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Amazonian Plant Extinctions
Volume 12, Number 40: 7 October 2009

Writing in the pages of the Proceedings of the National Academy of Sciences, Feeley and Silman (2009) say that "ongoing development of the Amazon, including natural gas and oil production, large-scale cattle ranching, soy farming, extended networks of improved roads, and the various synergistic activities that invariably accompany increased access, is causing the rapid loss and degradation of natural habitat," which, as we all know, can lead to the extinctions of species that live there.

So just how serious is the situation?

To find out, the two researchers used various collections of pertinent data to map the potential ecoregion-based distributions of the more than 40,000 vascular plant species for which collections were available from the Amazon, after which they estimated rates of habitat loss due to future land-use changes, based on projections made by Soares-Filho et al. (2006) of areas that will be deforested by 2050 under a business as usual and a more optimistic governance scenario, which they finally translated into estimated extinction risks that will prevail in the year 2050. And these operations revealed that by AD 2050, human land-use practices will have reduced the habitat available to Amazonian plants by approximately 12-24%, resulting in 5-9% of species becoming "committed to extinction" at that future date.

Some regions, however, will suffer a whole lot more. In the case of the largest Amazonian ecoregion -- the seasonal Cerrado savannahs of southwestern Brazil that cover about two million square kilometers -- Feeley and Silman applied a habitat loss of 1.5%/year, characteristic of the past three decades, even though they indicate that "habitat loss in the Cerrado has actually accelerated to 3.1-4.3%/year." And they say that if they include "historic habitat loss and use a contemporary habitat loss rate of 3.7%, extinction risk for Cerrado species rises to more than 2 times greater than for non-Cerrado species."

Is this something about which we should be particularly worried? You bet it is, because the Cerrado has been losing "natural habitat to agricultural and pastoral land over the past three decades," in the words of Feeley and Silman; and with the climate-alarmist push for greater biofuel production, those habitat losses will only accelerate with time. Indeed, this is the great threat to the Amazon's biodiversity, not the ongoing rise in the air's CO2 content. In fact, the region's only hope for salvation resides in the atmosphere's CO2 concentration continuing to rise; for it has been demonstrated that without the aerial fertilization and water-conserving effects of atmospheric CO2 enrichment, mankind will have to appropriate most of the remaining untapped land and freshwater resources of the planet -- leaving next to nothing for what we could call wild nature -- just to provide the food our expanding population will require to sustain ourselves a mere four decades from now (see, in this regard, our Editorial of 4 Sep 2002 and our review of the paper of Ceballos et al. (2005).

Yes, it is humanity's growing usurpation of both land and water that is the real threat to the biodiversity of Amazonia, as well as all other parts of the world; and we need the productivity boost and water use efficiency increase that is provided to earth's plants by the ongoing rise in the air's CO2 content in order to help the other species with which we share the planet maintain their presence on it.

Sherwood, Keith and Craig Idso

Ceballos, G., Ehrlich, P.R., Soberon, J., Salazar, I. and Fay, J.P. 2005. Global mammal conservation: What must we manage? Science 309: 603-607.

Feeley, K.J. and Silman, M.R. 2009. Extinction risks of Amazonian plant species. Proceedings of the National Academy of Sciences, USA 106: 12,382-12,387.

Soares-Filho, B.S., Nepstad, D.C., Curran, L.M., Cerqueira, G.C., Garcia, R.A., Ramos, C.A., Voll, E., McDonald A., Lefebvre, P. and Schlesinger, P. 2006. Modelling conservation in the Amazon basin. Nature 440: 520-523.