Which ecosystem makes up approximately 70% of the earth's surface?

The answer is:  marine ecosystem (also known as salt water Eco system)

Explanation: marine ecosystem makes up approximately 70% of the earth's surface. This includes coral reefs, lagoons, mangrove forests, sea beds, Salt marsh, Estuaries and the list continues. They are found in various and in different geographic locations across the globe. Salt water ecosystems support nearly half of all Earth’s species and are a habitat to millions of creatures.