Cities, Roads, And The Sixth Extinction Event
Earth’s biosphere entered the stage of large, complex, multicellular life (following an extended – approximately three billion year – period of dominance by unicellular life) starting approximately 650 million years ago. This ‘metazoan’ stage saw the tree of life proliferate and complexify, and has expanded into a huge variety of niches across the planet through to the present day. A key phenomenon over this period has been extinction events; this describes periods of rapidly changing environmental conditions which have resulted in species die-offs and restructuring of ecosystems at different scales.