Agroforestry Carbon Sequestration Rates

Executive Summary

At the Green Earth Appeal, we are planting trees in tropical climates along with the provision of tools, education and infrastructure to provide aid-reliant communities with sustainable and profitable agroforestry farming businesses now and for generations to come.

As well as helping end poverty, the trees we plant have another significant benefit to our planet. Through the process of photosynthesis, trees absorb CO2 and push it down through their root system where it remains harmless beneath the ground.

In summary, whilst the Carbon Sequestration rates are lower in cooler climates, in the projects that Green Earth Appeal funds, research and evidence demonstrates that in a tropical climate a tree will sequester a minimum of around 25kg of CO2 per year for a useful life span of 40 years (ie 1000 KG per tree planted in its 40 year useful lifetime).

Carbon Sequestration

By burning fossil fuels and destroying forests, we are releasing dangerous and harmful greenhouse gases, importantly carbon dioxide (CO2), into the atmosphere. These heat-trapping gases are warming the planet, resulting in changes that are taking us outside the climate bounds within which civilisation as we know it developed. 1

Last year a report by the UNE found that the amount of carbon dioxide in the atmosphere passed 400 parts per million (ppm), its highest level since the Pliocene Epoch 2.6 million years ago. Human activities in the meanwhile, from driving fossil fuel burning cars to burning coal, are increasing this 400 ppm by roughly 2 ppm a year.

Studies over the last thirty years have shown variance in the amount of carbon that trees sequester. However recently, environmental analyst Lester R Brown, the man considered “one of the great pioneer environmentalists” studied this field in depth and realised sustainable development and in particular reforestation and afforestation. In his book ‘Time for Plan Lester R Brown founder of the World Watch Institute and former president of the Earth Policy Institute said that whilst deforestation has already been banned in some areas to moderate flooding, stabilize soils, and prevent erosion. The world’s remaining forests store massive amounts of carbon, therefore the need for forest protection now goes beyond that of local environmental protection to global climate protection.

His research showed that a newly planted tree in the tropics can remove up to 50 kilograms of CO2 from the atmosphere each year during its growth period of 20–50 years; on the other hand, a tree in the temperate regions can take in 13 kilograms. 2

Additional carbon can be sequestered through improved agricultural land management. This includes expanding the area of minimum- or no-till cropland, planting more cover crops during the off-season, and using more perennials instead of annuals in cropping patterns.

These carbon-sensitive farming and land management practices can produce a huge increase in the number of tons of carbon sequestered per year, while also improving fertility, raising food output and reducing soil erosion. 3

Further research into sequestration rates was carried out by Dexter Dombro CEO of Amazonia Reforestation. His studies backed up by Science Daily, state that natural African tropical forests absorb approximately 600 kg (1,323 lbs) of carbon per hectare per year. If you take 600 kg by 25 times more wood per hectare in a plantation setting, the result is 15,000 kg (33,000 lbs) per hectare per year divided by 600 plantation trees per hectare, which results in an average of 25 kg (55 lbs) of carbon sequestered per tree per year.

Another study carried out by Myers and Goreau 4, showed that tropical tree plantations of pine and eucalyptus can sequester an average of 10 tons of carbon per hectare per year. Therefore, the plantation can sequester an average of 20,000 lbs * 3.6663 = 73,326 lbs CO2/ha/year, or, taking an average of 1,000 trees per hectare, 33.33 KG or 73.326 lbs CO2/tree/year.

The amount of CO2 a tree sequesters varies based on the growth rate, age, and species of the particular tree. Young, quickly growing trees uptake significantly more carbon than mature trees with a slower growth rate. Warm and wet climates with long growing seasons also contribute to rapid plant growth and indirectly promote higher rates of carbon sequestration. 5

The age of the forest plays a role as well. A recent study in found that new rainforests grown on land considered to be degraded, known as secondary forests, are capable of storing up to 11 times more carbon than old-growth rainforests, where tree growth has largely plateaued, this is backed up by a report by the FAO. 6

Conclusion

In summary, whilst the Carbon Sequestration rates are lower in cooler climates, in the projects that Green Earth Appeal funds research and evidence from the UNE, the FAO and scientists and environmentalist from around the globe all point to the fact that in a tropical climate a tree will sequester a minimum of around 25kg of CO2 per year for a useful life span of 40 years (ie 1000 KG per tree planted in its 40 year useful lifetime).

References

1 Intergovernmental Panel on Climate Change, Working Group 1, Climate Change 2007: The Physical Science Basis, Summary for Policymakers (New York: Cambridge University Press, 2007), pp. 2–17

2 Ibid., pp. 1, 16; sequestration per tree calculated assuming 500 trees per hectare, from UNEP Trillion Tree Campaign, “Fast Facts,” at www.unep.org/billiontreecampaign, viewed 10 October 2007; growing period from Robert N. Stavins and Kenneth R. Richards, The Cost of U.S. Forest Based Carbon Sequestration (Arlington, VA:Pew Center on Global Climate Change, January 2005), p. 10.

3 Ziadat, F. (2017). B7 Sustainable soil and land management for CSA. [online] Food and Agriculture Organization of the United Nations. Available at: http://www.fao.org/climate-smart-agriculture-sourcebook/production-resources/module-b7-soil/b7-overview/en/?type=111.

4 Myers, N., and T. J. Goreau. 1991. Tropical forests and the greenhouse effect: A management response. Climatic Change 19: 215-26.

5 Köhl M, Neupane PR, Lotfiomran N (2017) The impact of tree age on biomass growth and carbon accumulation capacity: A retrospective analysis using tree ring data of three tropical tree species grown in natural forests of Suriname. PLOS ONE 12(8): e0181187. https://doi.org/10.1371/journal.pone.0181187

6 Joshi Meenakshi, Preet Pal Singh (2003) Carbon sequestration by rehabilitating degraded forests in India 0405-B2