Question

Scientific evidence indicates that the CO2 added to the air by the burning of wood and fossil fuels is contributing to global warming, a rise in global temperature. Tropical rain forests are estimated to be responsible for approximately 20% of global photosynthesis, yet the consumption of large amounts of CO2 by living trees is thought to make little or no net contribution to reduction of global warming. Why might this be? (Hint: What processes in both living and dead trees produce CO2?)

Answer 1

Answer:

The trees in tropical rainforests exhibit very less or no effect on the decline of global warming as these living species by themselves donate to the emanation of carbon dioxide via the process of respiration. Though the trees use carbon dioxide in the process of photosynthesis, however, they balance this is donating the carbon dioxide back to the atmosphere via respiration.  

The process of photosynthesis takes place only at the time of day, however, the process of respiration takes place both during day and night and in certain plants known as C3 plants, who exhibit one more kind of respiration known as photorespiration, which takes place in the existence of light and again discharges carbon dioxide.  

With some exemptions, the majority of the tropical trees are C3 plants. Thus, in spite of contributing 20 percent of the global photosynthesis, their contribution to diminishing global warming is negligible or nil because of the production of carbon dioxide by the process of respiration.  

Answer 2

Answer: At night when no light is present plants can only utilize cellular respiration so the overall net change of co2 they "consume" is pretty low but still beneficial at the rates humans seem to be dishing co2 out.