Large scale deforestation leads to decreases in the amount of gas A in the atmosphere whereas the amount of gas B increases. The increased amount of gas B in the atmosphere causes an effect C which leads to excessive heating of the earth and its atmosphere producing an undesirable phenomenon D. What are A, B, C and D?

Gas A is oxygen, which decreases when large-scale deforestation occurs because trees are the primary producers of oxygen through photosynthesis. Gas B is carbon dioxide, which increases because trees that normally absorb CO₂ are removed, and burning or decomposition of felled trees releases stored carbon back into the atmosphere. This creates a double impact—losing carbon-absorbing capacity while simultaneously adding more carbon dioxide to the air.

Effect C is the greenhouse effect, where increased atmospheric carbon dioxide traps heat radiating from Earth's surface, preventing it from escaping into space. Phenomenon D is global warming, the long-term increase in Earth's average temperature caused by enhanced greenhouse effect. This leads to serious consequences including melting ice caps, rising sea levels, extreme weather events, disrupted agricultural patterns, and threats to biodiversity. The connection between deforestation and climate change demonstrates why forest conservation is critical for maintaining planetary health and requires urgent attention from governments, industries, and communities worldwide.