Recovering endemic plants of the Channel Islands.
The northern five islands comprise Channel Islands National Park, established by Congress in 1980. Programs to protect the islands' flora and fauna and restore habitat damage caused by earlier management began shortly after the park's creation. The park islands support 75 endemic plant taxa, 14 of which are listed as threatened or endangered under the Endangered Species Act.
From the beginning, the restoration of the Channel Islands was a daunting task. For about 150 years, these islands had been used for ranching, and large areas of native scrub and woodland were converted to stands of non-native annual grasses. An important first step was the removal of non-native grazing animals from the islands. This task, nearly complete, is a major step toward ecosystem recovery.
For the last decade, U.S. Geological Survey (USGS) research has focused on gaining the scientific knowledge needed for recovering the listed plant taxa, searching for remaining populations, sampling their habitats, monitoring population changes and distribution, and conducting recovery experiments. Our research approach has asked three basic questions:
* Where are the listed plants found now?
* How are their populations doing?
* Are there threats that we can identify and do something about?
We use the answers to develop recovery actions, along with our partners in management, the National Park Service, the Santa Barbara Botanic Garden, the University of California Reserve System, the U.S. Fish and Wildlife Service, and The Nature Conservancy.
The 14 listed plant taxa span a range of life histories, from tiny annuals that complete their life in one year to slow-growing shrubs that can live for decades (Table 1). Although they differ vastly in stature and longevity, they have all had to contend with the same environmental challenges. For example, each of the listed taxa evolved in response to a particular suite of environmental factors that made them successful at reproducing in the unique conditions found on the Channel Island environments. The ranching that had been practiced for decades before establishment of the park changed their ecosystems, reducing their populations and restricting them to a few small patches of the specialized habitat.
The largest native mammal on the islands is an endemic fox, so the island endemic plants did not evolve mechanisms for coping with the grazing and trampling of large grazing animals. Invasive plants, intentionally introduced for forage and crops or accidentally brought to the islands, became widespread. Most of the endemic plants were unable to cope with the combination of grazing impacts and aggressive invasive species, and these natives became trapped in ever-shrinking habitats. Ultimately, they became endangered because they were reduced to a very low number of populations with only a few plants each, isolated from one another and from unoccupied but otherwise good patches of habitat.
Almost all of these endangered plants grow best in shaded locations, or in places with substantial amounts of fog, such as coastal bluffs or terraces. Climate change is shifting these moisture patterns, with the result that a few of the endangered taxa are not able to reproduce as well as before. The effects of these ecological changes--grazing, invasive species, and climate change--can be seen in the listed plants today. However, our monitoring and research results are showing us ways to help them recover, now that non-native animals are being taken off the islands and we have begun to control invasive plant species. Our goal is to help the native plants reoccupy enough of their former ranges and grow in population size so that they can become resilient enough to cope with continuing environmental challenges, such as those anticipated with climate change.
The good news for these rare Channel Island plants is that the raw material for recovery is still there. Most rare plant populations known earlier in the 1900s still persist, even though they are small. Their habitats are usually dominated by more common native plants, some of which appear to be expanding into the surrounding areas, thereby creating additional shaded habitat suitable for colonization by these rare plant species. Our studies show that most of the endemic taxa produce seeds that germinate readily, and we have found ways to encourage more seed production by such actions as hand pollination or by weeding competitive, non-native plants. Some native plant populations may be able to expand on their own as habitats recover.
Another successful recovery technique has been to find suitable but unoccupied habitats for many of the endangered plants. That enables us to "jump start" recovery by establishing new populations in places where it might take years for these plants to colonize on their own. So far, we have had good success developing new populations of two taxa from seeds and cuttings. We have also documented that existing populations of a few native taxa have expanded soon after non-native animal removal. We have high hopes that ecosystem recovery spurred by the non-native animal removal programs will stimulate recovery of these endemic plants, and we are developing ways to help those taxa that have problems recovering on their own. USGS research is guiding rare plant management in the Channel Islands National Park, and together with our partners, we are translating our research results into successful recovery actions.
Kathryn McEachern, senior plant ecologist with the USGS Western Ecological Research Center's Channel Islands Field Station, can be reached at 805/658-5753 or email@example.com.
Table 1. Listed plants of Channel Islands National Park Taxon Status * Total Islands ** populations Herbaceous Annuals Hoffmanns's slender- flowered gilia (Gilia tenuiflora ssp. hoffmannii) E 2 SRI Santa Cruz Island chicory (Malacothrix indecora) E 6 SCI, SRI, SMI Island malacothrix (Malacothrix squalida) E 1 SCI Island phacelia (Phacelia insularis var. insularis) E 1 SRI, SMI Santa Cruz Island lace pod (Thysanocarpus conchuliferus) E 8 SCI Herbaceous Perennials Hoffmann's rock cress (Arabis hoffmannii) E 5 SCI, SRI, (AI) Succulent Perennials Santa Cruz Island live- forever (Dudleya nesiotica) T 1 SCI Santa Barbara Island live-forever (Dudleya traskiae) E 10 SBI Small Shrubs Soft-leaved paintbrush (Castilleja mollis) E 2 SRI Sea-cliff bedstraw (Galium buxifolium) E 8 SCI, SMI, (SRI) Island rushrose (Helianthemum greenei) T 36 SCI, SRI, SCT Full Shrubs Santa Rosa Island manzanita (Arctostaphylos confertiflora) E 3 SRI Island barberry (Berberis pinnata ssp. insularis) E 5 SCI, (AI, SRI) Santa Cruz Island bush mallow (Malacothamnus fasciculatus var. E 4 SCI nesioticus) * T means threatened; E means endangered. ** AI = Anacapa Island, SBI = Santa Barbara Island, SCI = Santa Cruz Island, SCT = Santa Catalina Island, SMI = San Miguel Island, SRI = Santa Rosa Island; parentheses () indicate presumed extirpated.
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|Publication:||Endangered Species Bulletin|
|Date:||Sep 22, 2008|
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