Paleontologist Anna Holden's work on the insects of the Rancho La Brea Tar Pits is reshaping our view of the last 50,000 years of climate history for this region. Most scientists have thought Los Angeles used to be cooler and wetter than it is today, but Anna's work suggests that its climate has in fact changed very little. And that got her to wondering why:
Finding out that the climate of the Los Angeles Basin has been similar to the present day for about 50,000 years without major or lengthy fluctuation except for the Last Glacial Maximum — that was interesting and surprising. I had to think deeply about it. Evidence from other sites in southern California suggests that they were, at some point, cooler and wetter during the late Pleistocene. But that evidence was different for Rancho La Brea. So why was the climate of the Los Angeles Basin different from other places in southern California? I don't know yet. But it's possible that the basin represents an insulated refugium: it's near sea level, it's surrounded by mountains, it's not as affected by the marine layer, so maybe it was protected from climatic drivers that affected other regions. I am currently investigating this hypothesis.