UPSC Prelims 2018 Q65: Environment & Ecology – Climate Change & Greenhouse Gases
- (a) Increased plant growth due to increased concentration of carbon dioxide in the atmosphere
- (b) Increased temperature of Earth due to increased concentration of carbon dioxide in the atmosphere
- (c) Increased acidity of oceans as a result of increased concentration of carbon dioxide in the atmosphere
- (d) Adaptation of all living beings on Earth to the climate change brought about by increased concentration of carbon dioxide in the atmosphere
Answer: (a) Increased plant growth due to increased concentration of carbon dioxide in the atmosphere
Explanation
Carbon Fertilization - Definition
Carbon fertilization refers to the phenomenon where elevated atmospheric CO2 concentrations enhance plant growth and photosynthesis because CO2 is a key input for photosynthesis.
| Option | Correct? | Detail |
|---|---|---|
| (a) Increased plant growth due to increased CO2 concentration | YES | Textbook definition. C3 plants (rice, wheat, soybean) respond more strongly than C4 plants (maize, sugarcane, sorghum). Effects are partially offset by heat stress, water limitations, nutrient deficiency, and reduced nutritional quality of crops. |
| (b) Increased Earth temperature due to CO2 | NO | This describes greenhouse effect / global warming, not carbon fertilization. |
| (c) Increased ocean acidity due to CO2 | NO | This is ocean acidification (CO2 dissolves to form carbonic acid), not carbon fertilization. |
| (d) Adaptation of all living beings to climate change | NO | Vague and inaccurate; not the definition of carbon fertilization. |
Answer: (a) Increased plant growth due to increased concentration of carbon dioxide in the atmosphere.
Why each option is right or wrong
- (a) CORRECT. Carbon fertilization refers specifically to enhanced plant growth from elevated atmospheric CO2 - a direct photosynthesis effect.
- (b) Incorrect. Rising temperature from CO2 is the greenhouse effect, not carbon fertilization.
- (c) Incorrect. Increased CO2 raising ocean acidity is called ocean acidification, distinct from carbon fertilization.
- (d) Incorrect. General 'adaptation' is not the definition of carbon fertilization.
Key point
Carbon fertilization = elevated CO2 boosting plant photosynthesis and growth. Strongest in C3 plants (rice, wheat, soy). Offset by heat stress, water limits, and reduced protein/nutrient content of grains. Documented by FACE experiments globally.
Remember
Carbon fertilization is the phenomenon where increased atmospheric CO2 boosts plant growth by enhancing photosynthesis, particularly in C3 plants like rice, wheat and soybean. However, this benefit is partly offset by heat stress, water limitations and reduced protein content in crops, so it is not an unqualified gain from climate change.
Common mistakes
- Confusing carbon fertilization (plant growth benefit) with the greenhouse effect (climate warming) or ocean acidification (chemical change).
- Overstating the benefit - carbon fertilization is real but offset by heat stress, water stress, and reduced crop nutritional quality.
- Missing the C3 vs C4 differentiation - C3 crops benefit more; C4 crops (maize, sugarcane) are less responsive.
Exam tip
CO2 impacts trilogy: (i) Greenhouse warming (climate), (ii) Ocean acidification (chemistry), (iii) Carbon fertilization (biology). Each affects a different sphere - atmosphere, hydrosphere, biosphere.
Sources
- IPCC AR6 - Working Group II (Impacts, Adaptation) - Agriculture chapter
- NCERT Class 11 Biology - Photosynthesis (Chapter 13)