California gray ant, formica spp. (photo from UC IPM: http://www.ipm.ucdavis.edu/)
Have you been worrying about the health and safety of native ants in Golden Gate Park? I recently realized that maybe I should be paying more attention to these small creatures. This epiphany occurred after I read a scientific paper published in 2008 in the journal Urban Ecosystems, co-authored by Kevin M. Clarke, Brian L. Fisher (California Academy of Sciences) and Gretchen LeBuhn. The authors begin by observing that “ants are an integral part of almost every terrestrial ecosystem, including urban environments.” And they note that urban parks harbor a variety of ant species and may play an important role in maintaining biodiversity in the face of rapid urbanization at a global scale. But which characteristics of urban parks best support ants and which ants are thriving in these park environments? Do invasive Argentine ants outnumber native ant species in San Francisco’s urban parks? With these questions in mind, the authors surveyed 24 protected natural areas within urban parks in San Francisco “including mosaic, scrub, herbaceous and forest habitats. . . . The data provide[d] insights into the distribution and abundance of ant fauna in San Francisco natural areas, as well as which characteristics of parks have the most influence on ant community composition.”
They found considerable species diversity in the areas surveyed. “A total of 2,068 ant individuals representing 15 species were collected.” They also found that “there was little or no impact of the Argentine ant on native ants.”
As far as landscape characteristics, they found that “natural area size and shape were not important in explaining variations in overall ant species richness and abundance . . . with many smaller natural areas harboring ant populations that are just as diverse and robust as larger areas.” But the type of vegetative cover did appear to affect ant populations. “A regression analysis revealed that urban forests [such as those found in Golden Gate Park] reduced ant richness and abundance.”
So, what does this study signify for Golden Gate Park? It seems unlikely that we will start removing trees in Golden Gate Park to provide better native ant habitat. But this study clearly illustrates (for me, at least) the complexity of urban ecology and how difficult it is to create and maintain habitat that maximizes species diversity, a measure of ecosystem health. It makes me wonder about other efforts at habitat restoration, targeting more charismatic fauna, such as birds or butterflies in our parks. Do we fully understand the ecological ramifications of these efforts?
I don’t know the answer to these questions, but I really appreciate this study of ants because it seems like the right direction. I would love to see more of this kind of scientific research to help us better understand the habitat value of urban parks like Golden Gate Park and the relationship between native and invasive nonnative species in urban parks.
Here’s a link to the full article: http://www.univet.hu/users/pszabo/teaching/oak/2_adag/urban_ants.pdf
golden gate park: views from the thicket 
Thanks for publishing this… it’s interesting. They looked at all the parks managed by the RPD. The study found no ants in the forest (the Interior Greenbelt, which is on the side of Mount Sutro), which they attribute primarily to its being so wet, cool, and densely vegetated. No surprise, since it’s a de facto cloud forest.
I must say it’s encouraging that the Argentine ant isn’t actually displacing other ant species in San Francisco — we’v been hearing so much about how they’re an invasive species that inexorably wipes out other ant species.
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Interesting article. Speaking for the Panhandle Park Stewards, we would love to support any efforts to identify the ants and other creatures in our park.