All of us can sense change—the reddening sky with dawn’s new light, the rising strength of lake waves during a thunderstorm, the changing seasons of plant flowering as temperature and rain have their effects on the landscapes around us. Some of us see longer-term events and remember that there was less snow last winter or that fishing was better a couple of years ago. It is the unusual person who senses with any precision changes occurring over decades. At this time scale we are inclined to think of the world as static and we typically underestimate the degree of change that does occur. Because we are unable to sense slow changes directly, and because we are even more limited in our abilities to interpret cause-and-effect relations for these slow changes, processes acting over decades are hidden and reside in what I call “the invisible present (Magnuson et al. 1983).