Monday, January 19, 2009

Why It Burns

1874, Castle Creek Valley, South Dakota

Same location, 1973

In nature, as in human life, it’s hard to pin an event on a single cause.

A half-degree change in average annual temperature translates into a winter warm enough to let a particular beetle survive from one year to the next. The beetle, let’s say, is from another continent but was brought to this forest by tourists or free trade.

And just for fun let’s say the dominant tree species in the forest used to be less common, but because of loss of habitat—subdivisions have been popping up all over the hills—the deer that used to eat its seedlings are no longer around. So the trees have grown in thick where they used to be sparse.

The beetle, able to survive the recent milder winters, decimates the dense forest, leaving the trees dead but standing, tinder-dry in fire season. A fire starts. Subdivisions are threatened. What’s the cause of the fire?

Duh. It’s kids playing with matches. It’s always kids playing with matches. That’s the first lesson of wildlife preservation.

In 1874 Bvt. Maj. Gen. George Armstrong Custer—yeah, that Custer—led an expedition 1,000 strong into the Black Hills of Dakota Territory, winding through what today is eastern South Dakota and parts of Wyoming, Montana, and North Dakota.

They took a photographer, William H. Illingworth, from St. Paul, Minnesota.

In 1973, American West published a series of Illingworth’s photos in tandem with more recent shots, from the same locations, taken by Donald R. Progulske, head of Department of Wildlife and Fisheries Sciences at South Dakota State University, and Richard H. Sowell, a university photographer, as they retraced Custer’s route.

Eventually Progulske published a book with more photos in it. I don’t have that book. But I did run across the American West article lately, and the pictures tell quite a story.

Near Deerfield, South Dakota

1800s European explorers in the heart of Africa were convinced that the natural state of the continent was dense jungle cover.

What they missed was that (watch for gross historical oversimplification) dengue fever epidemics in the 1790s had caused a collapse in widespread farming populations. Without farmers tending fields, the jungles encroached. Does that mean the untouched land would naturally have been all jungle? Probably not.

It means the jungle had been first and fastest to take over formerly tilled land. If Europeans had arrived 100 years before, they might have described the continent differently. A hundred years later, first impressions could have been different again.

Preservation is a funny critter. Do you preserve something in a frozen state, not allowing it to change, like a book or a Victorian house? Do you freeze a process, allowing change but only according to the way it used to be done, like planting and harvesting crops in Colonial Williamsburg or choosing a President in the Electoral College?

When you “preserve” nature, who’s to say what a natural state is? No buildings—O.K. so far. But if a redwood tree takes 2,000 years to grow, how can we watch it for 40 years and assume the environment it’s in is typical of what it’s had for the other 1,960? Nature’s natural state is one of change.

(In a city, preservation gets even more complicated. How do you preserve a neighborhood? How do you keep the open-air greengrocers from closing and changing the way the streets feel? Preserve it the way it was 40 years ago, or 10 years ago, or 200 years ago? Does a tenement have historic value? Do you preserve the cockroaches? The Saturday-night knife fights? What does it mean to preserve Tin Pan Alley? Difficult questions.)

Whatever you’re trying to preserve, in someone else’s eyes it was probably ruined already when you first set eyes on it.

In these pictures the landscape has changed vividly. Is the burgeoning forest cover part of a natural cycle—one that starts with bare meadow and builds up to a climax level, then gets wiped out by fire and restored to bare meadow?

Or do we preserve the number of trees that were there when Custer first saw it?

Or do we preserve the grasses and cut down the trees? The grasses fed the elk; the elk fed the grizzlies. When trees choke the meadows, the elk leave, and then the bear. What should we be preserving?

Near Custer, South Dakota

And if a single cycle of alternation between pine forest and grassland takes 200 years, how long do we have to watch—how many cycles—before we’re comfortable that we have seen all the major variants in that cycle? Who judges what’s abnormal? Who has time to wait?

The U.S. Forest Service is committed to “many uses” for the resources it manages. The 1973 American West article notes that, perversely, a thicker forest tends to yield less lumber, since the “trees do not reach saw-log size and proper thinning becomes costly.” But nearby property owners tend to get sniffy about unchecked wildfires. The extent of Yellowstone National Park’s 1988 fires raised a lot of media eyebrows. When smoke rises on the horizon, politicians need something to thump their chests about.

But it’s easy to see in the pictures above that a fire in the 1870s would have moved through the more widely spaced trees with a whole different force from the firestorm that could devour the thick stands of the 1970s.

“Only you,” says Smokey Bear, “can prevent forest fires.” Maybe it’s also fair to say that only a human would try to.

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