Posts Tagged: climate change
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.
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.
UC Cooperative Extension researchers convey need for more climate change communication and curriculum tools
Reducing greenhouse gas emissions from natural and working lands is one of California's key climate change strategies. In particular, the potential for farm and rangeland soils to serve as carbon sinks has been getting a lot of attention lately in the national media — and during California Healthy Soils week, which wrapped up Dec. 7.
These are areas where UC Cooperative Extension, with its local presence across the state, is well-positioned to drive change. But as a recent survey of UCCE advisors, specialists and faculty found, while there is a good deal of climate work happening, there are also some significant obstacles.
The survey results — reported in an article by UCCE academics Ted Grantham, Faith Kearns, Susie Kocher, Leslie Roche and Tapan Pathak in the latest issue of California Agriculture — showed that while nearly 90 percent of respondents believe it is important to incorporate climate science into extension programming, only 43 percent currently do so.
Respondents pointed to a number of issues. One was "limited familiarity with climate science fundamentals." It's one thing to cite the overwhelming scientific consensus that climate change is real and is being driven largely by human activity; it is another to be able to respond quickly and convincingly to detailed questions from doubters. This list from Grist, for instance, details more than 100 common arguments raised by climate skeptics, many of which have non-trivially complex answers.
Another important issue cited by respondents was "fear of alienating clientele by talking about a contentious topic," a response that highlights the importance of personal relationships in UCCE's work, and the challenge of communicating an area of science that is highly politicized.
The authors conclude: "To further increase the capacity of UC ANR staff to support the needs of their clientele and the broader public, professional development around climate science fundamentals, communication, and adaptation strategies is critical." As an initial follow-up, the UCANR climate change program team (led by authors Grantham, Kocher and Pathak) is presenting a workshop and professional development meeting for extension professionals in February.
For more from California Agriculture, the research journal of UCANR, see the full issue with articles on mapping soil salinity in the San Joaquin Valley via satellite; choosing forage seed mixes for rangeland restoration; growing oilseeds in winter without irrigation; keeping dairy cows cool in the summer; breeding better carrots; and more.
Agriculture in California is on both sides of the climate change challenge. It is a sector that releases significant quantities of climate-warming greenhouse gases into the atmosphere. At the same time, it is vulnerable to the expected effects of climate change, including increased drought and flooding and more intense and longer heat waves.
Three review articles in the current issue of California Agriculture, the research journal of UC Agriculture and Natural Resources, summarize the state of knowledge on three topics at the intersection of climate and agriculture in California: agricultural resilience to climate change (“climate-smart” agriculture); cropland emissions of nitrous oxide, the most important non-livestock source of agricultural emissions; and opportunities for working lands to contribute to meeting state greenhouse gas targets.
The first article, Long-term agricultural experiments inform the development of climate-smart agricultural practices, discusses the research underway to incorporate resiliency in agriculture to extreme and unpredictable weather patterns induced by climate change.
The authors describe the “Century Experiment” at UC Davis. Established in 1992, the Century Experiment is a replicated research project that includes 72 one-acre plots planted to 10 different cropping systems. The plots will be monitored and data collected for a period of 100 years, but Californians won't have to wait that long to see results.
In the first 20 years, for example, testing has found that soil carbon increased significantly more in the organic tomato-corn system than it did in any other crops and management systems. Soil infiltration rates and aggregate stability were also greater in the organic than conventional tomato-corn system.
Soil amendments – such as agricultural and food wastes and winter cover crops – have led to increased soil carbon sequestration, higher infiltration rates and greater aggregate stability in the organic system, compared to conventional systems.
The authors believe maintaining healthy soils is a key to climate-smart agriculture. Properties such as porosity, water retention, drainage capacity, carbon sequestration, organic matter content and biodiversity all help to confer resilience to new pests, diseases and weather extremes brought on by climate change.
The second article, Nitrous oxide emissions from California farmlands: A review, presents the results of 16 California-based studies.
Nitrous oxide emissions are the largest direct source of greenhouse gases from cropland in California and nationally.
The studies reviewed in the paper indicate that the nitrous oxide emissions factor – the fraction of applied nitrogen that ends up being released as nitrous oxide – can vary widely depending on crop, irrigation method, climate and other variables. Accounting for these large differences is important in improving the accuracy of estimates of overall nitrous oxide emissions from farmland, and in designing measures to reduce those emissions.
The final article, Review of research to inform California's climate scoping plan: Agriculture and working lands, covers the range of ways that California's diverse agricultural systems can contribute to meeting the state's commitment to reduce greenhouse gas emissions by 40 percent from 1990 levels by 2030.
