Agricultural expansion a major cause to doubling of annual tropical
carbon loss over past two decades
Date:
March 22, 2022
Source:
The University of Hong Kong
Summary:
Using multiple high-resolution satellite datasets, researchers found
that tropical carbon loss has doubled over the past two decades
due to excessive forest removal in the tropics. The tropics are
an important ecosystem as they store massive amounts of carbon in
their woody vegetation and soil -- but they have suffered from
extensive forest clearance since 2001. The researchers analyzed
the gross forest carbon loss associated with forest removal in
the tropics during the 21st century.
FULL STORY ========================================================================== Using multiple high-resolution satellite datasets, researchers from
the Department of Civil Engineering at the University of Hong Kong
(HKU) and Southern University of Science and Technology (SUSTech) found
that tropical carbon loss has doubled over the past two decades due to excessive forest removal in the tropics.
==========================================================================
The tropics are an important ecosystem as they store massive amounts
of carbon in their woody vegetation and soil -- but they have suffered
from extensive forest clearance since 2001. The researchers analysed the
gross forest carbon loss associated with forest removal in the tropics
(between 23.5DEG N and 23.5 S but excluding northern Australia) during the
21st century. They revealed a two-fold increase in gross tropical forest
carbon loss worldwide from 0.97 gigatons of carbon per year in 2001-2005
to 1.99 gigatons of carbon per year in 2015-2019 due to rapid forest loss.
The study has been published in the academic journal Nature Sustainability
in an article entitled "Doubling of annual forest carbon loss over the
tropics during the early twenty-first century." Given the key role of the tropics in the carbon cycle, the study poses serious implications. "The findings are critical because they suggest that existing strategies
to reduce forest loss are questionable; this failure underscores the
importance of monitoring deforestation trends following one of the
new pledges made -- to halt and reverse deforestation -- by UN climate summit-the twenty- sixth Conference of the Parties (COP26) in Glasgow
in November 2021," said Professor Ji CHEN from HKU's Department of
Civil Engineering.
Tropical forests are the largest terrestrial component of the global
carbon cycle, storing about 250 gigatons of biomass carbon in its woody vegetation and absorbing about 70 gigatons of atmospheric carbon per
year through photosynthesis. The rapid and steady loss of forests could
be devastating because it leads to the loss of stored carbon in biomass
and soil.
Deforestation also obstructs carbon sequestration or the process of
capturing and retaining carbon dioxide.
"The doubling and acceleration in the loss of forest carbon, including
biomass and soil organic carbon, is primarily driven by agricultural
expansion which differs from current estimates of land-use change
emissions in the assessments of the global carbon budget that shows a
flat or decreasing trend. In addition to carbon, conversion of forests
to agricultural lands also induces other environmental consequences,
like biodiversity extinction and land degradation," said Yu FENG, a PhD candidate of the HKU and SUSTech joint programme.
Most of the tropical forest carbon loss (82%) was set off by agricultural expansion, for example shifting cultivation, particularly in Africa.
"While some agricultural lands may reappear as forested due to abandonment
or policies, we still observed about 70% of former forest lands converted
to agriculture in 2001-2019 remained so in 2020, confirming a dominant
role of agriculture in long-term pan-tropical carbon reductions on
formerly forested landscapes," said research team member Dr Zhenzhong
Zeng, Associate Professor at SUSTech.
"The 2014 New York Declaration on Forests promised to halve tropical deforestation by 2020. However, our results demonstrate a failure to
the commitment and highlight the colossal challenge posed by the 2021
Glasgow Leaders' Declaration on Forests and Land Use, which pledges to
halt forest loss by 2030," said Dr Chunmiao Zheng, Chair Professor at
SUSTech and a member of the research team.
========================================================================== Story Source: Materials provided by The_University_of_Hong_Kong. Note:
Content may be edited for style and length.
========================================================================== Journal Reference:
1. Yu Feng, Zhenzhong Zeng, Timothy D. Searchinger, Alan D. Ziegler,
Jie Wu,
Dashan Wang, Xinyue He, Paul R. Elsen, Philippe Ciais, Rongrong
Xu, Zhilin Guo, Liqing Peng, Yiheng Tao, Dominick V. Spracklen,
Joseph Holden, Xiaoping Liu, Yi Zheng, Peng Xu, Ji Chen, Xin Jiang,
Xiao-Peng Song, Venkataraman Lakshmi, Eric F. Wood, Chunmiao
Zheng. Doubling of annual forest carbon loss over the tropics
during the early twenty-first century. Nature Sustainability,
2022; DOI: 10.1038/s41893-022-00854-3 ==========================================================================
Link to news story:
https://www.sciencedaily.com/releases/2022/03/220322111320.htm
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