Long-term ecological research and the invisible present: Uncovering the processes hidden because they occur slowly or because effects lag years behind causes
II of us can sense change-the reddening sky with dawn’s new light, the rising strength of lake waves during a thunderstorm, and the changing seasons of plant flowering as temperature and rain affect our landscapes. 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. But 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 directly to sense slow changes and because we are even more limited in our abilities to interpret their cause-and-effect relations, processes acting over decades are hidden and reside in what I call the invisible present (Magnuson et al. 1983). The invisible present is the time scale within which our responsibilities for planet earth are most evident. Within this time scale, ecosystems change during our lifetimes and the lifetimes of our children and our grandchildren. This is the time scale of acid deposition, the invasion of non-native plants and animals, the introduction of synthetic chemicals, CO2 -induced climate warming, and temporal context provided by longterm research, serious misjudgments can occur not only in our attempts to understand and predict change in the world around us, but also in our attempts to manage our environment. Although serious accidents in an instant of human misjudgment can be envisioned that might cause the end of Spaceship Earth (sensu Fuller 1970), destruction is even more likely to occur at a ponderous pace in the secrecy of the invisible present.