A buggy inventory of Abbotts Lagoon

06/13/2013

No one really knows what the Anomalon californicum, a wasp, does at Abbotts Lagoon. Perhaps it parasitizes beetle larvae under ground, as its closest relatives do. Entomologist Paul da Silva just knows the Anomalon frequents a spine flower that usually goes unnoticed until someone sits on it.

The College of Marin professor, who has spent 13 years making an inventory of insects living at the lagoon, does know that the Lithariapteryx abroniaella, a moth, is restricted to the dunes because it feeds exclusively on the leaves of the yellow sand verbena growing there. He also knows that species like Habropoda miserabilis and Melissodes pallidosignata, both solitary bees, need a particular kind of sand to build their nests in.

Dr. da Silva’s inventory is an informal part of a larger restoration project underway at Abbotts Lagoon  and in similar habitats throughout Point Reyes National Seashore. Scientists with the National Park Service have been experimenting with the removal of European beachgrass, an invasive plant brought in to anchor sand that has become a sprawling monoculture crowding out native species. Native plants support native insects, which in turn support native plants. 

An environmental assessment on the dune restoration project is due out this fall, and Dr. da Silva’s survey of bugs and their habitat, together known as entomofauna, could help inform its success.

The study has taken place in one square kilometer around Abbotts, considered a pristine example of the seashore’s endangered dune habitat, according to Kim Cooper, a former NPS ecologist who encouraged Dr. da Silva in the project. 

“If you look at all of the coast of California, there are very few areas that have really extensive sand dunes,” Dr. da Silva said. “Unfortunately, invasive species of plants had pretty much obliterated
everything.” 

He said he studied the lagoon while he still could: “You might say it was the last stand of the native plants of Point Reyes. If we lost that, there wouldn’t be anything left.”

Dr. da Silva and co-investigator Bill Lenarz, a retired professor at College of Marin, have recruited about 100 students and citizen scientists over the years to trap the insects and to identify them in the lab. Help has included Dr. da Silva’s wife and, one year, two interns supported by a grant from the NPS.

Dr. da Silva stresses the importance of the collaboration. “There just aren’t that many professional biologists to do it all themselves,” he said.

Most of the past 13 years’ work took place in the spring, when flowers bloom, butterflies and bees come out, and when Dr. da Silva teaches “Introduction to Insect Biodiversity.” Over the years, samples took place at least once from every month to account for insects only spotted at certain times—like Paraphymatopsis californicus, a moth that “flies for 20 minutes before sundown on calm afternoons in March.”

Specimens have been captured with pan traps, a “golf-course” of cups of water buried in the sand, as well as with pitfall traps—the same thing, without the water.

So far they’ve collected about 5,000 specimens and identified 350 species of up to 1,000 believed to be at the lagoon. Dr. da Silva thinks that 99 percent of those species are native. 

None, so far, are endangered, though the lack of that designation is more a function of insects’ unlikelihood of making it on the federal endangered species list to begin with. An insect’s habitat determines whether it’s endangered anyhow, Dr. da Silva said.

Since January, traipsing around the lagoon and trapping insects is on indefinite hold. Identification takes time—consider dissecting flies less than two millimeters long—and every hour in the field can mean 10 spent in the lab. Specimens are stored at the College of Marin Biology Museum; check back for the exact count in five to 10 years. 

The seashore’s intensive dune restoration project continues, and any ensuing small-scale interventions—“continuing to mop up the little spots”—are just the nature of conservation work. The seashore may always need humans to steer it back to how it once was before them.

“There’s probably no going backwards to when humans didn’t have a big impact on the planet,” Dr. da Silva said. “What we’re really doing is always having some impact—we just have to be careful about choosing to maximize our positive impacts and minimize our negative impacts. I think the work at Abbotts Lagoon shows that we may have been able to tip the balance to have this intervention at this crucial time.”