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Biodiversity and CO2
Volume 3, Number 8: 15 April 2000

"Habitat destruction is the leading cause of species extinction" and "humanity is rapidly destroying habitats that are most species-rich ? largely in the tropical humid forests."  With these words, Pimm and Raven (2000) introduce their commentary upon the recent study of Myers et al. (2000), who estimate that 44% of all species of vascular plants and 35% of all species in four important vertebrate groups (amphibians, birds, mammals and reptiles) are confined to 25 individual "biodiversity hotspots" comprising just over 1% of the surface land area of the globe.  Myers et al. further point out that these hotspots have already lost 88% of their original primary vegetation, comprised predominantly of trees, and that in the absence of greatly increased conservation efforts, they are likely to lose much, if not most, of their remaining primary vegetation in the near future.

In calling for increased funding to save what remains of these endangered repositories of much of earth's biodiversity, Myers et al. note that "the mass extinction of species, if allowed to persist, would constitute a problem with far more enduring impact than any other environmental problem."  Yes, you read that correctly, far more enduring impact than any other environmental problem.  And we agree; for a species lost is a species gone forever.  In fact, Kirchner and Weil (2000) have recently calculated that fully ten million years are required for a somewhat analogous species to reappear on the scene.  Hence, they conclude that "today's anthropogenic extinctions will diminish biodiversity for millions of years to come."

Clearly, the grand problem facing the biosphere today, and the specter that will cast its gloomy shadow over the face of the earth for as far as we can peer into the future, is the threat of massive species extinctions.  Even global warming pales beside the magnitude and immediacy of this modern sword of Damocles, suggesting that we must, first and foremost, consider the pressing issue of doing all that we can to preserve the planet's biodiversity.  It is a well established fact, for example, that we can safely wait a full quarter-century before instituting measures to combat global warming (George C. Marshall Institute, 2000), if it happens to be proven in the interim that this phenomenon is indeed aggravated by anthropogenic CO2 emissions.  But we do not have that luxury in the case of impending species impoverishment; for as Myers et al. state in their concluding remarks, "what we do (or do not do) within the next few decades will determine the long-term future of a vital feature of the biosphere, its abundance and diversity of species."  And that, we need hardly remind you, is the very long-term future.

So what has all this to do with CO2?  No, it is not an attempt to divert attention from the world's most infamous greenhouse gas and place it somewhere else; that would be unconscionable.  Rather, it is to demonstrate that the ongoing rise in the air's CO2 content, as we have written elsewhere (Idso et al., 2000), "may well be one of the best allies we will ever have in our battle to preserve the planet's biodiversity."

Consider, for example, the concluding statement of Pimm and Raven.  They say that "unless the large remaining areas of humid tropical forests [in addition to the biodiversity hotspots] are also protected, extinctions of those species that are still wide-ranging should exceed those in the hotspots within a few decades."  This fact is what drives Andrew Lee of the Worldwide Fund for Nature to state that "we want to save species from all types of ecosystems" (Pearce, 2000).  And this acknowledgement of an even more widespread potential for imminent species demise suggests that something far more wide-ranging and ubiquitous than hotspot protection must be done to preserve what we can of the planet's biodiversity.  It also suggests that it must be done now; and that's where CO2 enters the biodiversity-preserving equation.

In a major review of plant-animal interactions in 51 terrestrial ecosystems, McNaughton et al. (1989) found that the biomass of plant-eating animals is a strongly-increasing function of aboveground primary production.  Likewise, in a review of 22 aquatic ecosystems, Cyr and Pace (1993) found that the herbivore biomass of watery habitats also increases in response to increases in vegetative productivity.  Hence, it is abundantly clear that greater plant productivity - both terrestrial and aquatic - leads to greater populations of plants and the animals that feed upon the plants, which should therefore lead to greater ecosystem biodiversity, because each species of plant and animal must maintain a certain "critical biomass" to sustain its unique identity and insure its long-term viability.

