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2: What is Biodiversity?
Pages 20-42

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From page 20...
... The Convention on Biological Diversity similarly defines biodiversity as the "variability among living organisms from all sources". Those definitions are so broad that they can be clearly understood only by considering particular levels of biological organization genes, species, communities, ecosystems, and even our planet.
From page 21...
... Local populations that make up a metapopulation experience extinction, and habitat left open is recolonized at some finite probability by other local populations within the metapopulation. The genetic variability among individuals within a species can result from gene recombination or mutation, genetic polymorphism (the presence of different forms of the same gene)
From page 22...
... Genetic diversity provides an economic basis for protecting and conserving biodiversity (McNeely and others 1990; Oldfield 1984; Potter and others 1993; Reid and Miller 1989; Reid and others 1993; WRI/IUCN/UNEP 1992~. For example, Douglas fir trees grow abundantly across the western United States.
From page 23...
... This represents natural evolutionary potential, which can be particularly important in the face of rapid global change. For managers of biodiversity, there are practical implications in the observations that some species have many locally distinct populations but others show little geographic variation and that some species have no close relatives but others occur in genera that include hundreds of species.
From page 24...
... is taken into consideration in counting the number of species in an area. Species counts are the most visible and most widely known measures of biological diversity.
From page 25...
... The country's protected areas and wildlands contribute important economic benefits to the nation, including water and electricity, tourism, and scientific research. A growing economic contribution of wildlands involves trade in biochemical and genetic resources for use in the pharmaceutical and biotechnology industries (discussed further in chapter 3~.
From page 26...
... Costa Rican forests are rich in birds, but whether the forests are relatively rich in other species fungi, for example is unknown. Areas rich in one group of species are often rich in another, but not always.
From page 27...
... Fewer than 25 of eastern North America's birds are endemic (Pimm and Askins 1995~. The distinctiveness of an area's flora and fauna leads to several concerns of managers: why some areas with few species contribute greatly to biodiversity, why endemic species contribute so much to biodiversity, and why some species in some places contribute nothing to regional or global biodiversity.
From page 28...
... Replacing a region's endemic species with species that are more widespread can increase biodiversity locally, but it also reduces between-area diversity by homogenizing global flora and fauna. The Mediterranean regions are an excellent example: introduced grasses and fortes can increase diversity at the local level, but they generally reduce biodiversity in western rangelands (see the case study in chapter 11.
From page 29...
... Camp Pendleton has not only a large number of threatened and endangered species, but also a diversity of marine, estuarine, riparian, and terrestrial "habitat types" (see the Camp Pendleton case study in chapter 1~. Costa Rica (see the case study this chapter)
From page 30...
... In either case, the maintenance of landscape diversity controls the overall exchange of nutrients between terrestrial and aquatic ecosystems. On a coarser scale, the seasonal movement of migratory birds between tropical and temperate ecosystems connects these otherwise independent blames (see Everglades case study, chapter 3~.
From page 31...
... , the torrent salamanders (an endemic family of four species, distantly related to all other salamander taxa) , the Pacific giant salamanders (the endemic family Dicamptodontidae, the sister group of the well-known ambystomatid salamanders)
From page 32...
... They are distantly related to the dawn redwood of China, which is extinct in the wild but was preserved in Chinese monasteries and is itself a long-branch taxon. BIOLOGICALLY BASED RANKING AND RATING METHODS Biologists assess the importance of conserving biodiversity in various ways.
From page 33...
... Thus, Madagascar, some 80% of whose plant species are found nowhere else, has higher conservation priority than a region with a lower proportion of endemic species.
From page 34...
... Rare Species and Habitats The Nature Conservancy's method for ranking "elements of natural diversity" is the best-known example of a valuation approach that is based primarily on the rarity of and threat to species and biological communities. The conservancy obtains information about the known or estimated numbers of subpopulations, the estimated numbers of individuals, the narrowness of ranges and habitats, trends in population and habitat, threats, and fragility, and then it assigns a rank of 1-5 (with 1 representing extreme vulnerability)
From page 36...
... Myers estimates the number of plant species in a region and the percentage of those species that are endemic, evaluates the threat of habitat loss for the region, and then ranks highest regions with large numbers of threatened endemics on relatively small areas. Birdlife International has followed a similar approach, identifying regions that have relatively high numbers of bird species with restricted ranges (less than 50,000 km.
From page 37...
... The management implications of changes on local species composition and therefore probably richness and of its capacity to alter ecosystem function are developed in chapter 3 in the Everglades case study and the section Ecosystem Services, and in chapter 6 in the Lake Washington case study. Nature is complex and highly interactive: management decisions increasingly consider the totality of the biological matrix; no species lives in isolation, and changes in one are certain to affect the ecological and evolutionary continuity and the performance of others and of the assemblage in which they are imbedded.
From page 38...
... Ann Rev Ecol Syst 23:481-506. Brooks JL, Dodson SI.
From page 39...
... 1991. Final consensus report of the Keystone policy dialogue on biological diversity on Federal lands.
From page 40...
... 1993. Global marine biological diversity.
From page 41...
... 1994. Viability analysis in biological evaluations: concepts of population viability analysis, biological population and scale.
From page 42...
... 1992. Convention on biological diversity.


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