Creating a habitat sounds like a complex, daunting task — a job for Mother Nature or perhaps even the local zoo — but it's something that can be accomplished on as small a scale as a home garden. And it starts with native plants.

"(Native plants) are not only a wonderful source for butterflies but flies, wasps, moths, a lot of things will come to your garden. So it's not just a pretty garden that's eye candy for humans, it's actually habitat for the plants that females will put (their) eggs on. And let your plants be eaten by creatures in your garden — think of it more as a habitat than as a botanical garden," said Liam O'Brien, a Bay Area lepidopterist (a person who studies butterflies and moths).

O'Brien is one of five speakers who will be featured at the California Native Plant Society's (CNPS) "Gardening for Biodiversity in a Climate Crisis" symposium on Sept. 21 at Foothill College. The event focuses on creating gardens that draw local wildlife, and in particular, attract pollinators. Many of the speakers are experts on insects, including Doug Tallamy, professor of entomology at the University of Delaware and author of "Bringing Nature Home," who will be the keynote speaker.

"Simply put, (gardening for biodiversity) is trying to get as many bugs and creatures into your yard, really. It's creating a garden that really welcomes wildlife," said Sherri Osaka, chair of CNPS Santa Clara Valley Chapter's Gardening with Natives group.

She said that the event's emphasis on pollinators was inspired by society members. CNPS hosts many free educational talks in the Bay Area throughout the year, and the subject came up a lot in the course of organizing those events.

"We kept noticing that pollinators were a real focus for our members. That's why we decided: The time is now," Osaka said.

Creating a garden for biodiversity means thinking about building a chain reaction, with native plants drawing insects, which then also attract other wildlife, Osaka said.

"If you have an oak tree or a willow — those are two of the best trees in our area — you're going to attract hundreds of insects and because of that, you're going to have lots and lots of birds feeding those insects to their babies," Osaka, who's also a landscape designer, said. "It just propagates this whole cycle. If you don't have them, the babies may starve or the birds just won't nest in your yard. That's why we're seeing such a demise of both insects and birds. Birds are really suffering too."

Speaker Kim Chacon, a PhD student at UC Davis concentrating on bee habitat analysis and landscape design, will share her research at the symposium.

"The key to a lot of biodiversity requires having these plants pollinated and then the plants play other roles as far as providing habitat for other organisms. Bees are really important group of species as far as supporting a lot of other species," she said.

Chacon has mapped the activity of various native bees in California and shares the results on her website, beelandscapes.com. She has found, among other things, that bee habitat is very fragmented — in other words, there are figurative "islands" planted with the resources that bees need, but they're isolated areas. "Little bee gardens that are planted far apart from each other and should be more strategically placed in order to have a better function in the landscape," she said

Choosing plants for the garden that native bees need for food, as well as reproduction, helps bridge islands of bee-friendly areas, offering more potential habitat.

"It creates a network for them in terms of genetic diversity and genetic exchange and not becoming inbred and in being able to move across the landscape in case of climate change, for example," she said.

Similarly, O'Brien is working on preserving and rebuilding habitat for butterflies. He got his start studying butterflies while helping the Green Hairstreak butterfly regain some ground in San Francisco, leading an effort to plant the insect's preferred "host" plant, coast buckwheat, and other nectar-producing plants in neighborhoods, which expanded the habitat for the butterfly. At the symposium, he'll discuss the Green Hairstreak Project's origins and share ideas on how to create similar grassroots — or "citizen science" projects.

"(I'll discuss) what people can do with single species-driven projects and how they can get involved, using it almost as a template if they have an idea for something they want to help maintain and survive," O'Brien said.

He noted that recent efforts to support the monarch butterfly population, with more gardeners planting the milkweed that monarchs rely on, is one of the better known examples of this type of work. "It's almost like some of us are in triage trying to help many of these things still hang on," he said.

Though O'Brien acknowledged that not all efforts are going to succeed in the face of climate change, he said that his efforts are also meant to inspire the next generation.

"I think more than anything, if the next Jane Goodall is 4 years old and their parents bring them on a Green Hairstreak walk to go see this butterfly, maybe that little 4-year-old will figure out better things after I'm gone. Right now it's just triage to keep it around so 4-year-olds can still see it."

If you're interested

The California Native Plant Society, Santa Clara Valley Chapter, presents Gardening for Biodiversity in a Climate Crisis, Sept. 21, 9 a.m.-5 p.m. at Foothill College, 12345 El Monte Road, Los Altos Hills. Admission is $125 general/$100 CNPS members/$50 students. For more information, or to register, visit cnps-scv.org/symposium

Gardening for biodiversity tips

— Get local native plant recommendations right down to a specific address from the California Native Plant Society database at calscape.org. The site features photos of recommended plants, shows which butterflies and moths eat the plants and lists nurseries that stock the plants.

—Plant native trees, such as coast live oaks, and instead of lawn, opt for low-growing native shrubs and ground covers, which attract pollinators and save water.

—Put out bee boxes for bees that nest in cavities and provide small areas of bare, unmulched ground for some bees that build their nests underground.

—Learn more about native plants with the website for the Santa Clara Valley chapter of CNPS, cnps-scv.org. The chapter also offers a listserv and a YouTube channel with instructional videos.

Sources: Sherri Osaka, Kim Chacon, Liam O'Brien