Final answer:
The main challenge with mapping coral reefs globally is the complexity and vastness of the marine environment. Factors such as sea temperature, human activities, and global climate change can impact the health and distribution of coral reefs, making it difficult to survey and map them comprehensively.
Step-by-step explanation:
The main challenge with mapping coral reefs globally is the complexity and vastness of the marine environment. Coral reefs cover a large area and are found in different regions around the world, making it difficult to survey and map them comprehensively. Additionally, factors such as sea temperature, human activities, and global climate change can impact the health and distribution of coral reefs, further complicating mapping efforts.