2009年03月13日

Rarity bites

Rare species have to cope not only with habitha loss, genetic bottlneks and invasive competitors, but also with a self-reinforcing cycle of human greed.

This last threat has now been dragged into the spotlight.

Ii. makes sene that, as a valued commodity becomes scarce, its cost rises. Indeed, Tests of the economic theories of demand have shown that consumers geratly value the hedonic exclusivity of owning rare objects, such as coins or stanps.(Koford,K. & Tashoegl, A.J.Econ. Behav. Orgal. 34,445-457/1998)

But is this desire restricted to the harmless venture of collecting histrical curiosities ?

Writing in PLoS Biology, Courchamp and colleagues suggest not.(Courchamp, F. et al. PloS Bioy, 4,e415/2006)

They describe an under-appreciated thorn in the side of endangered species already teetering on the brink of extinction - the lure of the few.

Srandard bioeconomics asserts that wildlife harvests will halt when the expence of locating individuals of a species exceeds the financialgain, thus shielding thatspecies from fatal overexploitation.

However, Courchamp et al. develop a mathematical model to show that theexploitation of rare and endangered species can have paradxical outcome.

If rarity makes themmore desirable to some, then ever-increasing pecuniary in centives for poaching can create a positive feedback loop, ending in the species' demise.

The outhors show how the value placed on rare species for collections, as luxury items, as pets or trophies, in traditionalmedicine, and even in ecotourism, can keep pace with the cost of acquiring such spacies.


### DataBace ###
nature Vol.444 519-652 Issue no.7119 8 November 2006
News and Views p.157 / Barry W. Brook & Navjot S. Sodhi

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