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UC study seeks street trees that can cope with climate change

Reposted from UCANR News

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.

Palo verde is a drought-resistant tree. (Photo: Bri Weldon, flickr, CC BY-SA 2.0)

Blue palo verde – A tree that reaches about 25 feet in height, the Blue palo verde is drought resistance and lives 50 to 150 years. Its trunk, branches and leaves have a blue-green hue. Native to the southwestern U.S. and Mexico.

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.

Climate-ready trees planted in 2016 at the UC South Coast Research and Extension Center.

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.

Posted on Wednesday, April 18, 2018 at 3:45 PM
  • Author: Jeannette Warnert

In memoriam: Doug McCreary

Doug McCreary speaking at an oak regeneration field day. Photo by Rick Standiford.

Douglas DeWitt McCreary, UC Cooperative Extension natural resources specialist, died on Feb. 15 in Grass Valley. He was 72.

“Doug was the epitome of what a CE specialist should be - a world-renowned researcher, a first-rate teacher, and an attitude that could bring people from diverse backgrounds and philosophies together,” said Richard B. Standiford, UC Cooperative Extension forest management specialist emeritus and long-time colleague of McCreary.

Born in San Mateo and raised in Berkeley, McCreary earned a bachelor's degree in economics at UC Riverside. After graduating from UCR, he studied at the London School of Economics for one year, then traveled throughout Europe. He earned his master's degree and Ph.D. in forestry at Oregon State University.

In 1986, McCreary joined UC ANR as part of its statewide Integrated Hardwood Range Management Program, newly created in response to public concern that oaks, the most common tree species in California hardwood rangelands, and their habitats were declining through neglect.


McCreary and daughter Megan walk among the oaks in a photo published in California Agriculture journal article “Urbanization crowds out oaks” in September 1995.
McCreary's research and extension work revolutionized oak regeneration in the state.

“Prior to Doug's work, oak planting on rangelands was a costly and low-success enterprise,” Standiford said. “Natural oak regeneration of white oaks was lacking in many areas, raising concerns about the long-term sustainability of oak woodlands. Doug developed low-cost, practical techniques for planting oaks, predominantly blue and valley oaks, on rangeland sites. This work was widely adopted throughout the state.”

McCreary introduced the use of tree shelters from Europe, and found that they increased survival of oak seedlings in California's Mediterranean climate. He also developed the timing for successfully gathering acorns for regeneration. After the 49er Fire, which started near Highway 49 in Nevada County in 1988, he organized Project Acorn, a county-wide effort with dozens of volunteers who collected and planted acorns in areas devastated by the fire. In 1990, McCreary was honored for Project Acorn with the Take Pride in America Award from the U.S. Department of the Interior in Washington, D.C.

McCreary, who was based at the Sierra Foothill Research and Extension Center, worked with state, federal and private nurseries to produce high-vigor bare root and containerized seedlings. He also developed silvicultural techniques to encourage natural seedlings to recruit into larger size trees.

“Doug was not content to just produce voluminous scientific journal articles on oak regeneration, but organized countless oak regeneration field days, workshops and symposia throughout the entire state,” Standiford said. “His biannual oak regeneration field days at the Sierra Foothill Research and Extension Center were must-attend events for the restoration and conservation community.”

The ANR publication, “Regenerating Rangeland Oaks” written and updated by McCreary in 2009, Standiford said, “is the bible for oak restoration, and provides a practical guide for all parts of the regeneration cycle for landowners and professionals.”

McCreary retired in 2011.

From left, Joni Rippee, McCreary, Bill Tietje, Greg Giusti, Sherry Cooper, James Bartolome and Rick Standiford at Sierra Foothill Research and Extension Center in May 2017. Photo courtesy of Rick Standiford.

“We will all miss Doug very much. He was a wonderful colleague and friend,” Standiford said.

“I concur with Rick,” said Mel George, UC Cooperative Extension rangeland management specialist emeritus.

McCreary is survived by his partner, Therese Hukill-DeRock, his children Tyson McCreary and Megan Cielatka, and his grandchildren Hazel, Sybil, Ian and Isaac.

A celebration of McCreary's life is planned for June 10 in Grass Valley.

Read more about McCreary at


Posted on Thursday, April 5, 2018 at 9:19 AM
  • Author: Pam Kan-Rice

Walleye fish populations are in decline

Reposted from UC Davis Climate Change News

Quick Summary

  • It now takes 1.5 times longer to produce the same amount of walleye as it did in 1990
  • Walleye decline accompanied rise in lake temperatures
  • Anglers, agencies and tribes need to work collaboratively on strategies to move forward

Walleye, an iconic native fish species in Wisconsin, the upper Midwest and Canada, are in decline in northern Wisconsin lakes, according to a study published this week in the Canadian Journal of Fisheries and Aquatic Species.

