Forests absorb carbon like a giant sponge into what scientists call a carbon sink. This fact is well known throughout the scientific community. However, what scientists weren’t sure of until now is the amount of carbon forests can store.
For years scientists knew a large amount of carbon was somehow being stored but could not identify exactly how this was done. This is because less than half of the carbon dioxide released through fossil fuel use remains in the atmosphere. The remaining carbon enters the oceans and other carbon sinks including forests.
Although oceans serve as one of the natural sinks for absorption of significant amounts of carbon, they did not account for all the carbon absorption that occurs. A new report from the U.S. Forest Service has uncovered the mystery. And the missing carbon is standing in front of you -- that is if you’re in a forest.
The study, conducted in collaboration with the U.S. Forest Service’s Northern Research Station and a team of scientists from around the world, was recently published in Science Express and will be published in Science magazine later this summer.
One of the key findings in the study is that global forests have annually removed 2.4 billion tons of carbon which absorbs 8.8 billion tons of carbon dioxide from the atmosphere, about one-third of fossil fuel emissions annually for the period of 1990-2007.
“The new information suggests forests alone account for the most significant terrestrial carbon sink, and that non-forest lands such as agriculture, grass, desert and tundra collectively cannot be considered a major carbon absorption sink,” said Dr. Yude Pan, a U.S. Forest Service scientist and a lead author of the study.
The study reveals the dominant role of tropical forests. Tropical forests, which have not suffered from deforestation, absorb enormous amounts of carbon -- more than all other northern hemisphere forests combined. The analysis also identified an additional large carbon uptake of 1.6 billion tons per year in tropical re-growth forests that are recovering from deforestation and logging, which partially compensates for a large carbon source from tropical deforestation.
The study also highlights risk of passively relying on forests to continue to remove carbon from the atmosphere. Such carbon sequestration is reversible through increased drought, wildfire and forest degradation.
If forests remove less carbon from the atmosphere in the future because of threats to forest health, the need to reduce fossil fuel emissions will become even more critical.
The study is an important example of the use of monitoring data on the state and change of forests around the world, and of the need for global cooperation among the scientific community to address the impacts of human activities on the earth system.
The study found forest carbon sinks are found in every continent on earth. To learn more about climate change and carbon sinks please visit the Forest Service website.