The correct option is (a).
Explanation
Forests act as significant carbon sinks within the biogeochemical carbon cycle. They regulate atmospheric composition by sequestering carbon through photosynthesis. Deforestation disrupts this equilibrium, impacting both the concentration of greenhouse gases and the Earth's thermal balance.
Statement-wise Analysis:
- Statement 1 is Correct: Trees absorb carbon dioxide (CO2) from the atmosphere during photosynthesis. When forests are cut down, this absorption ceases. Additionally, the carbon stored in the trees is released back into the atmosphere as CO2 if the wood is burned or decomposes. Consequently, the concentration of CO2 in the air increases.
- Statement 2 is Incorrect: Carbon dioxide is a potent greenhouse gas responsible for trapping heat in the atmosphere. An increase in atmospheric CO2 intensifies the greenhouse effect, leading to a rise in the Earth's average temperature (Global Warming), not a decrease.
- Statement 3 is Incorrect: Photosynthesis is the process performed by plants to convert light energy into chemical energy, utilizing CO2. Deforestation reduces the total vegetation cover, thereby decreasing the overall rate of photosynthesis. This reduction diminishes the ecosystem's capacity to absorb CO2, exacerbating the imbalance rather than correcting it.
Key Takeaway: Deforestation disrupts the carbon cycle by simultaneously releasing stored carbon and removing the natural mechanism (photosynthesis) required to sequester atmospheric carbon dioxide, directly contributing to global warming.