Posts Tagged: invasive species
In agricultural systems, invasive species may reduce yields, render crops unmarketable, or make rangeland unfavorable to livestock. In natural areas, they may squeeze out native species, change soil quality, and increase the frequency or intensity of wildfires.
Some of these species have been introduced intentionally (e.g., yellow sweetclover, which was originally imported from Europe as a forage species for livestock), while others arrived by accident (e.g., the glassy-winged sharpshooter which came to California inadvertently through nursery stock shipments).
The spread of invasive pests has become more prevalent in recent decades, and is linked to several factors, including global travel, produce trade and climate change. Many invasive pests spread by human movement — medusahead, for example, has long awns on its seeds that easily attach to clothing and animal fur, to be carried to other locations. A recent study by UC scientists also determined that due to climate change, invasive weeds are shifting their ranges at a faster rate than native plants, and will likely cause more problems in agriculture and natural resources in the future. The yellow starthistle, an invasive plant that dries out soil and degrades rangelands, is one of the pests that will expand its range further north in California (and beyond) due to climate change.
While invasive pests can be a major challenge to growers and land managers, there are successful stories of stopping exotic pest invasions with well-coordinated eradication efforts. Recently, the California Department of Food and Agriculture (CDFA) declared the European grapevine moth eradicated from California after no moths were found in the state from 2015 to 2016. This was due to a rapid response, largely by UC Cooperative Extension scientists after the moth was discovered in Napa vineyards in 2008.
Here's what you can do to keep from introducing or spreading invasive species:
- Fully cooperate with agricultural inspections at the California state border and in your fields. When coming into California from another state, declare any plant or animal material that you have in your vehicle. Inspectors will thoroughly examine your materials or crops to make sure that they do not hold any invasive pests. This greatly reduces the chance that your activities will spread harmful invasive species.
- Check and clean your clothes, shoes, and equipment before you move from one location to another. For example, thoroughly cleaning your shoes with water and a disinfectant after hiking through an area known to have sudden oak death will prevent you from tracking the pathogen into uncontaminated areas. Similarly, checking your clothes or shoes for weed seeds before leaving an area will keep you from spreading invasive weeds.
- “Burn it where you buy it.” Burn firewood in the same place you purchased it, rather than buying it and transporting it elsewhere. If you must transport firewood, be sure to declare it at the border and have it inspected, as described above.
- Report invasive pests in your area. CDFA has a tool for reporting pests, but you can also contact your agricultural commissioner or UC Cooperative Extension to do so.
To learn more about invasive species, visit the UC IPM website. You will find a list of invasive insects, plants, diseases, and vertebrates in California, as well as links to other organizations and regulatory agencies that are also working to reduce their numbers.
You don't have to dig too deep into the scientific literature and popular media to find perspectives on threats posed to biodiversity in California and around the globe. Two UC Davis scientists in the Department of Wildlife, Fish and Conservation Biology have published fresh insights into endangered species in recent months.
Endangered Species Act sets a high standard
After passage of the ESA, Moyle and his graduate students initially searched for three species they suspected were in trouble: Modoc sucker, rough sculpin and bull trout. They found the sucker in trouble but easy to protect, the sculpin reasonably secure, and the bull trout near extinction in California. It has since vanished.
"As an untenured professor then, I thought it a bit risky to base a career on finding rare fish," Moyle wrote in an opinion piece published in The Sacramento Bee. “So I also undertook a study of Delta and longfin smelt, which at the time were two of the most abundant fish in the Sacramento–San Joaquin Delta.”
Moyle began a monthly sampling program to keep track of smelt populations and other fish in the Suisun Marsh. A few years later smelt counts dropped dramatically. The data eventually led to the U.S. Fish and Wildlife Service listing the Delta smelt as a “threatened” species under the ESA.
His ongoing research has recorded a statewide decline of most native fishes. With other researchers, Moyle has just completed detailed accounts of the biology and status of more than 60 native fishes — all potential candidates for ESA listings. This study will soon be released by the California Department of Fish and Wildlife.
“Most of our recommendations for preventing extinctions call for more and better water for the fish, or at least for protecting existing water they depend on,” Moyle said. “Funny how it almost always comes down to fish needing water.
“The Endangered Species Act sets a high standard in this regard because it not only forbids extinction; it also mandates recovery of each species to a more sustainable state.”
Moyle's opinion piece can be viewed in its entirety here.
Human longevity an indicator of endangered species
The researchers analyzed data from 100 countries, representing 87 percent of the world's population. They examined 15 social and ecological variables, such as tourism, per capita gross domestic product, water stress and political stability. The study showed that as human life expectancy increases, so does the percentage of invasive and endangered birds and mammals.
