DRAFT Biogeographic Assessment of Tomales Dunes, Marin County, California: Vegetation, Flora, and Invertebrates

Baye, Peter; Wright, David

1.0 Scope and Purpose of Report Biological assessments of sensitive species are conventionally prepared for sites of proposed land use change: in California, pursuant to various state and federal regulations, such as CEQA (California Environmental Quality Act), NEPA (National Environmental Policy 1\ct of 1969), or ESA (federal Endangered Species Act). Biological assessments typically consist of either presence/absence surveys for sites within an artificial project boundary, or limited database searches for past reports of species occurrence at or near the site evaluated. The site boundary or "project footprint" bias of biological assessments distort a broader biogeographic perspective: the relation of the communities and species to larger geographic patterns of distribution. They generally focus narrowly on species with special legal status. The tendency for biological assessments to emphasize legally elite species at the expense of other components of biological diversity may substantially underestimate cumulative impacts of land use changes on regional biodiversity. Rote searches of databases for reported historic localities of federal or state-listed endangered, threatened or rare taxa do not address the conservation significance of many other significant components of biodiversity. These include: populations of many non-listed but uncommon and declining "species of concern"; distinctive or unique populations of ecotyes (locally adapted, specialized genetic varieties), stable hybrids and introgressants (natural parent-back crossed hybrids), old relict stands, geographic range limits or extensions, type localities (source populations of original definitive species descriptions) core populations (main populations, the sources of founders of new populations), and complex or distinction suites of species (i.e. unique communities). Even for legally protected rare species, the biological assessments often emphasize short-term presence/ absence surveys, or narrow spatial focus on reported species distributions. This emphasis tends to inflate the significance of negative reports based on poor or erratic past sampling, and may underestimate the biological significance of unoccupied suitable habitats of limited distribution within historic species ranges. It is precisely the distribution of suitable unoccupied habitat within historic ranges, in relation to the distribution of modern species populations, that is the concern of conservation and recovery of endangered species - the primary goal of the Endangered Species Act. 'l'his conservation and recovery context is also usually lacking in biological assessments. This assessment of the flora and insect fauna of Tomales Dunes adopts a broader biogeographic focus than typical biological assessments. It gives full weight to species of limited distribution or taxonomic significance- objective components of biological diversity without prejudice to their current legal status. It also considers the relation of biological resources at Tomales Dunes in relation to the larger distribution of landforms, communities, and populations to which they belong.

DRAFT Biogeographic Assessment of Tomales Dunes, Marin County, California: Vegetation, Flora, and Invertebrates

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