Visualizing Environmental Science

380 CHAPTER 15 Biodiversity and Conservation

© John Mitchell/Alamy © David Evan

s/National Geographic

Society/Corbi

s

George Grall/NG Image Collection

The SMBC certifies

shade-grown and

organic coffee.

The scarlet tanager spends its summers

in eastern North America and its winters

in Central and South America.

Available bird habitat is much greater in shade coffee

plantations (left) than in sun plantations (right).

Myers and ecologists at Conservation International iden-

tified 25 biological hotspots around the world (see What

a Scientist Sees). Interestingly, these 25 hotspots for plants

contain 29 percent of the world’s endemic bird species,

27 percent of endemic mammal species, 38 percent

of endemic reptile species, and 53 percent of endemic

amphibian species. Many humans—nearly 20

percent of the world’s population—live in the

hotspots. Of the 25 hotspots, 15 are tropical,

and 9 are mostly or solely islands. Many biolo-

gists recommend that conservation planners

focus on preserving land in these hotspots to

reduce the mass extinction of species that is

currently under way.

Perhaps the most unsettling outcome of tropical
deforestation is its disruptive effect on evolution. In
Earth’s past, mass extinctions were followed over mil-
lions of years by the evolution of new species as replace-
ments for those that died out. In the past, tropical rain
forests may have supplied ancestral organisms from
which other organisms evolved. Destroying
tropical rain forests may reduce nature’s abil-
ity to replace its species.

Earth’s Biodiversity Hotspots

In the 1980s ecologist Norman Myers of Oxford
University coined the term biodiversity hot-
spots. In 2000, using plants as their criteria,

biodiversity

hotspots Relatively

small areas of land

that contain an

exceptional number

of endemic species

and are at high risk

from human activities.

EnviroDiscovery

Is Your Coffee Bird Friendly

®

?

Many species of migratory songbirds, favorites
among North American bird lovers, are in decline,
and Americans’ coffee habits may play a role. In the
tropics, high-yield farms cultivating coffee in full
sunlight—known as sun plantations—are rapidly
replacing traditional shade plantations. This switch
is affecting wintering birds common to southern
Mexico, the Caribbean, Costa Rica, and Colombia.
Shade plantations grow coffee plants in the shade
of tropical rainforest trees. These trees support a vast diversity of
songbird species that winter in the tropics (one study counted 150
species in 5 hectares [12.4 acres]), as well as large numbers of other
vertebrates and insects. In contrast, sun plantations provide poor
bird habitat. Sun-grown varieties of coffee, treated with large inputs
of chemical pesticides and fertilizers, outproduce the shade-grown
varieties but lack the diverse products that come from the shade
trees. A substantial portion of the region’s shade plantations have
been converted to sun plantations since the 1970s: 17 percent in
Mexico, 40 percent in Costa Rica, and 69 percent in Colombia.
Songbird populations have declined alarmingly during this
period. Researchers counted 94 to 97 percent fewer bird species on
sun plantations in Colombia and Mexico than on shade-grown coffee
plantations. Various conservation organizations and development
agencies, such as the Smithsonian Migratory Bird Center (SMBC)
and the U.S. Agency for International Development have initiated
programs to certify coffee as “shade grown,” which allows consumers
the chance to support the preservation of tropical rain forests. Shade-
grown coffee typically costs more than sun-grown coffee because it
is hand picked, involves more care in selecting only ripe beans, and is
often certified organic.