Comprensión auditiva TOEFL

🎧 Transcripción de audio

Narrator: Listen to part of a lecture in an environmental science class. Professor: Today we're going to talk about a fascinating example of ecosystem engineering—beavers. Beavers are often called 'ecosystem engineers' because they physically alter their environment in ways that affect other species. When beavers build dams across streams, they create ponds that slow water flow and increase water retention. This change in hydrology can lead to the creation of wetlands, which support a diverse array of plant and animal life. However, the benefits are not without costs. The flooding caused by beaver dams can damage human infrastructure, such as roads and agricultural fields. Interestingly, some researchers have proposed using beaver reintroduction as a low-cost method for stream restoration, especially in areas where beavers were historically hunted to near extinction. These researchers argue that beaver dams can naturally filter pollutants and reduce erosion, saving money compared to artificial structures. Yet, critics point out that beaver populations may not thrive in all environments, and their dams can conflict with human land use. So, while beavers offer promising ecological benefits, careful management is necessary to balance their impact.