Biology Now, 2e

Amazon on Fire ■ 325

Balch and other scientists have been inves-

tigating whether it might be possible to inter-

vene in that cycle to slow or stop the loss of the

Amazon rainforest. Their latest experiment,

burning plots of Amazon rainforest to see what

happens afterward, is an experiment in ecology.

Ecology is the scientific study of interactions

between organisms and their environment,

where the environment of an organism includes

both biotic factors (other living organisms)

and abiotic (nonliving) factors (Figure 18.3).

Ecology helps us understand the natural world

we live in, but humans continue to change our

biosphere in ways that are difficult, perhaps even

impossible, to fix.

Hot and Dry

Balch began setting fires in the Amazon in

2004 as a graduate student at the Yale School of

Forestry and Environmental Studies. She is an

ecologist, a scientist fascinated by how organ-

isms and environments interact with and affect

each other.

Balch has always been interested in the link

between humans and fire. “Fire is integral to the

human experience. We play with fire as kids,

and we use fire in our cars, through combus-

tion, on a daily basis,” says Balch. “But humans

have an imperfect relationship with fire. We are

vulnerable to fire; we don’t completely control

this tool.”

Balch decided to try to control it just enough

to learn about fire’s impact on the Amazon.

By performing a planned burn in a restricted

area, her team could collect data that cannot be

obtained by studying an accidental or escaped

fire: inventories of the plants in the area before

and after a fire, a census of the animals in the

area, and other measurements (Figure 18.4).

With a crew of other researchers, Balch orches-

trated an experiment using three 0.5-square-

kilometer plots of forest. One control plot would

never be burned, one experimental plot would be

burned once every 3 years, and a second exper-

imental plot would be burned once every year.

Figure 18.2

The biosphere is Earth and all of its

inhabitants

This is a view of Earth from space. The

atmosphere, Earth’s surface, and all of the

organisms make up the biosphere.

Figure 18.3

Amazon rainforest ecology

Ecology is the study of how living organisms (biotic factors) interact with

other organisms, and how they all interact with their nonliving (abiotic)

environment.

Abiotic factors:

rocks, water, air

Biotic factors:

plants, animals, microbes

Q1: List as many biotic and abiotic factors in this photograph as

you can.

Q2: Is the forest part of the biotic or abiotic environment? Explain.

Q3: Is the river part of the biotic or abiotic environment? Explain.