Trees on farms: The missing link in carbon accounting

Trees on farms: The missing link in carbon accounting
Faidherbia and tomatoes on a farm in Salima District, Malawi. Credit: Tracy Beedy/World Agroforestry Centre

While tropical forests continued to decline, a remarkable change is happening: tree cover on agricultural land has increased across the globe, capturing nearly 0.75 Gigatonnes carbon dioxide every year. A new study titled "Global Tree Cover and Biomass Carbon on Agricultural Land: The contribution of agroforestry to global and national carbon budgets" provides insights into the patterns of this tremendous change at global, regional and national scales.

According to the International Panel on Climate Change (IPCC), agriculture and land-use change account for about 24% of the world's greenhouse gas emissions. Climate change will also have strong impacts on food security in the long-term. Therefore agriculture needs to reduce its climate footprint. But a recent study has shown that the potential to reduce greenhouse gas emissions from crop and livestock production is limited. At the same time, large forest areas, primarily in the tropics, are still being converted into agricultural land to feed the world's growing population.

For these reasons, agricultural practices that can significantly reduce carbon emissions are in high demand.

Trees on agricultural lands - also known as agroforestry systems - have the potential to contribute to climate change mitigation while improving livelihoods and incomes and providing invaluable ecosystem services at the same time. The World Bank estimates that globally 1.2 billion people depend on agroforestry farming systems, especially in developing countries. However, trees on agricultural lands are not considered in the greenhouse gas accounting framework of the IPCC.

A team of researchers from various institutions in Africa, Asia and Europe carried out a study to assess the role of trees on agricultural land and the amount of carbon they have sequestered from the atmosphere over the past decade. The study, entitled "Global Tree Cover and Biomass Carbon on Agricultural Land: The contribution of agroforestry to global and national carbon budgets", looks at biomass carbon on agricultural land both globally and by country, and what determines its distribution across different climate zones.

Biomass on agricultural land globally

"Remote sensing data show that in 2010, 43% of all agricultural land globally had at least 10% tree cover, up from eight percent in the preceding decade," said Robert Zomer of the World Agroforestry Centre, lead author of the study. "Given the vast amount of land under agriculture, agroforestry may already significantly contribute to global carbon budgets."

However, regional differences in the trend are significant. The distribution of tree cover on agricultural land depends on climatic conditions in different parts of the world. High tree cover is found in humid areas such as South East Asia, Central America, eastern South America, as well as central and coastal West Africa. Tree cover on agricultural land was moderate in south Asia, sub-humid Africa, central and western Europe, the Amazonia and mid-west North America. On the other hand, low tree cover was found in east China, northwest India, west Asia, the southern border of the Sahara Desert, the prairies of North America and southwest Australia.

Biomass on agricultural land by country

Remarkable differences are noted in changing biomass carbon stocks over time among countries. Brazil, Indonesia, China and India had the largest increases, while Argentina, Myanmar, and Sierra Leone had the largest decreases in carbon stored on agricultural land.

High average carbon mass levels were to be found in 26 countries in the humid tropics, with the Democratic Republic of Congo, Papua New Guinea, Malaysia and Indonesia in the lead. On the other hand, 60 countries found in arid and desert parts of the world around the Sahara Desert in North Africa, the Kalahari in southern Africa, Middle East, as well as central and southern Asia recorded low carbon levels over the ten-year period.

"Study results show that existing tree cover makes a major contribution to carbon pools on agricultural land, demonstrating the potential to add to climate change mitigation and adaptation efforts," said Jianchu Xu of the World Agroforestry Centre. "If tree cover is accounted for, the total carbon stock is over four times higher than when estimated using IPCC tier 1 estimates alone."

Given the large amount of agricultural land where tree cover is below its potential, the study suggests that a huge mitigation potential exists and should be explored more systematically.

"The results of our spatial analysis show that trees on agricultural land sequestered close to 0.75 Gigatonnes of globally per year over the past decade," said Henry Neufeldt, Head of Climate Change research at the World Agroforestry Centre. "If we can harness good policies to enhance positive examples and stop negative trends, trees in agricultural landscapes can play a major role in greenhouse gas mitigation. But no one should say that this is already solving the problem for agricultural emissions as long as we do not know what is actually happening on the ground."


Explore further

Agroforestry can ensure food security and mitigate the effects of climate change in Africa

More information: Robert J. Zomer et al, Global Tree Cover and Biomass Carbon on Agricultural Land: The contribution of agroforestry to global and national carbon budgets, Scientific Reports (2016). DOI: 10.1038/srep29987
Journal information: Scientific Reports

Citation: Trees on farms: The missing link in carbon accounting (2016, August 2) retrieved 16 July 2019 from https://phys.org/news/2016-08-trees-farms-link-carbon-accounting.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
144 shares

Feedback to editors

User comments

Aug 02, 2016
human caused climate change is a fraud designed to drive the citizenry into granting extraordinary control of industry and agriculture to Marxists, Malthusians and nihilists. Not a good solution to a non-problem.

$2.00 a gallon gasoline? Kiss a fracker today.

Aug 02, 2016
human caused climate change is a fraud designed to drive the citizenry into granting extraordinary control of industry and agriculture to Marxists, Malthusians and nihilists. .

Are you joking?
I honestly hope so because the alternative is that you have wildly by far a delusional mind; human caused climate change being a fraud would require an absurd vast totally unmanageable mass conspiracy with absolutely no apparent motive from virtually all scientists and politicians across the entire globe fabricating all the data and you have no rational reason to think Marxists or Malthusians or nihilists to be no more likely to be either in favor of preventing harmful climate change or being part of an absurd vast unmanageable mass conspiracy with no apparent motive than the average person who isn't any of those three.
If such a conspiracy is a Marxist thing, why haven't the majority of none Marxist politicians from none Marxist countries blown the conspiracy just to spite Marxists?


Aug 02, 2016
Are you joking?
I honestly hope so because the alternative is that you have wildly by far a delusional mind; human caused climate change being a fraud would require an absurd vast totally unmanageable mass conspiracy *snip*
If such a conspiracy is a Marxist thing, why haven't the majority of none Marxist politicians from none Marxist countries blown the conspiracy just to spite Marxists
He's not joking per se, he just doesn't have any idea what he is talking about. Shootist is an old man of feeble mind. He also believes Vikings farmed wheat in Greenland and that the Scots had vineyards. He has been shown these are wrong so he just trolls by on occasion to remind us all of how little in touch with reality he is.

Aug 02, 2016
This comment has been removed by a moderator.

Aug 03, 2016
Maggnus,

You seem to be the one on the wrong side of the facts today. Corn, which is actually barley, was grown in Greenland by the Vikings. But changing the facts is as easy as adjusting the temperature data, I guess.

http://sciencenor...reenland

Aug 03, 2016
Maggnus,

This comment has nothing to do with global warming, just facts, and......

You seem to be the one on the wrong side of the facts today. Corn, which is actually barley, was grown in Greenland by the Vikings. But changing the facts is as easy as adjusting the temperature data, I guess.

http://sciencenor...reenland

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more