Warming planet shifts life north and early

Huge studies analyse climate change's toll on plants and animals across globe.

Spring is arriving earlier each decade. Credit: © GettyImages

Two massive studies have charted the impact of an average rise in global temperature of 0.6 °C in the last 100 years on plants and animals around the world.

They conclude that global warming has moved ranges northwards and shifted spring events earlier¹,², as many individual observations of single species have been hinting over the past decade.

These impacts, although not as huge and immediate as regional problems of habitat loss and invasive species, are leaving a sweaty fingerprint over the whole of Earth's natural systems, the studies' authors argue. And, they worry, the picture is set to get worse if warming reaches the 6 °C that some have predicted by 2100.

Previously, Camille Parmesan from the University of Texas, Austin, who led one of the studies, had shown that European and US butterflies have shifted their ranges northwards. "People said 'that's really cool, but it's just one species'," she says. "Biologists were aware that something much bigger than that was going on but we needed a global quantitative analysis of natural systems."

Parmesan, together with economist Gary Yohe of Wesleyan University in Middletown, Connecticut, analysed studies covering 1,700 species over 20-100 years. They found that, on average, ranges have crept about 6 kilometres towards cooler latitudes each decade. Also, spring activities - such as frogs' mating, nest building, and tree buds bursting - have occurred about two days earlier per decade.

Richard Tol, a member of the Intergovernmental Panel on Climate Change, says that the studies are a good step forward from the panel's past work. "This is much more solid collection of literature, more systematic and statistical - it is not easy to collect this type of data," says Tol, who works as an environmental economist at Hamburg University in Germany.

Matching prints lifted

The second study, led by Terry Root, an ecologist at Stanford University in California, found a strikingly similar global fingerprint for about 80% of the 1,500 species that her team studied. The researchers calculate that spring has arrived an average of five days earlier per decade.

"Animals and plants, of all different types, around the globe are feeling the effects of global warming of only 0.6 °C over the last 100 years," says Root. She says that although wildlife has adapted to climate change in the past, the current rate is ten times faster than previous global swings in temperature.

Warming of 6 °C would tear communities apart, Root envisions. The different range and life-cycle movements in different directions and at different rates would disrupt predator-prey and competitor interactions.

"These findings stress the importance of parks as anchors within the landscape where natural processes are the dominant mode," says Lee Hannah, a climate-change biologist with Conservation International in Washington DC. Studies such as these will be invaluable in the future, he says, "if our conservation is going to keep pace with how climate change is affecting species".