The changing climate predicted for California – including less rain and higher day and nighttime temperatures – is expected to cause chronic stress on many street tree species that have shaded and beautified urban areas for decades.
Realizing that popular trees may not thrive under the changing conditions, UC Cooperative Extension scientists are partnering with the U.S. Forest Service in an unprecedented 20-year research study to expand the palette of drought-adapted, climate-ready trees for several of the state's climate zones.
“The idea is to look at available but under-planted, drought-tolerant, structurally sound, pest resistant trees for Southern California that do well in even warmer climates,” said Janet Hartin, UCCE horticulture advisor in San Bernardino County.
Hartin, a 34-year veteran advisor, said the project is her first to stretch to 20 years; it will likely extend past her tenure with UCCE.
“I'd like to retire in five or six years,” she said. “But I'm very excited about being a pioneer in a study that will continue with my successors. I think it's important for our children and our children's children, as well as for the environment.”
At the end of 2019, with three years of data on tree health and growth rates, the scientists expect to be able to publish the first results and make them available to arborists, urban foresters and residents throughout the regions of the study.
Twelve tree species were selected for each climate zone in the comparative study, with several area parks used as control sites. Hartin and her Southern California research collaborators – UCCE advisors Darren Haver of Orange County and Jim Downer of Ventura County – worked closely with UC Davis plant biologist Alison Berry, UC Davis research associate Greg McPherson and USFS research urban ecologist Natalie van Doorn to select promising species.
They looked for trees that are already available at local nurseries, but are underutilized. The trees in the project exhibit drought tolerance and disease resistance, plus produce minimal litter. The researchers also sought trees that would provide ample cooling shade for a long time – ideally 50 years or longer.
The varieties come from areas around the world with climates similar to California. Two trees planted in replicated plots at the UC Riverside Citrus Field Station are native to Australia, two are native to Oklahoma and Texas, one is native to Asia and two are non-native crosses of other trees. Three of the trees are native to California: the netleaf hackberry, Catalina cherry and island oak.
“Trees are a long-term investment,” Hartin said. “A tree will live 50, 70, 90 years. The proper selection is very important to help ensure longevity.”
Making the long-term investment with the proper selection yields considerable returns. In a warming world, trees are natural air conditioners.
“Urban areas create heat islands, with dark asphalt surfaces reradiating heat. Cities can be 10 to 20 degrees warmer than the surrounding environment,” Hartin said.
Other tree benefits include soil health and stability, wildlife habitat and aesthetic beauty.
Following are a sampling of trees that are part of the comparative study:
Acacia – A 20-foot-tall, 20-foot wide evergreen that is drought resistant, and withstands moderate irrigation. Native of Australia.
Brazilian cedarwood – A native of Brazil and Paraguay, the deciduous tree grows to 50 to 65 feet. The tree produces pale yellow tubular flowers in the spring.
Catalina cherry – Native to the chaparral areas of coastal California, the Catalina cherry grows to 30 feet high. The evergreen tree tolerates drought when mature. It produces sweet purple-to-black edible fruit.
Chinese pistache – A deciduous tree with beautiful fall color. Grows to 35 feet tall, 30 feet wide. Drought resistant, but tolerates moist soil. Native to central and western China.
Desert willow – Growing to 30 feet tall and living 40 to 150 years, the desert willow tolerates highly alkaline soil and some salinity. A deciduous tree, it boasts large pink flowers all summer that attract hummingbirds and other wildlife. Native to the southwestern U.S. and northern Mexico.
Escarpment live oak – Native to west Texas, this tree is cold hardy and drought tolerant. Typically evergreen, it can be deciduous in colder climates.
Ghost gum – Very tall at maturity and drought tolerant. An Australia native.
Indian laurel – Commonly called a ficus, this is a 35-foot-tall, 35-foot-wide tree at maturity that is drought resistant and tolerates highly alkaline and saline soils. Shade potential is high. Native of Asia and Hawaii.
Ironwood – A southwestern and northern Mexico native, Ironwood is semi-drought resistant once mature and tolerates alkaline soil. Ironwood, which grows to about 33 feet tall, can live 50 to 150 years.
