Picture in your mind a farmer’s field that was left fallow for a year. What would you expect to see growing? Weeds, mostly. Right? How about after 5 years? Maybe some shrubs and small trees? 50 years? A young forest, perhaps? In one hundred years you’ll likely see a mature forest and in 500 years, probably a different forest type altogether – the “climax” forest. This process is called succession and all landscapes go through it. The pattern and speed of the succession may differ among locations, and there may not truly be any set endpoint or “climax” for any particular area. But, you get the idea.
What natural disturbances like fire, flood, avalanche, and tornadoes do is knock succession back a few “seral stages,” a few years, tens of years, or even hundreds of years. Take fire, for instance. Some fires are hot enough that they can take a mature forest and bring it back to, basically, bare dirt. Here in Glacier, avalanches tend to take mature forest and convert it to shrubs. Even bear digs are a natural disturbance. These are areas that look like a rototiller has gone through. It’s just bears digging up roots and bulbs. They take a meadow and return it to dirt. Dirt that has been nicely seeded with the plants they turned over.
You call them “natural disasters” back home, but these natural disturbances are the reason you go to a place like Glacier National Park! You could have just gone to the zoo in your home town or an arboretum or botanical garden. That would have been much easier than coming all the way out here! But you didn’t. Why? Because something is happening here. There are processes. It is a system. There are interactions. Ecology.
Natural disturbances are part of that process and a part that creates the diversity of habitats that we birders love. The reason why Glacier has an amazingly high number of breeding bird species is, in part, those disturbances. We have been taught by Disney to cherish the “balance of nature.” There is no true balance, there is constant change and chaos. And life has evolved to deal with and take advantage of this lack of balance.
Top of page photo by Randy Patrick
David Benson Ph.D.
White-tailed Ptarmigan researcher and National Park Service Ranger Naturalist in GNP since 1995. "The Bird Ranger"