Southern California a Hotspot of Biodiversity
One of the things I most enjoy about reporting on the environment is learning about the natural world. To bend over a flower with a botanist who points out the nectar guide—a structure or marking some flowers have evolved to draw in pollinators. If you’re curious about local landscapes, check out these stories. Then you can impress friends with such offhand comments as, "Well, southern California IS one of only five places in the world with a Mediterranean climate.” You might want to have an idea what a Mediterranean climate is, so read on….
Our Mediterranean Plants
The modest shrubs and small plants that dominate our local natural landscapes may not look all that impressive when you whiz by on the road, but southern California is one of the world’s hotspots of biodiversity. In the first of two reports, KPCC’s Ilsa Setziol introduces us to some of the unique plants that have evolved in our uncommon climate.
(sound of creek)
SETZIOL: On a late spring morning in the Santa Monica Mountains, a small creek weaves through slanting sycamores and wispy-leaved willows. Nearby, botanist Phil Rundel strolls along a hillside dappled with wildflowers, twisted oaks, and delicate-flowered shrubs. He stops to point out a spurt of bluish purple blossoms.
RUNDEL: Those are delphiniums. There’s two native delphiniums….this one comes up in grasslands every year.
SETZIOL: It looks like the kind you find in the nursery, just with a slimmer stalk and smaller flowers--
RUNDEL: yeah, just a little less robust, ..probably one in nurseries are just bred from these.
SETZIOL: The delphinium, like many of our native plants, is only found in southwestern California.
(sound of bee buzz)
SETZIOL: Around the bend, a rotund black bee is sampling the tiered blooms of a white and magenta flower called Chinese Houses.
Rundel bends over a neighboring plant: an orange-flowered bush called Sticky Monkey flower.
RUNDEL: Bees and birds both pollinate that. Flowers like this you can see they’re really designed more for bees, though, because they have a landing strip… these markings on the lower lips of the flower are kind of like a landing strip for bees come in.
SETZIOL: Rundel is walking in UCLA’s 300-acre preserve called Stunt Ranch. It’s one of the places where he researches the world’s Mediterranean ecosystems. These are five areas of the planet that sit at about the same latitude and have similar climates: mild, wet winters and warm, dry summers. They are: of course, the actual Mediterranean basin; central Chile; the cape region of South Africa; southwestern Australia; and ….California—with the exception of our deserts. Rundel says conservation biologists have singled out these areas as crucial for preserving the world’s biodiversity.
RUNDEL: Only about 2 percent of the world has this kind of climate regime…it’s one that attracts a lot of us…but as a result, they’re some of the most threatened areas ecologically in the world because of population growth, urbanization, clearing of native habitats. We worry about rainforests and rainforests are clearly worth saving, but this 2% of the land area of Mediterranean climates has 20% of the plant species of the world.
SETZIOL: Botanist Phil Rundel says because the plants in these areas have evolved to survive in similar climates, many of them share similar traits: for example, California’s evergreen shrubs like Manzanita and Toyon resemble Mediterranean olive and strawberry trees.
RUNDEL: being an evergreen shrub with leathery leaves is a good solution to living in these environments and that’s what the dominant species are, particularly where water is limited. Their leaves don’t lose moisture very readily so they’re here all year round. In the summer they hunker down and if it’s cool they can start growing again.
SETZIOL: These plants take advantage of the mild climate, photosynthesizing year-round. And their tough leaves help them fend off herbivores … plant-eating animals. These shrubby, evergreen plant communities in southern California are called Chaparral. Our other Mediterranean shrub community—called sage scrub—is even rarer. About 80% of the coastal variety of sage scrub has been lost.
Because everybody loves living on the coast.
Ileene Anderson is a botanist with the California Native Plant Society.
ANDERSON: It’s made up of plants that usually have very small leaves. It’s often called soft chaparral because it’s smaller and easier to walk through than true chaparral. It’s also seasonal… loses its leaves during the summertime when resources are really limited…waiting out the drought, for fall rains to grow again.
SETZIOL: Anderson is hiking a section of the Verdugo Mountains, near Burbank, where sage scrub and Chaparral intermingle—the sage scrub dominating in the hotter, drier places. At the top of a steep hill, she’s greeted by a minty and lemony smell.
ANDERSON: (out of breath) This is black sage, salvia melifera…another key component of coastal sage scrub. Little petite purple flowers… the different sages have different smells. To me that is the classic California smell, it’s a pungent aromatic, wonderful scent…
SETZIOL: Nearby, a plant called wooly blue curls--because of the velvety bracts at the base of its chiffon-blue flowers—emits a perfume that mingles mint with hints of pine. Many plants from the Mediterranean basin—rosemary, lavender, thyme—are similarly aromatic. It’s a way plants in both places repel grazing animals; and makes them great companions in southern California gardens.
But some plants from the Mediterranean basin have become unwelcome guests here. They’ve taken up permanent residence and are threatening our native plant communities.
JON KEELEY I can easily picture in the next several decades southern California looking like the Kona coast of Hawaii, where you almost can’t find a native plant anywhere on that landscape.
SETZIOL: That’s our story tomorrow.
