A Northern Pintail. This dabbling duck can be found in much of the Northern Hemisphere, including the San Joaquin Bay-Delta, although in considerably lower numbers than in the past. Credit: Dan Cox, USFWS. Download.
More Photos: San Francisco Bay-Delta on Flickr
As federal, state and local experts continue to examine the factors contributing to the recent decline of California’s Bay-Delta ecosystem, the effects of climate change have surged to the forefront of study.
The Bay-Delta (Sacramento/San Joaquin River Delta-San Francisco Bay Estuary) is considered one of the most vital estuary ecosystems in the U.S. The Delta is at the crossroads of federal and state operated delivery systems that transport water from Northern California to agricultural and urban water users to the south. It’s a source of drinking water for approximately 22 million people while supporting an approximate $30 billion agricultural industry. The Delta and its watersheds also support several threatened and endangered species, and a popular recreational and commercial fishing industry.
But the Bay-Delta is in the throes of a well-chronicled crisis. Four recent years of below average precipitation have hammered this fragile ecosystem, contributing to the puzzling decline of the Delta fishery and the collapse of California's salmon fishing industry. The combination of decreased water supplies (from the drought), and seasonal water restrictions to protect the threatened delta smelt, endangered Chinook salmon and other species, has created a volatile political situation.
|Credit: Steve Culberson, USFWS.|
Climate change, barely mentioned a decade ago, is now considered a major factor in the Delta planning picture. The rise in sea level, temperature, and changes in the timing of rainfall and snowmelt– all considered effects of climate change – are altering the landscape.
The Service’s Bay-Delta Fish and Wildlife Office, in Sacramento, California, is involved in examining the near-and long-term effects of climate change on Bay-Delta species through several planning efforts. The Service in 2008 established criteria for managing water flows through the Delta and issued a biological opinion that determined the effects of operating the state and federal water projects were putting the delta smelt at risk of extinction. Climate change research and projections were a key element of that biological opinion.
As a collaborator on the joint agency Bay-Delta Conservation Plan (BDCP), the Service is involved in modeling that incorporates climate change at three future intervals until 2060. When complete, the BDCP will be a comprehensive protection and restoration agreement for the Delta and its water supply.
Preliminary modeling for the BDCP shows mean annual temperatures increasing by as much as 3 degrees (°C) by mid-century, and sea levels rising up to 1 ½ feet.
“As our understanding of climate change has improved, climate change has been added to the list of factors affecting the Delta ecosystem,” said Dan Cox, the Pacific-Southwest Region’s Regional Habitat Conservation Plan Coordinator. “With climate change, what we’re seeing is that the past is not a good indicator of the future. Changes are occurring at a much more rapid pace than before.”
|Credit: Heather Webb, USFWS.|
Total precipitation and temperature changes are two obvious factors linked to climate change, Cox said. Those changes can affect the timing of snowpack release into the Delta, which has the potential to affect fish migration patterns or other conditions which cue the behavior of fish and wildlife species.
|Map of the Bay-Delta. Download full-size.|
“We’ve already seen shifts of snowpack melting earlier and shifts of temperature, both of which change the timing of water moving through the rivers and into the Delta,” Cox said. “It’s not just the amount of water that’s important; it’s when the water comes. Both of those factors can have a profound impact on fish habitat.”
Current analysis takes into account many factors, including assumptions about emissions from car exhaust and factories and natural variability of future climate.
Even with all these assumptions about future development and future uncertainties, preliminary analyses show that the conditions in the Delta today are not the same as the conditions that will be there in the future, Cox said.
“If there are changes, how will species respond?” Cox asked. “Will they respond by adjusting? Will fish spawn earlier? Will they spawn at the same time and sustain higher mortality? Uncertainty is huge. We know the past 80-year record fairly well. But the future is not quite so clear.”
To learn more about the work of the Bay-Delta Fish and Wildlife Office, please visit http://www.fws.gov/sfbaydelta/. To learn more about climate change and wildlife in California, please visit http://www.fws.gov/cno/climate.html
Author: Steve Martarano, USFWS.
Contact: Steve Martarano, USFWS, 916-930-5643 (o); 916-335-8841(c)
- Climate Change Focus: Adaptation
- Basin Report: Sacramento and San Joaquin Rivers (from the Bureau of Reclamation)
|On April 25, the U.S. Department of Interior released a report on the climate change risks for water resources across eight major river basins in the West that are dammed and regulated by the Bureau of Reclamation, including the Sacramento and San Joaquin Basin. The report found that moisture falling as rain instead of snow will increase wintertime flows and decrease summertime flows. In addition, warmer conditions might result in increased stress to fish and reduced salmon habitat. To read the full report, visit http://www.usbr.gov/climate/