Now, urban landowners — including the Mormon temple on Santa Monica Boulevard in Los Angeles — have decided to let their lawns go brown to save water, leaving trees thirsty in the process. Cities have stopped watering medians on parkways.

“Everyone’s concerned about what they’re seeing but no one has any real control over what can be done,” said Nancy Hughes, executive director of the California Urban Forests Council, who said some people are uprooting trees to abide by water conservation rules. “In many cities, the trees are watered when the lawns are watered.”

Homeowners are being warned that dying trees can be a safety hazard and that keeping them alive will cost less than removing them.

State agencies and non-profit organizations are joining forces to launch a new campaign to let people know that they can and should water their trees, at least once in a while. By the end of this month, the message on highway electronic signs reminding people to save water during the worst drought in more than a thousand years will be tweaked. The new dictum: Save water, save trees.

“The reaction was to turn off irrigation in many locations,” said John Melvin, urban forester at the California Department of Forestry and Fire Protection. “If you do that, you lose a long-lived community asset. A tree is not something that can be easily replaced.”

Now, trees in city parks, along boulevards and in residential neighborhoods are dying because homeowners, businesses and municipalities have stopped watering.

Nature has already killed an estimated 12 million trees in California’s forests since the drought began four years ago — most falling victim to an outbreak of the bark beetle pests that attack trees weakened by drought.

The good news is that conservation goals are being met. The bad news is that there are millions of unintended victims of this civic allegiance: Trees.

Since then, green lawns have turned brown or been ripped out to heed the governor’s conservation mandate and state officials announced Wednesday that residential water use this May was down an impressive 29 percent from May 2013.

LOS ANGELES — California Gov. Jerry Brown issued a stern warning when he ordered unprecedented 25 percent cuts in water use from every one of the state’s 400 urban water suppliers in April: “People should realize we are in a new era. The idea of your nice little green lawn getting watered every day, those days are past.”

The city is postponing planting trees in areas that don't have landscape irrigation, "which really means, not too many new trees," Sartain said.

“With this newfound normal for water, we are evaluating the best of the drought-tolerant and drought-resistant trees,” said Robert Sartain, Santa Clarita city arborist.

Because so many of the trees that are dying are species that probably shouldn’t have been planted in California in the first place, communities are learning their lessons and replacing dying trees with native plants.

“Try to envision this area back 200 years ago,” Conway said. “We would not have seen any trees at all except in valleys.”

About a quarter of the city’s 34,000 trees are pines, trees that thrive in cooler coastal counties in northern California. Many were imported in the 1930s and 1940s as more people populated what is essentially a desert.

“Unfortunately, the less-tolerant specimens like pines are suffering greatly because they require a lot of water intake,” said John Conway, city arborist. “We’re removing them as they die … there won’t be any pines left.”

In Orange County’s Newport beach, the city has had to increase its tree budget by $400,000 to remove dying trees and plant new, more drought-resistant ones.

This dying Aleppo pine in Newport Beach was removed by the city because of the drought. City of Newport Beach

This wave of dying trees in California comes on the heels of a two-decade push for the greening of cities. Tree cover in metropolitan areas plummeted in the 80s and 90s. Last decade, cities from Chicago and Charlotte, North Carolina, to Cincinnati and Salem, Oregon, adopted “green infrastructure” strategies, including tough ordinances that require trees in new developments and incentives for landowners to plant them.

Studies by American Forests, a non-profit conservation group, show that trees clean the air by filtering pollutants and producing oxygen. Trees also reduce energy costs by providing shade and cooling the air, a natural way to offset the scorching heat that can be reflected from concrete. They can also soak up rain water rather than letting the precious liquid go down the drain, dragging oil, auto coolants, pesticides and other chemicals that eventually get flushed into rivers.

A recent report by the U.S Department of Agriculture Forest Service show that the number of street trees in California have not kept up with population growth. The 9.1 million street trees make up 10 percent to 20 percent of the state’s total urban forest. The report also found that tree density has declined 30 percent since 1988 “as cities added more streets than trees.” Tree density fell from 105.5 trees per mile to 75 trees per mile in that period.

Despite that, the agency estimates that California street trees save the amount of electricity equivalent to what’s required to air condition 530,000 households every year.

But if they die during this drought, many may not be replaced.

That's why the upcoming California save-the-trees campaign will try to educate people to ways they can let their lawns go brown but still save their trees. Water them – not at the base but to the point where the roots extend – and use recycled water.

Another, more expensive, way to bring water to thirsty trees without wasting it on lawns and sidewalks is to install a drip irrigation system that uses less water and targets tree roots.

At the Compton Creek Natural Park in Compton, on the southern end of Los Angeles County, the non-profit Los Angeles Conservation Corps has taken four acres of land owned by the school district and is turning it from junkyard to ecological wonder. Between an elementary school and a senior housing complex, the park landscaping is gently sloped to retain water. Beneath the soil, seven tanks can hold 110,000 gallons of water from runoff. Only native trees, such as oaks and sycamores, were planted along a walking trail and outdoor amphitheater. In stark contrast, one of the fern pines in the concrete schoolyard next door is showing signs of distress and a dying palm tree in an adjoining residential neighborhood towers over the park.

“The solution is to separate your irrigation system,” said Larry Smith, community development director for the LA Conservation Corps. “In Compton, we designed it with a separate system for turf and ground cover.”

Cities such as San Pedro and Pacoima are redesigning their streets to collect rainwater that would normally run down the drain, and redirecting it to trees, he said.

Longtime San Francisco resident Margo Freistadt was stunned when the apple tree she planted in her backyard 23 years ago to celebrate her husband’s recovery from a heart attack didn’t blossom this year for the first time. It’s not that she had stopped watering it but just that she never had to before.

“I didn’t realize it but our tree gets its water from the rain,” said Freistadt, 58, a self-employed and self-described “handyhuman” who does home repairs. “But we’ve had four winters without rain … I wasn’t even aware it was happening.”

Desperate to save a tree that had become part of family traditions – annual apple-picking and applesauce-making parties – she followed expert advice and soaked the roots. A few blossoms appeared within a week. She knows now to save water without killing her tree. She collects two to three gallons a day from water used to wash vegetables and water that runs in the shower while she waits for it to warm up. All of it goes to douse the tree.

“The tree is alive,” Freistadt said.