Natural ecosystems provide an array of basic processes that affect humans. Those processes include maintenance of the quality of the atmosphere, generation of soils, control of the hydrological cycle, disposal of wastes, and recycling of nutrients. Humans are changing many of these basic processes, and the changes may be detrimental to humans. Dams reduce flooding but may force people, animals and farm land to be relocated or lost. Weather modification is an attempt at man to adapt the water cycle, however, creating precipitation in one area may reduce precipitation in other areas.
Many factors influence environmental quality.
Factors that students might investigate include population growth, resource use, population distribution, over consumption, the capacity of technology to solve problems, poverty, the role of economic, political, and religious views, and different ways humans view the earth. Changing population demographics have changed the demands of water across the world. Changing cultural, farming and industrial practices have changed our sources of clean and accessible water supplies. There are competing interests for water between cities, agriculture and the environment. Some hazards, such as earthquakes, volcanic eruptions, and severe weather, are rapid and spectacular.