How does forestry affect global warming

Forests remove and store carbon from the atmosphere, representing a cost-effective solution for mitigating climate change. The loss or degradation of forests compromises their ability to remove emissions.

Forests provide a natural solution for removing carbon from the atmosphere. Forests absorb and store carbon emissions caused by human activity, like burning fossil fuels, which include coal, natural gas and oil.

Forests' ability to absorb carbon from the atmosphere can be compromised by conversion into agricultural lands, commodity production, urbanization, disease and fires that cause forest loss. When a tree burns or decays, the carbon stored is released into the atmosphere further exacerbating climate change. With fewer trees to help absorb and regulate carbon in the atmopshere, the Earth's temperature rises and the effects of climate change increase.

Sustainable forest management, improved land tenure, conservation and restoration are all valuable strategies for preserving forests as a natural climate solution. These solutions can have positive economic, biodiversity and societal impacts. They and other researchers say that such studies are hamstrung by sparse data sets on forest emissions. The latest findings are piling on even more complexity.

Ecologist Sunitha Pangala at Lancaster University, UK, spent much of and in the Amazon rainforest, where she placed gas-measuring chambers around the trunks of more than 2, trees. Researchers had previously assumed that methane leaked into the air directly from the soil, where it is produced by microbes. The new work suggests that trees could be another conduit for that microbial methane, potentially explaining why more methane has been detected above tropical wetlands than has been measured emanating from soil alone.

In a study first published last October, Gauci and other colleagues added another wrinkle when they found both methane and nitrous oxide, also a greenhouse gas, leaking from trees in upland forests 6.

The global significance of these findings is still unclear. Pangala and Gauci both estimate that the cooling effect of trees taking up carbon greatly outstrips the warming from tree emissions of methane and nitrous oxide.

But Kristofer Covey, an environmental scientist at Skidmore College in Saratoga Springs, New York, has found methane leaking from non-wetland trees in temperate forests 7 , and argues that such emissions could, in some places, diminish the climate benefits of trees more than researchers and environmentalists realize. The recent explosion of results underscores the need for a full account of the impacts of forests, says Unger.

Scientists who champion forests say that although more research is always good, existing results are mature enough to support the use of forests to fight climate change, especially given the urgency of the problem. Researchers are now turning to sophisticated computer models and using larger and more-comprehensive data sets to nail down exactly what forests in different places do to the climate.

In some cases, the results have been sobering. Last October, a team led by ecologist Sebastiaan Luyssaert at the Free University of Amsterdam modelled a variety of European forest-management scenarios 8. The researchers concluded that none of the scenarios would yield a significant global climate impact, because the effects of surface darkening and cloud-cover changes from any added forests would roughly eliminate their carbon-storage benefits.

To estimate the climate impact of planting forests in different parts of the United States, ecologist Christopher Williams at Clark University in Worcester, Massachusetts, is combining global satellite data collected over more than a decade with carbon-sequestration figures based on data from the US Forest Service. He has found in preliminary work that adding trees to the US west coast and to regions east of the Mississippi River makes sense, climatically speaking.

But albedo changes make forest planting in the Rockies and the southwestern United States a bad deal for the climate in most cases, because the conifers that thrive in those regions are dark and absorb more sunlight than do underlying soils or snow.

Getting planners to adopt such methods could prove challenging, however. Williams has found that some resist considering albedo effects, including representatives of companies hoping to sell carbon credits for forest projects.

More data about the climate impacts of forests could come from long-term studies that track the gases and chemicals that trees emit and absorb. Researchers are using a metre tower in the Amazon to monitor carbon, water and other chemical fluxes over a roughly square-kilometre area of intact rainforest northeast of Manaus in Brazil. A companion tower in Siberia does the same. Teams have erected smaller research towers to collect similar samples at hundreds of sites around the globe amid different types of forest; a tower in Norway, for example, will soon be the first in that country to start taking data in a forest.

But many important areas have not yet been covered. Scientists who debate the climate impacts of forests are eager to get their hands on these data. And even those who are firmly convinced that forest projects can fight climate change welcome the added rigour of more-comprehensive studies.

Ellis, for one, acknowledges that the analysis he co-authored 1 considered albedo effects only crudely; the team did not consider VOCs and methane emissions from trees. Griscom, B. Natl Acad. USA , — PubMed Article Google Scholar. Pan, Y. Science , — Unger, N. Nature Clim. Change 4 , — Article Google Scholar. Scott, C. Nature Commun. Pangala, S. Welch, B. Change Biol. Covey, K. Keeping forests intact is therefore a no-brainer in the fight against climate change.

While all forests have climate-cooling superpowers, tropical forests trap larger amounts of carbon dioxide and evaporate more water. In doing so, they produce that thick and beautifully dramatic cloud cover that reflects sunlight back to space. Which is just one reason the Rainforest Alliance has been fighting deforestation in the tropics for more than 30 years, by innovating and promoting sustainable farming methods and responsible forest management.

In the Amazon, rains begin two to three months before seasonal winds start to bring in moist air from the ocean. The answer? Rong Fu, a climate scientist at the University of California, Los Angeles, and her colleagues, were able to prove that transpiration—a process by which plants and trees release water vapor from pores on the underside of their leaves—was creating clouds over the Amazon. Fu and her colleagues believe that this circulation is what shifts wind patterns to bring in more moisture from the ocean.

Protecting tropical forests, therefore, helps fight climate change and prevents drought, too. Preventing forest loss is only part of the climate solution. Expanding forests could actually provide significant cooling gains against our ticking climate clock.

In a recent study published in the journal Science , researchers at ETH Zurich concluded that the planet could support nearly 2.