Supply and Demand - negative ecological effects

A paper just got published in PLoS - Biology - "A Human Taste for Rarity Spells Disaster for Endangered Species" - describes how high monetary value of rare species leads to a vicious spiral in which each capture reduces the remaining number of individuals at the same time as increasing the monetary value - until the last individual is captured and stuffed in some rich guy's collection:

"This phenomenon, the authors explain, resembles an ecological process called the Allee effect, in which individuals of many plant and animal species suffer reduced fitness at low population densities, which increases their extinction risk. Reduced survival or reproduction can occur if individuals fail to find mates, for example, or suffer increased mortality by losing the benefits of pack hunting (more access to prey) or foraging in groups (minimized predation risk). Most studies assume the Allee effect is an intrinsic species trait that human activity cannot artificially induce. But the authors' model shows that humans can trigger an "anthropogenic Allee effect" in rare species through a paradox of value. When rarity acquires value, prices for scarce species can skyrocket, even though continued exploitation will precipitate extinction.

The model predicts that as long as there is a positive correlation between a species' rarity and its value, and the market price exceeds the cost of harvesting the species, harvesting will cause further declines, making the species ever rarer and more expensive, which in turn stimulates even more harvesting until there's nothing left to harvest. And as long as someone will pay any price for the rarest of the rare, market price will cover (and exceed) the cost of harvesting the last giant parrot, tegu lizard, or lady's slipper orchid on Earth."

You can read the synopsis, text or pdf.

So, what kinds of policies can counteract the effects of supply and demand?