Nutrient Flow Carbon cycles from organism to organism Carbon dioxide gas is produced by animals and used by plants. Other bacteria convert the ammonia to nitrates, which can be used to make proteins. Animals break down proteins into nitrogen wastes, like urea, which is excreted in urine, giving it a yellow color, and ammonia. Humans artifically fix nitrogen to make fertilizer. The amount of this industrial nitrogen fixation has risen to alarming levels and now is about equal to the amount of nitrogen fixed by natural processes.
Deforestation can cause high runoff of water, and loss of nitrates from the soil.
Global ecological problems which we face in the immediate future Acid Rain Nitrogen compounds such as nitric and nitrous oxide and sulfur compounds such as sulfur dioxide, are converted respectively to nitric acid and sulfuric acid and cause extensive damage to crops and forests. Global Warming Excess carbon dioxide produced by human activity is building up in the atmosphere.