Page 318 - Environment: The Science Behind the Stories

Stream National Park. Altogether roughly 25% of Tanzania’s The ecosystems of the world’s biodiversity hotspots
land area and 12% of Kenya’s land area is protected. together once covered 15.7% of the planet’s land surface.
Alas, protecting land may not be enough to assure effec- Today, because of habitat loss, they cover only 2.3%. This
tive conservation. Pressures from outside the reserves in small amount of land is the exclusive home for half the world’s
Kenya and Tanzania are causing declines in wildlife within plant species and 42% of terrestrial vertebrate species. The
the reserves (see The Science behind the Story, pp. 304– hotspot concept motivates us to focus on these areas, where
305). Similar situations occur in North America: Despite the greatest number of unique species can be protected per
the considerable size of Yellowstone National Park, animals unit effort.
such as elk, bears, bison, and wolves roam seasonally in and
out of the park. As a result, conservationists have tried to
find ways to protect animals and habitats across the Greater We can restore degraded ecosystems
Yellowstone Ecosystem, the larger region over which the
animals roam. Protecting natural areas before they become degraded is the
Moreover, as global climate change (Chapter 18) pro- best way to safeguard biodiversity and ecological systems.
ceeds, changing conditions are driving many species toward However, in some cases we can restore degraded natural sys-
the poles and upward in elevation, often forcing them out tems to some semblance of their former condition, through
of protected areas. Thus, a major challenge today is to link the practice of ecological restoration (pp. 110–111). Ecolog-
protected areas across the landscape so that species like wil- ical restoration aims not simply to bring back populations
debeest can move in response to climate change as it alters of animals and plants, but to reestablish the processes—the
habitats within protected areas. We will explore parks and pro- cycling of matter and the flow of energy—that make an eco-
tected areas and the issues they face more fully in Chapter 12 system function. By restoring complex natural systems such
(pp. 341–350). as the Illinois prairies (p. 110), the Florida Everglades (pp.
110–111), or the southeastern longleaf pine forest (p. 337),
restoration ecologists aim to recreate functioning systems
Biodiversity hotspots pinpoint regions that filter pollutants, cleanse water and air, build soil, and
of high diversity recharge groundwater, providing habitat for native wildlife
and services for people.
To prioritize regions for conservation, scientists have mapped In Kenya, efforts are being made to restore the Mau
biodiversity hotspots (Figure 11.22a). A biodiversity hotspot is a Forests Complex, Kenya’s largest remaining forested area and
region that supports an especially great number of species that a watershed that provides water for the Maasai Mara Reserve
are endemic (p. 77), found nowhere else in the world (Figure and for the people of the region. Over the years so much for-
11.22b). To qualify as a hotspot, a region must harbor at least est in this densely populated region has been destroyed by
1500 endemic plant species (0.5% of the world’s total plant agriculture, settlement, and timber extraction that the water
species). In addition, a hotspot must have already lost 70% of supply for the Serengeti’s wildlife and for millions of Kenyan
its habitat to human impact and be at risk of losing more. people is now threatened. Kenya’s government is working

(a) The world’s biodiversity hotspots (b) Ring-tailed lemur CHAPTER 11 • Bi odiv ER si T y A nd Cons ER vAT i on Bi ology

Figure 11.22 Biodiversity hotspots are priority areas for habitat preservation because they contain
many endemic species. In red (a) are the 34 hotspots mapped by the nongovernmental organization Conser-
vation International. (Only 15% of the areas in red are actually habitat; most area is developed.) These regions are
home to species such as the ring-tailed lemur (b), a primate endemic to Madagascar that has lost over 90% of
its forest habitat as a result of human population growth and resource extraction. Data from Conservation International. 317

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