Scientists Reach Agreement on Emissions from Tropical Deforestation

December 3, 2012 | 10:30 am
Doug Boucher
Former contributor

I’m now in Doha, Qatar, at the international climate negotiations (“COP18”), and today was Forest Day. This annual event focuses on the role of forests and deforestation in emissions of global warming pollution, and often is the venue for presenting some of the newest science from around the world.

I participated in two of the panel discussions, one of which, on the drivers of deforestation, was organized by my colleague Peter Akong Minang of the World Agroforestry Center (more about that in a future blog post). The other, organized by the Meridian Institute, featured a new estimate of the total global warming emissions from tropical deforestation, by not just one, but two world-renowned research teams working together. These groups collaborated in a way unusual in science, to reconcile their previously quite different estimates, and found that once one compared mangos with mangos rather than with pineapples, their numbers were remarkably similar.

Both research teams agree that the best estimate is 3.0 Gt CO2/year (billions of tons of carbon dioxide annually). They emphasized that the details of what is and isn’t included in this number are critical: It’s for carbon dioxide from forest biomass, across the tropical region, in gross terms (i.e. without subtracting out removal of CO2 from the atmosphere by forest regrowth). It’s for deforestation only, and doesn’t include emissions from kinds of forest degradation such as logging, fuelwood collection, or shifting cultivation. Nor does it include emissions from forest soils, whether mineral soils or the peat that contains large amounts of carbon in southeast Asia, and whose decomposition is a major source of the global warming pollution associated with the palm oil industry in Indonesia and Malaysia.

It’s important to note that the estimate refers to emissions in the period 2000-2005 — that is, fully a decade ago. We know that since that time, emissions in the Brazilian Amazon have dropped by 75 percent, but for other countries — including, critically, Indonesia — recent data is not yet available. So it’s not clear whether or how much emissions today have decreased from the 3.0 gigaton estimate.

Flowers of the Hombre grande tree (Quassia amara), a medicinal plant from the rain forest of southeastern Nicaragua. Photo: Doug Boucher

As Dan Zarin of the ClimateWorks Foundation pointed out in the event today, this kind of cooperation among scientists is unusual. This is particularly the case in prominent, high-impact areas of research such as tropical deforestation and climate.

The two research groups, led by Dr. Sandra Brown of the Ecosystem Services Unit of Winrock International and by Dr. Richard Houghton of the Woods Hole Research Center, deserve special praise for this cooperation and for working rapidly and intensively to answer an important question for international climate negotiators. So do ClimateWorks, Meridian and the Government of Norway’s International Climate and Forest Initiative, who brought them together and funded their collaboration.

What’s the significance of having a new and better estimate of emissions from tropical deforestation? First of all, it’s a major scientific advance — far more rigorous and reliable than the consensus statement, announced in a press release at the Barcelona climate negotiations in 2009, that estimated that “about 15 percent if peat degradation is included” was due to tropical deforestation. Furthermore, it proves a baseline or “reference level” to which reductions in deforestation emissions, in the past decade and in the future can be compared.

Picture of me standing in front of a fig tree in West Bali National Park, Indonesia, during a break in the 2007 climate negotiations which agreed to reduce emissions from tropical deforestation.

For several years now many countries and organizations have supported a goal of reducing emissions from deforestation by 50 percent by the year 2020 — but without saying what was the starting point for that 50 percent reduction. I remember hearing the saying, describing the importance of having controls in experiments, that the most important question in science is “compared to what?” For emissions from deforestation, we now have a good answer: 50 percent less than the 3.0 Gt CO2 of  a decade ago.

I spoke briefly in the panel, acted as a reviewer on the new Policy Brief, and gave advice to the authors and funders over the past few months. In addition, using my rusty but hopefully still serviceable French, I did interviews about the new estimate with journalists from Le Monde and Radio France Internationale (RFI). It was an honor to be involved in this effort, which I hope will be an example for researchers in many parts of the scientific community.