The Ecology Book

54

E

xperimentation is crucial

in ecology. Without it, our

ideas about why organisms

behave the way they do would be

largely speculative. Rigorous

observation is also essential, but,

much of the time, experimentation

is needed for a full understanding

of those observations.

Three main types of ecological

experiments are used to test

theories: mathematical models,

laboratory experiments, and field

experiments. Each method has its

merits, but it is only recently that

the benefits of field experiments

have been recognized. Before

the 1960s, experiments outside

a laboratory were a rarity.

A laboratory, however, is an

artificial environment, where

organisms may not behave as they

do in their natural habitat. For

example, bats leaving a roost at

dusk may follow different routes

to their foraging areas in spring

and late summer. The potential

reasons for the switch—changes

in prey distribution and predator

threats; seasonal differences in

tree cover; or human disturbance

and light pollution—cannot

be established in a laboratory.

Mathematical modeling might help

predict patterns, but would be less

effective at identifying the causes

of change. To understand the bats’

behavior, a study of their natural

environment is crucial, and

this is achieved only through

research in the field.

Field experiments allow different

factors to be manipulated to test

their relevance. In the bat example,

IN CONTEXT

KEY FIGURE

Joseph Connell (1923–)

BEFORE

1856 British scientists John

Lawes and Joseph Gilbert start

the Park Grass Experiment at

Rothamsted, to test how

different fertilizers affect the

yield of hay meadows.

1938 Harry Hatton, a French

ecologist, conducts one of

the first marine ecology field

experiments, on barnacles

on the Brittany coast.

AFTER

1966 American ecologist

Robert Paine removes the

starfish Pisaster ochraceus from

tide pools in a Pacific coast

ecosystem, to test the effect

of its absence on other species.

1968 The Experimental Lakes

Area, comprising 58 freshwater

lakes, is established in Ontario,

Canada, to study the effects

of nutrient enrichment

(eutrophication).

POOR FIELD

EXPERIMENTS

CAN BE WORSE

THAN USELESS

FIELD EXPERIMENTS

Rain forest ecosystems are some of

the most species-rich environments

on Earth. This makes them especially

valuable sites for ecologists to conduct

experiments in the field.

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