In the IMCG/IPS Wise Use Book, the total area of peatlands was estimated to be about 4 million square kilometres, or at least half of the entire global wetland area. Latest estimates, e.g. in the new CoCoGAP brochure, reduce that to just about one third.
Did the bad guys think up new ways to destroy our beloved mires? Are the peat fires, the drainage activities, and peat excavation so intense that they could cause such a dramatic decrease in such a short time?
The answer is no. The total area of peatlands has not changed at all, what has changed is the total area of wetlands. A new Global Lakes and Wetlands Database (GLWD) has been created using state of the art GIS techniques and drawing on the best available sources.
According to GLWD, lakes and reservoirs cover a total of approx. 2.7 million km2 or 2.0% of the global land surface area (except Antarctica and glaciated Greenland), while wetlands are estimated to reach about 8-10 million km2, or 6.2-7.6%. An extrapolation of GLWD data suggests that the total number of global lakes may reach or even exceed 1.5 million for lakes ≥ 10 ha, and 15 million for lakes ≥ 1 ha. With these numbers, lakes may cover about 3.2 million km2, or 2.4% of the total global land surface. Counting that all together, we end up with 10 to 13 million km2 of wetlands (including lakes).
Not only was the data re-evaluated, the interpretation of the Ramsar definition of wetlands has also been stretched some more to include ephemeral or intermittent wetlands. It is a bit strange to see large parts of the Sahara desert and the Arabic peninsula covered by wetlands.
The GIS data is available for free download from:
http://www.wwfus.org/science/data.cfm
A background paper published in the Journal of Hydrology is available from:
www.geo.uni-frankfurt.de/ipg/ag/dl/f_publikationen/ 2004/lehner_doell_JHydrol2004_GLWD.pdf