Posts Tagged: drought
“Landscape plants and the water they use are under unrelenting attack,” says Don Hodel, UC ANR Cooperative Extension advisor in Los Angeles County. “But most of these attacks are misguided when one looks at the facts.”
Hodel and Dennis Pittenger, UC ANR Cooperative Extension area environmental horticulturist in the Department of Botany and Plant Sciences at UC Riverside, wrote a six-page commentary, 9%: The California Drought and Landscape Water Use, with facts about the relatively small amount of California's water that goes into landscapes, and the tremendous benefits to residents, communities and the environment provided by these plants. The article was published in PalmArbor, an electronic journal for the green industry.
“Landscape water use in California accounts for only 9 percent of total statewide water use,” the authors wrote. “Yes, that's right, just 9 percent. If we never watered another home or public landscape, park, sports field, or golf course in California, the state would save 9 percent of its total water consumption.”
Pittenger and Hodel named 12 ways lawns and landscape plants enhance the quality of Californians' lives and make urban areas more livable. Trees, shrubs, groundcovers, lawns and flowers provide:
- Carbon sequestration to help mitigate global warming
- Rain capture, dust and erosion control
- Shade and energy savings in heating and cooling
- Wildlife habitat
- Beauty and ornament
- Enhanced property values
- Psychological well-being
- Cultural/historic value
- Jobs and economic value
Instead of shutting off the sprinklers, the authors call for “judicious irrigation,” providing just enough water to trees, plants and lawns to keep them alive. The authors believe judicious irrigation may be sufficient by itself to meet the 25 to 35 percent water reductions required by the state without changing the landscape to so-called “low-water use” or “drought-tolerant” plants.
“Most woody plants are actually drought-tolerant and low-water use once they are established and cared for properly,” the article says. “Research over the last 30 years has shown that water-reduction goals can be met while maintaining the quality-of-life benefits that landscape plants and functional lawns provide.”
Hodel and Pittenger also identified three urban water uses that should be considered priorities for outdoor irrigation, even in times of extreme water scarcity.
- Public parks, school play grounds and sports fields. “Children need to play and exercise on grass, not asphalt or dirt,” the article says. “And we all benefit from walking and exercising in a green, pastoral setting.”
- Bona fide botanical gardens and arboreta. “These research collections of plants have immense value,” the authors wrote. “For example, the plant collections at the world-famous San Diego Zoo actually have greater value than the animals.”
- Trees. “Mature trees are among the most valuable and difficult-to-replace plants in urban areas,” the UC ANR experts said. “Their loss would be devastating.
The director of UC ANR's California Institute for Water Resources, Doug Parker, is a spokesperson for the University of California on water issues of statewide importance. He agrees that, in much of the state, urban communities benefit from natural plantings and turf should be a priority for recreation areas.
“It's true that rock gardens, artificial turf and hardscape do not provide much wildlife habitat, carbon sequestration or environmental cooling,” he said. “But in places like Palm Springs, they are appropriate.”
Having worked closely with policymakers, scientists, government organizations and consumers during the past four years of drought, Parker said he has reached the conclusion that Californians cannot build or conserve their way out of periodic droughts.
“What we really need is a change in mindset to learn to live with drought and uncertainty,” Parker said.
Following are free water-conservation publications from UC ANR:
Water conservation tips for the home lawn and garden
By Pamela Geisel, UC ANR Cooperative Extension advisor emeritus
Carolyn Unruh, staff writer
Managing turfgrasses during drought
By Ali Harvandi, UC ANR Cooperative Extension advisor emeritus
Jaimes Baird, UC ANR Cooperative Extension turfgrass specialist, UC Riverside
Janet Hartin, UC ANR Cooperative Extension environmental horticulture advisor, San Bernardino County
University of California, Davis, which provides the first direct evidence of climate change impacts in the state's grassland communities.
The study, covered in TIME, LA Times, and elsewhere, was published in the journal Proceedings of the National Academy of Sciences. It's based on 15 years of monitoring about 80 sampling plots at McLaughlin Reserve, part of UC Davis' Natural Reserve System.
"Our study shows that 15 years of warmer and drier winters are creating a direct loss of native wildflowers in some of California's grasslands,” said lead author Susan Harrison, a professor in the Department of Environmental Science and Policy and a member of UC Agriculture and Natural Resources' Conservation Biology workgroup. “Such diversity losses may foreshadow larger-scale extinctions, especially in regions that are becoming increasingly dry.”
The researchers confirmed that drought-intolerant species suffered the worst declines.
Similar trends have been found in other Mediterranean environments, such as those of southern Europe, bolstering the case for increased climate change awareness in the world's semi-arid regions.
Taken together with climate change predictions, the future grassland communities of California are expected to be less productive, provide less nutrition to herbivores, and become more vulnerable to invasion by exotic species, the study said.
