Since its restoration in 2005, Thompson Reach near Crissy Field has become a butterfly “hotspot.” (Courtesy/Presidio Trust)

How to get off the path toward mass extinction

The same day that another dead gray whale was found on Ocean Beach last week, news that onemillion plant and animal species are on the verge of extinction made international headlines.

The same day that another dead gray whale was found on Ocean Beach last week, news that one million plant and animal species are on the verge of extinction made international headlines.

The report published by the United Nations linked the unparalleled loss in biodiversity directly to human activity.

Looking around, it’s easy to see why. The San Francisco Bay’s historic coastal, wetland, riparian and woodland ecosystems are being paved over and converted into buildings, sprawling grass lawns and exotic gardens. These uses are sucking up water and crowding out the plants, bugs and animals that have called The City home for millennia. Globally, about three-quarters of Earth’s land and 85 percent of wetlands have been severely altered or lost according to the report.

“We all know this is happening,” Dr. Gretchen LeBuhn, a contributing author to the report and a faculty member at San Francisco State University, told me. “We’re managing the environment in such a way that’s going to lead to decreases in biodiversity.”

We can, and must, do better. San Franciscans are uniquely positioned to protect local endangered species, such as the Mission Blue butterfly, California red-legged frog and Western snowy plover, as well as other rare and threatened species that call The City home. We must keep our pets away from their critical habitats. We must refrain from using toxic pesticides. And we must use land better, including planting bug-friendly shrubs, grasses and flowers.

To help understand which native and non-native plants support the most biodiversity, LeBuhn is currently working with the Presidio Trust. Her research will guide the Presidio’s volunteers and staff, who have worked for decades to transform the former military post into a space Red tailed hawks, coyotes and gray foxes can still call home. The study can also help San Franciscans understand how to better manage our yards, parks and community spaces.

“There are still things that can be reversed,” Jonathan Young, a wildlife ecologist with the Presidio Trust, told me. “Environmental restoration and conservation is worthwhile.”

The Presidio has already seen success from its environmental efforts. Thompson Reach near Crissy Field, for example, was a monoculture, grass field when restoration began in 2005. The Presidio re-exposed, or “daylighted,” a historic creek that was piped underground and volunteers planted 35,000 seedlings representing 156 native plants. Today, the site is a butterfly “hotspot” with birds and animals using the lush habitat.

Like much of San Francisco, not every site at the Presidio lends itself to complete habitat restoration though. The park’s historic military buildings are federally protected. To maintain their historic character, the Presidio Trust is limited to landscaping with only approved native and non-native species.

Agency officials have asked LeBuhn to determine which of these plants supports the most biodiversity. She and Morgan Belle, a graduate student at San Francisco State University, are currently monitoring and collecting samples from plants to document pollinator use, as well as use by other insects, birds and mammals. The research, which should be completed next year, will provide a better understanding of which plants are the best to use in landscaping.

“My guess is that native plants will support greater biodiversity,” she told me. “There are a number of generalist pollinators who will visit any plant. But herbivores tend to have much more specific requirements.”

San Franciscans who care about the environment should follow the research. Local pollinator and herbivore insects may not like trees, shrubs and flowers native to Australia, Europe and Asia. If insects don’t use these plants for food or nesting, they could damage the ecosystem.

Bugs are a huge food source for birds, amphibians and some mammals. If they disappear, so do the species that rely on them.

But it’s still possible to reverse this path toward mass extinction. The successful eradication of invasive bullfrogs in the Yosemite Valley helped local populations of the California red-legged frogs rebound. Similarly, the 2015 demolition of the San Clemente Dam, which blocked the Carmel River since 1921, made space for local steelhead trout counts to grow.

In the San Francisco Bay area, using land better can give our non-human neighbors space to grow too.

Robyn Purchia is an environmental attorney, environmental blogger and environmental activist who hikes, gardens and tree hugs in her spare time. She is a guest opinion columnist and her point of view is not necessarily that of the Examiner. Check her out at

If you find our journalism valuable and relevant, please consider joining our Examiner membership program.
Find out more at

Just Posted

Thousands flood Mission District for youth-led George Floyd protest

As civil unrest over the killing of George Floyd continued Wednesday in… Continue reading

Breed closes nearly $250M budget deficit in current fiscal year

Cuts include street repaving, firefighting hose tender trucks, childcare subsidies

DA drops charges against man seen in video of officer using knee restraint

Footage leads to calls for SF police to explicity ban move used in death of George Floyd

SF federal appeals court overturns U.S. EPA approval of herbicide made by Monsanto

The fact that the Trump EPA approved these uses of dicamba highlights how tightly the pesticide industry controls EPA’s pesticide-approval process.

SF mayor to end curfew after Wednesday night

Breed: ‘We know that the overwhelming majority of people out protesting are doing so peacefully’

Most Read