TOEFL統合ライティング

📖 読解文章

The concept of rewilding—restoring ecosystems to their pre-human state by reintroducing apex predators and keystone species—has gained traction as a conservation strategy. Proponents argue that rewilding can restore ecological balance, enhance biodiversity, and mitigate climate change. First, reintroducing apex predators like wolves controls herbivore populations, preventing overgrazing and allowing vegetation to recover, which in turn supports a wider range of species. Second, rewilding promotes biodiversity by creating habitat heterogeneity; for example, beavers build dams that create wetlands, which attract amphibians, birds, and insects. Third, rewilding can sequester carbon: restored forests and grasslands absorb CO2, and the presence of large herbivores and predators increases soil carbon storage through nutrient cycling. Critics, however, question the feasibility, but advocates insist that with careful planning, rewilding is both ecologically and economically beneficial.

🎧 リスニング講義

The lecture challenges the reading's claims about rewilding. First, while the reading says apex predators control herbivore populations, in practice, reintroducing predators often fails to achieve this due to human intervention—for instance, livestock depredation leads to predator culling, and herbivore populations may still exceed carrying capacity if their habitat is fragmented. Second, the reading's biodiversity argument is oversimplified; beaver dams can flood agricultural land and alter water chemistry, harming native fish species that require cold, fast-flowing streams. Moreover, the introduced keystone species are often from different genetic lineages or ecological contexts, leading to unintended consequences like disease transmission or competition with existing species. Third, the carbon sequestration claim is dubious: rewilding may reduce carbon storage in some ecosystems—for example, grazing by reintroduced herbivores can compact soil and reduce its carbon content, and the initial disturbance from reintroduction can release stored carbon. Furthermore, the time scale for meaningful carbon sequestration is decades to centuries, far too slow to address urgent climate targets. Therefore, rewilding is not a panacea and may even exacerbate some ecological problems.