The Ecology Book

258

farmers, and a third by commercial

interests. Urban development,

logging for the best-quality lumber,

mining and quarrying, and trees

cut for firewood account for any

remaining deforestation. In every

case, the environment suffers.

Biodiversity is particularly impacted,

because only a small number of

mammal, bird, and invertebrate

species can live on grassland or a

palm oil plantation, and even fewer

in industrial or urban settings.

Human conflicts also blight forest,

the worst example being the Agent

Orange chemical used to defoliate

trees during the Vietnam War.

The rain forest

Destruction of the rain forest

poses a severe threat to global

biodiversity because it has been

estimated that between half and

two-thirds of the world’s plants and

animals live in this environment.

Between 1.5 million and 1.8 million

species—mostly insects, followed

by plants and vertebrates—have

already been identified in rain

forests, and many others have yet

to be discovered and described. In

Borneo, Indonesia, for example, an

area of just 0.2 sq mile (0.5 sq km)

may contain more species of tree

than the combined landmass of

Europe and North America. Such

biodiversity is vitally important to

DEFORESTATION

Replacing trees with human

settlements destabilizes the soil on

slopes, and mudslides, such as this

catastrophic event in Sierra Leone

in 2017, are more likely to occur.

humans—not least because most

new medicines are derived from

plants, and so the eradication of

the rain forest’s rich store destroys

potential cures for disease.

Rain forests, together with all

other trees and woodland, also

act like a sponge for rainfall.

Tree roots drink up moisture and

limit surface runoff. When forest

is cut or burned, the soil is leached

of many of its nutrients. If it covers

a slope, the soil will wash away,

leaving the land unfit for growing

any kind of plants. Deep gullies

may undermine trees that have

not been cut, bringing them down.

After heavy rains, catastrophic

mudslides, which happen with

increasing frequency, sweep down

the slope, destroying everything

in their path—including human

settlements. In May 2014, for

example, heavy rainfall on the

deforested slopes of the Caribbean

island of Hispaniola caused

mudslides and floods that killed

more than 2,000 people. Conversely,

in extended periods of dry weather,

I became an ecologist

long before I had ever

heard the word.

Chico Mendes

US_254-259_Deforestation.indd 258 12/11/18 6:25 PM