New data helps quantify role of forests in global carbon cycle

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Rainforest in Malaysia | COURTESY: Wikimedia Commons

NASA scientists, in collaboration with other international researchers, have a new approach for assessing the important role forests play in our world’s carbon cycle. This revised evaluation now uses ground, aerial and satellite data to not only gauge the overall role forests play in absorbing carbon, but also the effect of various types of forests in the global carbon budget.

The Carbon Cycle

Trees and vegetation that make up a forest draw carbon dioxide out of the atmosphere through photosynthesis. This reservoir of carbon is known as a carbon sink. Activities such as agriculture, deforestation, degradation, etc. are known as carbon sources, which emit carbon dioxide into the atmosphere. Carbon sources can be both natural and artificial.

Simplified diagram of the carbon cycle | COURTESY: NOAA
  • IN-DEPTH: “The primary cause of the global carbon dioxide increase over the last century is from human activities that burn fossil fuels such as coal and oil.” -NASA

Over the last 20 years, forests collectively absorbed ~15.6 billion metric tons of CO2 from the atmosphere each year, while deforestation, fires and other disturbances released an average of 8.1 billion metric tons of carbon dioxide per year.

Forests are estimated to absorb ~1.5 times the annual emissions from the entire United States.

World map showing forested regions that are sources of carbon emissions (purple) and where they are carbon sinks (green) | COURTESY: Harris et al. 2021 / Global Forest Watch / World Resources Institute

New changes: more data

Despite standardized guidelines issued by the Intergovernmental Panel on Climate Change (IPCC), data between countries still varies due to lack of resources. The new methodology differs from what’s currently in place by using numerous sources of data to create a more consistent global framework. This additional data will help reduce the error where metrics are not uniform and estimates are made.

“All estimates come with an uncertainty around them, which is going to keep getting smaller and smaller as we get better datasets.”

-Lola Fatoyinbo, a scientist from NASA Goddard’s Space Flight Center

New instruments to be used in carbon monitoring:

  • NASA’s Carbon Monitoring Systems Biomass Pilot – combines satellite and field data to improve estimates of vegetation and carbon stocks
  • NASA’s ICESat-2, and the Global Ecosystem Dynamics Investigation (GEDI) – a laser-equipped instrument aboard the International Space Station (ISS) that records the three-dimensional structures of the world’s temperate and tropical forests

Already impletemented instrument:

  • NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) – primarily designed to track changes in ice sheet coverage but also provides topography and vegetation data

This additional data will give scientists a more accurate picture of the state of the Earth’s carbon cycle, and is expected to help better inform policy-makers.

  • IN-DEPTH: a recent study shows that 27% of the world’s net forest carbon sinks are found within protected areas, such as national parks.

For more information, visit NASA: Global Climate Change website.

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