Which of the following is a negative externality when the government provides a public good such as building a dam?
a. decreased leisure activities
c. a potential decrease in the species of fish
b. an increase in hydroelectric power
d. the potential for increased flooding

c. a potential decrease in the species of fish

Explanation:

Dams block the migration of fish, deplete oxygen from rivers, and interfere with the biological triggers that guide fish. They also reduce self-cleaning ability of rivers. Due to the construction of dams and other factors, the population of freshwater fish species declined 37% between 1970-2008 - more than the populations of all other ecosystems. Populations of tropical freshwater fish species declined by as much as 70%.