Hollister Ranch is located along 8.5 miles of coastline in the south western portion of Santa Barbara County, a few miles east of Point Conception. This area is appropriately regarded as being at the end of a bold, seaward extending promontory along the otherwise relatively smooth contour of the California coastline. Aspects of the climate, geography, and topography are summarized in Hendrickson et al. (1998).

Hollister Ranch occupies the southern slope of the western end of the Santa Ynez Mountains, one of about ten mountain ranges that comprise the Transverse Ranges. The Transverse Ranges are unique in California in that they tend east and west and are therefore crosswise to the northwester-trending fabric of California. These ranges represent the land ward extension of major sea-floor structures. The geology of the Transverse Ranges is understandably complex and interesting. Sedimentary rocks predominate in the western ranges around Hollister Ranch and igneous and metamorphic rocks, including some of the most ancient in southern California (1.7 billion years) predominate in the eastern ranges (Sharp 1972). Folding is prominent in the sedimentary rock of the Santa Ynez Mountains and other western ranges, and the resulting synclines and anticlines form the valleys and ranges, respectively. Significant oil and gas has been produced from the area from regions of the Santa Barbara Embayment, described as the Santa Maria Basin, primarily from faulted anticline formations of the Tertiary Period.

Point Arguello, the western-most terminus of the Transverse Ranges, is the most prominent seaward extending landform of the otherwise fairly smooth California coastline. At this point, the coastline makes an abrupt 90-degree bend to the east. Sea conditions encountered in this area have given mariners a rough passage since the times of the Manila galleons in the 1500s and 1600s. Two oceanic currents meet at the Point Arguello-Point Conception area: 1) the cold, southward flowing California current, part of the great, planetary, clockwise rotating gyre in the north Pacific and 2) the warm, northward flowing California Counter Current also called the Davidson Current.

The Santa Ynez Mountains also create a similarly important bio-geographic boundary for plant species in California. Many plant species typical of northern California coast areas reach their southern range limits in this area, and many southern species have their northern limits near Point Conception (Hendrickson et al. 1998). Hollister Ranch supports an unusual and interesting native flora due in part to this geographical location as well as to the complex geology and related soil varieties, the wide variety of microclimates, and the relatively benign human activities.

Hendrickson et al. (1998) noted that 4 major wetland systems (marine, estuarine, riverine, and palustrine) are represented on Hollister Ranch. Although limited in size and occurrence, these wetlands support a rich diversity of plant and animal life. Several of the endangered species present on Hollister Ranch depend on the wetland habitat for survival: red-legged frog, southwestern pond turtle, snowy plover, tidewater goby, and southern steelhead. Eighteen riparian (stream) corridors on Hollister Ranch together comprise a significant coastal biological resource.

Hollister Ranch is situated at the margin of a shoreline that has a variety of substrate types and exposure regimes. Among the more productive habitats is the rocky inter-tidal that supports a high diversity of algae and invertebrates. Shallow subtidal regions include prolific surfgrass beds, a habitat recognized as an important nursery area for many species, including the California spiny lobster. The extensive sandy beach habitat also supports a diversity of benthic infauna (clams, worms, crustaceans), which provide a food source for fishes and shorebirds. To marine biologists, Point Conception is well recognized as a biogeographic boundary. Species' distributions are determined by a range of biotic and abiotic conditions that provide acceptable habitats for certain species. Only occasionally, on a global scale, do large numbers of species share common boundaries to their distributions. These locations are biogeographic boundaries, separating very different groups of marine species. All major marine biogeographic boundaries, such as at Point Conception, are at points or headlands where ocean currents converge in such a way that water temperature changes abruptly. Two hypotheses, discussed later, attempt to explain how these biogeographic boundaries exist and how these boundaries, and therefore entire marine ecosystems, might be affected by changes in global weather conditions associated with the green house effect and global warming. Various experiments, observations, and physical data designed to test these hypotheses in the field are collected at sites centered at Point Conception and extending varying distances to the north and west. The site at Hollister Ranch, only a few miles from Point Conception and with biological resources that show little evidence of direct human impacts (trampling, collecting, harvesting) and limited access, is a very important study site for investigators doing research in this area of marine ecology.