Island oak – This tree is native to five of six California off-shore islands. Drought tolerant, it grows to nearly 70 feet tall when mature.
Maverick mesquite – Native to the southwestern U.S. and northern Mexico, this tree does well in full sun and is drought resistant once established. The tree grows to 35 feet tall. The Maverick mesquite is a thornless variety.
Mulga – A versatile and hardy tree that grows 15 to 20 feet in height, the mulga – a Western Australia native – tolerates hot and dry conditions. The leaves are evergreen and the tree has yellow elongated fluffy flowers in spring.
Netleaf hackberry – A California native, the netleaf hackberry grows to 30 feet. Its deep root systems and heat resistance makes the tree idea for urban conditions.
Rosewood – Native to southern Iran, Indian rosewood grows to 65 feet tall, and 40 feet wide. Evergreen. Semi drought resistant and intolerant of alkaline soil.
Shoestring Acacia – Evergreen and 30 feet tall when mature, shoestring acacia is drought resistant and thrives in slightly acidic to highly alkaline soils. Native to Australia.
Tecate cypress – A native of Southern California and Mexico, the Tecate cypress is very drought tolerant. Its foliage is bright green. Young trees are pyramidal in shape, becoming more rounded or contorted with age.
Partners in the tree study are Los Angeles Beautification Team volunteers, LA Parks and Recreation team, Chino Basin Water Conservation District, and Mountain States Wholesale Nursery.
Funding and other support is provided by LA Center for Urban Natural Resources Sustainability, ISA Western Chapter, Britton Fund, USFS Pacific Southwest Research Station, and the UC system.
Because periodic droughts will always be a part of life in California, the UC California Institute for Water Resources (CIWR) produced a series of videos to maintain drought awareness and planning, even in years when water is more abundant.
The final video of the three-part series, which focuses on drought strategies for citrus, was launched April 6 on the UCTV Sustainable California channel. The first episode, which centered on alfalfa production, premiered Feb. 2 on the UCTV Sustainable California channel. The second video, on almonds, was launched March 2 on Sustainable California. A trailer with clips from all three episodes is here.
The videos are inspired by a collection of 19 drought tips produced by CIWR in collaboration with UC Agriculture and Natural Resources researchers during the drought of 2010-16. The tips cover a broad spectrum of California crops, from alfalfa to walnuts. Topics also include salt management, use of graywater in urban landscapes, and the use of shallow groundwater for crop production.
The drought tips collection and the drought tip videos were sponsored by the California Department of Water Resources. Following are links to each of the videos:
The CIWR drought tip series opens with Cannon Michael of Bowles Farming in Los Banos. The alfalfa grower works with UCCE specialist Dan Putnam. “There's a lot of misunderstanding about alfalfa as a crop,” Michael said. “It does take water to grow it, as with anything, but you get multiple harvests of it every year.”
The second episode features almond producer Raj of Meena farms. He works with David Doll, UCCE advisor in Merced County. “One positive of this drought,” Meena said, “is that it has forced us all to be more efficient in how we use our water.”
The series finale features Lisa Brenneis of Churchill-Brenneis Orchard in the Ojai Valley of Ventura County. She worked with UCCE advisor Ben Faber to install a new water-efficient irrigation system. “Irrigation is the only job we really have to do,” Brenneis said, “and we have to get it as right as we can.”
For a complete list of drought tips, see http://ucanr.edu/drought-tips.
UCCE advisor Rachel Surls receives 2018 Bradford Rominger Agricultural Sustainability Leadership Award
The Agricultural Sustainability Institute at UC Davis has announced that Rachel Surls, UC Cooperative Extension sustainable food systems advisor for Los Angeles County, is this year's recipient of the Eric Bradford and Charlie Rominger Agricultural Sustainability Leadership Award.
UC Cooperative Extension Office in Los Angeles County, helping to bring city-grown food into the mainstream.
