Soil Organic Carbon : Preventing Land Degradation and Desertification - Current Affair Article for UPSC, IAS, Civil Services and State PCS Examinations


Soil Organic Carbon : Preventing Land Degradation and Desertification - Current Affair Article for UPSC, IAS, Civil Services and State PCS Examinations


Why in News?

The United Nations Convention to Combat Desertification (UNCCD)'s Committee on Science and Technology (CST) has released its report on Soil Organic Carbon (SOC) during the Ongoing Conference of Parties (COP) 14 of UNCCD in New Delhi. Titled Realising the Carbon Benefits of Sustainable Land Management Practices: Guidelines for Estimation of Soil Organic Carbon in the Context of Land Degradation Neutrality Planning and Monitoring, the report emphasises the importance of SOC in preventing land degradation and desertification.

Introduction

Today, nearly a quarter of our land has been degraded and it is estimated that by 2050, less than 10 per cent of the planet’s surface will have escaped substantial human impact. Such dramatic change has a huge effect on the soil organic carbon created by decomposing natural materials, which supports all life on Earth; growing food, creating jobs, reducing poverty, maintaining biodiversity and, crucially, providing the second largest carbon sink after our oceans. That’s why climate change and sustainable development can be significantly affected, for better or worse, by even the slightest change in the quantity and quality of soil organic carbon.

The clock is rapidly ticking down on the targets of the 2030 Agenda for Sustainable Development and a dangerous gap is growing between the Nationally Determined Contributions of the Paris Agreement and the emission levels actually needed to keep global warming below 1.5°C. Achieving our targets for land degradation neutrality (LDN) plays a key role in both, with soil organic carbon providing an ideal indicator and driver of progress, not only because it is responsive to land management practices, but because those practices can create much wider social, economic and environmental benefits.

India Status: Land Degradation and Desertification

India faces a severe problem of land degradation, or soil becoming unfit for cultivation. About 29 per cent or about 96.4 million hectares are considered degraded. And yet assessments in the last two years show that 23 per cent of the land is degraded, mostly in areas outside the drylands. That is about 1 in every 4 to 5 hectares (ha) of land. Moreover, 75 per cent of the land has been altered from its natural state. That’s about 3 out of every 4 hectares of productive land. What’s more, these changes have occurred over the last 50 years, primarily for agriculture.

Recently, during the COP 14 of UNCCD, India has raised its ambition of the total area that would be restored from its land degradation status, from 21 million hectares to 26 million hectares between now and 2030, by 10 per cent the amount of degraded land India has agreed to rehabilitate by 2030.

Earlier, India joined the voluntary 'Bonn Challenge' and pledged to bring into restoration 13 million hectares of degraded and deforested land by 2020, and an additional 8 million hectares by 2030. India’s pledge was one of the largest in Asia.

Land Degradation Neutrality (LDN)

LDN has been defined as a state whereby the amount and quality of land resources, necessary to support ecosystem functions and services and enhance food security, remains stable or increases within specified temporal and spatial scales and ecosystems. LDN represents a paradigm shift in land management policies and practices. It is a unique approach that counterbalances the expected loss of productive land with the recovery of     degraded areas. It strategically places the measures to conserve, sustainably manage and restore land in the context of land use planning. Because land is fixed in quantity, there is ever-increasing competition to control land resources and capitalize on the flows of goods and services from the land. This has the potential to cause social and political instability, fueling poverty, conflict and migration.

Soil Organic Carbon was selected as one of three indicators for LDN. The other global LDN indicators are land cover change and land productivity dynamics (LPD) (measured as net primary productivity). SOC is a fundamental ecosystem health indicator, and with its multifunctional roles, its sensitivity to land management, and its direct relevance to the missions of all three Rio conventions, constitutes a key criterion for the identification of suitable sustainable land management (SLM) technologies to contribute to the achievement of LDN.

Soil Organic Carbon

Soil organic carbon (SOC), the largest carbon pool in the terrestrial biosphere, is an important component of the global carbon cycle. SOC is the major constituent of soil organic matter (SOM), which plays a critical role in soil productivity and a wide array of ecosystem processes. SOM comprises the remains of plants and animals in the soil at various stages of decomposition, along with the microbial biomass and several by-products of complex biotic metabolic processes.

SOC is a measureable component of soil organic matter. Organic matter makes up just 2–10% of most soil's mass and has an important role in the physical, chemical and biological function of agricultural soils. Organic
matter contributes to nutrient retention and turnover, soil structure, moisture retention and availability, degradation of pollutants, carbon sequestration and sol i resilience.

In addition to soil organic carbon (SOC), soil inorganic carbon (SIC) is also a dominant form of carbon in soils of arid and semi-arid regions and comprises of carbonates and bicarbonates of Ca+2, Mg+2, K+ and Na+.
Indeed, SIC forms a larger proportion of total soil carbon (TSC) in drylands and plays an important role in the global carbon cycle.

Importance of Soil Organic Carbon

While the agricultural sector has the ability to impact the carbon cycle on a large scale, often through the release of carbon, farmers have a vested interest in retaining and increasing SOC for individual fields because soil and
yield tend to improve when the SOC level increases. Higher SOC promotes soil structure or tilth meaning there is greater physical stability. This improves soil aeration (oxygen in the soil) and water drainage and retention, and reduces the risk of erosion and nutrient leaching. SOC is also important to chemical composition and biological productivity, including fertility and nutrient holding capacity of a field. As carbon stores in the soil increase, carbon is “sequestered”, and the risk of loss of other nutrients through erosion and leaching is reduced. An increase in SOC typically results in a more stable carbon cycle and enhanced overall agricultural productivity, while physical disturbances of the soil can lead to a net loss of carbon into the surrounding environment due to formation of carbon dioxide (CO2).

