Scientists, conservationists and governments could have a new weapon to measure — and halt — the devastating effects of the wildlife trade on vulnerable species: the very markets where the animals are bought and sold.

Species that are disappearing as a result of the pet trade can be readily identified by changes in their market prices and trade volumes, a study led by researchers at Princeton University found.

The researchers studied open-air pet markets on the Indonesian island of Sumatra from 1987 to 2013 and found that bird species that increased in price but decreased in availability exhibited plummeting populations in the wild.

Through regular pet-market monitoring, conservationists and governments could use this information as an early indicator that a particular species is in trouble, the researchers report. At that point, more sophisticated measures could be taken to monitor and protect that species’ wild population.

Market monitoring can be done far more quickly and cheaply than field-based monitoring of wild populations, especially in developing tropical countries where fieldwork requires special expertise and can be difficult to conduct.