Studies show climate change's impact on CA
A spate of recent research offers new insight into how global warming is changing or could change California, from the mountains to the seashore, in both predictable and unusual ways.
The studies show that common trees are fading from their current ranges, premium wine grape varieties are under siege, marine creatures are shifting locales, the hub of the state’s water system faces increasing risks and — surprisingly — birds in the state are getting bigger as the weather warms.
Such reports are part of a larger effort to localize climate predictions, which often have been fuzzy at the regional level.
The potential for a more rapid pace of ecological change was underscored in October when U.S. Department of Energy data showed that global carbon dioxide emissions jumped by a record amount between 2009 and 2010. It was viewed by many as a sign that efforts to control greenhouse gases have stalled and climate-related impacts could be more severe than previously thought.
Well before that data was made public, scientists in San Diego County and elsewhere had forecast water shortages in the Southwest as the region becomes more arid, along with rising ocean levels that are leading seaside communities to rethink coastal development. Such projections prompted Gov. Jerry Brown to call a Dec. 15 conference in San Francisco to address “extreme climate risks and California’s future.”
“Worldwide we have seen an increase in volatile weather events that have had significant impact on global food supplies,” state agriculture chief Karen Ross said heading into her agency’s forum on the issue last week. “As one of the key growing regions in the United States, California must be prepared for effects of a changing climate and what this means for food production.”
Not everyone agrees that the warming climate is cause for alarm and some of them took Brown to task for believing “mad science.”
“Global temperatures are always rising or falling. They always have, and they always will,” said James Taylor, senior fellow for environmental policy at the nonprofit Heartland Institute, which advocates for free-market solutions to social problems.
He said people should be wary of scientific reports about climate change. “So long as these studies claim a global warming crisis, the funding will continue to flow,” he said.
While climate predictions are fraught with uncertainty, researchers are increasingly able to look backward for clues about how changes are playing out even as they try to gauge the future.
“The challenge is to use the long-term data we’ve been collecting to understand how, where and why these changes are occurring,” said Nat Seavy, a research director for PRBO Conservation Science on the Central Coast.
While changes aren’t necessarily bad, many could force people to revise their relationships to natural resources — for instance by using less water, scooting back from the seashore or choosing different plants to grow.
“Ecosystems are always changing at the landscape level, but normally the rate of change is too slow for humans to notice,” said Steven Running, a professor at the University of Montana and a co-author of a new study about how the climate is reshaping forests. “Now the rate of change is fast enough we can see it.”
Using remote-sensing technology over a span of four years, researchers discovered what they call a huge “migration” of trees across the western United States and Canada, driven by drought, insects and fire.
Their study suggests that once-common species such as lodgepole pine will give way to other kinds of trees or perhaps convert to grasslands. Warming conditions are more favorable for insect invasions — a dynamic that is playing out in San Diego County’s backcountry, where the gold-spotted oak borer has killed roughly 80,000 trees.
“We can’t predict exactly which tree (species) will die or which one will take its place, but we can see the long-term trends and probabilities,” said Richard Waring, study co-author at Oregon State University. “The forests of our future are going to look quite different.”
Heat threatens Northern California’s signature crop, which relies on moderate temperatures in places like Napa Valley. While warming in recent decades has generally had a positive effect on wine grape production, a study released in June by Stanford scientists said the trends could soon go too far. They projected that the amount of land suitable for cultivating premium wine grapes could shrink 50 percent by 2040 as the temperatures rise and prime growing territory shifts to Oregon.
“It’s risky for a grower to make decisions that consider climate change because those decisions could be expensive and the climate may not change exactly as we expect,” Stanford scientist Noah Diffenbaugh said when the study was published. “But there’s also risk in decisions that ignore global warming, because we’re finding that there are likely to be significant localized changes in the near term.”
Nowhere are climate changes more likely to affect large numbers of Californians than in the Sacramento-San Joaquin Bay Delta, which provides water for 25 million people and for crops valued at $36 billion per year.
The U.S. Geological Survey in November released what it called the first integrated assessment of how the delta region will respond to global warming. It was based on what the agency said were observed patterns of longer growing seasons, smaller snowpacks, higher sea levels and more extreme tides.
The study says the combination of higher water temperatures and higher salinity could further jeopardize the delta’s smelt and salmon, while higher sea levels will increase the potential for flooding in a region where decades-old levees already are under stress. In addition, USGS scientists said planners should prepare for longer dry seasons and less snow melt in the summer when it’s needed most.
“Today’s extremes could become tomorrow’s norms,” they said.
Off California’s coast, increases in tropical Humboldt squid and decreases in salmon abundance suggest marine creatures are trying to adapt to altered conditions, said William Sydeman of the nonprofit Farallon Institute for Advanced Ecosystem Research in Petaluma and science adviser for the California Ocean Protection Council.
“Geographic shifts in temperature bands … in the sea have outpaced those observed on land,” said Sydeman, co-author of a recent article on the topic in the journal Science. “We should not be surprised when we see substantial change in the whereabouts of marine populations or changes in their timing of breeding or migration dates.”
Scientists in Northern California found that birds’ wings have grown longer and birds are increasing in mass over the past 40 years.
Their discovery runs counter to an ecological rule of thumb that says animals tend to be larger at higher latitudes, in part to conserve body heat that allows them to survive the cold. Under this reasoning, some scientists have predicted that animals will get smaller as Earth warms.
But other forces could be at work, according to scientists at San Francisco State University who analyzed data collected by PRBO Conservation Science and San Francisco Bay Bird Observatory. For instance, they said birds might get bigger as they store more fat to endure severe weather events attributed to climate change. Also, global warming could affect plant growth patterns, altering avian diets and their size.