Invertebrate Extinction

The fast-moving decline and extinction of many species of detritivores--organisms that break down and remove dead plant and animal matter--may have dire consequences, an international team of scientists suggests in a new study.

The researchers observed a close relationship between detritivore diversity and plant litter decomposition in streams, noting that decomposition was highest in waters with the most species of detritivores--including aquatic insects such as stoneflies, caddisflies, mayflies, and craneflies, and crustaceans such as scuds and freshwater shrimp and crabs.

Decomposition is a biological process that's vital to life, explained study co-author Bradley Cardinale, professor and head of the Department of Ecosystem Science and Management.

But all over the world, detritivore populations are dwindling and disappearing at an alarming rate--a grim reality that spurred the study. There is good evidence that the rate of extinction for these organisms is 1,000 to 10,000 times faster than has occurred through the historic record, Cardinale pointed out.

There are several causes of extinction, Cardinale said. In order of importance, they are habitat loss, overharvesting, competition from invasive species, disease, pollution, and climate change--which he called "the big unknown at this point."

The study, published in Nature Communications, was global and uncommonly robust, involving 75 scientists analyzing decomposition in 38 headwater streams that were similar in size, depth, and physical habitat across 23 countries on six continents. The findings indicate that bacteria and fungi alone likely can't accomplish the amount of decomposition needed in stream ecosystems.

--Jeff Mulhollem