Cooperative Extension San Joaquin County
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Bleak future for spring-run Chinook salmon

Spring-run Chinook salmon, photographed in Butte Creek (Allen Harthorn/Friends of Butte Creek)
Warming streams could spell the end of spring-run Chinook salmon in California by the end of the century, according to a study by scientists at UC Davis, the Stockholm Environment Institute (SEI) and the National Center for Atmospheric Research (NCAR).

There are options for managing water resources to protect the salmon runs, although they would impact hydroelectric power generation, said UC Cooperative Extension associate specialist Lisa Thompson, director of the Center for Aquatic Biology and Aquaculture at UC Davis. A paper describing the study was published online recently in the Journal of Water Resources Planning and Management.

“There are things that we can do so that we have the water we need and also have something left for the fish,” Thompson said.

Working with Marisa Escobar and David Purkey at SEI's Davis office, Thompson and colleagues at UC Davis used a model of the Butte Creek watershed, taking into account the dams and hydropower installations along the river, combined with a model of the salmon population, to test the effect of different water management strategies on the fish. They fed in scenarios for climate change out to 2099 from models developed by David Yates at NCAR in Boulder, Colo.

In almost all scenarios, the fish died out because streams became too warm for adults to survive the summer to spawn in the fall.

The only option that preserved salmon populations, at least for a few decades, was to reduce diversions for hydropower generation at the warmest time of the year.

“If we leave the water in the stream at key times of the year, the stream stays cooler and fish can make it through to the fall,” Thompson said.

Summer, of course, is also peak season for energy demand in California. But Thompson noted that it might be possible to generate more power upstream while holding water for salmon at other locations.

Hydropower is often part of renewable energy portfolios designed to reduce greenhouse gas emissions, Purkey said, but it can complicate efforts to adapt water management regimes to a warming world. Yet it need not be all-or-nothing, he said.

“The goal should be to identify regulatory regimes which meet ecosystem objectives with minimal impact on hydropower production,” he said. “The kind of work we did in Butte Creek is essential to seeking these outcomes.”

There are also other options that are yet to be fully tested, Thompson said, such as storing cold water upstream and dumping it into the river during a heat wave. That would both help fish and create a surge of hydropower.

Salmon are already under stress from multiple causes, including pollution, and introduced predators and competitors, Thompson said. Even if those problems were solved, temperature alone would finish off the salmon — but that problem can be fixed, she said.

“I swim with these fish, they're magnificent,” Thompson said. “We don't want to give up on them.”

Other co-authors of the paper are graduate student Christopher Mosser and Professor Peter Moyle, both in the Department of Wildlife, Fish and Conservation Biology at UC Davis. The study was funded by the U.S. Environmental Protection Agency.

Posted on Friday, September 16, 2011 at 11:17 AM

Biodiversity is critical to future of California’s ecology and economy

"Biodiversity is critical to future health of California’s ecology and economy," an article by UC Ag and Natural Resources associate vice president Barbara Allen-Diaz and published in California Agriculture journal, provides important information for all Californians. It is vital that we have a clear understanding of these issues in order to make wise decisions now and in the future.

The “web of life” is a delicate interconnectedness of all organisms and environments on earth. We are a part of this intricate web and have a responsibility to take the best possible care of our planet. This can be best accomplished by learning more about the ecosystems around us.

Did you know that:

  • Biodiversity is directly linked to our quality of life?
  • That 3 of the 5 “hot spots” for unique diversity loss nationwide are located in California?
  • Biodiversity within our ecosystems provide such services as pollination, nutrient cycling and cleansing of air and water?

Over 4,800 native plant species live in California. Due to the geologic, topographic and climatic diversity of our state, biodiversity of plant life in our state far exceeds that of any other state, including Hawaii.

Posted on Wednesday, September 14, 2011 at 8:39 AM
  • Author: Chris M. Webb

Lack of pollination due to insecticide use affects onion seed yields, study finds

A lack of pollination by honey bees — brought on by increased insecticide use to control onion thrips — was linked to a sharp decrease in yields of California onion seeds, according to research published in the July-September 2011 issue of the University of California’s California Agriculture journal.

“Honey bee visits to onion flowers were negatively correlated with the number of insecticides applied per field and field size,” wrote the study’s authors, Rachael F. Long of UC Cooperative Extension in Yolo County and Lora Morandin of the Department of Environmental Science, Policy and Management at UC Berkeley. “Reduced onion seed yields in recent years could be associated with the increase in insecticide use, which may be repelling or killing honey bees, important pollinators of this crop.”

The research was conducted in May and June 2009, in 13 commercial hybrid onion seed production fields in Yolo and Sacramento counties. At each of six sampling sites per field, the researchers observed the numbers and types of insects visiting onion flowers that were potential pollinators of onions. To assess onion seed yields relative to insect pollinator activity, they collected onion umbels from the sampling sites and counted the seeds to obtain average yield data. Ground mapping was done around each field to determine whether other preferred floral resources were available to honey bees, perhaps luring them away from onion flowers.

Onion thrips were previously of minor importance in onion seed production. However, iris yellow spot virus is a new pathogen for California onions that is vectored by onion thrips, and it can cause significant onion seed yield losses if left unmanaged. The insecticides used by growers at these field sites to control onion thrips included spinosad, spinetoram, methomyl, cypermethrin, lambda-cyhalothrin and sodium tetraborohydrate decahydrate. The number of insecticides applied per field ranged from one to seven, including tank mixes, with all pesticides applied prebloom. The number of bee hives per acre ranged from four to 14, with the exception of one field that had resident hives at 42 per acre.

