Warming Climate Could Transform Bay Area Parks and Open Space

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By the end of the century, the Bay Area’s landscape could look more like Southern California’s, raising tough questions for land managers trying to preserve the region's protected lands.

A dead blue oak tree at the Blue Oak Ranch Reserve near San Jose. (Photo: Lauren Sommer/KQED)
A dead blue oak tree at the Blue Oak Ranch Reserve near San Jose. (Photo: Lauren Sommer/KQED)

It may not be an official record, but by some accounts, more open space has been preserved in the San Francisco Bay Area than in any other major U.S. metropolitan area. More than a million acres are permanently protected from development – that’s almost one-third of the 4.5 million acres that make up the 10-county region.

Now, with temperatures on the rise, land managers and scientists are beginning to ask how the Bay Area’s landscape will withstand climate change. As plants and animals are forced to shift, some of the Bay Area’s iconic parks and vistas could look dramatically different.

Scientists say signs of those changes may already be appearing in places such as the hills east of downtown San Jose.


“This is a blue oak,” says Nature Conservancy ecologist Sasha Gennet, examining the small, dark leaves of a towering tree on the Blue Oak Ranch Reserve, part of the University of California Natural Reserve System.

She pulls the branch down to eye level. “You can tell because they’re a little bit bluish or grayish,” she says. “They’re probably the hardiest of the oak species in the California. These are the ones that you see in those hottest, driest places, hanging on through the summer.”

“But even these have their limits,” she adds, “and we’re starting to see what those limits are.”

“Here’s another dead one that’s also pretty young,” says field researcher Corinne Morozumi, pointing to the dried-out trunk of dead blue oak. She and UC Berkeley researcher Blair McLaughlin recently catalogued blue oaks across 20 square miles in the area, looking for dead trees.

hdpublicplaces-mod“The computer models tell us that there’s going to be climate stress here,” says Kirk Klausmeyer of the Nature Conservancy, looking across the hilltops. “We know that the climate has already changed somewhat in the Bay Area. We’ve already seen some warming trends. So we wanted to see if there are any early indications.”

The results were surprising. Across the study area, there were three times more dead oak trees in drier, climate-stressed areas than were found in cooler, higher elevations. “We are seeing what our models are predicting,” says Morozumi.

Exactly what’s causing the trees to die is still unknown, though it doesn’t appear to be a disease like Sudden Oak Death. In the Bay Area’s dry Mediterranean climate, Gennet says, the oaks may already be living at their limit. “Some hot, hot summers,” she says. “Maybe a couple of stretches where they just can’t access water at all. It could just push them over the edge.”

Southern California Shift

About a hundred miles north, UC Berkeley ecologist David Ackerly walks across a wooded hillside, pulling small orange and yellow flags out of the ground. Each marks a young tree.

“One Doug fir juvenile,” he calls out. “Oak seedling.”

Ackerly and his field team are counting trees and gathering data inside a 60-by-60 foot research plot, one of 50 on the 3,000-acre Pepperwood Preserve in Sonoma County. “If you want to see the forest of the future, you look at the small plants,” he says.

UC Berkeley researcher David Ackerly measures a tree's diameter at the Pepperwood Preserve near Santa Rosa. (Photo: Lauren Sommer/KQED)
UC Berkeley researcher David Ackerly measures a tree's diameter at the Pepperwood Preserve near Santa Rosa. (Photo: Lauren Sommer/KQED)

The plots will become a baseline for studying climate change, as the study team returns in five and ten years to document changes in the plant community and water availability. Change is what Ackerly expects to see, in the form of warmer temperatures, heat waves and more intense drought.

“We know the direction things are moving and what we can expect is that our climate will be more like climates in Southern California,” he says. “So in 30 or 40 years, it might be like San Luis Obispo and in 60 or 70 or 100 years, it may become like Los Angeles.”

That could lead to an expansion of plants more commonly found in Southern California, like chaparral, the dense shrubs and bushes that thrive in drier conditions. Ackerly says under some climate scenarios in the Bay Area, there could be twice as much land with conditions that favor chaparral.

