More than half a century ago Aldo Leopold wrote of learning to think like a mountain. He claimed that this was essential to behaving ecologically. But how does a mountain think? Leopold provides one significant clue. He relates the story of seeing the dying “green fire” in the eyes of a wolf mother he shot. He tells us that a mountain must live in fear of its deer herd, for without predators the deer will eat her bare and the rains will strip her of soil.
Let’s follow Leopold’s trail and see where it takes us. His wolf story reminds me of another my friend tells about Yellowstone National Park: when wolves were reintroduced, they lowered the temperature of the water in many of the streams and rivers. How could this be?
In the absence of large predators, ungulates (elk, moose, deer etc.) were unafraid and spent most of their days lolling and grazing along the watercourses. They soon overgrazed the willows and other riparian growth, exposing the riverbanks to flood-damage and erosion, and stripping the water of all shade. The rivers got hotter, less stable, and full of silt. This lowered oxygen levels and clogged the clear gravel beds that trout need to thrive.
The wolves quickly put an end to that. Grazing animals quickly relearned to stay in the open uplands in tight groups where they could protect their young and weak members, coming to the streams only to drink. The grasses, willows, and cottonwoods rebounded, holding stream banks together and shading the water. Water flowed clear, cold and oxygenated—ideal trout habitat once again. Without the wolves the whole system had started to fray, like a sweater snagged on a nail.
Perhaps this is how a mountain thinks: all parts of the community are necessary, all provide essential services and restraints. The interconnections and exchanges are primary and the elements (individual animals and plants) are secondary. The whole (mountain or watershed) is the smallest unit of thought.