What percentage of u. s lakes is estimated to be affected by eutrophication due to human activity?

First you should know that eutrophication is the development by which a body water becomes enriched in liquified nutrients that stimulate the growth of aquatic plant life that usually can take oxygen from the water killing fishes and other animals. The percentage of US lakes affected by this process due to human activity is 65%.

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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.