Question 37 from UPSC CSE 2022 - Environme nt

Question

If rainforests and tropical forests are the lungs of the Earth, then surely wetlands function as its kidneys. Which one of the following functions of wetlands best reflects the above statement?

Accepted Answer

Correct Option: D. Aquatic plants absorb heavy metals and excess nutrients.

Strategy: The strategy focuses on identifying which function matches the analogy of 'kidneys'--namely, filtration and purification. Among the options, only the role of aquatic plants in absorbing heavy metals and excess nutrients directly connects to the concept of filtering out toxins or impurities, analogous to how kidneys cleanse blood. Other options reference ecological roles but not direct water purification.

Key Info: Wetlands are ecosystems characterized by saturation with surface or groundwater, often supporting aquatic plants adapted for life in saturated soil. They include swamps, marshes, bogs, and similar environments.

Wetlands play a crucial ecological role as natural water filters, removing pollutants like heavy metals (e.g., mercury, lead, cadmium) and excess nutrients (nitrogen, phosphorus) from water. This natural filtration, known as **phytoremediation**, is primarily carried out by aquatic and emergent plants such as Typha (cattails), Phragmites (reeds), and water hyacinths. These plants absorb, accumulate, or break down contaminants through their roots, stems, and leaves, reducing nutrient loading and preventing eutrophication, thus protecting water quality in downstream bodies.

Beyond their purification role (which aligns with the 'kidneys' analogy), wetlands also provide other vital ecosystem services:
- Support biodiversity
- Recharge aquifers
- Mitigate floods

The ecosystem services provided by wetlands are globally recognized under the Ramsar Convention (1971), an international treaty for wetland conservation and sustainable use.

Answer

Option A: The water cycle in wetlands involves surface runoff, subsoil percolation, and evaporation.

Answer

Option B: Algae form the nutrient base upon which fish, crustaceans, molluscs, birds, reptiles, and mammals thrive.

Answer

Option C: Wetlands play a vital role in maintaining sedimentation balance and soil stabilization.