Consider the following statements:

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

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

3. Protected areas are essential for conserving biodiversity.

4. Ozone depletion directly contributes to global warming.

Which of the statement(s) given above is/are correct?

The extinction of a keystone species can lead to ecosystem collapse. Correct: A "keystone species" is one that has a disproportionately large effect on its environment relative to its abundance. Think of it like the wedge-shaped stone at the top of an arch; if you remove it, the whole structure falls apart. Classic examples include sea otters or wolves. Climate change is solely a future concern and has no current effects. 

Incorrect: Climate change is a present reality. We are currently observing measurable impacts, including rising global temperatures, receding glaciers, more frequent extreme weather events, and shifting migration patterns of various species. Protected areas are essential for conserving biodiversity. 

Correct: National parks, wildlife sanctuaries, and marine protected areas provide a "safe haven" from habitat destruction, overexploitation, and pollution, which are the primary drivers of biodiversity loss. Ozone depletion directly contributes to global warming. 

Incorrect: This is a very common misconception. While they are both human-caused environmental issues, they are largely distinct. Ozone depletion (the "hole" in the ozone layer) allows more UV radiation to reach Earth, increasing skin cancer risks. Global warming is caused by the buildup of greenhouse gases (like $CO_{2}$ and $CH_{4}$) trapping heat in the atmosphere. Ozone depletion does not cause the planet to warm significantly. Summary Table Statement Status Reason 

1. Keystone Species True They maintain the structure of an entire ecosystem.

2. Future Concern Only False  Current data shows rising sea levels and record temperatures.

3. Protected Areas True They are critical tools for preventing habitat loss.

4. Ozone & Warming False They involve different gases and different physical processes.