Half of California could be occupied by new bird communities by 2070, according to a new study by researchers at Stanford University and partner institutions. The results are published in the Sept. 2 online issue of the journal PLoS ONE.

The study found that as the climate changes, bird species in California are expected to shift their distributions independently, in some cases resulting in combinations of co-occurring species that have not been seen before. These novel (or "no-analog") communities may disrupt complex webs of species interactions, with unanticipated consequences for species and ecosystems, the authors found.

"We know climate disruption will result in major ecological surprises," said study co-author Terry Root, a senior fellow at Stanford's Woods Institute for the Environment. "This work provides yet another wake-up call to scientists, managers and the public struggling with managing biodiversity in the face of rapid environmental change."

For the study, Root and her colleagues at PRBO Conservation Science, theUniversity of California-Santa Cruz and the Klamath Bird Observatory used bird survey data and newly refined regional climate model projections for California to project current and future statewide distributions for 60 relatively common bird species.

A few species, primarily those associated with coniferous forests (such as the Steller's jay and the red-breasted nuthatch), were projected to shift their distributions to higher elevations as the climate warms. But other species that often occur together were projected to shift in very different ways, resulting in novel species assemblages. For example, acorn woodpeckers and western bluebirds, which are often found together in oak-woodland habitats, are likely to shift independently and occur in different combinations in the future. Maps projecting the future ranges of individual species can be viewed online at www.prbo.org/cadc (click the "Where will the birds be?" banner).

"We were surprised to see such a wide range of responses across the species we studied," said study lead author, Diana Stralberg, PRBO landscape ecologist. "We know that many species may shift their distributions in response to climate change, but these results suggest that the cumulative effect on community composition may be of equal or greater importance."

Projecting the future effects of climate change on birds has implications for how ecosystems are conserved, managed and restored today, the authors added. "The likely emergence of novel, no-analog communities over the coming decades presents enormous conservation and management challenges," they wrote. "These challenges will be exacerbated in the high proportion of landscapes that are dominated by intensive human management, where it will be more difficult for species to move to new climatically suitable areas."

According to the authors, novel approaches will be needed to manage and conserve biodiversity, adding that single-species approaches will not work well in the context of rapidly changing climate and ecological communities. "As new combinations of species interact, some species will face new competition and/or predation pressures, while others may be released from previous biotic interactions," they wrote. "Managers and conservationists will be faced with difficult choices about how, where and on which species to prioritize their efforts and investments."

Long-term ecological monitoring, flexible management strategies and frequent communication among scientists, managers and decision makers will be needed more than ever, the authors concluded. "This is more than just an interesting finding about birds," said co-author John Wiens, PRBO chief conservation science officer. "Birds are nature's barometers. If birds occur in different combinations in the future, it's likely that other organisms, such as insects and plants, will as well. The reshuffling of bird assemblages that we project may just be the tip of the iceberg."

The study was supported by the Faucett Family Foundation, an anonymous gift to PRBO and the National Science Foundation.