Observations of the world of nature have confirmed the validity of this relationship again and again.  In a study of the vascular plants of 94 terrestrial ecosystems from all across the globe, for example, Scheiner and Rey-Benayas (1994) found that ecosystem species richness is more positively correlated with ecosystem productivity than it is with anything else.  It readily follows, therefore, that anything that enhances ecosystem primary production should also enhance ecosystem biodiversity; and that is precisely what atmospheric CO2 enrichment does, as has been demonstrated in numerous laboratory and field experiments (many of the most recent of which are reviewed on our website).

Viewed in this light, the ongoing rise in the air's CO2 content is seen to be a blessing in disguise.  It's aerial fertilization effect provides a much-needed boost to the vitality of the vegetation that serves as the energetic basis of all ecosystems; and the elevated levels of primary production that elevated levels of CO2 induce in earth's plants - and especially in its trees (Idso, 1999) - provides the basis for greater populations of herbivores and carnivores at all higher levels of the planet's many food chains.  And those greater numbers of individual plants and animals are what help to maintain the viability of their respective species.

Clearly, many other measures, in addition to allowing the air's CO2 content to continue to rise, must be taken to preserve earth's biodiversity.  But equally as clear is the fact that all effective measures that can be taken, must be taken; for even in their entirety, all the things that man can do will still be too few and too late for many species that will shortly be reduced to mere memories(da Silva and Tabarelli, 2000; Pimm and Raven, 2000).  Continued atmospheric CO2 enrichment, therefore, must play a major role in our crusade to save the many life forms that are currently in danger of being lost; and in this regard, the known biodiversity benefits of the ongoing rise in the air's CO2 content far outweigh the speculation that elevated CO2 concentrations might possibly lead to a modest warming of the globe in the decades to come.

Above all, we must never forget that those decades to come will determine the fate of earth's biosphere for the millions of years that follow.  Let's be certain, therefore, in fact, let's be real certain, that we are not "biting the hand that feeds us" - and all the rest of the biosphere - before we enact any measures to curtail life-sustaining and species-preserving anthropogenic CO2 emissions to the atmosphere.

Dr. Craig D. Idso
Dr. Keith E. Idso
Vice President

Cyr, H. and Pace, M.L.  1993.  Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems.  Nature 361: 148-150.

Da Silva, J.M.C. and Tabarelli, M.  2000.  Tree species impoverishment and the future flora of the Atlantic forest of northeast Brazil.  Nature 404: 72-74.

George C. Marshall Institute.  2000.  A Guide to Global Warming: Questions and Answers on Climate Change.  George C. Marshall Institute, Washington, DC.

Idso, K.E., Idso, S.B. and Idso, C.D.  2000.  Atmospheric CO2 enrichment: Implications for ecosystem biodiversity.  Technology (in press).

Idso, S.B.  1999.  The long-term response of trees to atmospheric CO2 enrichment.  Global Change Biology 5: 493-495.

Kirchner, J.W. and Weil, A.  2000.  Delayed biological recovery from extinctions throughout the fossil record.  Nature 404: 177-180.

McNaughton, S.J., Oesterheld, M., Frank, D.A. and Williams, K.J.  1989.  Ecosystem-level patterns of primary productivity and herbivory in terrestrial habitats.  Nature 341: 142-144.

Myers, N., Mittermeier, R.A., Mittermeier, C.G., da Fonseca, G.A.B. and Kent, J.  2000.  Biodiversity hotspots for conservation priorities.  Nature 403: 853-858.

Pearce, F.  2000.  Spread the wealth: When ecofunds are scarce, just what should we conserve?  New Scientist 165(2227): 12.

Pimm, S.L. and Raven, P.  2000.  Extinction by numbers.  Nature 403: 843-845.

Scheiner, S.M. and Ray-Benayas, J.M.  1994.  Global patterns of plant diversity.  Evolution and Ecology 8: 331-347.