Ecological impacts
Living creatures always adapt to their environment. There are organisms—microbes—that can live in boiling water, in the rock miles beneath Earth’s surface, and under the extreme pressure that exists at the deepest parts of the oceans. Yaks and musk oxen do not freeze to death. The only type of environmental change that is dangerous is a very fast change. A diver who goes up to the surface too quickly gets ”the bends”, and an otherwise well-prepared mountain hiker may perish in a snowstorm. So we need to examine what natural events may cause sudden ecological change.
The most devastating ecological event that could happen on Earth is the impact of a large extraterrestrial object. A meteorite with a diameter of one kilometer would kill not only hundreds of thousands of species but genera and families as well—a total ecological disaster. The risk of this kind of event happening, however, is negligible in our normal time perspective.
The second largest ecological event possible is the eruption of a so-called supervolcano. The Pinatubo eruption in the Philippines 1991 lowered Earth’s mean temperature by 0.6° C during 15 months, and a supervolcano eruption would eject 100 times more particles and gas and will cause a 3–4 degrees lowering of the global temperature during a full decade. The effect of the particles would be noticeable all over the planet, but the gases have the largest ecological impact.
The third largest ecological hazard from a human viewpoint is a pandemic. Highly virulent diseases can be spread very quickly, since we travel so much today, and densely populated areas are most at risk, especially large metropolitan areas. In addition to humans only a few other species acting as vectors would be affected. The total ecological effect would therefore not be as great from a pandemic as from a meteorite impact or from a supereruption.
Climate changes are slow processes but receive much attention. Large expenditures are being made to try to keep Earth’s mean temperature the same as it was a hundred years ago, acting on the belief that human carbon dioxide emissions are the cause of the increase. In a longer time perspective, we should be much more concerned about how we will fare when the next glacial period arrives.