The deep sea

Abstract

The deep ocean makes up the single, biggest portion of the earth's biosphere. Of all the habitable space available for living things to occupy, at least 95% is the deep. Beginning at the 200-m mark, with an average depth of around 4 km and a total volume of roughly a billion cubic kilometres, the deep ocean is inconceivably huge. Contrary to scientific theories of the past, it is not a lifeless, empty void. Despite the darkness, cold and extreme pressure, plenty survives and thrives in the deep. Previously unknown species are continually being discovered there and occasionally whole new habitats. So quite simply, if we want to understand life on earth, then we must look into the deep. The more we learn about the deep, the more it becomes clear that this enormous realm is critical for the health of our whole living planet. We are also learning that its remoteness and size are not enough to protect the deep ocean from human impacts.