The constant change happening in a sand dune system is the reason I have been able to stay fascinated with my job for over 25 years, says Andrea Pickart. One of the truly awesome things about dunes is the almost daily renewal I get to see when the wind erases all traces of past activities by humans. Its like being the first person there, over and over.
Pickart has been a U.S. Fish and Wildlife Service ecologist at Humboldt Bay National Wildlife Refuge since 1997 and a dunes manager along the northern California coast since 1986.
It may sound odd, but one the biggest challenges is managing public use, she says. Marking trails or boundaries in a shifting landscape is extremely difficult and timeconsuming. Keeping visitors off of fragile communities and away from endangered species, when its difficult for them to find the trail, is a huge challenge.
The refuges Lanphere and Malel Dunes units encompass 850 acres and three miles of dunes. Disturbance is constant. And thats the way plants and animals like it.
For example, Pickart says, our native dune grass will lose vigor if the sand around it stops blowing, and it will be replaced by species that require stability.
Dunes are landscapes of patches, each with its own disturbance history and each supporting different plant species, Pickart says. That varied vegetation creates microhabitats for varied insects. The richness of plants and insects supports a greater diversity of mammals, birds, amphibians and reptiles. Our management is geared to preserving this mosaic of microhabitats.
The biggest threat is invasive vegetation. European beachgrass, for example, has no natural predators, overwhelms native species and can overstabilize the dunes. The refuge has removed invasives, Pickart says, but reestablishment is a concern.
Pickart views dune management on at least two scales.
On a large scale, the dunes are part of an intact ecosystem that attracts more than 260 species of birds and includes a stable dune forest next to an estuary supporting brackish marsh, salt marsh, eelgrass beds and mudflats.
On a smaller scale, the dunes themselves benefit an array of wildlife. For instance, wind erosion can generate ponds that provide breeding habitat for redlegged frogs, Pacific chorus frogs, newts and other amphibians. A dune blowout can create unvegetated sand that provides nesting habitat for 40plus species of native bees. Beyond being crucial for native wildflower pollination, the bees nests provide pockets of food for burrowing animals like striped skunks and gray foxes.
And pollination is essential to the many kinds of berries in the dune forest that help sustain migratory birds and other wildlife.
The intricate network of mammal tracks that can be found every morning on the dunes attests to the importance of the more open habitats to larger mammals that emerge from the forest to seek their prey in the scrublike vegetation of the semistable dunes, Pickart says. Our job as managers is to be sure the natural processes that maintain disturbances at many different scales are functioning. That means removing overstabilizing vegetation.
Dunes require three conditions to exist: a sand source, sustained winds strong enough to move a lot of sand, and topography low enough to allow the dunes to migrate. Humboldt Bay Refuges dunes have existed for thousands of years and were reformed by a major earthquake in 1700. Today, seismic activity might help mitigate another challenge for the dunes: climate change.
A major issue for Pickart is trying to understand and project the way sealevel rise and extreme climatic events may interact with and/or amplify the disturbance regime.
Interestingly, Pickart says, evidence suggests that tectonic rebound of land may be slowing the effects of sealevel rise in parts of the dunescape.