Afforestation can be explained as?

Afforestation refers to the establishment of new forests on lands that historically have not been forested, making it an important practice for enhancing biodiversity, combating climate change, and improving air and soil quality. This process involves planting trees or establishing tree cover in areas where there were no forests previously, which can lead to various ecological and environmental benefits.

In contrast, the other options describe different practices or strategies that do not align with the definition of afforestation. For example, clearing existing forests relates to deforestation or agricultural expansion, replanting trees in existing forests refers to reforestation, and controlling urban sprawl involves land-use planning, neither of which addresses the establishment of forests in previously non-forested areas. This distinction highlights why the concept described in the question is specifically defined by the practice of planting new forests on historically non-forested lands.