Which of the following practices would most significantly impact global sustainability?

Reducing human population size would most significantly impact global sustainability by addressing the root cause of many environmental issues, such as resource depletion, habitat destruction, and pollution. A smaller human population can lead to diminished demand for natural resources, including water, land, and energy, making it easier to maintain ecological balance. It can alleviate pressures on ecosystems, allowing for biodiversity to thrive and giving more space for natural processes to occur without human interference.

While recycling aluminum cans, using fuel-efficient vehicles, and replanting deforested areas are all important practices that contribute to sustainability, they primarily focus on mitigating the impacts of human activities rather than addressing the underlying issue of how many individuals are consuming resources. Reducing the population can lead to more effective and lasting solutions for preserving the environment and ensuring that the needs of future generations can be met.