Outcrops of sand, deposited 15 million years ago when the region was under a vast sea, now create a unique ecosystem found only in Santa Cruz County. These sand outcrops or "sandhills" occur as islands of sand soil and are concentrated in the San Lorenzo River watershed. A unique community of plants and animals make their homes in the sandhills of Santa Cruz. The vegetation communities are dominated by sparse stands of Ponderosa pine and chaparral and include four plant species found only in the Santa Cruz sandhill environment: Ben Lomond spineflower, Santa Cruz wallflower, Ben Lomond buckwheat, and Bonny Doon (silver leaf) manzanita. The animal community includes two insect species found nowhere else in the world (the Mount Hermon June beetle and the Zayante band-winged grasshopper), as well as the Santa Cruz kangaroo rat, the coast horned lizard, and the western whiptail lizard (McGraw and Bean 2003).
This unique habitat is very fragile; disturbance results in erosion of exposed soils. Sandhill habitat in Santa Cruz County has been greatly reduced by mining and development. Although several reserves protect part of the remaining habitat, development threatens non-protected areas, while habitat degradation due to fire suppression and the invasion of exotic species threatens the sandhills in protected reserves. Degradation of the sandhills environment may have negative impacts on salmonid habitat as erosional processes associated with the disturbed environment contribute large amounts of sand and sediment to local streams. (McGraw and Bean 2003)