Ilsa Setziol, 89.3, KPCC.
Native Plants Threatened by Invaders, Fire
You can’t help but notice: whole canyons, entire hillsides that used to house communities of plants and animals are now budding with new homes for… humans. Less obvious, though, is another threat to our natural communities: innocuous looking foreign plants that—with human help—have the potential to radically change our rare ecosystems. KPCC’s Ilsa Setziol explains in our second report on southern California’s natural landscapes.
(Sound of bird)
SETZIOL: Stough Canyon in the Verdugo Mountains is a marvelous place to gaze at native plants. In a couple of hours of hiking on a May or June day, you can easily see about 100 species: 6-foot-tall scarlet delphiniums; caterpillar phacelia with curved, fuzzy purple heads; golden back ferns; holly leaf cherries; bright red members of the carnation family called “Indian pinks” …. and much more.
Botanist Ileene Anderson recently trekked up a fire road into the canyon. The hillsides were also covered with a deep pink flower that has four slender, diamond-shaped petals.
ANDERSON: This is an annual. It’s called elegant clarkia. It’s one of our later spring wildflowers, and it’s quite showy. These are 2-3 feet here but they can get substantially taller. They’re glorious, easy to grow in the garden, loved by a variety of insects, animals, etc.
SETZIOL: The tapestry of blooms exhilarates Anderson. But she also sees some plants she doesn’t welcome: she points at a gangly one with lemon-yellow flowers.
ANDERSON: This yellow mustard is of European origin and has spread to California. The story goes that when the Spanish were colonizing California they spread mustard seeds between the missions so they could find their way … by following El Camino Real, the mustard road. It’s done very well here, it’s suited to these conditions and has spread everywhere.
SETZIOL: The mustard is one of a suite of plants from the Mediterranean basin that has tagged along with people and livestock, and found our similar climate to be quite hospitable.
Alongside the fire road, Anderson points out other plants that are all-too-cozy in California:
ANDERSON: We see a patch up here of Mediterranean grasses of different sorts. And they have basically taken over all our native grasslands now. So native grasslands in California are a very rare plant community.
SETZIOL: UCLA botanist Phil Rundel says these alien plants—and others like the water-hogging, giant cane called arrundo—can do a lot of damage.
RUNDEL: Invasive species have dramatic potential to change fire frequencies, fire intensities, they can change nutrient levels, they can crowd out natives and change ecosystem function, change hydrologic flow in streams, a variety of impacts that have huge economic damage. Billions and billions of dollars in the US alone.
SETZIOL: One reason why some of these invaders do so well here in California is because the pathogens and predators they evolved with in their homeland are back there … not here.
Phil Rundel says some countries—places with similar climates, like South Africa—take aggressive steps to control invasives, essentially treating them like hazardous waste. But so far in California…
RUNDEL: There’s very little regulation. The state now has a few things they ask nurseries not to sell. There are state agencies that have lists of invasives we’re trying to control. Part of the problem is public education. People aren’t aware what’s dangerous and what’s not.
SETZIOL: Rundel says sometimes, alien plants don’t become invasive right away. They hang around benignly for several decades … then suddenly become aggressive - perhaps because the right pollinator or seed-disperser comes along to help them out.
The number of alien plants making their way to California is likely to climb as global trade and travel increases. But research scientist Jon Keeley of the U.S. Geological Survey says the plants that are already here are more than capable of wreaking havoc.
KEELEY: And the primary driver that affects that transition from native to non-native vegetation is fire…I see it just about every time I drive to southern California, I see a new portion of the landscape that seems to be on its way to being converted to alien grasslands, simply because as the urban development expands, we find that more and more fires are ignited at the most inopportune times for putting them out.
SETZIOL: Keeley says, yes, Southern California plant communities evolved with fire, but the shrub-dominated areas surrounding cities didn’t used to burn as frequently as they do now. Blame people for that.
KEELEY: If you put too many fires in the landscape, say for example two in five years, those plants don’t have enough time to recover … and as a result, alien species are able to invade and the reason they can invade is they’re a very different life form. The natives are a woody life form that takes a long time to recover, the alien plants are annuals that come in and can regenerate very, very quickly, produce seeds and withstand repeat fires.
SETZIOL: And that doesn’t bode well for all the animals that rely on native plants for food and shelter.
There’s a bit of good news in the face of this daunting problem: Jon Keeley of the USGS thinks federal land managers with the park and forest services are very aware of the problem .
Climbing up Stough Canyon, botanist Ileene Anderson arrives at a plateau thick with California buckwheats, blooming orbs of white flowers.
ANDERSON: The rain has definitely contributed to more blooms in general. This year, all the perennial shrubs have really benefited from the rain.
SETZIOL: But while the native plants thrive, their alien rivals - mustard, Mediterranean grasses and others - are also doing well … ready to take over when the next fire comes.
Ilsa Setziol, 89.3, KPCC.
Recommended Reading: Introduction to The Plant Life of Southern California: Coast to Foothills, Phillip Rundel and Robert Gustafson
Botany of Desire: A Plant’s-Eye View of the World, Michael Pollan. This is not about local plants, but an interesting look at our relationship to four domesticated plants.