Along with about 125 other scientists, researchers, and managers, I spent most of last Tuesday attending the Delta Invasive Species Symposium hosted on the U.C. Davis campus and organized by the Delta Stewardship Council, U.C. Davis, and the Delta Interagency Invasive Species Coordination Team.
It was a very interesting symposium that included talks, posters, and a terrific panel discussion. Topics covered a wide range of invasive species ecology, invasive species management techniques and efforts, the effects of invasive species on natural communities and human society, and how invasive species are likely to be effected by climate change.
There are a huge number of invasive species in the Sacramento-San Joaquin Delta. This list includes plants like Water Hyacinth and Giant Reed, vertebrates such as Northern Watersnake and Stripped Bass, invertebrates like Asian Gypsy Moth and Spotted Lanternfly, and many many others.
Dealing with the effects of these invasive species, and attempting to control their populations, costs millions of dollar every year.
Given these high costs, prevention is without doubt the best technique when dealing with invasive species. The costs of measures that are undertaken to prevent an invasive species from entering an area, the Delta for example, are certainly going to be less than the costs of controlling that species once it becomes established. Many efforts are being undertaken in the Delta to keep new invaders from entering. This is especially important because many invasive species are currently found near the Delta, that could become huge problems in they show enter the Delta system. Nutria are an example of this. The Nutria is a large rodent native to South America. A population was established in the southern Sierra in the hope of crating a source for furs, but the furs of Nutria did not catch on in the market place, and the effort was abandoned. The Nutria that had been released were hunted and almost completely exterminated in the 1960s, but small numbers have started showing up along the Merced and San Joaquin Rivers. If those populations are allowed to grow and spread, they will cause massive damage to the Delta ecosystem because of the feeding habits of Nutria which can leave extensive tracts of wetlands denuded of vegetation.
The next best technique is early detection and rapid responses. If an invasive species is expanding its geographic range, having lots of observations of where it is occurring is immensely useful. Knowing exactly where, when, and how many individuals are out there can mean that, with a swift response, it may be possible to control their numbers. This is where the value of citizen science networks is particularly dramatic. There is no way that professional biologists will be able to cover a whole area at small enough detail and high enough frequency to realistically be able to watch for any and all invasive species. But with online databases and citizen scientists out in the field, there may be enough eyes to pick up on new invasive arrivals. Projects like eBird, Calflora, and others allow individuals to add their observations together to form an enormous and very thorough observation net.
One reason that tracking and responding to invasive species is so important is the effects that they have on native species. Competition with invasive species is the second most common reason for species to be placed on the Endangered Species List (behind habitat destruction), and invasive species interactions are a contributing factor for listing 1/3 of all listed species!
And it is only going to get worse. Global climate change is opening up large areas that used to be unlikely places for invasive species to get a foothold. Alaska is just such a place. Historically, places like Alaska had harsh enough environments that, generally speaking, only species that had evolved with those conditions did well. With the warming climate, these harsh conditions that have protected such areas are becoming less harsh. Elodea is an aquatic plant that is often considered an invasive due its rapid growth rates and its tendency to exclude other species from an area. Historically, it was not found in Alaska at all, but in the past few years has started to appear in parts of the state.
All in all, I learned a lot at the symposium. There are definitely a lot of threats and dangers posed by invasive species in the Delta and many more from invasive species that are not currently present should they enter the Delta ecosystem. But there is also so much that can and is being done by dedicated professionals in the field, and also by communities and citizen scientists who care about the natural ecosystems in which we all live.
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