Our first view of the earth from the moon came in 1968. The most prevalent metabolic gas in the atmosphere is oxygen. Atmospheric and oceanic circulation patterns assure that pollutants produced in one part of the globe will remain in the same area. Although nitrogen-fixation resulting from human activity is high, it represents only a fraction of the amount fixed by natural processes. Fortunately, the country with the largest single tract of tropical rain forest has the lowest rates of deforestation.
Deforestation is a human impact limited to the tropics.
There is evidence that human industrial activity is responsible for the recent increase in carbon dioxide concentration in the atmosphere. The concentration of carbon dioxide in the atmosphere had fluctuated between 200-300 ppm prior to the year 1800. As a consequence of burning fossil fuels, the relative concentration of C-14 in the atmosphere is declining. The layer of the atmosphere most changed by human actions such as . Ozone reacts with and degrades chlorophyll, and thus lowers the plant's productivity.