Questions: Human Impact on Ecosystems

Question 1

Which of the following is the primary cause of habitat loss worldwide?

• A. Volcanic eruptions
• B. Earthquakes
• C. Human activities like agriculture and urban development
• D. Natural wildfires

Answer: (C)

While natural events like volcanic eruptions and wildfires can damage habitats, human activities — especially converting forests and grasslands into farmland and cities — are by far the leading cause of habitat loss globally. About half of the world's habitable land has been converted for agriculture.

Question 2

Once a species goes extinct, it can eventually return through evolution.

• T. True
• F. False

Answer: False

Extinction is permanent. While evolution can produce new species over millions of years, it will never recreate the exact same species that was lost. The passenger pigeon, the dodo, and the woolly mammoth are gone forever. This is why preventing extinction through conservation is so important — there is no undo button.

Question 3

Describe one example of how humans have positively impacted an ecosystem, and explain what made it successful.

Model answer: The bald eagle was nearly driven to extinction in the U.S. due to the pesticide DDT, which thinned their eggshells and prevented chicks from surviving. After DDT was banned in 1972 and conservation programs protected nesting sites, the bald eagle population recovered dramatically and was removed from the endangered species list in 2007. The combination of removing the threat (DDT) and actively protecting the species made recovery possible.

This example shows that human impact is not one-directional — we can also repair damage. Success required both stopping the harmful activity (banning DDT) and taking active conservation steps (habitat protection, breeding programs). Most ecosystem recovery stories follow this pattern.