TOEFL 2026 Listening

Talk 1: Tragedy of the Commons

Imagine a shared pasture where any farmer in the village can graze their livestock. Each farmer benefits personally from adding more animals to the pasture, but the cost — overgrazing and eventual destruction of the land — is shared by everyone. If every farmer acts in their own self-interest, the pasture is eventually destroyed, harming the entire community. This scenario is known as the Tragedy of the Commons, a concept introduced by ecologist Garrett Hardin in a 1968 paper.

Hardin argued that shared resources — what economists call common-pool resources — are inherently vulnerable to overuse when individuals prioritize personal gain. The logic is straightforward: the individual receives the full benefit of exploiting a shared resource, while the cost of that exploitation is distributed across all users. This creates a powerful incentive to overuse.

The concept has been applied to many real-world situations. Overfishing is a frequently cited example. When ocean fish stocks are treated as a shared resource with no restrictions, individual fishing operations have an incentive to catch as much as possible before others do. The result is the depletion of fish populations that everyone depends on.

However, Hardin's conclusions have been challenged. Economist Elinor Ostrom, who won the Nobel Prize in 2009, showed through extensive research that communities are often capable of managing shared resources sustainably through cooperation, agreed-upon rules, and social trust — without requiring either privatization or government regulation. Her work demonstrated that the tragedy is not inevitable.


Talk 2: Ocean Acidification

The world's oceans absorb a significant portion of the carbon dioxide released into the atmosphere by human activities. While this has helped slow the rate of climate change, it has created a serious problem of its own. When carbon dioxide dissolves in seawater, it reacts chemically to form carbonic acid. This process lowers the pH of the ocean — making it more acidic — in what scientists call ocean acidification.

Since the Industrial Revolution, the average pH of the ocean's surface has dropped measurably. While this may seem like a small change, pH is measured on a logarithmic scale, meaning even a small numerical shift represents a significant increase in acidity.

The consequences for marine life are serious. Many ocean organisms — including corals, oysters, clams, and some plankton — build their shells and skeletons from calcium carbonate. In more acidic water, calcium carbonate dissolves more easily, making it harder for these organisms to build and maintain their structures. Coral reefs are particularly vulnerable. Already stressed by rising ocean temperatures, they now face the additional threat of acidification, which weakens their skeletons and impairs their ability to recover from bleaching events.

The effects extend up the food chain. Plankton forms the base of most marine food webs. If acidification disrupts plankton populations, the impact ripples through the entire ecosystem, ultimately affecting fish stocks that billions of people depend on for food.

Reducing carbon dioxide emissions remains the most direct way to slow ocean acidification, though some researchers are also exploring localized interventions to protect particularly vulnerable ecosystems.