Agroforestry: A promising negative emissions technology (NET)
Agroforestry, unlike many other Negative Emissions Technologies (NETs), is a low-cost intervention and can be scaled up quickly. The blog gives a brief about NETs and the benefits of Agroforestry Systems.
The rising concentration of greenhouse gases in the atmosphere is a major anthropogenic cause of climate change. Currently, the global carbon dioxide (CO2) concentration is approximately around ~ 400 ppm in comparison to a preindustrial atmospheric CO2 concentration of 255 to 280 ppm (Mohan et al. 2018). Limiting global warming to below 1.5oC requires “negative emissions technologies (NETs)” i.e. technologies that remove CO2 from the atmosphere and store it on land, underground, or in the oceans (European Commission 2015, Minx et al. 2017, IPCC 2018). NETs are also referred to as “carbon dioxide removal (CDR)” strategies (Carbon brief 2018). According to Lal (2013), methods of CDRs can be divided into two broad categories: biotic and abiotic. Biotic strategies utilize the natural process of photosynthesis and transfer of CO2 from the atmosphere into vegetative, pedologic, and aquatic pools through mediation via green plants. Afforestation, reforestation, and blue habitat restoration are biotic NETs. Abiotic strategies use engineering techniques that prevent industrial emissions from reaching the atmosphere through the processes like separation, capture, compression, transport, and injection of CO2 emitted from industrial processes deep into the ocean and geological strata like old and unused mines or oil wells. A large number of research studies have modeled climate scenarios for achieving the global warming targets set by the IPCC and have discussed the need for deploying such mitigation technologies that can achieve net emissions reductions (Minx et al. 2017, Bui et al. 2018, IPCC 2018). However, each of the NETs or CDRs poses a range of economic and institutional barriers as well as potentially large risks to human lives, food security, and/or biodiversity (Minx et al. 2017, Carbon brief 2018). Although a large number of NETs have been proposed, the majority are not ready for upscaling and prudence suggests that careful assessments of the option’s feasibility will be needed before their implementation (Carbon brief 2016a, Minx et al. 2017).
Mitigating climate change by enhancing forest carbon sequestration through afforestation, i.e. planting trees on barren land, and reforestation i.e. planting native trees into a forest that has decreasing numbers of trees due to degradation or deforestation, are the relatively low-cost and environmentally beneficial NET options. Forests all over the world together store approximately 31 percent of the carbon in their biomass and 69 percent in their soil. The trees planted can capture CO2 from the atmosphere through photosynthesis for their biological functioning and store it as living biomass as they grow in their plant tissues above and below ground (Minx et al. 2017). In addition to being sequestered in vegetation, carbon is also sequestered in forest soils, generally in the humus on the surface and in the upper soil layers, in the organisms that decompose vegetation (decomposers), and in the fine roots (Gorte 2009, Lal 2014). According to estimates, afforestation and reforestation can sequester CO2 at a rate of 3.7 tonnes per hectare per year, at the cost of USD 20-100 per tonne (Carbon brief 2016b). Hence, the management of forest carbon stocks is a critical NET and natural climate solution for mitigating increasing atmospheric carbon dioxide concentrations.
Though forestation is one of the most feasible options, it still has some barriers. Land availability and suitability is one critical barrier to afforestation because of competing land use needs for agriculture or bioenergy. In most regions, there is rapid land use change and conversion of natural ecosystems like forests to agricultural ones (e.g., cropland, grazing land) to meet increasing food demands which also depletes soil organic carbon by as much as 50–80% (Lal 2013). One way to tackle such issues can be to promote sustainable Agroforestry systems as a climate mitigation solution where trees are incorporated into existing cropping systems. Converting unproductive croplands and grasslands to agroforestry systems has a large carbon sequestration potential. Globally, agroforestry can be adopted on 35 percent of our suitable lands (croplands and pastures) and has a global mitigation potential of between 0.11 – 5.68 billion tons of CO2 equivalents per year (IPCC 2019). Agroforestry systems also have secondary benefits like improving the nutritional and economic security of vulnerable communities. It increases farm income, helps in the restoration of biodiversity, and soil and moisture conservation.
In India, agroforestry systems include trees grown on farms, community forestry, and a variety of local forest management and ethno-forestry practices (Basu 2014). The average carbon storage potential in Indian agroforestry has been estimated to be 25tC.ha-1 over 96 million ha (Sathaye and Ravindranath 1998). Promoting such systems not only helps in achieving India’s INDC goals of creating an additional carbon sink of 2.5 to 3 billion tonnes of CO2 equivalent through additional forest and tree cover but also protects the poor and vulnerable from adverse impacts of climate change. DRF has already taken its first step towards promoting agroforestry as part of its climate action strategy with 275 marginal and smallholder farmers adopting agroforestry in approx. 200 acres in the Pydibhimavaram cluster of coastal Andhra Pradesh.
Basu, J.P. (2014). Agroforestry, climate change mitigation and livelihood security in India. N.Z. j. of For. Sci. 44 (Suppl 1), S11. Available online https://doi.org/10.1186/1179-5395-44-S1-S11
Bui, M., et al. (2018). Carbon capture and storage (CCS): the way forward. Energy Environ. Sci., 11, 1062
Carbon brief (2016a). In-depth: Experts assess the feasibility of ‘negative emissions’. Accessible online https://www.carbonbrief.org/
Carbon brief (2016b). Explainer: 10 ways ‘negative emissions’ could slow climate change. Accessible online https://www.carbonbrief.org/
Carbon brief (2018). In-depth Q&A: The IPCC’s special report on climate change at 1.5oC. Accessible online https://www.carbonbrief.org/in-depth-qa-ipccs-special-report-on-climate-change-at-one-point-five-c
European Commission (2015). COP21 Paris Agreement. Accessible online http://ec.europa.eu/clima/
IPCC. (2018): Summary for Policymakers. In: Global Warming of 1.5°C. An IPCC Special Report on the impacts of global warming of 1.5°C above pre-industrial levels and related global greenhouse gas emission pathways, in the context of strengthening the global response to the threat of climate change, sustainable development, and efforts to eradicate poverty. In Press.
Gorte, R.W. (2009). Carbon Sequestration in Forests. CRS Report for Congress
Lal, Rattan (2013). Soil carbon management and climate change. Carbon Management, 4(4), 439–462. doi:10.4155/cmt.13.31
Minx, JC., et al. (2017). Fast growing research on negative emissions. Environ. Res. Lett. 12 035007
Mohan, D., Abhishek, K., Sarswat, A., Patel, M., Singha, P. and Pittman C.U. (2018). Biochar production and applications in soil fertility and carbon sequestration – a sustainable solution to crop-residue burning in India. RSC Adv., 8, 508.
IPCC (2019). In: Climate Change and Land: an IPCC special report on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystem. In press.
Sudeshna Maya Sen | Manager – Climate Action
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