Plants have many different strategies to ensure their reproductive success. Sometimes they are passive participants in their propagation. Charles Darwin studied the dispersal of the seeds of plants and reported a particularly stunning example: “He raised more than eighty plants from the mud-ball gathered round a wounded French partridge’s leg.”* He also raised plants from seeds found in the stomachs of birds, which brings us to today’s topic: the non-native plants which are eaten by birds are categorized as “invasive” plants and are therefore doomed to be eradicated.
We often puzzle over the list of nearly 200 non-native plants on the list compiled by the California Invasive Plant Council (Update: Now nearly 300 in 2020). We know from horticultural experience and scientific studies that at least two of the trees on this list are not invasive. Aerial photographs of open space in the Bay Area taken over a period of 60 to 80 years, proves that neither the eucalyptus nor the Monterey pine forests are spreading.
There are also several species of non-native shrubs which produce berries on the list of “invasive” plants that we know don’t spread in our gardens: English holly trees, Cotoneaster, and Pyracantha. So, why are they on the hit list? The garden columnist in the San Francisco Chronicle recently told us why in answer to a question about planting a non-native holly tree for Christmas foliage in the garden:
“Berries are a little harder to come by if we follow the advice of native plant specialists who are concerned about escape of holly, cotoneaster and pyracantha into nearby wildlands, particularly in coastal counties. Birds that eat the fruit and deposit seeds are the culprits.”
In other words, native plant advocates don’t want gardeners to plant non-native plants that produce berries that birds eat because they don’t want the plants to spread. Obviously, their dedication to native plants trumps whatever concern or interest they might have in the welfare of birds. Native plant advocates frequently claim that their “restorations” will benefit wildlife. Clearly the eradication of berry-producing shrubs does not qualify for such a claim.
The loss of food and habitat for the wildlife that lives in our public lands is only one of many issues in the debate about native plant “restorations.” But for bird lovers, this is a high priority. In this regard, we were struck by one of the public comments that was recently submitted on the Draft Environmental Impact Report for the Natural Areas Program. This self-identified “birder” said this about the radical “restorations” in San Francisco:
“Restoration areas such as Land’s End, El Polin Spring, Crissy Field are seldom spoken about anymore by birders or others looking for populations of wildlife. Since the vast majority of the city’s resident bird species feed, roost and breed in trees, they leave, starve or are predated when their habitat is destroyed.”
As the Cedar Waxwings pass through the Bay Area on their annual migration, we see them eating the berries in our holly tree. They remind us that the eradication of non-native trees benefits neither animals nor birds, nor insects. Who benefits from these destructive projects besides the people making their living at it? It’s a mystery.
* Mabey, Richard, Weeds: In Defense of Nature’s Most Unloved Plants, HarperCollins, 2010, page 29