SFSU Professor and California Academy of Science Board of Trustees President John Hafernik introduced us to the green roof of the Academy’s new building, and research into what has been finding its way up there.
His graduate students, lead by Jessica Van Den Berg, have been methodically catching and cataloging the insects that find there way into traps both on top of and near the museum for over a year. The roof was designed by Renzo Piano to lift up the park, but it is a good deal different from the surrounding flora.
Nine species of native California plants were originally planted on the roof. Native plants that were thought best adapted to surviving the somewhat harsh conditions of the roof, and the shallow soil. Those plants have been joined since by another 70 species or so (mostly planted near the observation deck).
The results of the study so far show that the roof’s insect population is much more diverse than that on the ground (dominated by two imports: the devil’s coach horse and pill bugs) . They have been pleased and surprised to see how quickly a rich web of species has been established: from herbivores (beetles and grasshoppers), pollinators like honey bees (and their mimics: drone flies) and bumble bees, predators like lacewings and wolf and jumping spiders, plenty of recyclers, i.e. flies, and perhaps most surprisingly a host of parasites and parasitoids.
Over 55 morphospecies (morphologically different species but still unidentified) of tiny and tinier wasps have been found (they make for beautiful pictures, but these are wasps species that are parasitoids: laying their eggs inside another insect species which then hatch and the eat their way out and eventually kill the host).
Other surprises have been native californian species like pigmy locusts, tricolor beetles not previously found in SF, but thought to be stowaways — carried here along with the plants from their original nursery. The surprising thing is that these species are still surviving the conditions (both generally live long creeks).
Also found was Agonum Muelleri, a European-Siberian beetle that has been slowly spreading around the world (and had as recent as 2008 been found in the Presidio).
What hasn’t been found so much is butterflies — unsurprising since not many host plants have been planted — and ants. Native ant queens have been spotted landing, but so far no colonies have been found. The argentinian ant has not yet found its way up, though it seems only a matter of time.
What next? Once cataloged and photographed, large and small, the insect samples will be turned in for genetic studies, fine tuning the knowledge of what is what on the roof.
As for the roof there is plenty more to study and to decide: how much to further encourage natives insects: nesting sites for bees, wood and other items for shelters, more host plants for butterflies and moths, and perhaps even importing some species that otherwise might not find their way up (ground dwelling species for instance).
Other studies might be done on other native gardens and how they compare. The academy, using citizen science will carry on the study of what is up there, to see how things will change over time. The studies will also be good information for future green roof projects.
More information on the roof and future projects can be found on the California Academy of Sciences green roof website.