Rare coastal sage scrub habitat provides a home for threatened gnatcatcher and many other species

You’re walking on a trail in Southern California in early May – perhaps Palos Verdes or La Jolla or San Bernardino – and suddenly you are surrounded by fifty shades of green, brown, and gray. The strong smell of sage and mint reach your nose.  Shrub flowers of every shape and color.

“What is this?” you ask yourself. “How come I’ve never seen this before?”

Odds are that you’ve stumbled into a patch of coastal sage scrub, a community of plants that are uniquely native to the coastal lowlands of Southern California. And the reason you’ve never noticed it before is that it is increasingly rare in the United States.

The worldwide range of Southern Coastal Sage Scrub extends from Ventura south to San Diego County and east to Riverside County and is distinct from its northern relative. Northern Coastal Scrub in dominant shrub composition and other characteristics.

Coastal sage scrub is an entire ecosystem that not only includes a wide variety of plants, but also insects, mammals, and birds many of which are very rare. Among the birds you might see in coastal sage scrub include the California Thrasher, the Black-chinned Sparrow, Cactus Wren, and Wrentit. But probably no other single bird is more identified with this habitat than the Coastal California Gnatcatcher, which has been listed as Threatened under the Endangered Species Act.

The listing of the Coastal California Gnatcatcher took place in 1993, and resulted in about 200,000 acres of coastal sage scrub being protected as the bird’s critical habitat in Southern California. Because so much coastal sage scrub is in high value coastal areas, the land is prized for its development potential.

Why this habitat is so threatened isn’t a great mystery. If you overlay a map of California’s population density over a map of historical coastal sage scrub, you will see that most Californians live in these coastal sage scrub areas. And this development has been hard on the habitat type. One recent study called coastal sage scrub the single most endangered habitat type in the United States, and it’s no wonder. As little as 10 to 15 percent of California’s original coastal sage scrub has survived from its historic levels.

Global warming presents yet another challenge to both this habitat type and the Coastal California Gnatcatcher that is so directly tied to it. A 2011 study performed by Point Blue on the projected impacts of climate change predicted that in southwestern California, chaparral and coastal sage scrub would reduce between 38 percent and 40 percent by 2070.

Sandy DeSimone, director of research and education at the Audubon Starr Ranch in Orange County, spends a great deal of time studying coastal sage scrub and the wildlife it supports.

“It’s important to remember that the threats to coastal sage scrub are also threats to every species that is part of the community,” says DeSimone. “That goes beyond the plants to include insects, lizards, and other wildlife, such as the Coastal California Gnatcatcher.”

The 4,000-acre Audubon Starr Ranch Sanctuary includes about 2,500 acres of coastal sage scrub. DeSimone and her team have studied the habitat extensively and developed innovative ways to protect and restore the various shrubs that make up this unique community of plants. In particular, DeSimone has developed ways to reduce invasive, non-native plants without resorting to chemical herbicides.

“An important aspect of our work is developing management techniques that can be exported to land managers throughout the coastal sage scrub range,” said DeSimone. “If we want to bring back species like the Coastal California Gnatcatcher that rely on this habitat type, we need to encourage effective stewardship and restoration of coastal sage scrub throughout the region.”

(photos of coastal sage scrub at the Audubon Starr Ranch Sanctuary by Scott Gibson. Coastal California Gnatcatcher photo by Dinuk Magammana)

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