9.10 Human Impacts on Biodiversity

Human activities lower biodiversity through six main pressures summarized by HIPPCO: habitat destruction, invasive species, population growth, pollution, climate change, and overexploitation. Habitat fragmentation breaks large habitats into smaller isolated patches, and the level of harm differs from species to species.

Why This Matters for the AP Environmental Science Exam

Unit 9 carries a large share of the exam, and biodiversity loss connects to almost everything in it: climate change, ocean acidification, invasive species, and endangered species. You should be able to explain how a specific human activity reduces biodiversity and then propose a realistic strategy that fixes the problem, not just name one. Free-response questions in this unit often reward you for explaining how a solution actually works and what its trade-offs or unintended consequences might be.

This topic also pulls in earlier units. Habitat fragmentation links back to island biogeography and population dynamics, while pollution and overexploitation connect to land use, agriculture, and fishing from Unit 5. Being able to move between cause, effect, and solution is exactly the kind of thinking this part of the course tests.

more resources to help you study

practice multiple choiceFRQ practice & scoringcheatsheetsscore calculatorkey terms

Key Takeaways

• HIPPCO stands for Habitat destruction, Invasive species, Population growth, Pollution, Climate change, and Overexploitation, the main drivers of biodiversity loss.
• Habitat fragmentation splits large habitats into smaller, isolated areas, often from roads, pipelines, agriculture, development, and logging.
• The amount of fragmentation that harms a species varies from species to species within the same ecosystem.
• Climate change causes habitat loss through changes in temperature, precipitation, and sea level rise.
• Domesticating organisms for economic return, like honeybee colonies and livestock, can reduce that organism's biodiversity.
• Mitigation strategies include protected areas, habitat corridors, sustainable land use, and habitat restoration.

HIPPCO: The Main Drivers of Biodiversity Loss

Biodiversity is the variety of life on Earth, including different species, ecosystems, and the genetic diversity within a species. The factors that reduce it are easy to remember with the acronym HIPPCO.

Habitat Destruction

Habitat destruction, fragmentation, or degradation makes it hard for species to survive. Common causes include urban development, agriculture, and logging.

Clearing tropical rainforest for crops or plantations is a frequent application of this idea. Rainforests hold a large share of Earth's species, so converting them to farmland or monoculture removes habitat that many species cannot live without. (This is an illustrative example, not required AP content.)

Invasive Species

Invasive species live and sometimes thrive outside their normal habitat and threaten native species. They are often generalist, r-selected species, so they can outcompete natives for resources.

As an example, the Burmese python in the Florida Everglades has no natural predators there and preys on native mammals, disrupting the food web. (Example, not required content.)

Population Growth

A growing human population increases activities that harm wildlife and habitat, such as urbanization and resource extraction. More people generally means more demand for land, water, and materials, which puts pressure on ecosystems.

Pollution

Pollution harms species through toxic chemicals, plastic debris, and other contaminants that damage plant and animal health. Plastic in the ocean, for instance, can be mistaken for food and ingested or cause entanglement in marine animals. (Example, not required content.)

Climate Change

Climate change shifts temperature, precipitation, and other weather patterns, making survival harder for many species and altering migration and reproduction. It can cause habitat loss directly through changes in temperature, precipitation, and sea level rise. Melting Arctic sea ice, which removes habitat for polar bears and walruses, is a common illustration. (Example, not required content.)

Overexploitation

Overexploitation is the overuse of natural resources, including overharvesting wild animals and plants, which drives population declines and can lead to endangerment. The collapse of North Atlantic cod stocks from overfishing is a well-known case. (Example, not required content.)

Habitat Fragmentation

Habitat fragmentation happens when large habitats get broken into smaller, isolated areas. Causes include building roads and pipelines, clearing land for agriculture or development, and logging.

The key detail for the exam: the scale of fragmentation that hurts a species is not the same for every species. A small isolated patch may be fine for one organism but devastating for another that needs a large continuous range. So you cannot assume one threshold applies to a whole ecosystem.

Domestication and Biodiversity

Some organisms have been partly or fully domesticated and are now managed for economic returns. Honeybee colonies and domestic livestock are the standard examples. Managing organisms this way can reduce the biodiversity of that organism, since human selection narrows genetic variety.

Strategies to Reduce Biodiversity Loss

Humans can mitigate biodiversity loss in several ways:

• Protected areas set aside land or water where habitat and species are shielded from development and exploitation.
• Habitat corridors connect isolated habitat patches so species can move, find mates, and access resources, which helps counter fragmentation.
• Sustainable land use practices reduce damage from agriculture, logging, and development while still letting people use the land.
• Habitat restoration rebuilds lost or degraded habitat, such as replanting forests or restoring wetlands.

When you write about solutions, do not just name one. Explain how it works and consider its trade-offs. For example, a corridor only helps if it actually connects suitable habitat for the target species, and a protected area still needs enforcement to stop poaching or illegal logging.

How to Use This on the AP Environmental Science Exam

Free Response

When a question asks you to propose a strategy to protect biodiversity, name the strategy and then explain the mechanism. Saying "create a protected area" is not enough. Say what it protects, how it reduces a specific HIPPCO pressure, and what could go wrong. A strong answer also identifies a disadvantage or unintended consequence.

MCQ

Expect questions that connect a human activity to a HIPPCO category, or that ask which strategy best addresses a described problem. Read carefully for the specific pressure being described, since habitat loss, pollution, and overexploitation can all appear in the same scenario.

Common Trap

Watch for fragmentation questions that assume one patch size affects all species the same way. It does not. Match the strategy to the actual problem in the prompt instead of listing every conservation tool you know.

Common Misconceptions

• HIPPCO factors act alone. In reality they overlap. Climate change, habitat loss, and pollution often hit the same population at once, which makes the total impact worse.
• A small population automatically means an endangered species. Small size alone does not equal endangerment. What matters is whether the species can adapt, move, or recover from pressures.
• Naming a solution is enough on the FRQ. You need to explain how the strategy reduces a specific threat, not just list it.
• Fragmentation harms every species equally. The scale of fragmentation that causes harm varies from species to species within the same ecosystem.
• Domestication boosts biodiversity. Managing organisms like honeybees or livestock for economic return can actually narrow their genetic diversity.
• Climate change only affects biodiversity through heat. It also drives habitat loss through changes in precipitation and sea level rise, not just temperature.

Related AP Environmental Science Guides

• 9.1 Stratospheric Ozone Depletion
• 9.3 The Greenhouse Effect
• Major Environmental Disasters
• 9.8 Invasive Species
• Unit 9 Overview: Global Change
• 9.4 Increases in the Greenhouse Gases