TOEFLリスニング

🎧 リスニング原文

Listen to part of a lecture in an environmental science class. Professor: Today we're going to discuss a surprising phenomenon: the impact of beavers on river ecosystems. You might think of beavers as simple dam builders, but their activities actually create complex habitats that benefit a wide range of species. When beavers build dams, they slow down water flow, which allows sediment to settle and forms ponds. These ponds become breeding grounds for fish and amphibians. Moreover, the flooded areas around the ponds lead to the growth of water-tolerant trees, like willows, which provide food for beavers themselves and shelter for birds. Interestingly, recent studies show that beaver dams can also improve water quality downstream. The ponds filter out pollutants from agricultural runoff, acting like natural purifiers. However, some farmers view beavers as pests because they flood crop fields. This has led to conflicts and a decline in beaver populations in certain regions. Yet, conservationists argue that reintroducing beavers could reduce the need for expensive man-made water treatment plants. So, while beavers can be inconvenient, their ecological benefits are substantial.