Ecological and economical efficacy of endangered species habitat reclamation at the Elk Hills Oil Field (formerly Naval Petroleum Reserve No. 1) was evaluated. Revegetation success and level of site re-disturbance were evaluated 5 years post-treatment and 10 years post-treatment on 996 disturbed sites reclaimed between 1985 and 1989. Also, in 1994, vegetation cover and site usage by predators and prey of the endangered San Joaquin kit fox (Vulpes macrotis mutica) were recorded for a sample of these sites. Revegetation was considered successful when a site's vegetation cover at the end of the growing season was ~ 70 % of the average cover observed on reference sites or adjacent undisturbed areas. After 5 years 47.2% of sites met this criterion. After 10 years 74.4% of a sample of sites still being monitored met this criterion. Annual grasses comprised most vegetative cover during the first 2 years. Shrubs comprised most vegetative cover after 4 years. After 5 years, 70.3% of the reclaimed sites were still intact and 29.7% had been partly or wholly re-disturbed. Lagomorphs (Lepus californicus and Sylvilagus audubonii) appeared to use most sites almost immediately after reclamation. Site use by rodents (Dipodomys spp., Onychomys torridus, Perognathus inornatus inornatus, and Peromyscus maniculatus) stabilized by the second year and burrows or feces were observed at >90% of sites. Use of reclaimed sites by coyotes (Canis latrans) and kit foxes appeared to slightly increase 3 or 4 years following treatment. Because vegetative composition and structure on reclaimed sites >3 years old appeared to favor coyotes and bobcats (Felis rufus), the main predators of kit foxes, and on-site mitigation costs were more than 5 times higher than the estimated off site mitigation costs, reclamation of disturbed endangered species habitat at Naval Petroleum Reserve No. 1 was not considered to be efficacious.
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