California has exceptionally high plant biodiversity. It is home to 5,500 different plants species and – what is more remarkable – some 40 percent of these occur nowhere else. The reason is not that evolution would happen faster here, but that for 45 million years extinction rates among plant life have happened at a slower pace in California than elsewhere, researchers say. Photo credit: Jenn Yost, University of California Santa Cruz.

Well here is a picture that is really hard not to like. It was taken on Coyote Ridge, part of a low Pacific mountain range in Santa Clara County, close to San Jose, California. It shows a mountain meadow with high endemic diversity of spring wildflowers.

New research published in the journal Evolution shows California is a true plant biodiversity hotspot, because over millions of years extinction rates have been relatively low in the state.

Easier migrations under climatic shifts

That is not hard to imagine, as the geography allows close proximity for various climatic zones, from a mild coastal climate, to cold high mountain climate, dry and wetter regions and continental climates, including record-hot desert – all allowing for easy migrations by species, once climatic changes lead to habitat shifts.

One other crucial factor is that mountain ranges in California, and actually throughout North America, have a dominant North-South orientation. Compared to Eurasia, which has mountain ranges with dominant West-East orientation, this allowed for higher Pleistocene survival rates, as glaciations forced mild-climate-favouring plant species southwards – a blocked route, you’ll find when you approach the north slopes of the Pyrenees, Alps, Caucasus or the Himalayas.

What is news to California after these 45 million years of peace and quiet is that suddenly some 38 million people have settled in the middle of this climatic biodiversity safe haven. Let’s just hope their interests will not clash…

Elsewhere globally high mountain meadows are much threatened by climate warming for the exact opposite reason: cold climate zones often lack colder alternatives.

© Rolf Schuttenhelm | www.bitsofscience.org