Page 310 - Environment: The Science Behind the Stories

disturbance, bounce back from stress, or adapt to change. Thus, also vulnerable to the buildup of toxic pollutants in their tis-
when we lose biodiversity, this can diminish a natural system’s sues through the process of biomagnification (p. 392).
ability to function and to provide services to our society. “Ecosystem engineers” (p. 102) such as ants and earth-
Will the loss of a few species really make much differ- worms can be every bit as influential as keystone species, so
ence in an ecosystem’s ability to function? Consider a meta- the loss of an ecosystem engineer from a system can likewise
phor first offered by Paul and Anne Ehrlich (p. 210): The loss set major changes in motion. A decline in wildebeest on the
of one rivet from an airplane’s wing—or two, or three—may Serengeti, for instance, would have substantial consequences
not cause the plane to crash. But at some point as rivets are for grass growth, shrub invasion of grasslands, fire regime,
removed the structure will be compromised, and eventually soil quality, and populations of predators and other herbivores.
the loss of just one more rivet will cause it to fail. Keeping Ecosystems are complex, and it is difficult to predict which
this metaphor in mind, we would be wise to preserve as many particular species may be important. Thus, many people pre-
components of our ecosystems as possible to make sure these fer to apply the precautionary principle (p. 283) in the spirit of
systems continue to function. Aldo Leopold (p. 157), who advised, “To keep every cog and
That said, some species are more vital to an ecosystem wheel is the first precaution of intelligent tinkering.”
than others. Removing a species that can be functionally
replaced by others may make little difference in how the Biodiversity enhances food security
system functions. However, as with the keystone that holds
together an arch, removing a keystone species (pp. 101–102) Biodiversity provides the food we eat. Throughout our his-
can significantly alter an ecological system. If a keystone tory, human beings have used 7000 plant species and sev-
species is lost, other species may disappear in response. eral thousand animal species for food. Today many experts
Top predators are often considered keystone species. are concerned because industrial agriculture has narrowed
Think of lions, leopards, and cheetahs on the Serengeti, or our diet. Globally, we now get 90% of our food from just
wolves, mountain lions, and grizzly bears at Yellowstone 15 crop species and eight livestock species, and this lack
National Park (sometimes nicknamed “America’s Serengeti”). of diversity leaves us vulnerable to failures of particular
A single top predator may prey on many herbivores, each of crops. In a world where nearly 1 billion people go hungry,
which may consume many plants. Thus, the removal of a we can improve food security (the guarantee of an adequate,
single individual at the top of a food chain can have conse- safe, nutritious, and reliable food supply to all people at all
quences that multiply as they cascade down the food chain. times; p. 264) by finding sustainable ways to capitalize on
Moreover, top predators, and large animals in general, are the nutritional opportunities offered by wild species and rare
especially vulnerable to human impact. They are frequently crop varieties.
hunted and they need large areas of habitat, making them sus- Many new or underutilized food sources could be har-
ceptible to habitat loss and fragmentation. Top predators are vested or farmed in sustainable ways. Table 11.3 shows a

TABLE 11.3 Potential New Food Sources
Amaranths Capybara
(three species of Amaranthus) (Hydrochoeris hydrochaeris)

Grain and leafy vegetable; livestock World’s largest rodent; meat
feed; rapid growth, drought esteemed; easily ranched in open
resistant habitats near water

Buriti palm Vicuna
(Mauritia exuosa) (Lama vicugna) CHAPTER 11 • Bi odiv ER si T y A nd Cons ER vAT i on Bi ology
“Tree of life” to Amerindians; Threatened species related to
vitamin-rich fruit; pith as source for llama; source of meat, fur, and
bread; palm heart from shoots hides; can be profitably ranched

Maca Chachalacas
(Lepidium meyenii) (Ortalis, many species)

Cold-resistant root vegetable Tropical birds; adaptable to human
resembling radish, with distinctive habitations; fast-growing
flavor; near extinction

The wild species shown here are just some of the many plants and animals that could supplement our food supply. Adapted from Wilson, E.O., 309
1992. The diversity of life. Cambridge, MA: Belknap Press.

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