Carbon dioxide levels fall to the point at which C4 photosynthesis is no longer possible. Without plant life to recycle oxygen in the atmosphere, free oxygen and the ozone layer will disappear from the atmosphere allowing for intense levels of deadly UV light to reach the surface. However, in their book The Life and Death of Planet Earth, authors Peter D. Ward and Donald Brownlee stated that some animal life may be able to survive in the oceans. However, due to a lessening of organic matter and oxygen in the water,animal life would die off there too. By this time all multicellular life will die out. The only life left on the Earth after this will be single celled bacteria.