Conservation introduction of Bakersfield cactus in the southern San Joaquin Valley, California, USA

Summary

Bakersfield cactus (Opuntia basilaris var. treleasei), Federally and state Endangered and reduced by agricultural, urban and petroleum development to fragmented remnant populations in Kern County, California, was the subject of two experimental translocations by the Endangered Species Recovery Program and California Department of Fish and Wildlife, testing whether new populations could be established in suitable but unoccupied habitat within the species' historic range. The first effort, in October 2009, planted 10 small plants and 25 shed pads collected from a protected source population; the second, in January 2011, used pads and partial plants salvaged from an unprotected source population being converted to citrus orchards, testing three pad orientations (horizontal, vertical, on edge). At both sites vegetation was cleared and soil loosened before planting, with supplemental watering during dry periods and steel bars protecting plants from cattle. After 34 months, the first site showed 90% survival for transplanted whole plants but only 16% for pads, with heavier pads surviving better; the second site had 100% plant survival after 25 months, and vertically oriented pads outperformed horizontal or edge-oriented ones (89% versus 63% and 60%). Several plants at both sites flowered and some pads rooted after shedding. Difficulties included agency restrictions on how much material could be removed from source populations, pad breakage during transport, poor pad survival through dry summers, and weed colonization of cleared beds. The project rates itself successful, crediting proactive planning for anticipated problems and the ease of propagating succulent cacti vegetatively; the approach was later adopted by a local preserve to establish five further populations.