Grasses blow in the wind near Toms Point in Marin County, on the east side of Tomales Bay. Most of the grasses in the photo are exotic. Photo: Brody Sandel.

Full disclosure here: Brody, Emily and I were all grad students together in the same lab at UC Berkeley. So when Emily told me she had a new paper, I was curious to see what it was all about. It turns out their study is really cool. It looks at the interaction of two major world-changers: invasive species and climate change. Their paper talks about exotic species—species that are not native to a particular habitat but are not necessarily detrimental, and noxious weeds—species that are somehow disruptive, because they outcompete native species or alter the habitat. Noxious weeds are what we would also call invasive plants.

Brody and Emily’s study draws on existing datasets on current plant distribution across the state, plant traits, and current and future climate. They mapped the distribution of all the different species in California grasslands, using data from the Jepson Manual (the bible of California plant life), and a few other sources, to fill out an 800-cell grid of the state. They looked at the traits of the species—including how tall the plants are, whether they are annual or perennial, how much of their leaf mass comes from nitrogen, and the size of their seeds—and examined how the traits relate to the climate where the plants live today. Especially important was the proportion of exotic species in each of the grid cells. Then they turned up the temperature. They predicted the proportion of exotic species in each grid under climate change scenarios: higher average temperatures and less available water.

They found that as the temperature increases and water availability decreases, the proportion of exotic species increases. And, the proportion of noxious weeds increases. Higher temperatures favor traits that tend to be possessed by exotic species, such as tall plants with big leaves and annual lifestyles. These are the same traits that made the plants successful invaders in the first place. For example, a tall plant extends above a short plant, stealing its light. But burly exotic plants like Holcus lanatus outcompete native species for light. And generally, plants with big seeds grow to be hearty seedlings, which are better competitors than scrappy little seedlings grown from modest sized seeds. This study predicts that noxious weeds will become even more prevalent, because they have traits that will serve them well under the conditions of climate change. The changing climate acts as a filter, straining out the native species.

The noxious weed Holcus lanatus, a.k.a. “The Hulk,” so named because it towers above native grasses and outcompetes them for light. Photo courtesy of Brody Sandel.

Years ago, I asked a grad student friend why she studied grasslands. I just couldn’t understand the appeal of a field of grass—it seemed boring. My friend Tasha explained that she just loved the way grasses look when they blow in the wind. A few weeks later, I went with her to her field site near Point Reyes, and I immediately understood the aesthetic appeal of grasslands. If you’re picturing a green manicured lawn with short little blades of grass, toss that idea right now. Instead, think of taller grasses, shin height or higher, in all shades of green, brown, gold and even purple. Think of the colors shifting as the wind blows. It is really a beautiful sight. California’s grasslands are expected to expand as the climate changes. But the inhabitants of these grasslands won’t be the grasses that were there 100 or 200 years ago. Instead, there will be a bunch of weeds blowing in the wind.

To learn more about the interplay between California’s native plants and exotic species, check out the California Native Plant Society, the California Invasive Plant Council, or take a workshop with the Jepson Herbarium at UC Berkeley.

Jasper Ridge Biological Preserve

Jasper Ridge Biological Preserve can easily be missed: just off Highway 280 in the city of Woodside, the entrance is blocked by a rusted metal gate with a small sign that reads 'No Tresspassing, Area Patrolled.'

But some of the folks at QUEST – including yours truly – got a special tour of the preserve. I joined reporter David Gorn and biologist Scott Loarie on a three hour hike around Jasper Ridge's Searsville Lake.

I learned that plant-life on the preserve, and most endemic California plant-life, are in trouble.

At least, that's what Loarie and his team at Stanford predict. "If plants can't adapt to the climate changes," says Loarie, "Then by the end of the century two-thirds of California plants face an 80 percent reduction."

So which plants are most likely to go as the global climate changes, well, the plants that have a hard time with seed dispersion. Plants like Bay Laurel, the California Buckeye, Madrone and the Western Burning Bush have seeds that aren't easily dispersed. This gives them a very concentrated zone for growth. If the climate shifts slightly in that particular region, then the these California natives could all die out.

Bay Laurel

The plants that do have an easier time are those with a wide seed dispersion – like the beautiful but dangerous Poison Oak, the Coyote Bush, Clarkia, Virgin's Bower and Box Elder Maple. These plants all have small seeds that are easily dispersed by the wind, or by birds. By dispersing their seeds to various climates, these plants will have a better chance of surviving.

Virgin's Bower

So which California plants will survive a century from now? It's hard to say. But what is definite is that preserves like Jasper Ridge are crucial for monitoring and protecting California's unique plant life.


View a slideshow of the"Disappearing Plants" Radio Report online, as well as find additional links and resources.

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Quest Educational Resources

 Print Guide - Bothe-Napa Valley State Park

 Bothe-Napa Valley State Park KML file

 Tips to get the kids in your life out into nature

 Designing an Exploration on Google Maps

Additional Links

• Soil Survey of Napa County, California
• The Sparkling Science of Champagne
• Check Please! Bay Area – KQED