The Bradford Rominger award, given yearly, honors individuals who exhibit the leadership, work ethic and integrity epitomized by the late Eric Bradford, a livestock geneticist who gave 50 years of service to UC Davis, and the late Charlie Rominger, a fifth-generation Yolo County farmer and land preservationist.
“In her three decade career with UCCE, Rachel has developed a strong program addressing some of our most critical issues in sustainable agriculture,” says Keith Nathaniel, the Los Angeles County Cooperative Extension director. “She does so with innovative strategies, working with all aspects of the LA community. After 30 years doing this work, she continues to be active in the community she serves.”
In Surls' career, gardening has been a tool to build science literacy for school children, to increase self-sufficiency for communities impacted by economic downturn, and to create small businesses for urban entrepreneurs. As the interest in and support for urban agriculture has grown, she has been in the heart of Los Angeles, ready to respond to the needs of the city's farmers and gardeners.
Her role at Cooperative Extension started as a job to help start school gardens in LA. “I would drive to any school that wanted me and help them dig in the gardens,” Surl said. “I could find teachers who were interested in starting gardens, but I couldn't find principals and administrators to support it.”
Early on, some counseled Surls to find an area of expertise that was more serious than community and school gardens. Despite the criticism, “I just chugged along, doing what I knew was good and what I cared about,” Surl said.
And over time, the value of these programs has become more apparent, and support for them has grown. Surls continued along, working to start community gardens at public housing facilities, and overseeing the Los Angeles County UC Master Gardener program.
In 1997, she stepped into a role as the UC Cooperative Extension county director, ensuring the success of extension efforts for all of Los Angeles County for the next 14 years.
In 2008 came the great recession, and with it an uptick in public interest in home grown food.
“We were getting more and more calls in our office on how to be more self-sufficient,” Surls said. “The economics of the time rattled people, so they were thinking more about how to grow their own food, and how to maybe make some money by selling what they grow. And people needed the support and guidance to do that.”
Surls and her partners are working to meet that need through workshops in California's largest metropolitan areas and a website of resources to help new urban farmers get a leg up on farming in the city. Surls is also a member of the leadership board for the Los Angeles Food Policy Council.
The energy around urban agriculture today is palpable. And a career path that was once not taken seriously now is.
“That has really changed in our institution and culture,” Surl said. “We're hiring people to do this work!”
Persistent and focused, Surls' work is one of the reasons that progress is happening.
Surls will receive the award at the Celebrating Women in Agriculture event in Davis April 3. The event is free and open to the public. Learn more about the event here.
Stretching from the Death Valley to Calexico, California's vast dry desert is home to a unique and important agriculture industry.
It's a place where summertime temperatures often top the 115-degree mark. Where water supplies for irrigation depend on the Colorado River, but upriver states are claiming more of it. Where evapotrasporation – a reference rate of water use in unstressed turf grass – is 72 inches per year, but rainfall is rarely more than 4.
Still, stalwart farmers grow dates, carrots, lettuce, broccoli, cabbage, kale and more, plus plants for landscaping everything from family homes to beautiful and luxurious resorts. The agriculture output of the state's three desert counties – Riverside, San Bernardino and Imperial – exceeds $4 billion annually.
The California desert also impacts the quality of life across the nation. If Americans are enjoying a salad in the winter, the lettuce most likely was grown in the California desert. There are bountiful winter recreation opportunities available on the beautifully manicured golf courses, parks and landscapes.
A group of UC Agriculture and Natural Resources (UC ANR) academics formed a desert workgroup to better serve the state's desert region. The group organized a symposium in February to bring together representatives from desert farm and natural resources communities, related industry and academics working in the desert.
“The close exchange of information among desert researchers, non-profit organizations, industry and clientele groups will facilitate collaboration among UC ANR, Arizona and Mexico and foster how our programs should be shaped on a regional level,” said Oli Bachie, the director of UC Cooperative Extension in Imperial County and the current workgroup chair.
With saline soil, scorching summer temperatures and limited water supplies, the desert could be considered a hotbed of the “wicked problem.” A wicked problem isn't evil, said UC Associate Vice President Wendy Powers, the symposium's plenary session keynote speaker.
