New maps of global forest carbon flux offer fresh insights for action

Sapelli tree being cut near Imbolo, DRC. Photo by Axel Fassio/CIFOR

Forests are crucial for global efforts to prevent dangerous climate change. As the global community works out what to prioritize in this quest against catastrophe, figuring out which forests are gaining and losing carbon – and why – is an important piece of the puzzle.

Until now, however, data on carbon gains and losses in global forests has been piecemeal and variable, and that has serious implications for land-use decision making – from local to international scales. “I think a lot of the decisions that are taken within the [U.N.] Paris Agreement [on climate change] depend on incomplete data sets, because they come from national greenhouse-gas inventories, which  are frequently incomplete,” said Rosa Roman-Cuesta, an associate researcher at the Center for International Forestry Research (CIFOR), in an interview. “Many countries do not report all their forest activities nor all their carbon pools. This leads to  an inconsistency between what countries report and what global modeling and atmospheric observation offer – It is our role as scientists to help to bridge this gap towards the UNFCCC global stocktake in 2023.”

Roman-Cuesta and a team of scientists from CIFOR, NASA Goddard, NASA Jet Propulsion Lab, The Sustainability Consortium, University of Maryland,  Wageningen University & Research (WUR), Woodwell Climate Research Center and World Resources Institute (WRI), hope to address that discrepancy with a ground-breaking global set of forest carbon flux maps, which have just been released in the journal Nature Climate Change and made publicly available on the Global Forest Watch website. “We now have eyes everywhere to monitor changes of forest cover and carbon stocks globally,” said Sassan Saatchi, principal scientist for Carbon Cycle and Ecosystems at the NASA Jet Propulsion Lab and a co-author of the research, in a press release.

The team used a combination of ground measurements and satellite observations to obtain the first globally-consistent data set for forest carbon flux estimation over the years from 2000 to 2019. The data takes into account the full carbon pool provided by each forest, including above- and below-ground biomass, debris and soil carbon. “This paper, with whatever flaws it may have, offers comparable, complete and consistent data across all forest biomes of the planet and I think that provides valuable new insights on where hotspots for action are in forests worldwide,” said Roman-Cuesta.

“[This is] something that we in the forest remote-sensing community have been working towards for many years, but was a big scientific and computational challenge until now,” said Martin Herold, another co-author and a professor of geo-information science and remote sensing at WUR. “It’s the most up-to-date and detailed map of its kind ever produced — in that sense a really important global contribution in terms of better information on the forest carbon cycle, and on the functioning of forests and their interactions with the climate.”

The researchers found that the world’s forests absorbed twice as much carbon as they released each year. Carbon release was caused chiefly by deforestation and degradation. “Forests act as a two-lane highway in the climate system,” said Nancy Harris, co-author and research director at WRI, in the press release. “Standing forests absorb carbon, but clearing forests releases it into the atmosphere. A detailed view of where both sides are occurring – forest emissions and forest removals – adds transparency to monitoring forest-related climate policies.”

For instance, the fact that 27 percent of the world’s net forest carbon sinks sit within protected areas highlights the importance of prioritizing their continued conservation, said Herold. Meanwhile, the finding that tropical forests across Southeast Asia have collectively become a net source of carbon – due to clearing for plantations, uncontrolled fires and peatland drainage – underscores the importance of international attention on degradation in this region, the paper says.

The granular detail provided by the maps offers important opportunities for policy development and decision makers to choose wisely about where and how to take action on forests. “Many countries don’t [currently] have that level of detail,” said Herold. “Now, they can use this information to make things much more targeted, and ask: if we want to reduce deforestation, where should we go? Where are our emissions hot spots? Where should we do what for forest-related climate action?”

The maps paint a picture not only of where carbon loss is occurring, but also what’s driving it: they disaggregate the contributions of commodity production, shifting cultivation, timber harvesting or fire. That additional information will help decision-makers determine what kind of intervention is necessary, said Roman-Cuesta: for instance, nature-based solutions for fire management would be appropriate in areas where emissions come largely from fire, while emissions from deforestation could be addressed through avoided forest conversion and natural regeneration or assisted reforestation practices.

As countries and organizations around the world prepare to expand forest cover in line with initiatives like the United Nations Decade on Restoration and the Bonn Challenge, the research may also help them to decide whether to devote land to plantations, agroforestry, natural or assisted regeneration, given the relative carbon mitigation potentials of each and their potential as such to contribute to the countries’ nationally-determined contributions (NDCs) to the Paris Agreement.

“Many countries say, ‘we don’t really know how much we can quantify for the NDCs, because we’re not sure how much carbon our forests emit or capture’,” said Roman-Cuesta. “Well, now they have a better answer. And that knowledge will contribute both to [climate-change] mitigation and adaptation, because the number of hectares that you end up putting in one category or another will definitely have an effect on biodiversity, water, and other key services.”

There may also be indirect implications for zoonotic pandemic prevention. With a 30m resolution, the maps on forest sinks and emissions help navigate towards landscapes that are more likely to be degraded, damaged and fragmented, and “in those areas, there’s a high chance that fauna-human contacts will be enhanced,” said Roman-Cuesta. “and we are very likely promoting the emergence of more zoonotic diseases. Zoonotic malaria is a good example in Asia”

The maps’ accessibility is also a boon for transparency, said Herold. “People can essentially look in the forests in their own ‘backyard’ – and everybody else’s too – and gather what the forest carbon situation is. It’s very detailed locally: you get that same level of detail if you look at the Congo Basin or somewhere on the Brazilian Amazon or in the Netherlands.”

That means concerned citizens, environmental non-governmental organizations, journalists, investors and other stakeholders can all access the same data as governments and international organizations, and can use that to ask questions and call global leaders and private companies to account.

“We hope that with more information being openly available, all stakeholders that should be involved in making transformational changes that are needed to address climate change and deforestation, help with restoration and nature-based solutions and so on, will all have a common level of understanding,” said Herold. “If we all have the same level of information, people may feel more comfortable to move ahead. And also to trust that anything that is not going in the right direction, given a certain agreement, will be noted since these kind of data will now be regularly updated to help track forest-related actions in high level of spatial and temporal detail.”

Now that the maps are online, the scientists hope to be able to update them regularly – every year, or even more frequently if possible, said Herold. “If we increase the level of temporal detail now, we would make it even more actionable, as we could really track much more quickly what’s occurring where.”