The Ecology Book

149

Ecologists also studied the diversity

of beetles and flies in nine parks of

different sizes in Cincinnati, Ohio.

Area was the best predictor of

species richness, but when the

ecologists coupled their findings

with data on population sizes, they

calculated that an increased size of

parkland acts primarily to reduce

extinction rates rather than to

provide habitats for new species.

Conservation practices

Soon after the island biogeography

theory was developed, ecologists

began to apply it to conservation.

Nature reserves and national parks

were seen as “islands” in landscapes

altered by human activity. When

first creating protected areas,

ecologists debated the optimum

size: was one big reserve better than

several smaller ones? As the island

theory shows, biodiversity depends

on a number of factors, and different

species benefit in different settings.

A sizable mammal will not survive

in a small reserve, but many small

organisms will thrive there. In

places under pressure from human

activity, the island theory has also

encouraged the creation of wildlife

corridors. These link areas of

suitable habitat, which helps

maintain ecological processes—for

example, allowing animal movement

and enabling viable populations to

survive—without requiring a great

expansion of protected areas. ■

ECOSYSTEMS

The rebirth of

Krakatau

In 1883, volcanic eruptions

devastated the Indonesian

island of Krakatau, wiping out

flora and fauna on the island

and nearby Sertung and

Panjang. By 1886, mosses,

algae, flowering plants, and

ferns had returned to Krakatau,

borne either on the wind or as

seeds on the surf. The first

young trees emerged in 1887;

various insect species, and a

single lizard, were discovered

in 1889. Recent research shows

that the level of immigration

to Krakatau and its neighbors

peaked during the period of

forest formation, from 1908 to

1921, but extinctions were at

their height when the dense

tree canopy prevented sunlight

from reaching the forest floor,

between 1921–33. Although

the immigration of land birds

and reptiles has almost

stopped, new species of land

mollusk and many insect

groups are still arriving from

Sumatra and Java, both just

under 28 miles (45 km) away.

Krakatau’s deadly eruption sent

up an ash cloud 50 miles (80 km)

high that altered global weather

patterns and caused a temperature

drop of 2.2°F (1.2°C) for five years.

Central Park in Manhattan, New York

City, is an “island” in an urban setting.

Its checklist includes 134 bird species,

197 insect, 9 mammal, 5 reptile, 59

fungi, and 441 plant species.

I will argue that every

scrap of biological

diversity is priceless ...

Edward O. Wilson

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