“The term ‘wicked problem' was coined at UC Berkeley,” Powers said. “It's a problem with circumstances that resist resolution.”
She named climate change and the growth of the global population California must help feed as wicked problems faced by the state. Powers described UC ANR's statewide programs that are working to find solutions to formidable issues faced in California agriculture.
“We're on the verge of some serious breakthroughs as we look at solving wicked problems,” Powers said. “They are accelerated by conversations like those we're having today.”
UC Vice Provost Mark Bell said that the potential of UC ANR to reach every single Californian is what drew him to his position in 2017. Bell invoked Star Wars robot R2D2 for an acronym to reflect the characteristics that accurately define UC ANR.
“R2 stands for reach and relevance,” he said. “D2 is diverse and dispersed.”
UC Cooperative Extension offices serve 57 California counties and its nine research and extension centers are located in key agriculture ecosystems, including one in the low desert of the Imperial Valley.
The afternoon program of the symposium included breakout sessions to highlight programs and research efforts in three broad areas: irrigation and crop production, landscape management, and livestock and feed quality.
“This was the first attempt to organize such a regional desert-based symposium for the UCANR Desert Workgroup with the collaboration of desert-serving UCCE counties,” Bachie said. “I believe that we have registered a remarkable get-together.”
The symposium had speakers and participants from UC, USDA, California Department of Food and Agriculture, the desert agricultural industry, pest control advisors, non-profit institutions and organizations, agricultural commissioners, farm bureaus, Arizona and Mexico universities and the general public.
“I believe that the symposium is a stepping stone for future desert research and extension meetings, conferences and symposiums among people engaged or interested in desert agriculture and natural resources,” Bachie said.
Although individual extreme weather events cannot yet be reliably linked to global climate change, the warming planet may be contributing to recent weather disasters in California. Across the state, 129 million trees died as a result of the drought of 2011-2016, many of them in the Sierra Nevada. Last fall, the worst wildfires in the state's history whipped through wildland areas and neighborhoods, and then were followed by a January deluge and deadly mudslide.
Climate change is also impacting agriculture. The winter chill that farmers rely on to re-boot cherry, pistachio, walnut and other important fruit and nut crops has been curbed by unseasonably warm nighttime temperatures. Sustained summertime heat waves are damaging crops and putting diminishing water resources under stress.
Climate change isn't just about the planet. Increased frequency and intensity of climate extremes impact peoples' lives by forcing evacuations and migration from fire- and flood-prone areas, reducing the availability and safety of food, and dampening emotional well-being.
How can Californians grapple with climate change?
On the front lines of climate change education, mitigation and adaptation is UC Cooperative Extension (UCCE), with its network of scientists headquartered throughout the state, living and working in communities where local climate change impacts must be addressed.
In 2015, UCCE's parent organization, UC Agriculture and Natural Resources (UC ANR), formed a Climate Change Program Team to lead a coordinated effort by UC ANR staff and academics dealing with climate change. The team surveyed UC ANR academics to find out about their current role in California climate change resilience.
“Eighty percent of respondents thought incorporating climate change impacts, mitigation and adaptation in their programs is important,” said UCCE specialist Ted Grantham, a member of the program team. “Less than half are actually doing so.”
The barriers respondents shared to working on climate change include technical complexity, lack of relevant information, and discomfort with the difficult conversations climate change can trigger. The program team brought together a diverse group of specialists, advisors and staff for a two-day workshop in February to increase capacity to raise public awareness about climate change, find practical ways to reduce the impacts of climate change, and help communities adapt to the reality of a changing planet.
Keynote speaker Michael Crimmins, a climate science extension specialist at the University of Arizona, said land-grant outreach programs have the interdisciplinary expertise and connections to provide decision support to farms and communities facing a warming world.
“Climate change is too big to tackle alone,” he said. “We have a lot of programs that can nibble at the edges. If everyone nibbled at the edge, we can make a difference.”
