global food production would need to increase by 50% to feed the more than 9 billion people expected to live on our planet. However, it becomes challenging as land degradation and climate change together are predicted to reduce crop yields by an average of 10% globally.
Degraded lands also mean livelihood loss for the poorer sections like farmers and pastoralists. They are dependent on ecosystem services and natural capital for their sustenance.
Increased Conflicts and Forced Displacement - In dryland areas, food insecurity and loss of livelihood exacerbate poverty. This often results in resource-driven conflicts. As per the UN, every 5% loss of gross domestic product, itself partly caused by degradation, is associated with a 12% increase in the likelihood of violent conflict. Land degradation and climate change are likely to force 50 to 700 million people to migrate by 2050.
How does Climate Change Cause Land Degradation?
Climate change acts as a threat multiplier for land degradation in the following ways:
- Climate change has increased the frequency and intensity of droughts in regions like north-eastern Brazil, Patagonia, most of Africa, north-eastern China and the Mediterranean. Droughts act as a trigger for desertification.
- Global warming has resulted in an increased frequency, intensity and duration of heat waves globally. In dryland areas, heat waves increase evapotranspiration and decrease precipitation, thus contributing to desertification. These areas include Sub-Saharan Africa, the Mediterranean, parts of East and Central Asia and Australia.
- Extreme heat events and moisture stresses can trigger wildfires thus causing land degradation. Future climatic variability can cause wildfires even in tropical rainforest biomes.
- As rainfall patterns change with climate change, it can drive changes in vegetation cover too. For example, reduced rainfall over a region can reduce vegetation cover. Soils with reduced vegetation cover are more prone to soil erosion-induced degradation.
- Warmer temperatures globally are causing permafrost thawing in the Arctic region. This means that ice inside the permafrost is melting, leaving behind water and soil. Soils become unstable leading to landslides and floods.
- Climate change can exacerbate land degradation in low-lying coastal areas and river deltas due to sea level rise. Sea level rise increases the coastal erosion and intrusion of brackish seawater inland causing land degradation.
Sustainable Land Management
Sustainable Land Management (SLM) was defined by the UN 1992 Rio Earth Summit as “the use of land resources, including soils, water, animals and plants, for the production of goods to meet changing human needs, while simultaneously ensuring the long-term productive potential of these resources and the maintenance of their environmental functions”.
SLM practices address the degradation of water, soil and vegetation, as well as the emission of Greenhouse Gases that contribute to climate change. It aims to simultaneously conserve natural resources, reduce emissions and store carbon.
Examples of SLM Include:
- Application of organic fertilisers to agricultural fields- It enhances productivity by increasing the level of organic matter in the soil(humus). Humus stimulates soil biological activity and improves soil structure, water infiltration and retention and nutrient storage. The most commonly used organic fertilisers include compost using animal manure with household waste.
- Afforestation, Reforestation, ShelterBelts - All these prevent soil erosion as the roots of the trees bind the soil particles together. Vegetative growth over soil also adds organic matter to the soil which makes it more fertile.
- Mulching - Mulching involves spreading waste crops after harvesting. Covering the soil with mulch protects it against wind and water erosion and provides nutrients that have a positive effect on yields and food security. Mulching also helps to improve the infiltration of water and reduce the evaporation of moisture from the soil.
- Integrated pest Management (IPM)- IPM aims at controlling pests by a combination of methods like mixed cropping, biological control of pests, some methods of planting crops and using certain limited chemical pesticides.
Frequently Asked Questions
Question - What is land Degradation?
Answer - Land Degradation means reduction or loss in arid, semi-arid and dry sub-humid areas of the biological or economic productivity of rainfed cropland, Irrigated cropland, pasture, forest and woodlands resulting from land use. it can arise from the following processes:
- soil erosion caused by wind and/ or water;
- Deterioration of the physical, Chemical and biological or economic properties of the soil;
- Long-term loss of natural vegetation
Question: What is called desertification?
Answer -Desertification is land degradation in arid and semi-arid areas caused by human activities and climatic changes. Desertification is therefore, the deterioration of land in arid, semi-arid and dry sub-humid regions (also called dryland) of the world due to climatic variations and human activities.
It occurs slowly, as different areas of degraded land spread and merge, rather than through advancing deserts. It is a slowly but progressing ‘skin disease’ over the planet.
Question: What is the difference between land degradation and desertification?
Answer - Land Degradation is defined as the persistent reduction in the capacity of land to support biodiversity, ecosystem services and human needs. The process of land degradation is gradual. The major symptoms of land degradation are long-term reduction or loss in biological productivity,
And Extreme form of land degradation in aris, semi-arid and dry sub-humid regions of the world is called Desertification
Question: What are the major causes of Desertification?
Answer - Major causes of desertification include both natural and human-induced causes. Climate change, Drought and Forest fires are the natural cause.
Human activities that contribute to desertification include faulty irrigation practices, deforestation, overgrazing and Excessive use of chemicals like chemical fertilisers, pesticides etc.
Question: What are the major types of land degradation?
Answer - Major types of land Degradation are
- Soil Erosion - Loss of top cover of the soil either by the action of wind, water or gravity.
- Soil Salinisation - Saline and alkaline encrustations consisting of sodium, potassium and magnesium salts appear on the top layers of the soil through capillary action.
- Soil Acidification - Excessive build-up of hydrogen or aluminium cations in soil due to long-term rainfall or acid deposition due to mining activities.
- Soil Pollution - Presence of chemicals in soils that are either out of place or higher than normal concentrations.
Question: What are the effects of desertification?
Answer - Major consequences of desertification are felt both across natural and human systems.
The impacts of desertification on natural systems are - Climate Change, Loss of biodiversity, increased poverty, threats to Food Security and Livelihood Loss, violent conflicts for land, migration, and pollution from wind-blown dust particles coming from distant lands.
Question: What are the solutions available for combating Land degradation and Desertification?
Answer - Sustainable land management practices provide solutions for preventing land degradation and desertification:
1. Integrated crop, soil and water management measures which include:2. Crop diversification;
3. Cultivation drought tolerant crops;
4. Reduced tillage;
5. Improved irrigation techniques like drip irrigation;
6. Maintaining vegetation and mulch cover.
- Improved irrigation practices;
- Chemical remediation measures;
- Application of compost and mulch.
Land degradation can be avoided, reduced or reversed by implementing sustainable land management, restoration and rehabilitation practices that simultaneously provide many co-benefits, including adaptation to and mitigation of climate change.
Also Read - Acid Rain | Causes and Effects of Acid Rain