It doesn't take a scientist to know what the major causes of animal extinctions are today. Even youngsters learn in school that habitat loss or degradation, invasive species, hunting, and pollution are the major causes.
A much more difficult topic is trying to to predict when a population will become so endangered that it it is doomed to extinction if no action is taken.
Theoretical biologists study this "tipping point" and look for signals of a critical slowing down that indicates that a population is taking longer to bounce back from small declines.
A recent article in Science magazine, discusses a simple laboratory experiment that might help land managers know when they need to step up their conservation efforts.
Using tanks with established populations of water fleas, the scientists mimicked environmental degradation in half the tanks by gradually cutting back on the blue-green algae they were fed and watching for that tipping point.
The study provides experimental evidence for generic early-warning signals that have been theoretically predicted, so that studies of populations might not require detailed knowledge of the species, but only a comparison group or baseline data on population trends.