How Island Size Affects Extinction Rates

• Larger islands support larger populations, offer more resources and habitats, and are less susceptible to random events that can wipe out species. This means larger islands have lower extinction rates.

• Smaller islands have limited resources and smaller populations, making species more vulnerable to extinction due to stochastic events, competition, and environmental fluctuations. Thus, smaller islands have higher extinction rates2357.

How Island Distance Affects Colonization Rates

• Islands closer to the mainland are easier for new species to reach, resulting in higher colonization rates.

• Islands farther from the mainland are less accessible to dispersing organisms, so they experience lower colonization rates145678.

Applying the Theory to Islands A and B

• Island A is smaller (160 sq. km) and farther (180 km) from the mainland.

• Island B is larger (220 sq. km) and closer (100 km) to the mainland.

Based on island biogeography theory:

• Island A will have a higher extinction rate (because it is smaller) and a lower colonization rate (because it is farther from the mainland).

• Island B will have a lower extinction rate (because it is larger) and a higher colonization rate (because it is closer to the mainland).

The Correct Statement

Given these facts, the correct answer is:

(1) Island A is likely to have higher extinction and lower colonization rates than Island B.

Why This Matters

Understanding these dynamics is crucial for conservation planning and biodiversity management. Islands (or habitat patches) that are small and isolated are at greater risk of species loss and are less likely to be naturally recolonized, making them priorities for conservation intervention. Conversely, larger and nearer islands are natural refuges for biodiversity.

Conclusion

The interplay between island size and distance from the mainland is fundamental to predicting species richness and turnover on islands. In the scenario described, Island A’s smaller size and greater distance make it more vulnerable to species loss and less likely to gain new species, compared to Island B. This principle underpins much of modern conservation biology and guides the design of protected areas and wildlife corridors.