A commentary on: Tropical deforestation and atmospheric carbon dioxide

Abstract

Richard Houghton’s contribution confirms what many had suspected: that the rate of CO2 emission to the atmosphere from tropical deforestation is substantially larger than what it was in 1980, the year on which previous analyses of the role of tropical deforestation in the global carbon cycle have been based. Houghton estimates a likely 1989 emission of 1.5−3.0 × 1012 kg C, compared to a 1980 emission of 1.0−2.0 × 1012 kg C using the same methodology and assumptions. This increase is a direct consequence of a dramatic increase in rates of deforestation for a variety of social, political, and economic reasons. The most serious consequence of this deforestation in my opinion is not its effect on climate or atmospheric carbon dioxide, but the massive species extinctions — a biological holocaust — which it implies. Absorption of atmospheric CO2 by the oceans will remove about 85% of the emitted CO2 within a few hundred years, dissolution of marine carbonate sediments will remove another 10% or so within a few thousand years, and silicate weathering will take care of the rest within about 100 000 years, which is a very short period of time from an evolutionary perspective. Species extinction, in contrast, is irreversible.