Horns and stripes

However, for other species a ban has merely spawned a thriving illegal trade. After trade in all five species of rhino was banned, the black rhino became extinct in at least 18 African countries. The global rhino population has fallen from 75,000 in the early 1970s to around 11,000 today, and some species are on the verge of extinction. Tigers have fared no better.

The point is not that bans never work. They can, especially in the short term or when species are in dire danger. But their longer-term success depends on three factors. First, they must be coupled with a reduction in demand for the banned products. If a ban helps to shift people’s tastes, so much the better. Second, they must not undermine incentives to conserve endangered species in the wild. Third, they have to be supported by governments and citizens in the countries where these species live. If these conditions are not met, bans are unlikely either to reduce trade or to maintain endangered species. They may even make matters worse.

Take demand first. Trade in cat and seal skins, and in parrots, has fallen because consumer campaigns destroyed demand at the same time as trade bans cut the legal supply. Trade is reduced most when demand is sensitive to price: cat and seal skins and parrots fall into this class. Demand is also influenced by fashion.

For tigers and rhinos, demand has proved more resilient. The trade ban has served to increase the price of horn, but demand has stayed strong – and so, therefore, has the incentive to poach. The resulting illegal trade has proved hard to combat.

Second, consider incentives to conserve. Bans may cut out legal wildlife trade, but some economists say they undermine efforts to conserve animals and plants in the wild and may even create incentives to get rid of them. If people have no economic interest in maintaining wild animals or their habitat, the attraction of converting the land to some other use, such as agriculture, increases.

In addition to removing incentives to conserve, bans also remove a source of income with which to manage conservation. Partly for this reason, some countries have asked CITES for permission to sell elephant ivory, rhino horn or tiger bone. The third lot of factors affecting the success of trade bans is the effectiveness of government and social institutions. National enforcement of CITES trade bans is vital for them to work.