Many examples are possible. Changes in the environment may be detrimental (e.g., accumulation of pollutants) or favorable (e.g., reduction in pollutants). Environmental changes may have a negative or positive impact on human population and economic activity. Three specific examples are:
(a) Contamination of rivers and streams by industrial and/or human wastes, leading to illness (via drinking water) and disease.
(b) Increased levels of particulate (or other) air pollution, causing human illness and loss of economic productivity.
(c) Transformation of arid lands into croplands for agriculture (via massive irrigation), with resulting improvement in human diet (health) and economic productivity. (A more complete analysis must also consider sustainability and other impacts related to sources of water for irrigation and the nature of agricultural activities).