The researchers expect these negative to cascade up through the food web—affecting insects, seed-eating rodents, birds, deer and domesticated species like cattle, all of which rely on grasslands for food.
Rescue effect may be too late
Grasses and wildflowers may be able to withstand the current drying period through their extensive seed banks, which can lie dormant for decades waiting for the right conditions to germinate.
However, California's drought is expected to intensify in the coming decades, so this rescue effect may end up being too late for some species.
Author: Kat Kerlin
UC Agriculture and Natural Resources turf expert Jim Baird.
“People have gone from one extreme to another,” said Baird, UC ANR Cooperative Extension turf specialist based at UC Riverside. “When we weren't in a water crisis, people were watering seven days a week, 365 days a year. Now, people feel like they're doing the right thing by putting no water on their lawn at all.”
Baird developed a keen appreciation for turf as a teenager playing golf and later working at a municipal golf course in Pueblo, Colo. “I found my passion,” he said. “The rest is history.” He earned a bachelor's degree in horticulture, a master's degree in agronomy, and a doctorate in botany, all the while focused on turf.
Baird's research and the lawn in front of his own Riverside home show that turf can be kept alive, and even attractive, with a minimal amount of water. And maintaining lawns rather than letting them die or replacing the grass with synthetic turf, concrete or so-called drought-tolerant plants offers important ecological services.
As anyone who has enjoyed a picnic in the park can attest, grass is cool. In contrast, the surface of artificial turf has been found to reach 180 degrees on a hot day. It often must be cooled with water before it can be used for sports. Bare soil, concrete and asphalt get significantly warmer and hold heat longer than a grassy lawn, which functions like a natural evaporative cooler.
“The more we let our grass lawns die or go away, the hotter it's going to get,” Baird said.
Grass, like all plants, absorbs carbon from the atmosphere and sequesters it in the soil, a vitally important quality as the country searches for ways to slow global warming. The production of plastics to make artificial turf has the opposite impact. And after a decade or so, artificial turf will wind up in the landfill, where it could take hundreds of years to decompose.
With all these benefits, Baird is dismayed to see the abundance of unnecessarily dead and dying lawns in California. The loss of green growing grass is an ecological loss in the short term, and difficult and expensive to revive once the drought ends.
“A dead lawn could come back as nothing but weeds,” Baird said.
He and his UC ANR colleagues wrote an eight-page publication on managing turfgrass under drought conditions that will help homeowners and lawn managers keep their lawns alive with minimal water.
The publication outlines the concept of deficit irrigation, a system in which the grass has just enough water to maintain an adequate appearance, but with less growth. Irrigation can be cut back to two times per week. If the blades spring back after being walked on, the lawn doesn't need more water.
“The grass may not be as lush and green as usual, but you can still have a lawn where kids and pets can play and families can enjoy outdoor barbecues,” Baird said.
Additional water savings can be achieved by carefully managing the sprinkler system. Areas shaded by trees or a house need less water than grass with day-long sun exposure. Irrigating before dawn reduces evaporation, leaving more water for the plant roots to absorb. Using sprinklers when there is less wind will help prevent overspray onto sidewalks and the street.
Mowing practices also impact the lawn's water use. The grass should be maintained at the tallest height recommended for the species being grown to encourage development of deep roots. Leaving the grass clippings on the lawn with a mulching mower will reduce evaporation from the soil surface.
If new lawns are being considered, water use can be cut by selecting a turfgrass species that uses less water. For example, Baird is studying kikuyugrass in plots at UC Riverside Turfgrass Research Facility. A native of East Africa, kikuyugrass is well adapted to warm, temperate climates in coastal areas and inland valleys of Southern and Central California. Other drought-tolerant grasses being studied at the facility are Bermudagrass and seashore paspalum.
For professional landscapers and home gardeners interested in detailed turfgrass research information, UC ANR is hosting a Turfgrass and Landscape Research Field Day Sept. 17. Registration is $90 before Aug. 28, $100 on or after Aug. 28 and $120 onsite. The complete agenda, registration form and previous research reports can be found on the field day website.
An initiative to improve California water quality, quantity and security is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.
Author: Jeannette Warnert
The fourth winter in a row of disappointing precipitation has triggered a die off of trees in the Sierra Nevada, most of which is now in ‘exceptional drought' status. The US Forest Service conducted aerial monitoring surveys by airplane in April 2015 and observed a large increase in tree mortality in the Southern Sierra (from Sonora south). Surveyors flew over 4.1 million acres of public and private forest land and found that about 20 percent had tree mortality on it, totaling over 10 million dead trees.
The Forest Service found severe mortality in many pine species especially ponderosa pine. On private lands along the foothills of the Sierras, surveyors found extensive areas of dead pines. Large areas of blue and live oak mortality were also suspected though it was too early in the season to be sure.
