The water cycle, nitrogen cycle, and carbon cycle are three important ones. The success of plant and animal life depends on them. The atmosphere is in delicate balance. Too much C02 could increase atmospheric temperatures while a decrease in ozone levels may raise exposure to harmful UV rays. Change in weather patterns could change a normally high precipitation area into a low precipitation area.
Industrial pollutants can cause acid rain.
Plants and animals may be affected in unpredictable ways by these climactic changes. Measuring ecosystems is an important part of ecology. Water tests can indicate nutrient and gas levels and may be performed in several ways. If you have a commercial water test kit, use it, following its' directions. If not, see the skill building activities for water and air tests.