Corridors link disconnected fragments of plant and animal habitat. It can be as big as a swath of river and forest miles wide that links two national parks, or as small as a tunnel under an interstate highway.

Without such connections, animals cannot travel for food, water, mates and shelter. Plants cannot disperse their pollen and seeds to maintain healthy, genetically diverse populations.

"Human beings tend to think in terms of regular, symmetrical structures, but nature can be much more irregular," said University of California's postdoctoral researcher Matthew Holland, the study's co-author.

"We found that symmetrical systems of corridors may actually do less good for natural communities than designs with some randomness or asymmetry built in," he said.

Designing and implementing corridors is a new subfield in environmental science. Holland's research is among the first to help land managers and community planners designing corridors to know what will work and what will not.

Holland's co-author is UC Davis theoretical ecologist Alan Hastings. Hastings is one of the world's mostly highly regarded experts in using equations to understand natural systems, according to a University of California press release.

His analyses have shed light on environmental issues as diverse as salt marsh grass invasions in San Francisco Bay; climate change and coral reefs; and marine reserves and fish populations.

In 2006, Hastings received the Robert H. MacArthur Award, the highest honour given by the Ecological Society of America.

The new study was published online in Nature Sunday.