It is often said that biodiversity is crucial for staving off extinctions. Ecosystems are complex and are essentially defined by the interdependencies among the various animals and plants. It stands to reason that removing species from an ecosystem can have significant effects up and down the food chain. Extinctions are much more likely when biodiversity diminishes.
While this makes good sense, the fact is that until now, this concept has not been demonstrated in a controlled experiment.
Researchers at the University of Exeter in the United Kingdom have recently published a study that shows that when you remove a species from a simple community – meaning a community with fewer overall species – it can trigger extinctions in other species. They then provided evidence that more complex communities are better able to stave off the chain of events where one species loss leads to another and another – something known as an extinction cascade.
True biodiversity acts as a buffer against such cascades because in a complex community with many species, if you lose one animal, the chances are good that something else will fill its role.
The Exeter researchers studies a micro-ecosystem consisting of bean and barley plants inhabited by several species of aphids and three parasitic wasp species that each ate only specific aphids. By selectively eliminating one wasp species, certain aphid populations exploded, crowding out other aphid types and thereby decimating other wasp species. By creating microcosms with more aphid and wasp species at the outset, these extinction cascades were less likely to occur.
Scientists believe we are in the sixth mass extinction and are losing species at an accelerated rate. If we can focus our efforts on preserving as much biodiversity as possible, we can give ecosystems the best chance to survive.
Photo, posted August 4, 2013, courtesy of Dace Kirspile via Flickr.