Cyanobacteria produce from nitrogen gas as part of the nitrogen cycle. Only about percent of Earth's water is available to be consumed by humans or used for agriculture.
Animals can't consume nitrates directly. They must obtain nitrogen by plants or other herbivore animals.
from forest fires and volcanoes, as well as the decay of dead plants and animals, causes a type of pollution from carbon oxides.
One of the primary reasons that freshwater is unevenly distributed around the world is due to variation in amounts of .