Fundamentals of Conservation Biology. Malcolm L. Hunter, Jr.. Читать онлайн. Newlib. NEWLIB.NET

Автор: Malcolm L. Hunter, Jr.
Издательство: John Wiley & Sons Limited
Серия:
Жанр произведения: Биология
Год издания: 0
isbn: 9781119144175
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target="_blank" rel="nofollow" href="#ulink_afa03158-ce1b-5c35-86b5-e7d975a9ec5a">Figure 3.11 The ecological impacts of keystone species take many forms. The purple sea star (a) is a keystone species because its predatory activities allow many species to coexist, while beavers (b) shape entire communities because of flooding by their dams (c).

      ([a] Olympic National Park/Flickr/Public domain; [b] Hubert/Shutterstock. [c] Procy/Shutterstock)

      When assessing the ecological roles of species, conservation biologists are typically conservative and assume every component of an ecosystem is important unless proven otherwise (Berlow 1999; Montoya et al. 2006). Our understanding of ecosystems is usually so limited that it is sensible to take this position, even though most species probably do not play irreplaceable roles. Furthermore, it is possible that one should look beyond the role of individual species because overall species richness of an ecosystem may be an important attribute. We will return to this issue in the next chapter, “Ecosystem Diversity.” Finally, it is important to realize that a species that is relatively unimportant now may become more important as an ecosystem changes through time. For example, since the last glaciation some trees species, such as eastern hemlock, have shifted between being ecosystem dominants over large areas and being quite uncommon (Williams et al. 2004).

      Incidentally, there are many ways in which ecological values interface with economic values. Most notably, the health and productivity of people have huge economic consequences, and these are directly dependent on ecological integrity. One paper examined the relationship between deforestation by an invasive insect, the emerald ash borer, and human mortality, and suggested that through higher stress, lower air quality, and reduced physical exercise the insect might be linked to an increase of 20,000 deaths across 15 states in the United States (Donovan et al. 2013). Similarly, each species we use directly for economic gain as food, medicine, materials, and so forth depends on ecosystems and the continuing existence of a whole suite of other species.

      Strategic Values

      Large mammals, especially those with big brown eyes, are often the most successful flagships, but many other species have been successfully used too. In northern Maine an inconspicuous rare plant with an unprepossessing name, Furbish’s lousewort, became a flagship species for the effort that stopped a dam that would have flooded 35,000 hectares of forest. This was a case where concern for an ecosystem pushed a species into the flagship role. A better‐known example of the flagship process in reverse comes from the northwestern United States where concern for old‐growth forests made the spotted owl a flagship species.

      Conservationists sometimes focus on umbrella species on the assumption that addressing the habitat needs of a particular species can, under the right circumstances, benefit the habitat of many species, even whole ecosystems, thus making the target species an umbrella for many species. For example, to secure a viable population of snow leopards you will, by extension, have to secure a large population of various species of ungulates – the snow leopard’s prey – and the large mountain and grassland areas those herbivores require to survive, and hence all the plants and smaller animals that also live in such places. Typically umbrella species are relatively large animals and thus many umbrella species are also flagship species. However, the terms are not synonymous because it is their patterns of habitat use, not popularity, that make some species good umbrellas.

Photo depicts (top) a tiger walking in a boreal forest and (bottom) a tiger walking in a rain forest.

      (Martin Prochazkacz/Shutterstock and Ondrej Prosicky/Shutterstock)