Study suggests it is already too warm in tropics for some species to survive

Fish at Wetar island in Indonesia. Scientists say the fall in marine diversity around the equator could have profound consequences that are hard to predict. Photograph: agefotostock/Alamy

Global heating has made the ocean around the equator less rich in wildlife, with conditions likely already too hot for some species to survive, according to a new study.

Analysis of the changing locations of almost 50,000 marine species between 1955 and 2015 found a predicted impact of global heating – species moving away from the equator – can now be observed at a global scale.

It said further global heating, which is now unavoidable, would cut the richness of species in the ocean in tropical regions even further.

Scientists said the consequences of the shift could be profound and would be challenging to predict.

Species attached to the ocean floor had not declined, but the diversity of free-swimming species such as fish had dropped significantly between 1965 and 2010, said Prof David Schoeman, a co-author of the study.

Schoeman, of the University of the Sunshine Coast, said the drop in the richness of species would likely affect communities that relied on the ocean for food in areas where the fish they used to find were no longer there.