WHEN supply outpaces demand prices go down. That simple premise of economics works for the trade in creatures as well as it does for the oil market. But similarity is lost when these two resources get close to running out. The last dregs of oil will be so difficult and costly to tap into that they will persist in pockets of awkward geology long after humans have given up on the stuff.
Living animals, on the other hand, must meet and mate to maintain their numbers. The final, surviving specimens of a species find meeting one another as difficult as the most ardent trophy hunters do locating them. Thus populations ultimately disappear when their demography crosses an invisible point of no return, descending into what conservationists call an “extinction vortex”. This is why banning the trade in highly endangered creatures seems to make sense. In this week's Nature, however, Philippe Rivalan of University Paris-Sud and his colleagues propose the opposite policy.
Banning the buying and selling of a species involves listing it under Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES). That treaty has a second tier of control. Organisms in Appendix II can be traded in a regulated manner, with permits and licences. Any member state can propose that a species be moved between appendices (or newly on or off the CITES register). Other countries then vote on that suggestion. Switching takes about a year.
Dr Rivalan and his colleagues have shown that this long-winded process gives the market so much time to respond that bumping animals up from Appendix II to Appendix I can do more harm than good. Merchants anticipate a ban after many months of paper-pushing and stock up with all the goods they can. That drives up demand, price and, consequently, supply. During one such dawdling period of evaluation, some 2,800 Kleinmann's tortoises became the object of legal barter—a number representing half the total estimated population of that species. On average the 46 animal species moved from Appendix II to Appendix I between 1980 and 2003 were traded at 135% above normal volumes in the year before a ban (see chart). And even when a ban is in place, the perception of scarcity it promotes can increase values and illegal poaching.
What irks Dr Rivalan is that such sudden jumps in demand threaten the very existence of species that the bans are supposed to protect. Conversely, downgrading species can do their numbers a lot of good. The Nile crocodile was demoted to Appendix II in 1981, a measure that allowed farmed populations to meet the demand for skins. That reduced pressure on wild ones.
The next CITES meeting begins on June 3rd. This time the Brazilian caiman and the Bolivian vicuña are up for tactical relegation to Appendix II. The 200 remaining Guatemalan bearded lizards, however, face the possibility of stronger legal protection. Maybe they can fight it off.