“This study found that the number of insecticides applied and field size were the strongest predictors of honey bee activity and onion seed yields,” the authors wrote.

Long and Morandin cautioned that to confirm a causal relationship, more information is needed on the specific effects of different classes and rates of insecticides on honey bee activity. In addition, cultivar can play a role in honey bee activity and needs to be further investigated with respect to pesticide use and bee activity.

“Our study suggests that growers should exercise caution when using insecticides, applying them only when needed as opposed to preemptively, to better protect both wild and honey bee pollinators,” the authors wrote. “Also, the negative correlation between field size and honey bee activity suggests that spreading honey bee colonies around onion fields rather than grouping them may increase honey bee activity and pollination in larger fields.”

Onion seed is primarily grown in Colusa County and the Imperial Valley on about 2,000 acres. The value of the seeds is $12 million to growers, according to agricultural commissioner county crop reports, and they generate an additional $40 million in subsequent retail sales.

“While clearly a specialty, small-acreage crop, onion seed production is important to the rural economies in California where onion seed is primarily grown,” Long and Morandin noted.

Rachael Long monitors pollinator activity in a hybrid onion seed field. Honey bee hives (foreground) are placed in fields to promote pollination. (Photo: Edwin Reidel)
Rachael Long monitors pollinator activity in a hybrid onion seed field. Honey bee hives (foreground) are placed in fields to promote pollination. (Photo: Edwin Reidel)

Posted on Wednesday, September 7, 2011 at 10:43 AM
  • Author: Janet Byron
Tags: honey bees (9), onions (1), pollination (9), Rachael Long (12)

New college degree: “Sustainable agriculture and food systems”

Students preparing food baskets at the UC Davis Student Farm (Photo: Ann Filmer)
The University of California, Davis, is launching a new undergraduate major — “Sustainable Agriculture and Food Systems.” The program integrates several subjects to give students an understanding of the many issues facing contemporary farming and food systems, including production, processing, distribution, consumption, and waste management.

As noted in the Los Angeles Times, “With rising public interest in where our food comes from — as well as in "green" living — it makes sense that higher education would be eager to attract students who want to tap into the intersection between these two fields.”

Students will focus on the social, economic, and environmental aspects of agriculture and food — from farm to table and beyond. The program is designed to help students obtain a diversity of knowledge and skills, both in the classroom and through personal experiences on and off campus.

Students will take courses in a broad range of disciplines, but will focus in one of three tracks:  Agriculture and Ecology, Food and Society, or Economics and Policy.

“This interdisciplinary curriculum will prepare students to become leaders in agriculture and food systems,” said professor Thomas Tomich, the major adviser for the program and director of the Agricultural Sustainability Institute at UC Davis.

The major is new, but UC Davis has been covering the subject in field- and classroom-based interdisciplinary learning opportunities at the Student Farm at UC Davis for more than 35 years, said Mark Van Horn, the Student Farm director who will teach a core course in the major.

“Learning through doing and reflection adds a valuable dimension to students’ education because it helps them see the connections between theory and practice in the real world,” Van Horn said.

“This is an exciting addition to the college that reflects a change in how we think about food and agriculture,” said Neal Van Alfen, dean of the College of Agricultural and Environmental Sciences. “Students will gain a broad perspective of what it takes to put dinner on the table in an era of greater demand and fewer resources.”

For more information:

Posted on Wednesday, August 31, 2011 at 7:43 AM

Understanding soil erosion in irrigated agriculture

Soil erosion threatens our ability to feed ourselves in the future. Current concerns regarding soil erosion include economic vitality, environmental quality and human health.

How can losing a little soil to erosion be such a concern? Soil formation is a very slow process. It takes nature between 300 to 1,000 years to replace soil lost over a 25-year period at a loss rate of 1 mm per year (25 mm is approximately 1 inch)

Erosion reduces the productivity in several ways: Plants are not able to use nutrients as efficiently, seedlings are damaged, rooting depth is decreased, soil’s water-holding capacity is diminished, permeability is decreased, runoff increases and the infiltration rate declines.  The loss of healthy soil leads to poor plant growth and lower crop yields.

In the United States we lose an estimated 6.9 billion tons of fertile topsoil to erosion each year. Losses of this size are far from sustainable. In an effort to continue food production, costly fertilizers and amendments are used to compensate for the lost soil. The loss of nutrients alone is estimated to cost U.S. farmers $20 billion a year.

As runoff carries sediment, nutrients, and agricultural chemicals off-site, the economic and environmental costs skyrocket.

The University of California has resources to help reduce the loss of soil through erosion. The free, five-page publication Understanding Soil Erosion of Irrigated Agriculture provides information to help maintain the productivity of land and reduce the enormous costs associated with erosion.

Topics include:

  • Impacts of soil erosion
  • Types of water erosion
  • Indicators of soil erosion
  • Soil survey interpretations
  • Land capability classification system
  • Soil erosion factors
  • New soil survey resources

Additional resources, can be found at the UC ANR free publication website.


Soil erosion from water runoff in avocado grove. Deep gully eroded in steep slope. Trees are growing among bare soil. Photo by David Rosen.
Posted on Wednesday, August 24, 2011 at 8:09 AM
  • Author: Chris M. Webb
Tags: erosion (4), soil (9)

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