What role will forests play in future climate change?

Scientists at NASA have taken a new approach to measure the global extent of carbon fluctuations in forests. The research could ultimately improve carbon cycle estimates and help predict the impact of forests on future climate change. 

The researchers used data from ground reports, aerial surveys, and satellites to assess how changes in forests have impacted atmospheric CO2 levels over the past two decades.

The method used by the experts made it possible to distinguish between the contributions of various types of forest, and confirmed that tropical forests play the biggest role in global carbon fluctuations. Tropical forests not only absorb more carbon, but also release more emissions as a result of deforestation and degradation.

The researchers determined that each year from 2001 to 2019, forests collectively absorbed around 15.6 billion metric tons of carbon dioxide from Earth’s atmosphere.

Meanwhile, deforestation, fires, and other disturbances released an average of 8.1 billion metric tons of carbon dioxide per year. 

“Forests act as a two-lane highway in the climate system,” said principal investigator Nancy Harris, who is the research director for the World Resources Institute (WRI) Forests Program. “A detailed view of where both sides are occurring – forest emissions and forest removals – adds transparency to monitoring forest-related climate policies.”

Despite standardized guidelines from the Intergovernmental Panel on Climate Change (IPCC), current annual reporting of national forestry data varies according to the resources available in different countries. A lack of consistency in the data creates a significant amount of uncertainty.

“The good thing is that we know there is uncertainty and we can actually quantify it,” said study co-author Lola Fatoyinbo, a scientist at NASA Goddard. “All estimates come with an uncertainty around them, which is going to keep getting smaller and smaller as we get better datasets.”

The Global Ecosystem Dynamics Investigation (GEDI), a laser instrument on the International Space Station, records the three-dimensional structures of the world’s temperate and tropical forests. Along with other NASA missions, GEDI data will provide even more insight into the carbon removal rates of these landscapes.

Fatoyinbo, who is part of the GEDI team, explained that tree canopy profiles and global maps of aboveground biomass will be useful for making future carbon estimates.

“This is kind of a major shift in the paradigm of monitoring forests,” said study co-author Sassan Saatchi of the Jet Propulsion Laboratory. 

“It brought in a new picture of where the big changes are happening, in terms of both the land surface losing carbon to the atmosphere and also absorbing carbon from the atmosphere.”

The study is published in the journal Nature Climate Change.

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By Chrissy Sexton, Earth.com Staff Writer