Learning about human impacts on natural resources and

biodiversity will draw on your understanding of ecosystems

and biogeochemical cycles (24.1, 24.4).

This chapter’s discussions of climate change and thinning

of the ozone layer will expand on your knowledge of the

carbon cycle (24.5).

Key ConCepts

LinKs to earLier ConCepts

Human Population Growth

Humans have sidestepped some

natural limits on population growth.

Soaring human population size has

led to many impacts on the natural

world. Sections 25.1–25.3

Global Climate Change

Warming of Earth’s lower atmo‑

sphere due to increases in green‑

house gases is changing climate

patterns. Sections 25.4–25.5

Impacts on Resources

and Biodiversity

Human activities and increasing

demand for natural resources are

creating pollution and straining

ecosystems in other ways. Sections

25.6–25.10

Top: © Darko Sikman/Shutterstock.com; Middle: © Cengage Learning;

Bottom: U.S. Navy photo by Chief Yeoman Alphanso Braggs

Seven billion humans make a lot of

trash. Stuff we toss out ends up everywhere—in huge landfills,

piled along roadsides, and washed up on beaches. But a planet

littered with garbage is just one of many impacts our species is

having on the biosphere. This chapter will help give you the tools

to think critically about human impacts on Earth’s environments.

Decisions we make today about climate change and other

environmental issues are likely to shape Earth’s ecosystems and

the quality of human life far into the future.

471

Human impaCts on

tHe BiospHere

25

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