Climate changes in San Diego

Human-induced climate changes are not just abstractions that will affect far-off lands in the distant future. A local expert explains what it means for San Diego… right now.

Global climate change is finally real. Scientists have believed the atmospheric, oceanographic, and ecological data for at least a decade. And businesses and elected officials followed in the past year. And now each of us wonders about how our lifestyles, jobs, and special places will be affected.

We’re beginning to think about how climate change will affect our ecology and economy – locally, nationally and globally. How will our climate change? What does it mean for San Diego’s ecology and economy? What should we expect from our business and community leaders? What can and should we do, as individuals? How will that matter?

How will our climate change in San Diego?

Warmer temperatures. There is clear evidence that the earth’s average temperature has been slowly increasing for some time. Weather records show that annual average temperatures in California are already warmer than just a decade or two ago. Extreme high and low temperatures are likely to be more common, as San Diego experienced in July 2006 and January 2007.

More drought years. San Diego has a Mediterranean climate characterized by winter rains, summer droughts and a pattern of large fluctuations from year to year. Most scientists predict that climate change will cause droughts to occur more often and to last longer in Southern California and in other areas with limited rainfall. But others predict more rainfall due to increased frequency of El Niño weather events. In fact, more severe droughts are predicted for the entire western U.S., which is likely to produce longer fire seasons and larger wildfire events.

More storms and extreme weather. Various global climate models predict that hurricanes, storms, and other extreme weather events are likely to increase, but their complexity makes it hard to say exactly how. Santa Ana winds are arguably the most destructive weather events in San Diego, and climate models are not exact enough to predict how they will change.

Higher ocean levels. Global warming will tend to melt polar ice masses, which will slowly raise ocean levels everywhere. Including San Diego.

What will it mean for San Diego’s ecology?

Climate changes may affect San Diego’s natural environments in many ways. Here are just 12.

1. Some plants may disappear from San Diego. Changes in rainfall, temperature and extreme weather events are likely to affect the distribution and perhaps cause the extinction of some San Diego species. Many local plants are highly specialized and limited geographically, adapted to a narrow range of physical conditions. Many are endemic, growing only in San Diego County (or perhaps areas of southern California and the peninsula of Baja California). Multiple Species Conservation Plans may not provide the protection for endangered and threatened plants, animals, and habitats that was promised in San Diego. The development will remain, and the protected plants and animals may become extinct.

2. Animals may not find food, shelter, or breeding places. Phenology is the timing of seasonal activities of animals and plants, and some of these are changing. Records have been kept for decades (sometimes centuries) on the arrival of bird species from their winter migrations or the time that certain caterpillars emerge from their cocoons. Warmer temperatures and less rainfall will affect bird migration patterns, as well as wintering locations, food supplies, and predators. San Diego birders report that some migrating birds are arriving earlier in the spring, compared with a few decades ago.

3. Plants and animals may have nowhere to go. With gradual shifts in climate conditions, plants can grow in other sites where their seeds have dispersed and have the necessary growing conditions. Larger animals can move or fly to other locations with sufficient water, food, and shelter. With global warming, some plants and animals are shifting northward (or in the southern hemisphere, southward) or to higher elevations to habitats that more closely match their requirements. Locally, high elevation species will have no higher places to go. In San Diego, as in many other places in the world, some of the plants and animals will not be able to make these shifts because the potential habitat has been claimed by development, invaded by non-native species, or is not graced with suitable soils and other necessary growing conditions.

4. Pollutants make plants more susceptible to drought. Pollutants from vehicles drift from the roads and freeways onto parks and natural areas. As more miles are driven in more cars, more pollutants are produced. Plants adapted to our Mediterranean climate in San Diego conserve water by closing their stomates (openings similar to pores) during the day. But pollutants such as ozone and nitrous oxide change the metabolism of plants, and they keep their stomates open longer. This allows water molecules to escape, and plants dry out much more quickly.

5. Drought makes plants more susceptible to insects. Bark beetles have always been present in our San Diego forests, and healthy trees are adapted to low populations of beetles. With more frequent drought years in the past decade, the trees are less resistant to beetle attacks, and many trees have died in the Julian, Palomar, Laguna, and Cuyamaca mountains.

