Climate change will alter the mix of vegetation on 49 percent of Earth's land surface by the end of this century, scrambling and shifting existing ecosystems, according to a new study.

Researchers at NASA and the California Institute of Technology say the changing climate will also convert 37 percent of the world's land ecosystems from one type -- such as tundra, forest or grassland -- into another by 2100.

Those vegetation shifts are likely to affect animals and insects that have evolved to live among particular plant species and within certain temperature and precipitation ranges, said the study's lead author, independent scientist Jon Bergengren.

"Animals that are dependent on plants will either have to migrate with the plants, if the plants can successfully migrate, or hang on with plants that are struggling to survive," said Bergengren, who conducted the research as a postdoctoral fellow at Caltech's Jet Propulsion Laboratory. "Either way, there are problems."

Bergengren said that widespread human development will complicate and in some cases prevent plants and animals from migrating to new habitats as climate change alters existing ecosystems.

"A lot of times, when a plant or animal wants to migrate, it runs into a monoculture agricultural zone, or it runs into a city," he said.

The study, published by the journal Climatic Change, is based on the output of a computer model of vegetation change. Researchers used the model to project how the world's vegetation would shift over the next three centuries under the "middle of the road" greenhouse gas emissions scenario developed by the Intergovernmental Panel on Climate Change. It assumes the world's greenhouse gas emissions will double by 2100, then stabilize.

Northern forests move into the tundra

The model projects the biggest changes in the world's plant life this century will occur in the far Northern Hemisphere, particularly in the boreal forest.

The forest's northern edge is poised to march closer to the pole, invading areas that are now tundra. At the same time, grasslands are expected to expand northward into area now covered by the boreal forest's southern edge.

Those changes are often slow, Bergengren said, because many plants and trees can survive in harsh conditions even if they aren't healthy enough to reproduce.

And not every plant species in an ecosystem will react the same way to climate change. Some may be more able to adapt to the new climate than others. Some may be more successful migrating to a new area as current climate zones shift poleward. And some, unable to move or adapt, may simply go extinct.

The research projects that most land areas not covered by ice or desert will see a dramatic change in their mixes of plant and tree species -- 30 percent or more -- with "hotspots" in the Himalayas and Tibetan Plateau, the Mediterranean, eastern equatorial Africa, southern South America, the Great Plains and the Great Lakes.

"It's like three notes in a musical chord," Bergengren said. "If you change a note, you have a new chord. It's not saying that everything is going to change."

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500