The study does not pinpoint the exact causes for the decline, though it suggests it is likely a combination of factors, including climate change, habitat degradation and harvest rates that might at times outpace production levels if not monitored closely. Additional research is ongoing regarding what declining production means for future walleye harvests in this region.

Walleye, like this one, is a popular game fish prized for its flaky meat and mild, sweet flavor. (Courtesy Andrew Rypel)

‘Something is not right'

For the study, researchers analyzed production statistics collected between 1990 and 2012 for adult walleye populations in Wisconsin lakes. They found that annual walleye production across all lakes decreased by 27 percent during that time. It takes 1.5 times longer to produce the same amount of walleye biomass, or fish weight, now as it did in 1990.

Lakes experiencing declines are often stocked with walleye to make up for a loss in natural production. However, the data show that stocked lakes have seen larger declines in walleye production. Lakes with a mixture of both stocked and naturally reproducing walleye experienced declines of 47 percent, while lakes with only stocking and no natural reproduction declined by 63 percent.  

“This is a clear warning sign that something is not right,” said lead author Andrew Rypel, an ecologist at University of Wisconsin-Madison and the Wisconsin Department of Natural Resources during the time of the study. He is currently an associate professor and the Peter B. Moyle and California Trout Chair in Coldwater Fish Ecology at the University of California, Davis. “The results suggest that anglers, tribes and resource management agencies will all need to work together to craft new science-based management policies for moving forward.”

About walleye


Rypel, who grew up in Wisconsin fishing walleye, notes that walleye are “kind of a big deal” in the area. As salmon are to the West, walleye are to this region. People travel to the state's Northwoods just to fish for walleye; a large Catholic population enjoys them for Friday fish fries; and Native American tribes spear walleye in the early spring in accordance with their cultural and religious traditions. The meat is prized for its flaky, mild and sweet flavor.

“People catch and release bass,” Rypel said. “That's not the case with walleye. People love to eat walleye.”

Lead author Andrew Rypel, currently an associate professor at UC Davis, holds a walleye in Wisconsin. (Courtesy Andrew Rypel)

Threats to walleye

Bass like warmer waters, and unlike walleye, their populations have increased over the study period. Walleye require cooler waters, and their decline has accompanied a rise in lake temperatures. This points to climate change as one factor in the loss of walleye that the authors say should continue to be examined.

Habitat alteration, residential development around walleye-bearing lakes and indirect food web interactions are likely additional factors.

Another complication is that while most Wisconsin lakes are dominated by low-producing walleye populations, some of the highest-producing walleye lakes are used to estimate sustainable harvest for the region. Consequently, studies on those healthier walleye lakes may not adequately represent the overall walleye population.

Action is underway

State, tribal and community leaders have already taken several actions to help the struggling walleye. These include major stocking initiatives, new fishing regulations, programs to enhance habitat, bass removals and even moratoriums on walleye harvests.

“Most people interested in the outdoors, fishing and hunting are interested in leaving something for future generations, hopefully something better,” Rypel said. “It's essential that we work collaboratively when we see trends that fisheries like these are in decline.”

Co-authors on the study included Greg Sass from the Wisconsin Department of Natural Resources, and Daisuke Goto and M. Jake Vander Zanden from the University of Wisconsin-Madison.

The study was funded by the Wisconsin Department of Natural Resources, the United States Geological Survey and the National Science Foundation's Long Term Ecological Research Program in North Temperate Lakes.

Posted on Thursday, March 29, 2018 at 2:09 PM
  • Author: Kat Kerlin

Utility to turn off power when fire risk is high

During periods of "extreme fire conditions," PG&E will shut off electric power lines to prevent wildfires, reported Dale Kasler in the Sacramento Bee.

The reporter spoke to Lenya Quinn-Davidson, UC Cooperative Extension area fire advisor in Northern California, about the utility's proposed actions. She said PG&E will have to give communities plenty of advance warning before turning off power so residents aren't left without a means of receiving emergency information.

"They're going to have to do a lot of good community outreach so people will be prepared," she said. Still, she called it "a reasonable short-term solution while they're figuring out other things" to reduce fire risks.