“It's not a random pattern,” Lotz said. “Out of all this data, that one factor — human life expectancy — was the determining factor for endangered and invasive birds and mammals.”
New Zealand, the United States and the Philippines had among the highest percentages of endangered and invasive birds. The study has been reported in the Los Angeles Times and other news media. Read more about the study's findings in our news release here. The journal article can be viewed here.
At least 13 of the 102 aquarium species that are imported into California have been introduced into California marine waters, according to a recent report by Susan Williams, professor in the Department of Evolution and Ecology at UC Davis and a marine ecologist the Bodega Marine Laboratory. These introduced species have a high success rate (69 percent) in establishing themselves.
Two very invasive species — the predatory lionfish and Caulerpa seaweed (aka “killer algae”) — have reportedly come from the aquarium trade. The lionfish, which has established itself along the East Coast where it eats smaller fish and threatens reef ecological systems, has not yet reached California waters, but the Caulerpa seaweed cost California more than $6 million to eradicate from two Southern California lagoons a decade ago.
At least 34 aquarium species were found to be potential invaders in California marine waters.
“Globally, the aquarium trade has contributed a third of the world’s worst aquatic and invasive species,” Williams said. "Lionfish are voracious predators in their native habitats, and in their invaded habitat any predator is a potential threat to the native ecosystem."
Williams’ advice: "To avoid releasing aquarium species into natural water, don’t dump your aquarium where they can become an expensive and harmful pests.”
She said that people should contact the vendor where the fish was purchased or the California Department of Fish and Wildlife to learn how to dispose of aquarium species responsibly.
- Complete UC Davis news release, by Kat Kerlin
- Our AmazingPlanet report
- Environmental News Network report
- Science on NBC News report
Invasive aquatic organisms can impact fish, shorebirds, marsh plants, and other wetland species, and alter functions of lakes, watersheds, floodplains, and coastal ecosystems.
Estuarine ecologist Ted Grosholz, a UC Davis professor and Cooperative Extension specialist in the Department of Environmental Science and Policy, is an expert on invasive species and addresses outreach education on zebra mussels and quagga mussels.
These two invasive, freshwater Eurasian mussels—zebra mussels and quagga mussels — could have a profound impact on California’s lakes and water distribution systems.
Los Angeles water districts are coping with the mussels, which are in Southern California watersheds, and reservoirs and canals of the Colorado River. The larval stage of the mussels disperses readily in water, so it gets moved around easily. There is tremendous concern about their potential spread into Lake Tahoe, and they have recently shut down a reservoir near San Jose. These mussels have cost the state tens of millions of dollars.
Zebra and quagga mussels pose a serious ecological threat in California. In the Great Lakes, where they became established 25 years ago, they have removed phytoplankton — a food source for juvenile fish — thereby impacting the food web. They have also concentrated the environmental contaminant botulism, resulting in massive kills of diving ducks and shorebirds.
Aquatic invasive species are moved long distances by ships — in ballast water, hulls and attached to ships’ surfaces. Within California they can be moved by recreational and fishing boats, trailers and other equipment.
Since the state doesn’t have the resources to adequately enforce zebra and quagga mussel control, areas such as Clear Lake and Fallen Leaf Lake are establishing local mandatory vehicle and boat inspection programs.
Grosholz works closely with resource agencies and other organizations to develop programs aimed at identifying and reducing the spread of invasive aquatic organisms. “It’s important to increase awareness of these species because they’re such a problem,” says Grosholz. “Their impact on ecosystems is big, and early control is very important.”
To read more about invasive aquatic species, including zebra and quagga mussels, see:
CA&ES Outlook magazine, pages 4–7
Quagga/Zebra Mussel Invasion, UC Cooperative Extension Coastal Resources
Quagga and Zebra Mussels, California Dept. of Fish and Game
Quagga and Zebra Mussel Prevention Program, San Luis Obispo County, California
Quagga and Zebra Mussel, Calif. Dept. of Boating and Waterways
A pair of leading UC Davis experts will provide a rare glimpse into efforts to protect California biodiversity at a public lecture May 10, 4–6 p.m., in the UC Davis Conference Center.
Their work is featured in the current issue of “CA&ES Outlook,” the magazine of the UC Davis College of Agricultural and Environmental Sciences. The magazine also examines the work of other UC Davis scientists and students working to conserve biodiversity in California.
The event concludes with a reception and an opportunity to visit with Thompson, Grosholz, CA&ES dean Neal Van Alfen, and other participants. The cost is $15 per person. To register, go to https://registration.ucdavis.edu.
For additional information about this event, please contact Carrie Cloud at (530) 204-7500 or firstname.lastname@example.org.