Because geologic evidence supported the existence of tropical swamps in the Northern Hemisphere
Subtropical / tropical wetlands are wetlands found along the coasts of subtropical or tropical regions. The Everglades in Florida, for example, is a well-known example of subtropical wetlands. These wetlands are often, but not always, dominated by mangrove trees. The
Northern Hemisphere includes North America, northern South America, Europe, the northern two-thirds of Africa, and much of Asia. The Southern Hemisphere includes most of South America, Africa, Australia, one-third of Antarctica, and some Asian islands.
The Northern Hemisphere refers to half of the planets north of the equator, and the Southern Hemisphere includes all planets south of the equator. Some continents pass through both hemispheres, but Europe and North America are all in the northern hemisphere.
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