The songbirds at the feeder outside your window are not the same as they used to be. The goldfinch, the grosbeak and even the ever-present sparrow are all a little bit bigger.
The reason is climate change, according to a new study, which found that 70 bird species, all common to Central California, have evolved a longer wingspan and greater body mass over the past 40 years.
Scientists think such adaptations, in annual increments of less than a tenth of a percent on average, help birds cope with food shortages and stronger storms already triggered by climate change.
"We need to be thinking about things like extreme weather and other ways climate change is going to impact our ecosystems, and those things are not just important for birds," said Nat Seavy, co-author of the bird study and research director at PRBO Conservation Science, a research facility in Petaluma. "They are important for farmers and all sorts of people."
The evidence is just one piece of a new wave of research slowly painting a more vivid picture of what climate change may mean for California. The studies also reflect a new effort by scientists to help the public understand climate change by speaking plainly.
"We struggled mightily to translate these results into lessons that could be useful to policymakers and resource managers," said James Cloern, a biologist at the U.S. Geological Survey in Menlo Park and lead author of a comprehensive new climate study on the Sacramento-San Joaquin Delta.
"We don't want to scare people with this paper. We want to put them in a position where they can start thinking and planning."
Cloern's study marks the first attempt to explain how climate change may affect habitat in an entire estuary, in this case the Sacramento-San Joaquin Delta. The study took seven years and is the most complex Cloern has undertaken in a 36-year career researching the estuary.
Among the projections:
Extreme water heights that cause flooding – a combination of sea level rise, high tide and storm surge – will switch from rare to routine. Water heights that now occur eight hours per decade at the Golden Gate are projected to occur 1,000 hours per decade by 2050, and worsen thereafter.
Changes in snowmelt may mean that long periods of flooding become rare in the Yolo Bypass by 2060. Such flooding creates an explosion of insect food that is important to imperiled fish, including salmon.
Water temperatures lethal to endangered salmon and Delta smelt will become common by 2080.
The findings raise important questions for the public and policymakers.
A Delta restoration and water management plan, now being drafted, could cost $15 billion or more. Some of this money would be spent to create additional habitat for salmon and smelt. Officials and the public will have to decide whether this investment makes sense if climate change is likely to doom the fish decades later.
Many such questions will bedevil society in the years to come.
"I'm not necessarily convinced the extinction of Delta smelt is inevitable," Cloern said. "But we do need to see these projections to get our attention."
One reason, Cloern and other scientists said, is that choices today can prevent undesirable outcomes.
For instance, Cloern's study presents two scenarios: one in which greenhouse gases continue to increase throughout the century, and another in which society halts that growth by 2050.
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