One of the most compelling passages from James Hansen’s Storms of My Grandchildren seeks to trace back responsibility for biodiversity lost to climate change to the facilities that caused the warming:
If we continue business-as-usual fossil fuel use, a conservative estimate is that by the end of the century we will have committed to extinction at least 20 percent of the Earth’s species, that is, about two million species. Based on the proportion of twenty-first-century carbon dioxide emissions provided by one large coal-fired power plant over its lifetime, I conclude that a single power plant could be assigned responsibility for exterminating about four hundred species, even though of course we cannot assign specific species to a specific power plant… Those coal trains are death trains. The railroad cars may as well be loaded with the species themselves, carrying them to their extermination.
This grim assessment is even worse when you think about how we have gone about cataloging species. The bigger and cuddlier something is, the more likely it is that humans will have investigated it and given it a taxonomical categorization. There are innumerable smaller creatures (most of them unicellular) that we haven’t gotten around to calling species, but which may play important or even critical roles in some ecosystems. Hansen is talking about the number of species we already know about that are in danger of being wiped out.