Keeping the Carbon in the Rainforests
THIS SECTION WAS WRITTEN NEARLY A DECADE AGO AND IS NOW BEING REVISED. CHECK BACK LATER FOR UPDATED VERSION.
Deforestation accounts for a substantial amount of the carbon being released into the atmosphere. Estimates vary, but, using the Stern Review (1) figures, current emissions would be 18 – 20%, of total emissions, which is more than the contribution of transport. If nothing is done to halt expected trends emissions from deforestation from 2008 to 2012 will exceed the total of all aviation emissions in the period since aviation began up to 2025(1).The world’s forests are estimated to be storing more carbon than what is currently present in the atmosphere (2). Clearly we want it to stay there.
Forests are cleared for many reasons: logging, large scale agriculture such as soy bean cultivation, palm oil plantations, slash and burn farming by small farmers, and cattle ranching being the main ones. Overall worldwide has been estimated that about 60% of the clearance is for slash and burn farming(3), though some recent estimates put it at only 40%, still a sizeable figure (4). In the Amazon region large-scale operations like cattle ranching have a proportionately greater impact, but slash and burn still accounts for a very substantial part. Overall, as the Amazon is the largest rainforest area, this is very important.
Diagram of the relative importance of different causes for deforestation in the Amazon. (Used with the kind permission of mongabay.com)
The Stern Review strongly recommends that action be taken to reduce deforestation as a fairly readily available means to reduce greenhouse gas emissions. Contrary to what most people would think, as much as 46% of the carbon stored by forests is actually stored in the soil(3) (though this varies with the type of forest). Increasing soil fertility increases the amount of carbon stored in the soil, whereas methods of cultivation that till the soil by turning it over encourage release of carbon from it. Inga alley cropping, as well as reducing the need for slash and burn farmers to move and cut new areas of rainforest, increases soil fertility. Indeed the Stern Review recommends agroforestry for this purpose.
Maize thriving in a sustainable Inga alley with pruned Inga regrowing down the centre. Photo by FUPNAPIB 2006.
‘Without satisfying the peasant farmer, deforestation for subsistence agriculture will only grow worse as the worldwide population of more than 600 million poor tropical farmers continues to expand at 4-6 percent annually” (Mongabay(3))
References and further reading
- The Stern Review. We recommend Ch. 25 for further reading.
http://www.hm-treasury.gov.uk/sternreview_index.htm
- GreenFacts. Gives a good summary of FAO report.
http://www.greenfacts.org/en/forests/l-3/3-climate-change.htm#0p0
- Mongabay. Recommended for further reading.