Consider the following statements Statement 1: The extinction of a keystone species can lead to ecosystem collapse.

Question

Consider the following statements:

Statement 1: The extinction of a keystone species can lead to ecosystem collapse.

Statement 2: Climate change is solely a future concern and has no current effects.

Statement 3: Protected areas are essential for conserving biodiversity.

Statement 4: Ozone depletion directly contributes to global warming. Which of the statement/s given above is/are correct?

1. A. 1 and 3 only (Correct answer)
2. B. 2 only
3. C. 1, 2, and 4
4. D. 1 and 4 only.

Correct Answer

Option A — 1 and 3 only

Detailed Solution & Explanation

The correct answer is 1 and 3 only.

Key Points

• Statement 1 is correct. The extinction of a keystone species can lead to ecosystem collapse. A keystone species exerts an influence on community structure far out of proportion to its abundance, and its removal triggers cascading change.
• Statement 2 is incorrect. Climate change is not solely a future concern. Its effects are already measurable — rising global mean temperature, sea level rise, glacier retreat, coral bleaching, shifting species ranges and an increased frequency of extreme events.
• Statement 3 is correct. Protected areas — national parks, sanctuaries, biosphere reserves and conservation reserves — are a cornerstone of in-situ conservation.
• Statement 4 is incorrect. Ozone depletion does not directly contribute to global warming. They are distinct problems with distinct causes, though the two are linked at the edges.

Additional Information

• Why ozone depletion and global warming are separate problems:
  • Ozone depletion is caused by CFCs, halons and related halogenated compounds destroying stratospheric ozone, allowing more UV-B radiation to reach the surface. It is addressed by the Montreal Protocol (1987), the most successful environmental treaty in history.
  • Global warming is caused by greenhouse gases trapping outgoing long-wave radiation in the troposphere. It is addressed by the UNFCCC, the Kyoto Protocol and the Paris Agreement.
  • The connection is indirect: many CFCs are themselves potent greenhouse gases, and the Kigali Amendment (2016) to the Montreal Protocol phases down HFCs — which do not deplete ozone but are powerful warming agents. Stratospheric ozone loss actually produces a slight cooling of the stratosphere.
• Classic examples of keystone species: the sea otter, whose loss allows sea urchins to destroy kelp forests; the **starfish *Pisaster* in Robert Paine's original experiments; elephants, which maintain savannah grassland by preventing woody encroachment; fig trees as keystone food resources in tropical forests; and beavers** as ecosystem engineers.
• Distinguish related terms: a flagship species is chosen for its public appeal to drive conservation funding (tiger, panda); an umbrella species requires so large a habitat that protecting it protects many others; an indicator species signals the health of an ecosystem (lichens for air quality); a keystone species is defined by its functional role.