Human Impacts: Overexploitation — Reading Comprehension

Overexploitation is a major threat to global biodiversity, affecting ecosystems and the species within them. Overexploitation happens when humans remove wild plants or animals from their environments faster than those populations can naturally recover. This causes population declines, disrupts food webs, and can even lead to extinction. Scientists have documented many cases where unsustainable harvesting has changed entire ecosystems and reduced species diversity.

Mechanisms and Examples of Overexploitation

One of the clearest examples of overexploitation is overfishing. When fish are caught faster than they can reproduce, their populations shrink dramatically. For instance, in the northwest Atlantic Ocean, commercial fishing led to a 99% drop in Atlantic cod populations by the early 1990s, causing the fishery to collapse. This not only affected the cod but also disrupted the entire marine ecosystem, as cod are top predators. Overhunting has also caused major losses. The passenger pigeon, once the most numerous bird in North America, was driven to extinction by hunting and habitat loss by 1914. Similarly, the dodo, a bird native to Mauritius, was wiped out in less than a century after humans arrived.

Illegal Wildlife Trade and Bycatch

Illegal wildlife trade is another form of overexploitation. Poaching for ivory and rhino horn has pushed species like African elephants and rhinos toward extinction. The illegal trade in exotic pets and animal parts threatens hundreds of species worldwide. Additionally, bycatch—when non-target species like turtles, dolphins, or seabirds are caught unintentionally—causes millions of animal deaths each year. In some regions, bushmeat hunting for wild animal meat has severely reduced populations of primates and other mammals, disturbing ecological balance and endangering species.

Sustainable Harvesting and Solutions

Scientists and resource managers use the principle of sustainable harvesting to combat overexploitation. This means taking fewer individuals than the population can naturally replace each year. Fisheries managers may set catch limits, protect breeding areas, and monitor fish populations using data such as catch rates and population models. In some areas, community-based management and international agreements help enforce laws and reduce illegal trade. These efforts aim to balance human needs with the health of wild populations and ecosystems. Success depends on scientific research, government regulation, and cooperation among countries and communities.

Overexploitation shows how human activities can disrupt natural systems and reduce biodiversity. By understanding the causes and effects of overexploitation, people can make choices that support conservation, sustainable use, and the long-term health of our planet.

Interesting Fact: 
The last wild passenger pigeon was seen in 1901, and the very last individual, named Martha, died in captivity in 1914.

What is overexploitation?

Which animal experienced a 99% population drop due to overfishing?

What does the term 'bycatch' mean in the passage?

What is an example of an animal that went extinct because of overhunting?

What is the main purpose of sustainable harvesting?

What is one effect of illegal wildlife trade?

Why is overfishing harmful to ecosystems?

If a country wants to reduce overexploitation, which action would help most?

True or False: Bycatch only affects fish populations.

True or False: The last wild passenger pigeon was seen in 1901.