Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”
With all of the negative effects predicted to occur in response to the ongoing rise in the air’s carbon dioxide (CO2) concentration—a result of burning fossil fuels to produce energy—it is only natural to want to see what has been happening to our Earth’s many ecosystems as the atmospheric carbon dioxide load has risen. (Its atmospheric concentration has risen from around 280 parts per million to nearly 400 ppm, an increase of about 43 percent).
A new study by the University of California’s Christopher Dolanc and colleagues does just that, for the diverse Sierra Nevada forests of California.
Dolanc and his colleagues analyzed two periods: historic measurements between 1929 and 1936, and modern data from 2001 through 2010. And when we said “diverse,” we meant it. They “classified 4,321 historical plots and 1,000 modern plots into nine broad groups of vegetation types that are widely used by land managers and researchers in the region.” This is what grad students are for!
They compared tree density and composition between the two periods, within and between the nine types of forest. The results shown in Figure 1 below.
Figure 1. Percent change in tree density by forest type in the Sierra Nevada Range, USA, as determined from historic (1929-1936) and modern (2001-2010) measurements. Green bars denote a statistically significant change. You might want to call this “California Greening.” Source: Dolanc et al. (2014).