The Ecology Book

137

The Eden Project, in Cornwall, UK,

simulates a rain forest ecosystem in

one of its giant dome greenhouses. The

domes’ panels are slanted to absorb

plenty of light and thermal energy.

earthquakes, floods, droughts, and

other natural phenomena, but are

increasingly the result of human

activity—through the destruction

of natural habitats by deforestation,

urbanization, pollution, and the

cumulative effects of anthropogenic

(human-induced) climate change.

Humans can also be responsible

for the introduction of invasive

species. Without these external

factors, an ecosystem would

maintain its state of equilibrium,

and retain a stable identity.

Resistance and resilience

Ecosystems are often strong

enough to withstand some natural

external disturbances and retain

their equilibrium. Some are more

resistant to disturbance than

others, and have adapted to the

particular disturbances normally

associated with their environment.

In some forest ecosystems, for

example, the periodic fires caused

by electrical storms cause only a

minor imbalance in the ecosystem.

Even when severely disrupted

by external disturbances, some

ecosystems have a resilience

that enables them to recover.

However, other ecosystems are

more fragile, and if they are

disturbed may never be able

to regain their equilibrium.

The resistance and resilience

of an ecosystem is generally

thought to be related to its

biodiversity. If, for example,

there is only one species of plant

performing a particular function

in the system, and that species is

not frost-resistant, an abnormally

severe winter could deplete the

species enough to have a major

impact on the system as a whole.

In contrast, if there are several

species with that role in the

system, it is more likely that one

will be resistant to the disturbance.

The human factor

Some disturbances can be severe

enough to be catastrophic for an

ecosystem, damaging it beyond

the point of recovery and so

causing a permanent change

in its identity, or even its demise.

The fear is that much of the

disturbance caused by human

activity has the potential to

cause such permanent damage,

particularly when it involves the

ECOSYSTEMS

wholesale destruction of habitat

and the consequent depletion of its

biodiversity. In addition, some have

suggested that human influence

has created a new category

of ecological systems, dubbed

“techno-ecosystems.” For example,

“cooling ponds” are manmade

ponds, built to cool down nuclear

power plants, but they have become

ecosystems for aquatic organisms.

The relationship between

humans and natural ecosystems

is not all negative. In recent years,

scientific data has fueled public

awareness of the benefits that

ecosystems afford humankind,

including the provision of food,

water, nutrients, and clean air,

as well as the management of

disease and even climate. There

is now a growing commitment from

many governments across the

world to use these benefits both

responsibly and sustainably. ■

There is no waste in

functioning ... ecosystems.

All organisms, dead or alive,

are potential sources of food

for other organisms.

G. Tyler Miller

Science writer

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