The Ecology Book

93

See also: Biodiversity hotspots 96–97 ■ Animal ecology 106–113 ■ Island biogeography 144–149 ■ Biodiversity and

ecosystem f unction 156 –157 ■ Biomes 206–209 ■ Mass extinctions 218–223 ■ Deforestation 254–259 ■ Overfishing 266–269

before 1800, when humans began

to dominate the planet. The first

use of the term “biodiversity,” in

1988, was by American biologist

Edward O. Wilson, who became

known as the “father of biodiversity.”

He later highlighted five key threats

to biodiversity using the acronym

HIPPO: habitat destruction;

invasive species; pollution; human

population; and overharvesting by

hunting and fishing.

Habitat wreckers

The Red List of the International

Union for Conservation of Nature

(IUCN) includes more than 25,000

threatened species. Of these,

85 percent are endangered by the

loss of habitats that once supported

particular species. This destruction

can occur as a result of natural

causes, such as fire or flood, or,

more commonly, through the

expansion of agricultural land,

timber harvesting, and overgrazing

by livestock. Deforestation, in

particular, has contributed hugely

to habitat loss, with around half of

the world’s original forests now

cleared, mainly for agricultural use.

Some habitats are not destroyed

but rather broken up or divided into

more isolated units by human

interventions, such as building

dams or other water diversions.

This habitat fragmentation is

particularly dangerous for migratory

ORDERING THE NATURAL WORLD

The five human activities

that most seriously affect

biodiversity on Earth can be

represented by HIPPO, the

acronym devised by Edward

Wilson, with the relative

severity of each reflected

in the order of the letters.

1. Habitat destruction
   2. Invasive
   species


2. Pollution


3. Overharvesting
   by hunting
   or fishing

The effects of human activity on biodiversity

4. Human population

It is that range of biodiversity

that we must care for—the

whole thing—rather than

just one or two stars.

David Attenborough

British broadcaster and naturalist

animals because they may no

longer be able to find places to feed

or rest along their normal routes.

Native species and ecosystems are

also disrupted by the introduction,

accidentally or deliberately, of new

species. These invasive species.

can threaten the food supply or

other resources of native species,

carry disease, and become a

predatory threat. The brown tree

snake, for example, was brought

accidentally to the island of Guam

on a cargo ship, and has caused

the extirpation (the extinction of a

species in a particular area) of 10 of

the island’s 11 native bird species.

Air and water poisoning

Any kind of pollution threatens

biodiversity, but air and water

pollution are particularly harmful.

Burning fossil fuels, for example,

releases the waste gases sulfur

dioxide and nitrogen oxide into

the air; these return as acid rain,

causing water and soil acidification

and affecting ecosystem health and

biodiversity. Ozone emissions at

ground level can also damage cell

membranes on plants, curbing their

growth and development. ❯❯

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