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

Автор: Malcolm L. Hunter, Jr.
Издательство: John Wiley & Sons Limited
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Жанр произведения: Биология
Год издания: 0
isbn: 9781119144175
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lizard species showing alpha diversity (within an ecosystem, a plus b), beta diversity (among ecosystems, a/b plus c), and gamma diversity (geographic scale, a–c plus d). See text.

      We can use this hypothetical example to show how a narrow‐scale perspective on maintaining biodiversity can lead would‐be supporters of biodiversity astray. Some people might look at Fig. 2.3 and think, “There are more lizard species in forests, so let’s plant trees in the field.” By doing so they might increase the alpha diversity of the field from one lizard to two (from banded lizards to spotted and long‐tailed lizards), but they might also decrease the beta diversity of the island from three species to two because banded lizards would no longer have any suitable habitat. Similarly, they might think, “Let’s bring some of the speckled lizards from the other island to our forest and have four species here.” However, the speckled lizards might outcompete and replace one of the local lizards or introduce a disease. The whole archipelago could end up with only three, two, or one lizard species instead of four and thus decreased gamma diversity.

      Diversity components usually vary dramatically from one scale to another, but not always. Take the extreme case of the native flowering plants of Antarctica. They include just two species – a grass, Deschampsia antarctica, and a cushion‐forming plant, Colobanthus quintensis – that usually co‐occur at the same sites. This is a very rare case where alpha and gamma diversity are the same. Or think about Madagascar with its high alpha diversity (many species at a given site), diverse ecosystems (high species turnover among ecosystems or beta diversity), and very high levels of endemism. In short, alpha and beta diversity and Madagascar’s unique contribution to gamma diversity make it a global priority for conservation.

Schematic illustration of a clear Lake in northern California used to be inhabited by 14 native species of fish until fisheries managers began introducing new fish species, 26 in all.

      People change, manipulate, and manage the world, and consequently affect biodiversity, often negatively. Conservationists promote positive actions and use a variety of verbs to describe these activities. The verb maintain is dominant in this book because a major goal of conservation biology is to keep all the elements of biodiversity on Earth, despite human‐induced threats. In this section we will evaluate some alternative verbs that are often encountered in the conservation biology literature. This may seem like a pedantic exercise, but some verbs carry implications that are not always consistent with the goal of maintaining biodiversity. For example, to maximize biodiversity implies manipulations such as increasing the alpha diversity of an ecosystem, even importing non‐native species, without considering the consequences for biodiversity at a larger scale. Manipulating the lizard populations in Fig. 2.3 was a good example of this. To increase or to enhance biodiversity may imply the same shortsightedness, unless we are referring to an ecosystem in which biodiversity has been diminished by previous human activity and the goal is to return it to its previous state. If this is the case, it is probably best to refer to restoring biodiversity. Protecting biodiversity is similar to maintaining biodiversity but with a heavier emphasis on the negative impact of most human activities. To preserve biodiversity carries a connotation comparable with “protect,” but it may also imply that the only way to maintain biodiversity is to isolate it from human influence as much as possible; this is not always feasible or desirable (as we shall see, many human activities support biodiversity). To benefit or optimize biodiversity is rather vague; these terms are sometimes used by people who have unusual ideas about what is beneficial or optimal, In reality, biodiversity – an ever‐changing and interacting entity – has no clear “optimal” state. To conserve biodiversity implies using it carefully in a manner that will not diminish it in the long term. This is a reasonable goal, but it tends to overlook the idea that many elements of biodiversity have little or no instrumental value for people. Finally, to manage biodiversity sounds value‐neutral, but in practice