CALIFORNIA DROUGHT: Grass may keep yards cooler


Living in a century-old bungalow without air conditioning, long-time Riverside residents Karen and Ray Renfro depend on their lawn to help keep their home comfortable in summer.googleoff: all

“We know it keeps the house cooler. The temperature of the asphalt on the street is way hotter than the grass, and the grass is cooler even than the cement walkway,” she said. “On the shady side of the house on a hot day, the air is cool.”googleoff: all

The Renfros have no intention of removing their lawn, even as the state enters a fourth year of drought. They worry that with so many people replacing greenery with rock and gravel, cities will grow hotter, magnifying the effects of climate change.googleoff: all

Some researchers agree, saying the mass extraction of turf and the demise of shrubs and trees as Californians stop watering their landscapes will have a detrimental effect on the environment.googleoff: all

Dennis Pittenger, an environmental horticulturist for UC Cooperative Extension at UC Riverside, and colleague Donald Hodel contend that the turf removal trend began as a knee-jerk reaction to the drought, without consideration for grass’ capacity to cool, store carbon, filter pollution and control erosion and dust.googleoff: all

“There’s really been no public discussion of this. It’s being forced down people’s throats whether it makes sense or not,” Pittenger said. “There’s some real value to landscapes, and the water they use is justified to provide those benefits.”googleoff: all

In April, Gov. Jerry Brown ordered mandatory 25 percent water rationing through February. He also ordered replacement of 50 million square feet of lawns with drought-tolerant landscaping and banned grass on street medians.googleoff: all

Facing $10,000-a-day fines for not reaching their conservation goals, water suppliers quickly offered hefty rebates to customers who remove their lawns.googleoff: all

More than 150 million square feet of grass have been removed in the past year by customers in districts served by Metropolitan Water District, Southern California’s main wholesaler.googleoff: all

But Pittenger and Hodel argue in a recent paper that all the water used outside homes and at parks, sports fields and golf courses amounts only to 9 percent of total consumption statewide. That figure is based on total developed water – that which is controlled and managed – and reported by the state Department of Water Resources.googleoff: all

Ceasing that outdoor irrigation would not save enough water to end the drought, Pittenger said.googleoff: all

Better management of existing lawns would be enough to help cities meet their state-mandated conservation goals, he said. That includes:googleoff: all

• Switching from fescue and other cool-season grasses to warm-season varieties such as Bermuda and St. Augustine, which go dormant in the winter. Warm-season grasses use 20 percent less water, when irrigated properly, than cool-season varieties.googleoff: all

• Ensuring sprinklers are working correctly, with overlap and good distribution.googleoff: all

• Using the appropriate amount of water. Lawns can survive on much less water than most people give them.googleoff: all

• Reducing or stopping fertilizer use, which prompts growth and increases water demands.