Science and the Endangered Species Act (1995) / Chapter Skim
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Pages 71-93
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From page 71... ...
It is important to make estimates of the probability of survival for given periods to help keep that relationship in mind. CONCLUSIONS AND RECOMMENDATIONS Habitat conservation and recovery planning are essential components of any program to protect endangered species.
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1994. Preliminary Draft Handbook for Habitat Conservation Planning and Incidental Take Permit Processing.
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1993. Status and prospects for success of the Endangered Species Act: a look at recovery plans.
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The Endangered Species Act encapsulates part of this wisdom in its explicit statement of purpose "to conserve the ecosystems upon which threatened and endangered species depend." Recognizing that species and habitats are two components of a single system puts the language of the ESA in a specific scientific light. Although a substantial portion of the language of the Endangered Species Act focuses on the organismal part of the species-habitat system (harassing, prohibitions against the killing or pursuit of listed species, etc.)
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A lanclscape is a large area in which a certain array of ecosystem types is linked by natural disturbance O - ~
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"Sources" are areas where local reproductive success is greater than local mortality. Populations in source habitats produce an excess of individuals, which disperse outside their natal habitat patch to find a place to settle and to breed.
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METAPOPULATIONS Metapopu1lation is a more encompassing concept than that of source and sink dynamics, because demographic rates in metapopulations might not be the same in different patches of habitat. Source and sink dynamics are a special case of metapopulation dynamics in which some habitat patches (sources)
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From page 79... ...
SPATIALLY EXPLICIT MODELS Landscape ecology and conservation biology have made clear that the geometry of habitat patches in a landscape can influence population trends and extinction probabilities. Metapopulation models have generally ignored the complexities of dispersal behavior and habitat geometry by assuming that individuals are equally likely to disperse to near and distant sites.
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From page 80... ...
by the large-scale Yellowstone fires of 1988 and should be useful in future land-use management and fire-control planning. One of the best studies of patch dynamics for a plant species was carried out before the recent development of spatially explicit models by Menges and coworkers on Furbish's lousewort (Pedficularis furbishiae)
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work would be required to parameterize the models. However, a wale array of new ecological concepts ant} information can be applied to the conservation and recovery of endangered species.
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(conservation strategies and recovery planning often must cleat with tne como~necl effects of all four factors, because many endangered species, especially large vertebrates, exist in small populations. The recovery plans for endangered species should!
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Such changes can be rapid and unexpected or gradual and difficult to detect. In either event, the changes can have untoward results for a target species, necessitating adjustments in conservation efforts.
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1993. The contemporary paradigm in ecology and its implications for endangered species conservation.
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1987. Analyzing population viability of the spotted owl in the Pacific Northwest.
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1985. Tile ecology of natural disturbance and patch dynamics.
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1979. Pattern, process, and natural disturbance in vegetation.
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From page 89... ...
The important ecological characteristics of mosaics for conservation of endangered species are that the resources, interactions, and constraints of endangered species can originate in the mosaic in components other than the current location of the listed entity (Risser, 19851. Although it is difficult to learn about the important ecological fluxes between patches that affect listed species, neglecting such fluxes can result in failures to preserve targeted species (Saunders et al., 1991; Tyser and Whoriey9 1992~.
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WINTER-RUN CHINOOK SALMON AND DELTA SMELT Another example involves the enciangerect winter-run chinook salmon and the threatened delta smelt, two species of fish that occur where the Sacramento and San Joaquin rivers meet in the Central Valley region of California (see Box 6-2~. The 1992 Central Valley Improvement Act (Title 34 of P
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BOX 6-! Northern goshawk and Mexican spotted owl.
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In one case, however, a provision of the Central Valley Improvement Act might benefit one of the threatened species and have an adverse effect on the other. Provision 14 calls for modification of the flow and control structures at the Delta Cross Channel; it is primarily for the benefit of striped bass, a popular nonnative sport fish.
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From page 93... ...
Nevertheless, it is unclear whether these actions will be able to help both species, or if one will still suffer at the expense of the other. BACHMAN' S SPARROW AND RED-COCKADED WOODPECKER Management decisions designed to improve conditions for a threatened or endangered species may inadvertently affect dozens of nontarget species found in the same habitats.
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