Peter Gallagher

One of the themes of the Copen­hagen Syn­the­sis Report (avail­able here) by a group of uni­ver­sity researchers asso­ci­ated with the IPCC, is the impact of global defor­esta­tion on total CO₂ emissions.

Regret­tably, the Report’s mate­r­ial on defor­esta­tion and on the role of forests in the car­bon cycle is short on data and analy­sis. The Report con­tents itself with a ref­er­ence to the IPCC esti­mate (Fourth Assess­ment Report) that defor­esta­tion con­tributes about 15 of total anthropic emis­sions but ignores the cur­rent sci­en­tific con­tro­ver­sies rel­e­vant to that esti­mate: espe­cially the ques­tion of the rate and dis­tri­b­u­tion of defor­esta­tion and whether trop­i­cal forests are net car­bon emit­ters or sinks.

Prof Roger Pielke Jr. (not a ‘skep­tic’ about AGW) attacks the Syn­the­sis Report for sloppy sci­ence and a per­sonal mis­rep­re­sen­ta­tion. His father, Prof. Roger Pielke Sr. (more skep­ti­cal) ticks off other gross inac­cu­ra­cies. Sta­tis­ti­cian David Stock­well details a con­ve­nient manip­u­la­tion of the sur­face tem­per­a­ture out­look by one of the lead­ing Copen­hagen researchers in a series of posts start­ing here.

I’ve never looked closely at the alle­ga­tion that forests (espe­cially trop­i­cal forests) are dis­ap­pear­ing, although any­one who has expe­ri­enced the great Malay Penin­sula smoke hazes (due to Indone­sian burning-off) either on the ground or fly­ing across the region, must be tempted to find the alle­ga­tions of a gen­eral dis­as­ter plau­si­ble. As it turns out, only a lit­tle research shows that the over­all scale and emission-impacts of defor­esta­tion is unclear and the data thin and sub­ject to revision.

A place to start is the NASA Earth Obser­va­tory site that sum­ma­rizes the known and unknown:

On the scale of the problem:

“Some sci­en­tists and con­ser­va­tion­ists argue that the FAO pro­vides too con­ser­v­a­tive an esti­mate of rates of defor­esta­tion because they con­sider any area larger than one hectare (0.01 square miles) with a min­i­mum tree cover of 10 per­cent to be forested. This gen­er­ous def­i­n­i­tion of ‘for­est’ means that a sig­nif­i­cant amount of degra­da­tion can occur before the FAO cat­e­go­rizes an area as defor­ested. On the other hand, some satellite-based stud­ies indi­cate defor­esta­tion rates are lower than even the FAO reports sug­gest. In the FAO’s most recent for­est assess­ment report, pub­lished in 2005, the orga­ni­za­tion itself revised down­ward the defor­esta­tion rates for the 1990s that it reported in 2001. Despite revi­sions and dis­crep­an­cies, the FAO assess­ment is the most com­pre­hen­sive, longest-term, and widely used met­ric of global for­est resources.” Extract from Trop­i­cal Defor­esta­tion : Fea­ture Articles

On the emission-impacts:

“It is not cer­tain whether intact trop­i­cal forests are a net source or sink of car­bon. Cer­tainly, the trunks of trees are a large, sta­ble pool of car­bon that grows as forests mature or regen­er­ate on pre­vi­ously cleared land. But trees, plants, and microor­gan­isms in the soil also respire, releas­ing car­bon diox­ide as they break down car­bo­hy­drates for energy. In the Ama­zon, huge vol­umes of car­bon diox­ide escape from decay­ing leaves and other organic mat­ter in rivers and streams that flood large areas of for­est dur­ing the rainy sea­son. Undis­turbed trop­i­cal forests may be nearly neu­tral with respect to car­bon, but defor­esta­tion and degra­da­tion are cur­rently a source of car­bon to the atmos­phere and have the poten­tial to turn the trop­ics into an even greater source in com­ing decades” Extract from Trop­i­cal Defor­esta­tion : Fea­ture Articles

The FAO, which is respon­si­ble for col­lect­ing the data on for­est extent, pro­vides its cur­rent (2005) data in dif­fer­ent sum­maries avail­able from the Forestry Divi­sion. This is the adjusted data to which NASA (above) refers. As the spread­sheets show, much of it is based on rel­a­tively old and appar­ently imper­fect data col­lec­tion meth­ods. For exam­ple, the spread­sheet reveals that in the five-years lead­ing up to the 2005 report, only 25 countries/regions of 230 (admit­tedly includ­ing the biggest ‘defor­esters’ and ‘refor­esters’) were sur­veyed using ‘remote sens­ing’; for­est change in the oth­ers was esti­mated by other sur­veys or ‘expert esti­mates’. FAO’s planned 2010 sur­vey should be much more accurate

What does the data from FAO tell us? I’ll leave it to you to down­load the sur­vey data, but here are a few of my observations:

• The ‘annual rate of change’in for­est extent as esti­mated by FAO is very small: in 2000–2005 it was less than one-fifth of one per­cent of the total for­est extent (7.3 mil­lion hectares).
• The defor­esta­tion rate is falling from an annual rate of 0.22 per­cent in 1990–2000 to 0.18 per­cent in 2000–2005
• In the biggest ‘defor­esters’ (Brazil and Indone­sia), how­ever, the annual rate of for­est loss has risen (from 0.5 to 0.6 per­cent per year in Brazil)
• In con­trast, some of the biggest ‘re-foresters’ such as China—whose total for­est extent is a lit­tle less than half that of Brazil—have seen their annual rate of re-forestation grow from 1.2 per­cent to 2.2 per­cent per year over the same periods.

The extract from the spread­sheets that I have made (click the thumb­nail at the top of this post) to illus­trate the worst of the de-forestation esti­mated by FAO shows:

• The twenty-seven top de-foresters (I used a 100k ha. cut-off) have a higher, not a lower rate of defor­esta­tion than the rest of the world
• Weight­ing their hectares ‘lost’ to for­est by their share of global forests they accounted for an annual 0.257 per­cent loss of global for­est in 1990–2000, and an annual loss of 0.281 per­cent of global forests in 2000–2005 (their higher rate of loss was off­set by gains in for­est cov­er­age in 56 coun­tries, led by China)