FIGURE 6–18 Hunted and Sold as Pets These caged green parrots were captured in the Amazon rainforest and brought to a market in Peru. Infer What impact do you think hunting has on the animals left behind?

Hunting and the Demand for Wildlife Products Humans can push species to extinction by hunting. In the 1800s, hunting wiped out the Carolina parakeet and the passenger pigeon. Today endangered species in the United States are protected from hunting, but hunting still threatens rare animals in Africa, South America, and Southeast Asia. Some animals, like many birds, are hunted for meat. Others are hunted for their commercially valuable hides or skins or because people believe their body parts have medicinal properties. Still others, like the parrots in Figure 6–18, are hunted to be sold as pets. Hunted species are affected even more than other species by habitat fragmentation because fragmentation increases access for hunters and limits available hiding spaces for prey. The Convention on International Trade in Endangered Species (CITES) bans international trade in products from a list of endangered species. Unfortunately, it's difficult to enforce laws in remote wilderness areas.

Introduced Species Recall that organisms introduced to new habitats can become invasive and threaten biodiversity. For example, more than 130 introduced species live in the Great Lakes, where they have been changing aquatic ecosystems and driving native species close to extinction. One European weed, leafy spurge, infests millions of hectares across the Northern Great Plains. On rangelands, leafy spurge displaces grasses and other food plants, and its milky latex can sicken or kill cattle and horses. Each year, ranchers and farmers suffer losses of more than $120 million because of this single pest.

Pollution Many of the pollutants described in the last lesson also threaten biodiversity. DDT, for example, prevents birds from laying healthy eggs. In the United States, brown pelican, peregrine falcon, and other bird populations plummeted with widespread use of the chemical. Acid rain places stress on land and water organisms. Increased carbon dioxide in the atmosphere is dissolving in oceans, making them more acidic, which threatens biodiversity on coral reefs and in other marine ecosystems.

In Your Notebook Why is acidic water harmful to coral?

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