Michael McGowan spoke before the Natural History crowd on May 16, 2013 about his thinking and philosophy around invasive species in the San Francisco Bay.
Our current attitudes to managing invasive species come from Charles Sutherland Elton who brought this sub-discipline into being after the Second World War. He recommended quarantine, eradication, and controls to suppress invasive species. The chief goal of which was to prevent extinction of native species and a homogenization of the local ecosystem.
There are many examples of where invasive species have wrought havoc on local ecosystems. Many of these examples involve islands, where species diversity is already low. And there are places like Australia where there are many examples of introduced species gone wrong.
What can we say about the Bay, in this regard? There are any number of invasive species: striped bass, oyster drills, mitten crabs, clams, cord grass, various copepods, and a mud shrimp species that Michael only recently discovered. These have been introduced intentionally, and unintentionally and have all in some degree affected SF Bay, at the same time there have been changes wrought to the environment by man through other means: run-off from gold mining, the filling in of wetlands, the run-off from our growing towns and cities, ship traffic, damming and altering of rivers, climate change, etc.
One question then is how much harm have these invasive species brought to the bay? Of the species Michael went through, the Corbula clam may have had the greatest affect altering the processes of the North Bay, but there has been no species extinctions as a result of these species, and no homogenization of Bay diversity. In fact, one could say that the diversity of the Bay has increased, that there’s been some net gain.
That isn’t to say we shouldn’t try to preserve & protect native species, or introduce new species willy-nilly, or not worry about things like ballast water (the standard practice these days is for ships to exchange ballast water offshore where travelling species won’t be released into more protected waters). Michael stressed the importance of good data and monitoring over time to work towards understanding these complex systems on top of which we are living.