Biology Reference
In-Depth Information
find nesting sites when sea levels rise, and how will moisture-dependent frogs lay eggs when
rain forests face prolonged droughts, in some cases by the middle of this century? When the
microclimate at the summit of Mount Udzungwa in southern Tanzania changes in a profound
way, will the African violet—ancestor of the familiar houseplant—and the Udzungwa part-
ridge disappear, or will they be able to adapt to the new conditions?
During the 1980s, leading biologists began to suggest that we were in the midst of the sixth
great extinction event in the history of Earth. And in 1995, Stuart Pimm, one of the fathers
of modern conservation biology, calculated that the current rate of species extinctions was as
much as 1,000 times the normal background extinction rate. If so, newly rare species may
face different, and more serious, problems from those encountered by species that have his-
torically been rare—another major reason for exploring rarity in the natural world.
Beyond the extinction crisis, some scientists refer to our current epoch, the Holocene, as
the Anthropocene or the Homogenocene, terms that describe two aspects of a new ecological
state that is still poorly understood. The first refers to our period, wherein the human footprint
extends everywhere in nature. The second refers to another kind of affront in which certain
species have spread or been introduced by humans far beyond these species' original range
and, as a result, natural habitats around the world, full of invasive species, begin to resemble
one another. Being rare in this brave new homogenized world, as we'll see in the case of
Hawaii, could mean something much different from when these same species first appeared
in relative isolation. Rarity is not just a condition of nature; it is a condition that can be—and
has been—imposed on species by human activity, all too often sending them on the road to-
ward endangerment and extinction. In short, viewing the natural world through the lens of
rarity can bring certain facts and species traits to our attention that we might otherwise over-
look. Understanding these facts and traits may in turn provide insights that can help us save
species from the current state of environmental deterioration.
Many conservation biologists target “saving rare species” as the ultimate aim of their work.
Yet rarity, as a phenomenon in nature, can take many forms, not only among species, al-
though that is central, but also in the building blocks of the natural world: genes, populations
of species, habitats, assemblages, and ecological and evolutionary phenomena. Species, with
few exceptions, are made up of populations distributed across the landscape. Saving only one
population of each rare species simply as a token gesture would be of little ecological value,
especially where those species play a role in maintaining a given ecosystem's integrity. So
an essential goal is to conserve multiple populations of species and the genetic, ecological,
and behavioral features that these building blocks contain. Conserving dispersed populations
and their genetic variability gives species a better chance of adapting to and persisting amid
changing conditions, such as a rapidly changing climate or invasion of their homeland by in-
troduced species.
