Marine biodiversity could undergo drastic changes in as much as 70% of the world's oceans if global warming is not limited to below 2 °C by 2100.

Grégory Beaugrand at the CNRS Laboratory of Oceanology and Geosciences in Wimereux, France, Richard Kirby at the University of Plymouth, UK, and their colleagues modelled how patterns of biodiversity across the oceans would change under different future climate scenarios, and compared them to patterns over the past 50 years and during prehistoric warm and cold periods.

With low levels of warming (mean temperature rise of roughly 1 °C), around 16% of the ocean would see increased biodiversity through species invasions and about 6% of oceans would experience a decrease. In the most extreme warming scenario, of roughly 3.7 °C, these numbers rise to about 32% and 44%. Such severe warming could produce a greater change in marine biodiversity than has been seen over the past 3 million years or so.

Nature Clim. Change (2015)