The truly scary figure is not the number of Lake Eries but the figure of 100 years - that's only around four generations.

Let's say that the human race has been on this planet for (off the top of my head) 2 million years - that's 80,000 generations. And the last tiny fraction of those generations have nearly used up at least one natural resource. Something tells me that we're probably not going to be around for another 80,000 generations - perhaps not even for another four ...