Slowing farmland conversion to urban uses and reducing emissions from the intensive livestock sector appear to provide the best opportunities for agriculture-related reductions. About two-thirds of direct agricultural emissions are from livestock production, particularly the dairy sector (the largest sector of the state's agricultural economy by annual revenue).
Because of the dairy sector's comparatively large contribution to agriculture's greenhouse gas emissions, the authors expect it to be a primary target for state climate regulations and incentives for emission reduction. They note, however, that policies should account for the already high levels of resource efficiency at California dairies.
The best opportunities for reductions in emissions from livestock operations center on feed and manure management. A report submitted to the California Air Resources Board says it may be feasible for California to achieve a 50 percent reduction in methane emissions from dairy if supportive practices are taken. Such practices might include:
- Switching from flush water lagoon systems to solid-scrape or dry manure management.
- Covering manure lagoons to capture biogas.
- Installing anaerobic digesters to capture and use methane.
- Use pasture-based dairy management.
The Legislature recently approved using $99 million in funds from the state cap and trade program to support the expansion of manure digesters and other technologies designed to greatly reduce emissions from livestock operations.
The review article also discusses potential for reducing greenhouse gas emissions from agricultural land in California by engaging in farmland and rangeland preservation, improved soil and nutrient management, integrating and diversifying farming systems, employing alternative practices in rangeland management and producing energy with biomass.
To help California forest property owners adapt to the changing climate, UC Agriculture and Natural Resources (UC ANR) has produced a 13-page peer-reviewed paper that outlines actions owners can take to sustain their forests' value even when temperatures rise.
“Managers of forest land have always had to adapt to changing conditions – such as markets, urban encroachment, droughts and floods,” said Susie Kocher, UC Cooperative Extension forestry and natural resources advisor. “We wrote this paper to help forest managers better understand the evolving science of climate change and how they can help their forests adapt to the climate of the future.”
Forests are shaped by the climates in which they grow. The current rapid pace of climate change has not happened for thousands of years, according to climate scientists. Nevertheless, the authors assure forest landowners that there are land management decisions they can make to ensure the resiliency of their resources, and perhaps even improve them.
“Some trees may grow faster under the warmer conditions we experience with climate change,” Kocher said, “especially those at highest elevation where there is adequate precipitation.”
The paper details the solid scientific evidence that indicates the rise in global average temperatures over the past 100 years. The temperatures, it says, “will likely continue to rise in the future, with impacts on natural and human systems.”
The document provides specific recommendations for care of three common types of forest in California: mixed conifer, oak woodland and coastal redwood forests.
Mixed conifer forests – typically composed of white fir, sugar pine, ponderosa pine, incense cedar and California black oak – are susceptible to moisture stress caused by warmer temperatures and reduced snow and rain. The drier conditions make the trees more vulnerable to fire and insect attack.
The drought of 2010-2016 has already had a substantial impact on mixed conifer forests in the Sierra Nevada. Aerial detection surveys show that more than 102 million trees have died since 2010; more than 62 million died in 2016 alone.
The UC ANR climate change adaptation paper suggests reducing competition for water by thinning trees and managing for species and structural diversity. The authors suggest property owners consider the source of seedlings when planting new trees.
“Select seedlings adapted to a slightly lower elevation or latitude than your property,” Kocher said. “These would be more likely to thrive under the 3- to 5-degree warmer temperatures we expect in 50 years or so.”
Oak woodlands are widely distributed and diverse in California, which gives them moderate to high capacity to adapt to climate change. Mature oaks are more resilient than young trees and seedlings.
One potential impact of climate change on oak woodlands is increasing precipitation variability and increasing spring rains. The moisture change could increase the spread and prevalence of Sudden Oak Death (SOD), a disease caused by a bacterium that was introduced into California from outside the U.S. SOD is primarily a concern in areas with tanoaks in Central to Northern California coastal areas.
“To reduce the spread of sudden oak death, land owners should prevent the movement of infected leaves, wood and soil,” according to the paper.
The primary concern for coastal redwood forests is the decline in fog. Fog frequency in coastal redwoods is 33 percent lower now compared to the early 20th Century. Less fog and rain plus warmer temperatures would leave coastal areas where redwoods typically thrive drier. But that doesn't mean redwoods will disappear. Areas with deep soil and areas close to streams and rivers may provide refuge for redwood forests.
The new publication, Adapting Forests to Climate Change, can be downloaded free from the UC ANR Catalog. It is the 25th in the Forest Stewardship series, developed to help forest landowners in California learn how to manage their land. It was written by Adrienne Marshall, a doctoral student at the University of Idaho; Susie Kocher, UC Cooperative Extension forestry and natural resources advisor; Amber Kerr, postdoctoral scholar with the UC John Muir Institute of the Environment; and Peter Stine, U.S. Forest Service.