Anza-Borrego has one of the most diverse collections of plants in the world. One of its main attractions is the spectacular display of springtime wildflowers. But those wildflowers — and the region’s biodiversity — are being threatened by an invasive plant known as Sahara mustard.
Jon Rebman, the botany curator at the San Diego Natural History Museum, says the mustard is changing Anza-Borrego's biodiversity.
"To have something that is well-adapted to desert that comes in and ... it’s starting to ... take resources from the other native plants that are in this area, that’s a real problem. That’s changing that ecosystem extremely,” Rebman said.
Anza-Borrego resident Paul Johnson is a naturalist who's studied the Sahara mustard. He says the plant thrives in the harsh desert environment.
“The first thing it does, as it sprouts, is to grow a rosette of dark green leaves, which is rather rare in the desert," Johnson said. "If you look at desert vegetation, most of it is light colored to reflect heat. Mustard is only here for three or four months, so it doesn’t worry very much about getting too hot because by the time it gets hot here it’s done.”
Another Anza-Borrego resident concerned about Sahara mustard is David Garmon. He founded the Tubb Canyon Desert Conservancy to address the threat.
“I became concerned about Sahara mustard three years ago,” Garmon said, “I went to Henderson Canyon thinking that I would see an incredible display of wildflowers and when I got there, I saw an incredible display of Sahara mustard.”
For the past three years, a team from AmeriCorps has been working with the conservancy and the Anza-Borrego Desert State Park to eradicate the mustard.
In a three-week period, AmeriCorps workers bagged three-quarters of a ton of mustard. It is estimated that 200,000 to 300,000 acres of parkland are impacted by the mustard.
Anza-Borrego Desert State Park Superintendent Kathy Dice worries about the impact of plants like mustard to the overall health of the park.
"If something comes in and alters the landscape enough, then we don’t know what the changes are going to be that’s going to affect the overall health of this park and other deserts in the U.S.,” she said.
Garmon says the Sahara mustard threat to biodiversity is like the game "pick-up sticks."
"That’s a pretty good metaphor for the interdependent nature of all of the life species — the plants and animals in an area or on this planet. And, one at a time, right now, these species are being driven to extinction which means we’re pulling out one more stick. Nobody knows when the whole pile will collapse, but it certainly is headed in that direction,” Garmon said.
