Exploring the Potential of Agro-Forestry in
Climate Change Mitigation
 

There is growing concern about the rising levels of greenhouse gas emissions and their contribution to climate change. Carbon dioxide (CO₂), one of the most important greenhouse gases is added into the atmosphere naturally (volcanoes, respiration etc) and unnaturally by human activities (Dhandet et.al., 2003). CO₂ concentration in the atmosphere has increased from 280 ppm at the beginning of the Industrial Revolution to 368 ppm by the year 2000. It is projected to increase up to 540 ppm by 2100 (Houghton et al. 2001). This increase in CO₂ concentration has been identified as one of the prime reasons for the rise in the average annual temperatures across the world, commonly known as global warming and its negative consequences.

A carbon sink is anything that absorbs more carbon dioxide than it releases. Oceans and trees form natural carbon sinks that remove carbon from the atmosphere and store it. The process of capturing and storing CO₂ for long durations is known as carbon sequestration. If we are to curb global warming, we need to reduce the CO₂ levels in the atmosphere and one of the ways to achieve this is to promote accelerated carbon sequestration by investing in the creation of natural carbon sinks.

Wadi, an agro-horti based livelihood development model being promoted by Development Alternatives in the climate sensitive Bundelkhand region of Central India, presents itself as a promising solution in this quest to establish natural carbon sinks. Under the Wadi model, mini-orchards comprising of guava, gooseberry (amla) and mango plantations are established on one acre farms owned by small and marginal tribal farmers. With support from the National Bank for Agriculture and Rural Development (NABARD) under its Tribal Development Fund, Development Alternatives has already established over 600 wadis spread across two districts - Jhansi in Uttar Pradesh and Shivpuri in Madhya Pradesh.

This article explores the potential of wadi to act as an effective carbon sink even while it delivers its directly intended livelihood development outcomes – a win-win solution based on the inter-connections between rural agrarian livelihoods and a healthy natural resource base.

Estimating the Carbon Sequestration Potential of a Wadi

The science of calculating the carbon sequestration effected by tree plantations is a relatively new area of research and is still evolving. Much of the methodologies and algorithms that have been developed are based on studies carried out in temperate zones and may not be directly applicable to tropical systems without some loss of accuracy. This section is thus a preliminary attempt at estimating the sequestration effected by wadis using simplified methods that are currently available.

A number of characteristics of a plantation govern its potential to sequester carbon. Some of the important parameters include species composition, tree canopy, plant height, age of plants, leaf litter and other decaying matter on the surface of the soil. In addition, the climatic context and prevailing conditions for plant growth also influence the carbon sequestration potential of the plantation.

Outlined below are the key steps in the calculation of the sequestration resulting from the growth of a single tree. The data used for the calculations is based on a survey of the existing wadis in Jhansi district that were established around 5 years back and are now at a mature stage.

• Determining above-ground (green) weight of a tree: This is calculated using the formula W = 0.25D²H (where W is the above-ground weight in pounds, D is the diameter of the trunk in inches and H is the height of the tree in feet). This algorithm is applicable for trees with trunk diameter of less than 11 inches. For trees with a larger trunk diameter, the algorithm to be used is W = 0.15D2H. The wadis established in Jhansi mostly have gooseberry (amla) and guava trees and the average tree has a height of 12 feet and a trunk diameter of 8 inches. The above-ground green weight is thus calculated as 192 lb.

• Determining total (green) weight of a tree: The root system weighs about 20% as much as the above-ground weight of the tree. Therefore, the total green weight of the tree is calculated by multiplying the above-ground weight of the tree by 120% giving a value of 230.4 lb.

• Determining dry weight of a tree: Data for temperate species indicates that on an average 72.5% of the green weight is dry matter and the rest is moisture. Thus, to calculate dry weight, the green weight is multiplied by 72.5% giving a value of 167.04 lb for an average tree in a wadi.

• Determining weight of carbon: The average carbon content is generally 50% of the dry weight. Thus the weight of carbon is calculated to be 83.52 lb.

• Determining weight of CO₂ sequestered: This is calculated by multiplying the weight of carbon by 3.6663 giving a value of 306.21 lb or 138.89 kgs.

As the above calculations indicate, each tree in the wadis in the Jhansi district of Uttar Pradesh has sequestered 138.89 kgs of CO₂ over five years which may be understood as a rate of sequestration of 27.77 kgs of CO₂ each year. However, it must be remembered that the above calculations are based on methods applicable to temperate systems, and given that the wadis under analysis are in Jhansi district i.e. tropical conditions, there may be a degree of inaccuracy in the results. Certain studies carried out in tropical regions have indicated that about 50 lb or 22.68 kg of CO₂ is sequestered by agro-forestry trees per year. Adopting this more conservative estimate of the rate of sequestration, calculations for the 500 wadis in Jhansi shows that about 6,235 tCO₂ has been sequestered in the past five years i.e. approximately 2.5 tCO₂ per wadi per year. For the sake of perspective, it may be noted that the estimates for per capita carbon footprint of India range between 1.6 to 1.7 tCO₂.

It is also pertinent to note that this estimation of the carbon sequestration potential of a wadi is based only on the analysis of tree biomass generated. It does not take into account the carbon stock represented in the soil organic content, which in the case of wadis is significantly high owing to the improved soil nutrient and water management practices adopted. Moreover, the sequestration potential of wadis can be further enhanced by incorporating forestry species on the periphery that will not only provide fuel and fodder but also act as a bio-fence and check soil erosion.

The agriculture sector currently accounts for about 17% of the carbon footprint of India and the promotion of agri-horti and agro-forestry based models such as the wadi can go a long way in reducing the carbon intensity of the sector. Conventional agriculture has been witnessing depleting productivity levels as a result of a combination of factors that include the adoption of unsustainable land, water and nutrient management practices, diminishing farm sizes and farm investment and increasing climate change impacts. The Wadi model provides an alternative that not only allows for improved productivity levels, even on small farms, but also demonstrates improved resilience to climate change impacts and regenerates the production potential of the land and the health of the natural resource base.

There is a need to undertake empirical research on the carbon sequestration potential of wadis and agro-forestry plantations in general based on more extensive field data and methodologies adapted to the tropical context and specific agro-ecological conditions. This will serve to strengthen the argument for enhanced public investment in scaling up the adoption of wadis as an alternative to conventional agriculture towards achieving both livelihood security and ecological security outcomes.

References:
www.broward.org
http://wgbis.ces.iisc.ernet.in

Back to Contents