Historical photo of vegetation of California from the early 20th century. This image is part of a US Forest Service effort to document the flora of the state in the 1920’s and 1930’s. Credit: Marian Koshland Library, UC Berkeley
Californian plants have responded to climate change in a surprising way, data collected under the direction of a forester born almost exactly 121 years ago have helped show. Albert Everett Wieslander headed surveys in the 1920s and 1930s covering 28 million hectares, over most of the state’s natural environment outside of deserts and larger agricultural areas. The data was originally intended to provide 220 detailed vegetation maps, but publication was halted by the Second World War after just 23 maps were released. Then in 2005 a digitized version of the raw data, now known as the Wieslander Vegetation Type Mapping (VTM) collection, was made available online.
Now, Solomon Dobrowski, from the University of Montana’s Department of Forest Management and his colleagues have compared this record with modern studies of plant populations for Northern California. “We used their survey plots,” Dobrowski told Simple Climate. “Basically they’d delineate a fixed area on the ground as roughly 800 square metres in size and they would document the types of trees and shrubs and other plants they found within that location.”
Prior studies of how plants are reacting to climate change have shown them moving to habitats in pursuit of their preferred temperatures as the planet warms. This typically means that they move towards the poles, or up mountainsides to higher altitudes. However, what Dobrowksi’s team found from their comparison, and published in top journal Science yesterday, at first glance seems to almost directly disagree with this. “I was mildly incredulous when my graduate student Shawn Crimmins first approached me and said that things are moving downhill,” Dobrowski admitted. “I asked him to go back and revisit his analysis and make certain that it was right. When he came back and said yes, we’ve dotted our i’s and crossed our t’s, I realised we had to revisit our assumptions about what was going on.” Read the rest of this entry »
