Back in the early days of coal mining, miners used to take canaries into the mineshafts to alert them about deadly gasses. If the birds died the miners knew it was time to get out fast.

People also use animals to indicate how healthy the environment is in other contexts. Mining companies in Australia track the types of ants they find near abandoned mines to see if the sites have been fully restored. Waste treatment plants in the United States keep an eye on the bluegill fish to monitor the quality of their water.

For some time, scientists have been looking for something similar to assess the impact of logging companies on biodiversity. They hope that by examining what happens to specific species of animals or groups of species in particular forests they will be able to say whether logging has damaged those forests too much.

So far they have not had much luck. Claudia Azevedo-Ramos and Oswaldo de Carvalho Jr. from a Brazilian NGO called IPAM and Robert Nasi from CIFOR recently reviewed previous attempts to identify species that might be used for this purpose and concluded that to-date no one has come up with any really good candidates.

The authors accept that logging clearly influences which animals survive in the forest and in what numbers. The problem is that each species responds differently. What happens to one species tells surprisingly little about what will happen to others. There are some promising leads like the fact that logged over forests usually have fewer birds that eat insects and more that eat fruits, but these leads still do not amount to much.

Nor is that the only problem. Counting animals in forests is difficult and expensive, particularly if they are rare, hard to identify, or move around a lot. It may also be tricky to figure out whether animal populations decline due to logging or because of hunting.

It would be wonderful if we could find something like the miners’ canaries to help manage forests. But this review suggests it is not likely to happen. Perhaps it is time to put our resources somewhere else.