Forests play an integral role in the Earth’s climate, and each forest type – tropical, temperate and boreal – has varying impacts on the climate, serving to both cool and warm the Earth. Credit: Nicolle Rager Fuller, National Science Foundation.

Last Friday Science published their special issue entitled ‘Forests in Flux’. The issue focuses on the future of the world’s forests in light of unprecedented change, largely resulting either directly or indirectly from intensifying human activity. Amongst the News reports, Perspectives articles and online podcast and video, a Review article caught my eye which explains how forests influence climate through physical, chemical, and biological processes.

‘Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests’, by Gordon Bonan of the National Science Foundation’s National Center for Atmospheric Research in Colorado, presents the current state of understanding for how forests impact global climate and emphasises the importance of gaining a better understanding of these influences as forests become more central in global warming mitigation policies – "Forests have been proposed as a possible solution, so it is imperative that we understand fully how forests influence climate."

While even the earliest European settlers in North America recognised that the downing of forests affected local climates, the global impact of such activities has been uncovered more recently as new methods, analytical tools, satellites and computer models have revealed the global harm that deforestation can cause.

As studies have explored the mechanisms behind these effects, and the effects themselves, researchers have come to recognize that calculating the specific harm from a specific local impact is a highly complicated problem. Among other problems, Bonan explains that there is also uncertainty over the impact of temperate forests: “Tropical forests mitigate warming through evaporative cooling, but the low albedo of boreal forests is a positive climate forcing. The evaporative effect of temperate forests is unclear. The net climate forcing from these and other processes is not known."

He concludes, "We need better understanding of the many influences of forests on climate, both positive and negative feedbacks, and how these will change as climate changes. Then we can begin to identify and understand the potential of forests to mitigate global warming."

To find out more about Bonan’s review paper and for a link to a video of Bonan discussing the latest research on how forests impact climate, go to the National Science Foundation press release: If a Tree Falls in the Forest, and No One Is Around to Hear It, Does Climate Change? 

Bonan, G. B. (2008) Forests and Climate Change: Forcings, Feedbacks, and the Climate Benefits of Forests. Science 320 (5882), 1444-1449.

Perspectives papers from Science 320 (5882):

  • Forests of the Past: A Window to Future Changes. Rémy J. Petit, Feng Sheng Hu, and Christopher W. Dick.  Science 13 June 2008: 1450-1452.
  • Predictive Models of Forest Dynamics. Drew Purves and Stephen Pacala. Science 13 June 2008: 1452-1453.
  • Reducing Greenhouse Gas Emissions from Deforestation and Forest Degradation: Global Land-Use Implications. Lera Miles and Valerie Kapos. Science 13 June 2008: 1454-1455.
  • Managing Forests for Climate Change Mitigation. Josep G. Canadell and Michael R. Raupach. Science 13 June 2008: 1456-1457.
  • Beyond Deforestation: Restoring Forests and Ecosystem Services on Degraded Lands. Robin L. Chazdon. Science 13 June 2008: 1458-1460.
  • Changing Governance of the World’s Forests. Arun Agrawal, Ashwini Chhatre, and Rebecca Hardin. Science 13 June 2008: 1460-1462.

For more information on the affect of human activity on the biosphere, keep an eye out for our new internet resource, Environmental Impact – coming soon!

The abstracts for this issue of Science will be appearing on CAB Abstracts, Forest Science Database and other relevant subsets shortly.

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