The Bonn Challenge

The 'Bonn Challenge' is a global effort to bring 150 million hectares of the world’s deforested and degraded land into restoration by 2020, and 350 million hectares by 2030. It was launched in 2011 by the government of Germany and IUCN, and later endorsed and extended by the New York Declaration on Forests at the 2014 UN Climate Summit.

Underlying the 'Bonn Challenge' is the forest landscape restoration (FLR) approach, which aims to restore ecological integrity at the same time as improving human well-being through multifunctional landscapes.

The restoration of 150 million hectares of degraded and deforested lands in biomes around the world – in line with the FLR approach – will create approximately USD 84 billion per year in net benefits that could bring direct additional income opportunities for rural communities. About 90 per cent of this value is potentially tradable, meaning that it encompasses market-related benefits. Achieving the 350 million hectare goal will generate about USD170 billion per year in net benefits from watershed protection, improved crop yields and forest products, and could sequester up to 1.7 gigatonnes of carbon dioxide equivalent annually.

The 'Bonn Challenge' is not a new global commitment but rather a practical means of realizing many existing international commitments, including the CBD Aichi Target 15, the UNFCCC REDD+ goal, and the Rio+20 land degradation neutrality goal. It is an implementation vehicle for national priorities such as water and food security and rural development while contributing to the achievement of international climate change, biodiversity and land degradation commitments.

Influences of Soil, Climate and Management Factors on Soil Organic Matter

Soil Type

  • Naturally occurring clay in soil binds to organic matter, which helps to protect it from being broken down or limits access to it by microbes and other organisms.
  • Organic matter in coarse-textured sandy soils is not protected from microbial attack and is rapidly decomposed.

Climate

  • In comparable farming systems with similar soil type and management, soil organic matter increases with rainfall. This is because increasing rainfall supports greater plant growth, which results in more organic matter accumulating in the soil.
  • Organic matter decomposes more slowly as temperatures decrease. Generaly under moist conditions, each 10°C increase in temperature doubles the rate of organic matter decomposition. This means moist, warm conditions will often result in the most rapid decomposition of organic inputs.

Land and Soil Management

  • Maximising crop and pasture biomass via better wateruse efficiency and agronomic management will increase organic matter inputs.
  • As a large proportion of organic matter is present in the top 0–10 cm of soils, protecting the soil surface from erosion is essential for retaining soil organic matter.
  • Tillage of structured soils decreases soil organic matter stocks by exposing previously protected organic matter to microbial decomposition.
  • Adding off-farm organic residues, such as manures, straw and char, can increase soil organic matter. The agronomic benefits should be measured to establish economic viability.
  • Landscape can influence biomass production (inputs) associated with water availability.
  • Transfer of soil and organic matter down slope via erosion can increase soil organic matter stocks in lower parts of the landscape.
  • Soil constraints decrease plant growth and decomposition rates. This could slow the amount and transformation rate of organic matter moving into more stable fractions.
  • Microorganisms and particularly bacteria grow poorly in strongly acidic or alkaline soils and consequently organic matter breaks down slowly in these soils.

Sustainable Land Management Practices

Management practices that can increase SOC and reduce carbon loss into the atmosphere are described below:

  • Conservation Tillage Practices: Conservation tillage practices including no-till management aid in storing SOC, keeping the physical stability of the soil intact. When reduced-till systems are combined with residue management and manure management, SOC can increase over time.
  • Crop Residue Management: Returning crop residue to the soil adds carbon and helps to maintain SOC.
  • Cover Crops: Cover crops can increase soil carbon pools by adding both root and above ground biomass. Covers also reduce the risk of soil erosion and the resulting loss of carbon with soil particles. Cover crops also enhance nutrient cycling and increase soil health over time.
  • Manure and Compost: Adding organic amendments such as manure or compost can directly increase soil carbon and also result in increased soil aggregate stability. This enhances the biological buffering capacity of the soil, resulting in greater yields and yield stability voer tiem.
  • Crop Selection: Perennial crops eliminate the need for yearly planting and increase SOC by root and litter decomposition post-harvest. Crops with greater root mass in general add to root decomposition and physically bond aggregates together. Using high residue annual crops can also help reduce net carbon loss from cropping systems.

Conclusion

To achieve the UN-mandated sustainable development goals (SDG 15.3) of restoring degraded land and soil by 2030, there is a need for “synergy between scientists, farming communities and their institutions that are the land users and managers. Research can help restoration initiatives to scale-up globally but only if farmers, their livelihoods and communities are at the heart of such initiatives.

Soil carbon management is an important strategy for improving soil quality, increasing crop yields, and reducing soil loss. Capturing carbon in the soil helps improve soil health and productivity, and stabilize the global carbon cycle, benefiting agricultural production. Because of its multifunctional roles and its sensitivity to land management, SOC is one of the three global indicators of Land Degradation Neutrality (LDN). Hence, predicting and monitoring change in SOC is vital to achieving LDN atrgets.

General Studies Paper- III

  • Topic: Conservation, environmental pollution and degradation, environmental impact assessment.

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