The hostilities between two racial subgroups of a riverfront community were dramatically reduced when the threat of the river flooding its banks required that they work together to save their town. this best illustrates the impact

Superordinate goals.

Explanation:

A superordinate goal is a goal so big that is enough to overlook personal or group differences in order to achieve it. It is, also, a goal rather big for anyone of this individuals to reach it alone, therefore, having the need to overlook said differences.

this statement is true.

forests are public goods, available for everybody. when usage of such a good becomes interesting for consumers and its usage increases, there can be a risk of overexploitation. it is a non rival good therefore, if one person consumes the good it does not reduce the availability for subsequent consumers.

these caracteristics require the establishment of measures in order to prevent the destruction of a commonly owned space, for example, to restrict the amount of people that have access to the same time.