The shape of things to come — sizing up the geometry of habitat loss

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Violet Sabrewing, a high-elevation rainforest hummingbird. (Photo by Walter Jetz / Yale University)

The shape of a lost habitat goes a long way toward predicting the future of species extinction and biodiversity, according to a study from researchers at Yale and in Europe.

Area loss is obviously a critical factor for biodiversity within an ecosystem, researchers say, but so is the geometry of that lost habitat. In fact, that geometry may separate the species that see swift change from those that experience slower change, they say. These species may differ in other attributes, too.

“The relationship between the size of an area and its species richness has been considered one of the few law-like ecological relationships and has been used by conservationists to gauge potential extinctions as habitable area is lost. Our study shows that any such applications require a much more nuanced approach,” said Walter Jetz, a Yale associate professor of ecology and evolutionary biology, and director of the Yale Program in Spatial Biodiversity Science & Conservation. Jetz is co-author of the new study, published in the Nov. 17 online edition of Nature Communications.

“As we show, the specific way suitable areas are lost is absolutely critical for predicting species losses and, moreover, the impact varies with species’ functional and evolutionary role,” Jetz said.

The researchers looked at extensive data for birds, mammals, and amphibians on four continents — North and South America, Africa, and Asia — in their analysis. They found that species and biodiversity loss is greatest when a habitat is nibbled away from the outside and losses move inward. All facets of biodiversity suffer less when habitat loss starts in the center and moves outward. The effects are least severe when a habitat dwindles in random pockets.

Lead author Petr Keil of the German Centre for Integrative Biodiversity Research, noted that current methods only consider the amount of area lost, rather than where it is lost, when estimating species extinctions. The new study indicates that species living at the periphery of a region and have smaller range sizes, may be most at risk.

“Many people would agree we now face a serious extinction crisis,” said co-author David Storch of Charles University. “We demonstrate that the knowledge of total area of habitat loss is not sufficient for a proper prediction of biodiversity loss — it is crucial to know exactly where that habitat is lost.”

The research received support from the People Programme of the European Union’s Seventh Framework Programme and grants from the National Science Foundation and NASA.

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