Lenya Quinn-Davidson, the UC Cooperative Extension area farm advisor who serves Humboldt, Siskiyou, Trinity and Mendocino counties. (Photo: Larry Luckham)
Posted on Wednesday, March 28, 2018 at 2:31 PM
  • Author: Jeannette Warnert

California Indigenous perspectives on water and fire management

Reposted from the Confluence - Blog of the California Institute for Water Resources 

Don Hankins is a professor of geography and planning at Chico State and a Miwkoʔ (Plains Miwok) traditional cultural practitioner. He has spent his academic career working on water and fire issues in California, with a focus on applied traditional Indigenous stewardship.

You've done work on the use of Indigenous traditional knowledge related to fire and water. A major result of your research and practice has been to reveal a disconnect between current environmental management and Indigenous approaches to working with the environment. Can you say more about what you have found?

Tribal knowledge and experience are often marginalized or devalued in environmental management, and relationships between managers and Tribes are often non-reciprocal. For example, when it comes to fire, there can be a sense that Indigenous knowledge is a relic of the past. This is not the case – Indigenous fire practice is alive and well. It brought us through the major climate events of the past and is absolutely relevant to the challenges we face today.  

Integrating Indigenous knowledge and people into ongoing management efforts can preserve traditional ways and invigorate agency approaches, but my own research has shown it can also subjugate Indigenous perspectives. For example, there is a great deal of resistance regarding how traditional cultural burning can be carried out in partnership with agency-based programs. Rather than recognize the knowledge and preparation that traditional cultural practitioners have, agencies see their standards-based approach as the only path to putting fire on the ground. This in turn risks traditional knowledge of fire and related cultural practices. Burning is a traditional sovereign right, but in many places, including the U.S. and Australia, legal systems work to regulate fire out of the land.

A culturally prescribed burn at the Cosumnes River Preserve to improve oak woodlands where Miwkoʔ traditional cultural practitioners worked alongside members of the Cosumnes Fire Department and Yocha Dehe Fire Department. Photo by Doug Bird.

These kinds of challenges also exist with water. For example, my ancestral homelands of the Delta are now used as a major water conveyance, compromising ecosystems and Indigenous cultural properties. Despite our deep understanding of the area, Indigenous perspectives are really not considered in its management.

I also think about what nature has provided in terms of water storage within the landscape and the fact that we still see interest in building dams rather than restoring natural basins and sinks. Luckily, some headway is being made in recognizing that natural landscape features contribute a great deal to recharge and storage.

What about your work on fire and water in California do you find most challenging?

I wish I had more time to devote to research, publications, and outreach. A lot of my current work is unfunded or has limited support, despite the applicability to current issues. Some projects have started out of me seeing a research need, starting a pilot project, and getting students or community members engaged to help out in the field. I really strive to be in the field because that's where I can do what I'm most interested in: applying Indigenous approaches to management and using scientific methods to assess the results. This work provides me opportunities to advance science, but also to keep a cultural lens on the landscape to assess the condition of, and changes to, traditional resources and interspecies relationships in the places I work.

Hankins talks with students about fine fuels in advance of a meadow burn on the Big Chico Creek Ecological Reserve. Photo by Tyler Wright.

Every day I see news about new research or political initiatives, and I feel overwhelmed. Getting word out, particularly to decision makers, is challenging, likely because they are overwhelmed too. We have a lot of misinformation on major decisions. I'm thinking of the Governor declaring a drought, or referencing year round fire as the “new normal.” If we teach people to read the land, they will know it is a drought, and when good fire can be used, instead of being vulnerable to what nature will provide otherwise. If we are to succeed in living in this land, we must consider what it is telling us and not force unrealistic solutions on it. 

What do you see as some ways forward to better align Indigenous perspectives and current management efforts?

Vegetation sampling in a meadow the spring following a fall burn on the Big Chico Creek Ecological Reserve.
One way is to embrace traditional Indigenous law, which is rooted in nature and holds individuals accountable for their actions in a reciprocal relationship with environment. Realigning existing policies and management could work to create more resilient systems. This also means forming partnerships with Tribes to guide the process, as well as with public and private entities to support it.

It's a potentially exciting time to improve policy and management decisions for the betterment of conditions for future generations. I see a combined approach using traditional knowledge and science as being the solution to sustainable living and a resilient future. Really, that has been proven by the existence of the landscape that non-Indigenous people found when they arrived in California. We just need to facilitate a change in this society to see the benefits.

Posted on Tuesday, March 27, 2018 at 4:54 PM
  • Author: Faith Kearns

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