Resources are available for climate change extension
Myriad climate change resources were presented. UC Davis professor Arnold Bloom shared a free online college course posted at http://climatechangecourse.org. The course examines the factors responsible for climate change, the biological and social impacts, and the possible engineering, economic and legal solutions. Forty-eight mini-lectures, assignments and even exams are available to anyone willing to devote time to understanding climate change.
UCCE specialist Jeff Mitchell explained ongoing efforts to implement conservation agricultural practices on California row crop land. Research has shown the potential for climate change mitigation with precision irrigation and tillage reduction, practices that sequester carbon in the soil, reduce fertilizer needs, improve soil quality and increase yield.
Greg Ira, coordinator of the UC California Naturalist program, said a new advanced training module on climate stewardship is in development. The training will be provided to select certified California Naturalists, volunteers who work with partner organizations across the state on environmental stewardship, nature education and citizen science.
UCCE specialist Maggi Kelly introduced the website http://Cal-Adapt.org, which contains volumes of climate change projections and climate impact data from California's scientific community. Users can explore projected changes in temperature, precipitation, snowpack and sea level rise in California over this century with interactive climate data visualizations. They can download data, find peer-reviewed research and learn how to use climate projections.
Leslie Roche, UCCE rangeland management specialist, conducted rancher interviews after the 2011-2016 drought to gauge whether they consider climate change an important consideration for their ranching businesses, and whether they believe future climate will be different from the past. She found that ranchers are generally confident that they have the skills to manage for long-term drought, and that they are interested in learning about climate change and its potential impacts on their industry.
Roche has aggregated rangeland drought- and climate-management resources online at the Rangeland Drought Hub. The website includes “Voices from the Drought,” the personal stories of ranchers discussing the agonizing decisions they made during the drought – such as culling cattle, reducing staff, paying more for feed, and allocating limited water resources.
Steve Ostoja, the director of the USDA's California Climate Hub, said the program helps California farmers, ranchers, forest landowners and tribes maintain sustainable communities and ecosystems by adapting to climate variability and change. Guido Franco of the California Energy Commission said the organization recently released its fourth Climate Assessment. The assessment presents research on the impacts of climate change on the state, as well as strategies to dramatically reduce greenhouse gas emissions.
“I found the information and materials compiled by the Climate Change Program Team very useful,” Mitchell said. “I will be consciously using these in extension education when I can.”
UC California Institute for Water Resources academic coordinator Faith Kearns led a segment of the workshop on climate communication, taking into account the emotional side of climate change by practicing active listening and empathy building. She shared climate change communication strategies used by effective national advocates, such as Katherine Hayhoe, an evangelical Christian and climate scientist who recommends a soft approach that starts by establishing personal connections with individuals before diving into climate science.
Another approach is that of Sarah Myhre, a climate scientist at the University of Washington who believes scientists should speak boldly about climate change facts.
“… scientists are naturally risk-averse when it comes to public dialogue,” Myhre wrote in an essay on Guardian.com. “The verbal, argumentative skills common to professions in law, politics, or business do not come easily to most scientists. … Our job is not to objectively document the decline of Earth's biodiversity and humanity, so what does scientific leadership look like in this hot, dangerous world?”
At the meeting, UCCE advisor John Karlik pointed out that some listeners want to hear straight science, just facts.
“We're all needed,” Kearns said. “We all come with a difference set of circumstances and groups that we can connect with.”
The workshop closed with action planning and next steps. Among the needs presented during the session were:
- A climate change online portal with resources, tools and data that allow advisors and specialists to translate information into decision support.
- Simplified scientific information and case studies to personalize climate change impacts.
- Training for educators, advisors, specialists and volunteers.
- Research-based evidence on the impacts of climate change on food security and the cost of healthy food.
- A glossary of climate change terms.
In their article on the climate change survey in California Agriculture journal, the members of the UC ANR Climate Program Team said they believe UCCE is well positioned to understand and communicate the consequences of climate change to the public, and to identify strategies to mitigate negative outcomes for local economies, the environment and public health.
“UC ANR can become a powerful catalyst for climate adaptation and we should embrace a leadership role in advancing the knowledge and tools needed for a climate-resilient California,” they wrote.