Deforestation Role Demoted

How well can we slow the growth of atmospheric carbon dioxide (CO2) by slowing deforestation?

It has long been appreciated that fossil fuel burning is the major reason why atmospheric CO2 concentrations are on the rise — recently at a rate of about 2 parts per million (ppm) per year. It has also been widely known that the destruction of forests, especially tropical rain forests, leads to an additional source of human-caused CO2 emissions.

But many of us were shocked by the size of the deforestation source estimated to account for 20 percent of the total anthropogenic CO2 emissions, according to analysis of data from the 1980s and 1990s by the International Panel of Climate Change. It was also a shock to realize that when CO2 emissions from deforestation are included, Indonesia and Brazil — two countries not typically associated with large amounts of pollution — rank the third and fourth largest CO2 sources, respectively, behind the two leading sources, China and the United States. (See here [pdf] and another Grok post here.)

REDD Program Aims to Attack Problem at Some of Its Roots: Slowing Deforestation

While some of us reeled, others saw opportunity to broker a global deal. Why not set up a system whereby the countries of the developed world could offset their CO2 emissions from burning fossil fuels by paying the tropical rain forest countries to slow the rate of deforestation? Such a system would be a win-win-win:

1. The developed economies would have access to relatively inexpensive emission offsets to buy time while developing and implementing low-carbon energy technologies.
2. The tropical rain forest countries would have a new source of revenue that could help bring their citizens out of poverty without having to destroy one of their (and the rest of the world’s for that matter) most important natural resources while also reducing the air pollution that forest fires produce.
3. And the globe would see a slowing in the growth of greenhouse gas emissions while helping to save the precious but dwindling resources of the tropical rain forests.

And thus was born the concept of REDD: the Reducing Emissions from Deforestation and Forest Degradation program would formalize a system allowing the transfer of funds from developed economies to tropical rain forest countries in return for the flow of carbon offsets from the tropical rain forest countries to the developed countries. (More on REDD.)

There is a broad consensus that that REDD should be incorporated into the post-Kyoto climate treaty to be negotiated in Copenhagen in December. (Note that a similar system of transfers from the United States and the tropical rain forest countries is incorporated into the Waxman-Markey climate bill passed by the U.S. House of Representatives.)

But How Large Are the Potential Offsets Available from REDD?

Could we really reduce global emissions by 20 percent by stopping deforestation? Maybe not, argue the authors of a commentary published today in Nature Geosciences. Lead writer G.R. van der Werf of the University of Amsterdam and a number of other scientists including Prasad Kasibhatla and Rob Jackson, colleagues of mine at Duke University, argue that the deforestation source is not 20 percent of the total but 12 percent (with an uncertainty range between six and 17 percent). The downgraded percentage arises from:

• improved assessments from satellite data of the rates of forest loss in the topics and
• the fact that while fossil fuel emissions have continued to increase over the past decade, deforestation rates appear to have remained flat.

If correct, this new analysis suggests that REDD would not be as powerful an engine of CO2 emission mitigation as we’d been planning on.

Including Peatlands Could Pack a Better Climate Punch

But there is another aspect of the study that is probably more important. It has to do with the destruction of peatlands.

Tropical peatlands, located [pdf] primarily in poorly drained areas of Southeast Asia, are wetlands that have built up thick soil deposits of partially decomposed plant biomass (peat). While only covering a very small percent of the Earth’s surface, tropical peatlands hold vast carbon reservoirs on the order of about 70 billion tons of carbon.

When these lands are drained and cleared for agricultural purposes (typically for rice cultivation or oil palm plantations), the soil dries out and restarts the decomposition process releasing CO2 to the atmosphere — at which point they become very susceptible to fires, which release even more carbon more quickly.

The authors concluded from satellite data that CO2 emissions from peatland destruction are about three percent of the total emissions. So the combined emissions from deforestation and peatland degradation amounts to about 15 percent of global emissions (with an uncertainty range of between eight and twenty percent), which would bring us closer to the 20 percent initially estimated for deforestation.

The problem is that because peatlands have a low density of trees, they are not considered to be forests and so their destruction is not considered deforestation. For this reason, mitigating peatland destruction is not in REDD even though it would reduce CO2 emissions. The authors note in closing:

"If changes in terrestrial carbon storage are to have a role in a post-Kyoto agreement, a strong focus on monitoring changes in carbon content, irrespective of forest cover density would strengthen the effectiveness of REDD programmes. For example, replacing peat forest with oil palm plantations may not change the tree cover density, but it does lead to a large pulse of CO2 emissions because of reductions in both tree biomass and soil carbon8."

Something for the climate negotiators to think about as they prepare for the Copenhagen meeting.