Final answer:
The most potential for afforestation globally is in the temperate and boreal zones due to the increase in forest cover and the decline in agriculture in some areas, although deforestation is still prevalent in tropical regions.
Step-by-step explanation:
The latitudinal zone that holds the most potential for afforestation globally are the temperate and boreal zones. In these zones, forest cover is on the rise, particularly in eastern and western North America, Alaska, western and northern Europe, eastern China, and Japan. This regeneration is partly due to the abandonment of agricultural lands and urbanization. However, the new forests often lack the species complexity of natural old-growth forests and are typically secondary forests or forest plantations, frequently composed of non-native species. In contradiction, tropical and subtropical zones, alongside regions such as the South American cerrado, demonstrate high rates of deforestation and may not be ideal for afforestation due to ongoing land conversion pressures and scarcity of arable land.
Moreover, intensive agriculture in these regions is reducing the fallow periods, making the land less available for afforestation projects. Tree plantations can contribute to biodiversity conservation and provide structural complexity, so they should be considered as part of afforestation efforts, particularly in places where old growth forests have been lost, such as in tropical regions.