Overall, the data from the current study provide strong evidence that rising Ca since the start of the industrial age has, and will continue in the near term, to reduce the pollen protein concentration of Solidago, an important autumn pollen source for bees and other pollinators. (rspb.royalsocietypublishing.org)
If we set that at the concentration that existed at the start of the industrial age, or even at the time of the first oil wells in Oklahoma, we have much reduction to accomplish. (dotearth.blogs.nytimes.com)
The start of the industrial age generally reckoned to be around 1730? (judithcurry.com)