A group of researchers say receding glaciers due to global warming at the end of the last ice age, 20,000-100,000 years ago, resulted in the rampant biodiversity left behind in their wake.

Certainly it is true there is much less biodiversity at the poles, though likely there are limits in how hot we want the planet to be.

Investigating fossil clams and snails Steffen Kiel and Sven Nielsen at the Christian-Albrechts-Universität zu Kiel (CAU) say retreating glaciers created a mosaic landscape of countless islands, bays and fiords in which new species developed rapidly, geologically speaking. 

The southern Chilean coast has more than 500 species of clams and snails, twice as many as at comparable latitudes in the northern hemisphere. The reasons for this diversity have been speculative,  Kiel and Nielsen in Geology, "Opinions include that southern Chile is a museum of diversity where species survived for millions of years in addition to new arrivals; or that Antarctic species colonized this area from the south."

Their analysis of around 35.000 fossil clams and snails, belonging to about 400 species, allowed the paleontologists to draw more precise conclusions.

"Our fossils reject both hypotheses. Biodiversity in this area always decreased toward the south in the geologic past, and we didn't find any intruders from Antarctica", said Steffen Kiel. In addition, the researchers found that the vast majority of species and genera that lived in that area only 16 million years ago had become extinct. "This area is certainly not a museum of biodiversity."

The most species-rich groups of animals in the southern Chilean fiordlands are those inhabiting rocky shores. This is exactly the habitat that was created when the glacier retreated from their marine termini. "Molecular biologic investigations on phylogenetic relationships of these species show that they are geologically very young and descended from North Chilean ancestors. This agrees well with our results", says Sven Nielsen. "Charles Darwin, who was the first to discover fossils in this area during his voyage on the 'Beagle', would have been fascinated."

This research shows that for species conservation not only single, exceptional habitats need to be protected, but that a diversity of habitats needs be conserved to maintain a healthy biodiversity.