"Locking up" the land

This is a general question I’ve been pondering for quite a long time. Back when I was a kid I read science books that talked about the cycling that landforms undergo through time. There’s a good exhibit (that’s been there since the 1950s) at the American Museuim of Natural History on this, too.

What we see as a glade or a forest or a pond is not a permanent feature on the landscape. Even in the absence of huge and catastrophic changes, like continental drift, earthquakes, volcanic eruptions, and the like, there are constant changes that gradually transform a landscape. A forest fire will burn down an old stand of forest, but it will clear the way for new plants to grow (Some of which are, in fact, stimulated by high temperatures, so they’ve evidently adapted to this.) The plants and the character of the clearing changes through time, until it’s an old-growth forest ready for another fire. (There’s a display of this at the AMNH. John McPhee’s chapter on California in The Control of Nature talks about this, too.)
Winding rivers on a broad plainm change shape with time, forming wider and wider loops that eventually split off and become Ox-bow lakes, which eventually fill in and leave you with a straight river.

Beavers build dams to create a pool by flooding a small area. Eventually it fills in, and you’re left with marshy ground that may in time become a flat forest area.
And so on. I’m simplifying, of course, and some changes take very long (Grand Canyon), but the point is that the land is in a constant state of flux.
Now along comes modern civilization, which paves over vast stretches of ground, excluding it from participating in this cycle for long periods of time. People try to stabilize river beds, sometimes erecting stone walls and dams to do so. (See McPhee’s chapter on the lower Mississippi in that same book). We try to prevent beaver dams. Forest fires are prevented, too, with occasionally catastrophic results (California fires, followed by mudslides), or controversial ones (The Yellowstone fires of a decade back). One solution is to clear away all that brush so fires don’t start – but that costs money and doesn’t always get done. and some have argued that it prevents the beneficial effects of forest fires (clearing away of old trees, exposure of seeds to high temperatures). Where it doesn’t happen, brush buildup exceeds natural levels, and the resultuing fires are bigger.

Along shorelines people try to prevent erosion, even though such come-and-go of sandbars and beachfronts is the norm when people aren’t superintwending things. People eliminate shoreline and mudflats by using landfill and building bulwarks (Boston’s shoreline has changed enormously since colonial days. New York’s, too.)

In former times this probably wasn’t significant to the ecosyste as a whole, because cities weren’t enormous and were well-separated. But now we’re paving and trying to “lock in” the existing landforms across huge areas of the country – and precisely the kind of land that “wants” to change the most. As I say, we’re denying exposure to sun, rain, and change enormous quantities of soil. at the same time, anything adapted to changing conditions must be having a hard time with all this stability.

What are the long-term effects?

There have been books, or at least large chapers of books, written on that subject. Would you like to be a little more specific?

It seems true that wilderness and park management methods are starting to recognize that stasis in the physicl environment is neither natural nor good. I’m thinking of things like controlled burns rather than complete fire surpression in some forests. But as for human infrastructure holding back geomorphological cycles and such, I think there’s plenty of it but on rather small scales – no interstate highway is going to hold back the dunes, say. I think our disruptions to the hydrology (dams, e.g.) or to land use (forest to farms or cities) in general appears to encourage stasis, in that those places are less subject to year-to-year or seasonal changes, but really are accelerating the changes at longer temporal scales – drying up the floodplain below the dam, creating a patchwork of secondary vegetation as land uses change over a human lifetime, etc.

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