But increasingly, scientists who study ecosystems, as well as land managers who do restoration work, are questioning that model of ecological restoration, which relies on the idea of a stable “climax community,” even though many ecosystems are always changing.
The West’s forests, for one, are much more dynamic than many people realize. Notwithstanding individual tree outliers, such as millennia-old redwoods and bristlecone pines, most North American forest ecosystems are, at most, 400 or 500 years old, according to Don Falk, a forest ecologist at the University of Arizona. Reasons vary, from a severe drought in the late 1500s, to 1800s tree harvesting by Euro-Americans. Today, forests continue to undergo constant change. “Many of the forests we look at are in post-fire recovery, we just don’t see it,” Falk said. Outbreaks of insects such as bark beetles, which can decimate forests, add to the constant change. “We want to think of the primeval old-growth forest as having this stable characteristic, until we come along and introduce disturbance … but the idea of forests in equilibrium is probably wrong.” Indeed, events ranging from volcanic eruptions to the Pleistocene ice age have left their mark on the West’s forests.
But with climate change, landscape-level transformations are happening faster and becoming more extreme. As the West becomes warmer and drier, the idea of “recovery” becomes increasingly unrealistic. Instead, ecosystems transform, such as in northern New Mexico, where Gambel oaks may replace pine forest after a fire. “This is really a vexing problem for the field of restoration ecology, because our first instinct—and it’s not wrong—is always to want to put it back to the way it was before we screwed things up,” Falk said.