TOEFL統合ライティング

📖 読解文章

The construction of large dams has long been considered a cornerstone of modern water management, providing reliable water supply, flood control, and clean energy. However, recent assessments suggest that the era of mega-dams may be ending, as their costs increasingly outweigh their benefits. Three primary arguments support this view. First, dams cause significant ecological disruption. By altering natural river flows, they destroy habitats for fish and other aquatic species, leading to declines in biodiversity. The construction of reservoirs also floods vast terrestrial areas, further reducing wildlife populations. Second, dams are economically inefficient over the long term. While initial construction costs are high, ongoing maintenance, sediment removal, and eventual decommissioning add enormous financial burdens. Moreover, reservoirs often experience reduced storage capacity due to siltation, shortening their useful life and diminishing returns on investment. Third, dams pose serious social risks. Displacement of local communities is a common consequence, as people are forced to relocate, leading to cultural disruption and economic hardship. Additionally, the risk of dam failure, while rare, can result in catastrophic loss of life and property downstream. These combined factors suggest that investments in alternative water management strategies, such as water conservation and distributed storage, would be more sustainable and prudent.

🎧 リスニング講義

The reading presents a pessimistic view of dams, but I would argue that such conclusions are premature and overlook critical counterpoints. First, while dams do alter ecosystems, modern engineering has developed effective mitigation measures. For instance, fish ladders and fish-friendly turbines significantly reduce harm to aquatic life. Furthermore, reservoirs can create new wetland habitats that support diverse bird species, sometimes increasing local biodiversity. Second, the economic argument against dams ignores their long-term benefits. Although maintenance costs exist, dams provide inexpensive hydropower for decades, often paying back initial investments many times over. Advances in sediment management, such as controlled flushing and dredging, can extend reservoir life considerably. Additionally, many dams serve multiple purposes—irrigation, navigation, and recreation—which diversify economic returns beyond just power generation. Third, social impacts are not inherently negative. Properly planned dam projects include fair compensation and resettlement programs, which can improve living standards for displaced communities by providing better housing and infrastructure. Moreover, modern dam safety standards and monitoring technologies have drastically reduced failure risks. In fact, the flood control provided by dams prevents more casualties than any rare dam failure could cause. Therefore, the drawbacks highlighted in the reading are often overstated and manageable with responsible planning.