In 1949 Aldo Leopold wrote:
"To keep every cog and wheel is the first precaution of intelligent tinkering.”
(A Sand County Almanac, and Sketches Here and There, Oxford University press 1949).
Is this a realistic goal for conservation biology? How does this statement reflect the practices of conservation biology today?
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7 comments:
The precautionary principle (Myers 1993) echoes the sentiments of Leopold; in the face of scientific and societal uncertainties, it would be best to prevent irreversible environmental damage, especially species extinctions. Even though some extinctions appear to leave ecosystem function unharmed, the redundancy of species may provide a buffer against additional human-induced stressors to the ecosystem. A conservative approach to protecting the environment for future generations is to preserve as many species as possible, or “to keep every cog and wheel” possible within the ecosystem.
REF: Myers, N. 1993. Biodiversity and the Precautionary Principle. Ambio 22, 74-79.
http://ucsb.piscoweb.org/~teck/EEMB168/Myers_1993.pdf
Leopold presents the FIRST rule of intelligent tinkering but this does not mean it is the only rule. Perhaps it could be better stated as ‘all else being equal, keep all the bits’. But in life all else is rarely equal. Mankind has already deliberately eradicated the smallpox virus and, hopefully shortly, the poliovirus. Whilst some may argue that viruses are not ‘alive’ this argument will be moot when former President Jimmy Carter’s 25 year program to eliminate Guinea Worm, a multicellular eukaryote, finally succeeds. Others, (Judson 2003) have suggested the deliberate extinction of certain mosquito species as a way to eliminate malaria. The technology for such eradication is already available and theory suggests that it is possible under certain circumstances (Burt 2003). This will lead to a slippery slope once we start to eradicate species for our health and convenience rather than simply through greed or carelessness however the potential benefits to human health and welfare (over half a billion cases of malaria occur each year) demand that we take deliberate species extinctions seriously. Perhaps there are certain cogs and wheels we would sooner do without,
REFS
Burt, A. 2003. Site-specific selfish genes as tools for the control and genetic engineering of natural populations. Austin Burt. Proc. R. Soc. Lond. B vol. 270 no. 1518 921-928.
http://rspb.royalsocietypublishing.org/content/270/1518/921.full.pdf+html
Judson, O. 2003. A Bug’s Death. Op Ed. New York Times, September 25th 2003.
http://query.nytimes.com/gst/fullpage.html?res=9805E5DF143DF936A1575AC0A9659C8B63&sec=health&pagewanted=all
When Leopold wrote this comment in 1948 most people interpreted the cogs and the wheels to be species. But in 1948 scientists had little idea of the amount of genetic diversity that species contained. Today we realize that biodiversity is more than just species diversity. But how much genetic diversity do we need to preserve? This is a much harder question – do we need to keep every single slight variation of a particular cog? Geneticists can suggest how many individuals will be required to maintain a ‘healthy population’, ie to avoid the perils of inbreeding or genetic drift (Shaffer 1981), but the loss of any individual of a species involves the loss of some genetic diversity. Although ‘species’ can be preserved in zoos, gene banks or seed banks it is highly unlikely that more than a fraction of the genetic diversity in a species could be preserved in this way. How much genetic diversity we need in order to keep a healthy population under present conditions is already reasonably well known but how much genetic diversity we need to keep in order to allow species to cope with future environmental change is far less well known. This is unfortunate given that the one thing we know about the environment is that it is constantly changing and that human induced change (eg global climate change) is increasing.
REFS
Shaffer, M.L. 1981. Minimum Population Sizes for Species Conservation. Bioscience, 31, 131-134.
http://www.jstor.org/stable/1308256?seq=1
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Leopold’s statement summarizes the way that conservation biologists have acted over the last 60 years. This principle, that all species should be saved regardless of the cost, is also included in the Endangered Species Act, although the funding to support such actions is rarely provided. This lack of funding, combined with an accelerating problem has led some to suggest that Leopold’s aim is not a realistic goal for conservation biology and that a triage approach should be taken so that resources are most efficiently allocated (Bottrill et al 2008). Because this approach would involve removing funding from certain species, and thus making their extinction inevitable, there are others who argue strongly that we can, and should, aim for zero extinction (Parr et al 2009).
REFS
Bottrill, M.C. et al. 2008. Is conservation triage just smart decision making? Trends in Ecology & Evolution, 23, 649-654
http://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347(08)00281-4
Parr et al. 2009. Why we should aim for zero extinction. Trends in Ecology & Evolution, 24, 181
http://www.cell.com/trends/ecology-evolution/fulltext/S0169-5347%2809%2900045-7
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