The insects killing trees in the Sierra are all native insects that are multiplying because of drought conditions. Native insects are a necessary part of the forest ecosystem that speed decay of wood back into nutrients, prey on other insects, and provide food for wildlife. They are normally present at low levels and cause tree mortality only in localized areas.
However, drought weakens trees and reduces their ability to withstand insect attacks. Normally trees use pitch to expel beetles that attempt to burrow into the tree through the bark. Weakened trees cannot produce the pitch needed to repel these beetles which are able to enter under the bark and lay eggs. Larvae feed on a tree's inner bark cutting off the tree's ability to transport nutrients and eventually kill it. Attacking beetles release chemicals called pheromones that attract other beetles until a mass attack overcomes the tree. Many beetles also carry fungi that weaken the tree's defenses.
Western pine beetle is one of the main culprits killing pines in the Sierra during this drought. It is a bark beetle, one of a genus of beetles named Dendroctonus which literally means ‘tree-killer'. Adult beetles are dark brown and about a quarter-inch long. Adults bore into ponderosa pines, lay eggs which develop into larvae in the inner bark then complete development in the outer bark. When beetle populations are high, such as during drought periods, even healthy trees may not be able to produce enough pitch to ward off hundreds of beetle attacks.
Western pine beetle often attacks in conjunction with other insects. Other beetles causing tree mortality in Sierra forests include mountain pine beetle, red turpentine beetle, Jeffrey pine beetle, engraver beetles (Ips) and fir engravers. Forests with a higher diversity of tree species are typically less affected because beetles often have a preference for specific tree species. Some species may attack only one tree type. For example Jeffrey pine beetles attack only Jeffrey pine.
The best defense against bark beetles is to keep trees healthy so they are able fight off insects themselves. Widely spaced trees are typically less susceptible to successful attack by bark beetles since they face less competition for moisture, light, and nutrients compared to densely growing and overcrowded trees. Forest health can be promoted by thinning to reduce overcrowding (so each tree has access to more resources) and removing high risk trees during thinning (such as those that are suppressed or unhealthy).
For landscape trees of high value close to a home, watering may be one option to increase tree vigor against bark beetle attacks. Apply about 10 gallons of water for each inch of tree diameter (measured at chest height) around the dripline of the tree once or several times a month during dry weather.
There are some insecticides registered for bark beetle control, but all are preventative only. Carbaryl may prevent attack for up to two years, while pyrethroids can deter attack for up to a year. Spraying can be tricky because the chemical must be applied up to 50 feet up the trunk of the tree usually while standing on the ground. Since misapplication may have toxic consequences, any insecticide must be administered by a licensed pesticide applicator. All applications must follow the label. Though some systemic treatments applied to the soil or inserted into the tree may work in some cases, there is not a lot of documented evidence that they are effective against western pine beetle. No insecticide can prevent tree death once a tree has been successfully attacked.
Author: Susie Kocher, UC Agriculture and Natural Resources Cooperative Extension advisor
In short, grasscycling involves leaving grass clippings on the lawn, rather than collecting them in a bag and shipping them off to a landfill.
“The clippings sift down to the soil surface and act like a mulch, reducing water evaporation so you can cut back on irrigation,” said Karrie Reid, UC ANR Cooperative Extension environmental horticulture advisor in San Joaquin County. “This is a simple and elegant way to save water that requires very little extra effort.”
If you don't have a mulching mower, Reid says, “It's probably time to replace the mower.” As an alternative, a mulching blade can be attached the bottom of most mowers. The special blade makes a second cut when mowing over grass, cutting grass clippings into finer pieces.
In most California climates, mowing once a week with a mulching mower is sufficient. If grass is growing so quickly a once-per-week mowing cuts off more than one-third of the blade, it's a sign that too much water is being applied.
In addition to reducing water use, grasscycling cuts down on fertilizer needs.
“As the clippings break down, nutrients are returned to the soil,” Reid said. “Most of the fertilizer that is applied to lawns ends up in the leaf blades, so it only makes sense to retain as much of that on the lawn as possible.”
A five-page UC ANR publication on mowing and grasscycling is available for free download from the UC ANR Catalog. The publication includes a table with mower height settings for the most common types of turf grass grown in California.
In addition to working with horticulture professionals, Reid serves as advisor to the coordinator and volunteers of the UC Master Gardener program in San Joaquin County. Master Gardeners are UC ANR volunteers who are trained by UC academics in sustainable landscape, ornamental tree and garden development and maintenance.
More than 6,000 volunteer Master Gardeners form a network to disseminate research-based gardening information across the state, donating upwards of 350,000 hours of time each year.
An initiative to improve California water quality, quantity and security is part of the UC Division of Agriculture and Natural Resources Strategic Vision 2025.