The Amazon rainforest constitutes a region because

Explanation:

The Amazon rainforest, alternatively, the Amazon jungle or the Amazon rainforest, is a humid deciduous rain forest in the Amazon biome that covers most of the Amazon basin in South America. The basin covers 7,000,000 km 2 (2,700,000 sq mi), of which 5,500,000 km 2 (2,100,000 sq mi) is covered by rainforest.

answer; direct observation;