As for what’s here today, “one way to think about it is we have plants living in the wrong place,” he says. “We have an oak tree that’s living here because of past conditions, but now it’s living under these future conditions that are very different.”

Oak trees and other plants may need to move, either to higher elevations or closer to the coast where it’s cooler.

“But oaks don’t pick up and move to the coast,” Ackerly says. “These oaks are never going to move that we’re looking at today. Their seeds will be picked up by a jay or a squirrel and moved half a kilometer or maybe some jay flies over to the next hillside, occasionally."

For some oak trees, it could become an “acorn-by-acorn” race with climate change. Human management and fire also play a major role in how fast plants can move.

“The biggest concern right now is not that things are changing,” Ackerly says. “It’s how fast.”

“You can have huge areas where a tree species might suddenly hit a drought it can’t survive,” he says. “Imagining large areas of the Bay Area with dead trees across the landscape - it’s not an image we’re used to, but it really can happen if conditions are changing very fast.”

If chaparral shrublands expand, the Bay Area could also be facing a fire regime that’s closer to Southern California’s. “That’s a very different picture than what we’ve lived with,” Ackerly says. “We haven’t settled this landscape under the idea that we would have wildfires of that frequency or magnitude.”

Managing Change on the Ground

For land agencies, applying global climate change projections on a local level is no simple task. Parks and open spaces are often managed to maintain the historical landscape.

“Until now, our management objectives have been to keep the preserve essentially the same: have the same amount of grassland, the same amount of woodland,” says Lisa Micheli, executive director of the Pepperwood Preserve.

“The really big take-home message for managers is that history can no longer be the basis for long-term planning,” she says. “We may need to let the systems adjust to the climate as it’s changing and stay out of the way. There may also be some places where we need to help native trees adapt.”

Planning for climate change may also require taking a longer view. “When do land managers start that process?” says Ryan Branciforte of the Bay Area Open Space Council. “Their horizon for planning for land management may be days, weeks, months, maybe years, but it’s surely not 50 and 100 years."

The Bay Area Open Space Council is working with the scientific community to develop localized climate change planning information for Bay Area land agencies, something many are eager to use.

“The changes are going to happen,” says Mike Anderson, Assistant General Manager at the East Bay Regional Park District, which manages 113,000 acres in Alameda and Contra Costa counties. “We can’t change that. It’s a matter of giving things room to adapt.”

Anderson says the park district is planning for sea level rise at their shoreline parks with wetland restoration, currently underway at Breuner Marsh in Richmond, part of the Point Pinole Regional Shoreline. Wetlands act as natural buffers against rising seas.

“Sea level rise is easier to see,” he says. “Inland changes will be much more subtle.”

A New Look at Conservation Goals

With dynamic changes on the horizon, the Bay Area’s conservation community is grappling with a tough question: are today’s open spaces the places that should be protected tomorrow?

“The conservation work that has been done in the Bay Area is actually really effective at protecting a very wide range of habitat types,” says Sasha Gennet of the Nature Conservancy. “So good conservation is going to stand the test of time.”

Preserving what’s on the ground today will depend on connecting up the Bay Area’s existing open spaces with corridors, Gennet says. “As things need to move, they can get across. They can get through wildlife corridors or have permeable lands to move through.”

The Nature Conservancy recently purchased a 100-acre property in Santa Clara County with climate change in mind. They plan to restore habitat on the Upper Pajaro River, potentially improving the corridor between the Santa Cruz Mountains and open spaces near San Jose.

With the Bay Area’s growing population, connecting the region’s entire open space network may not be possible. Gennet says it’s not just about buying land. “It’s a range of options,” she says. “Some of it is keeping private rangelands open. Some of it means working on riparian corridors that animals can move through.”

Ultimately, adapting to climate change could mean doing more of they do already, says Kirk Klausmeyer. “Good conservation helps plants and animals persist in the face of threats, whether it’s invasive species or disease or a really dry year,” he says. “Planning for climate change is just doing good conservation.”


It does lend more urgency to the work, says Branciforte of the Bay Area Open Space Council. “If we don’t connect these final pieces and build out the rest of the network, then we run the risk of losing the things that we originally intended on protecting.”