6. Warmer winters increase beetle populations. Many insects and plants have evolved together in ways that allow each to survive. For example, winter temperatures are often low enough to “knock back” insect populations at low levels. Warmer winter temperatures can increase insect survival and population levels, but the droughts and abnormally warm years that began in the 1980s have resulted in record pest outbreaks and tree dieback throughout western North America. San Diego’s forest-lovers will find large areas of forest dieback in some of their favorite Rocky Mountain vacation places.

7. Extended droughts increase the severity of wildfires. Increased droughts are predicted for the entire western U.S., which is likely to bring longer fire seasons and larger wildfire events. Scripps Institute researcher Tony Westerling analyzed the frequency and length of large wildfires, and found that both increased in the mid-1980s. During these years, there were much higher spring temperatures, less summer precipitation, drier vegetation, and longer fire seasons. Closer to home, five years of droughts preceding the 2003 fires had drastically reduced the fuel moisture in local vegetation, contributing to the fires burning so quickly. With one ignition and extreme Santa Ana winds, 380,000 acres of shrublands and forests were burned in San Diego County in the Cedar, Otay, and Paradise Fires in 2003 – almost one-sixth of the entire county.

8. Pine trees will not return to Cuyamaca in our lifetimes. The wildfires burned 25,000 acres forests of Cuyamaca Rancho State Park so hot that trees and seedlings were completely combusted. Janet Franklin, Professor of Biology at San Diego State University, surveyed areas in Cuyamaca Rancho State Park during the first two post-fire growing seasons following the Cedar Fire. She and her graduate students found that most conifers were killed by the fire and that pine seedlings have not re-established. The oaks have re-sprouted and chaparral is growing in areas where sugar, coulter, and Jeffrey pines once stood.

9. Imported water supplies will be limited. Snow is a “reservoir” that holds moisture and releases it slowly, as the days and nights warm up in the spring. With warmer temperatures, the snow melts faster; the runoff happens more quickly in the spring; and reservoirs fill up earlier and overflow. More moisture falls as rain instead of snow. All this means that less water will be available as imported water from the Sierra Nevada and the Colorado River basin, water that San Diego depends on for 90% of its water supplies. At the same time, drier weather will increase demands for domestic landscape watering. Agricultural irrigation supplied may become limited or more expensive, affecting the local agricultural economy. If irrigation for fuel breaks, golf courses, and other public landscaping is reduced in San Diego, these areas may become bare and eroded, weedy and highly flammable.

10. Local water supplies will be tapped out. In the backcountry, excessive groundwater pumping is already drying out local streams, habitats, and wells. Less precipitation will mean less groundwater recharge, reducing the water supply for the majority of San Diego County’s land area that relies on wells. In drought years when creeks remain dry even longer, fish, frogs and other aquatic animals will find fewer places to eat and live.

11. Rising oceans will erode beaches and bluffs. Higher ocean levels will cover more of San Diego’s beaches with water, and there will be much greater loss of beach sand and beach-front properties. In addition, the higher water level and loss of beach sand will permit storm waves to attack coastal bluffs more aggressively, increasing erosion and endangering bluff-top structures.

12. Local estuaries will be under water. Higher ocean levels will submerge the areas of coastal estuaries closest to the current shoreline. The rising salt water will also increase salinity and change freshwater habitats much further inland. In areas where houses or highways have been built along the estuaries, low tide may reach these property lines, and the natural estuaries - critical habitat for many of San Diego’s diverse plant and animal species – will disappear.

What does it mean for San Diego’s economy?

Climate change will affect all aspects of our lives. It will affect San Diego’s housing, transportation, tourism, trade, and technology sectors. Climate change impacts will remind us about how we have “taken for granted” the clean air, clean water, beaches, and the other special places in San Diego – canyons, creeks, chaparral, forests, and deserts.

The global effects of pollutants were buffered for many decades by the ocean, atmosphere, and natural ecosystems. Excess, human-generated energy and chemicals were absorbed without apparent, external change until a certain level was reached that resulted in markedly warmer temperatures and changes in ocean chemistry. These global effects were also buffered by the economic and political interests of the energy, automobile, manufacturing, housing, tourism, and other industries.

For centuries, we’ve disposed of our wastes and industrial byproducts in the air, water, oceans and soil - at low cost or for free. We used to think these “deals” would last forever. We used to think it was Economy versus Environment. And we didn’t think human activities had the power to radically change the entire earth.

But now we know better. And San Diego’s business and community leaders are beginning to respond. Several local coalitions have been established to identify actions that we can each take to reduce carbon and other emissions resulting from our production and use of energy, buildings, technology and water.


The San Diego Regional Energy Office aims to “create a sustainable energy future.” It offers dozens of programs for business, homeowners and governments, along with this succinct explanation:

• Energy affects all of us. Whether it’s used to generate electricity or power our cars and machines, energy runs our economy and provides us with the comforts and lifestyles to which we’ve become accustomed.

• Yet, fossil fuels, our primary current source of energy, are being depleted at a rapid rate while carbon emissions continue to rise worldwide. With demand for energy increasing, we must seek out and implement alternative solutions. Whether it’s being more efficient or switching to renewable energy sources, it will require a total commitment from everyone in the community – businesses, residents and political leaders.

• So be proactive. Make energy efficiency a priority for your organization. Reduce your power consumption during peak periods. Learn about renewable energy sources and help implement them.


San Diego is home to an active chapter of the U.S. Green Building Council, which promotes sustainable design. The group represents over 100 organizations active in “green” building design throughout our region. In addition, there are more than 60 LEED Accredited Professionals in San Diego. LEED stands for Leadership in Energy and Environmental Design. LEED’s Green Building Rating System® is a voluntary, consensus-based national standard for developing high-performance, sustainable buildings.


Local businesses can adopt, develop and market more energy-efficient technologies. In fact, the March 2007 issue of the Harvard Business Review suggests that businesses do just that: measure the sources and levels of their own greenhouse gas emissions; identify potential impacts of new regulations or products, droughts, storms, etc.; and address these threats and opportunities by adapting in a way that gives them a leg up on competitors.


Local water authorities are challenged to continue supplying San Diego’s growing economy with water for residential, commercial and agricultural uses. They must plan for reduced water supplies and higher costs. If water uses are rationed in the future, we may lose irrigated fuel breaks, landscapes and golf courses. Desalinization of ocean water will be considered, even with its high costs and energy requirements.

What can we do about it?

We have to start “at home.” A “Climate Smart” Web page hosted by the San Diego Foundation
( offers a great list of ideas for personal actions we can take to combat climate change. For example, hanging laundry outside - a wonderful reminder of the free natural energy of the sun and wind. Buy a folding drying rack, hang clothes right from the washing machine, and set it on your patio or balcony.

Here are some personal actions and related links:

• Reduce landscape water requirements (visit ).

• Install fluorescent lights.

• Invest in the most energy efficient applications.

We can also learn more about climate change. Here are a few ways to do that:

• Attend the popular lecture series at the San Diego Natural History Museum, part of the Climate Smart Initiative co-sponsored by the Museum and the San Diego Foundation, the San Diego Regional Energy Office, and Birch Aquarium at the Scripps Institution of Oceanography. These presentations have drawn 300 to 550 people every month and may continue next year.

• Visit the exhibition at the Birch Aquarium that opens in May: “Feeling the Heat: The Global Climate Challenge” (

• Read what scientists are saying about global trends ( ) and changes likely to occur in California

We can also become citizen scientists and collect data about today’s plants and animals. Discouraging as it seems, we may want to document past and present ecological conditions before our climate changes further, much as historically significant properties are photographed and documented before they are destroyed. You can be a citizen scientist in many ways:

• Become a parabotanist and collect plants for the San Diego County Plant Atlas.

• Participate in the bird counts organized by the San Diego Audubon Society.

• Train to join a San Diego Wildlife Tracking Team.

• Collect water quality data for the San Diego Citizens Water Monitoring team.

We can also simply take time to enjoy our local natural environments and share with our children and grandchildren the wonders of nature and its importance in our lives. In his best-selling 2005 book, Last Child in the Woods: Saving our Children from Nature-deficit Disorder, local columnist Richard Louv writes, “Lacking direct experience with nature, children begin to associate it with fear and apocalypse, not joy and wonder.” We can help children develop lifelong commitments to environmental and community stewardship. In turn, we can learn from them as they find the joy and wonder in nature.

Global climate change is real. It will affect us. And our response – as individuals, businesses and communities – really does matter. Let’s start an honest dialogue about San Diego’s future and how we will contribute to a sustainable economy and environment.

Anne S. Fege, Ph.D., is a Botany Research Associate at the San Diego Natural History Museum, and retired Forest Supervisor, Cleveland National Forest.

Phil Pryde, Ph.D., is the Professor emeritus, Department of Geography, San Diego State University, and the editor and primary author of San Diego: An Introduction to the Region (2004).