Two clumps of tall grasses stand in the foreground. They're the only visible reminders of the ancient prairie that waved here for millennia.

Autumn daybreak spills over a curved dome of dark-leaved ancient oaks. Probably nothing in this photo aside from the two grass plants, the oak horizon, and the sun looks as it did thousands of years ago. But the raw power of nature is here.

The grass on the left — the taller, darker, more erect one — is big bluestem. On the right, the paler one with the plumed heads is Indian grass. They're surrounded by countless stems of the weedy native, tall goldenrod. There's actually an ugly process going on here. Before the goldenrod, this was pasture grasses mixed with strawberries, daisies, yarrow and similar meadow flowers. Its structure actually had a lot in common with a prairie — if the rare native flowers and grasses had been interseeded, and the site had been burned from time to time, we could be seeing a rich sustainable prairie here now.

But the goldenrod is a step towards brush. It crowds out an untended pasture. It won't carry a fire well on most days and it isn't so receptive to interseeded prairie species, so ten years from now we'll likely be looking at shrubs and young trees - the process people once confidently called "natural succession" but in fact led to sickly forests of little quality or use.

What would happen if we managed this field?

We could burn the field occasionally, releasing the sunlight stored in the dried plants each fall — and then see what comes up. But the likely result of that strategy is Indian grass racing to cover the entire meadow, with big bluestem hot on its heels. Soon there would be a near monoculture of the more aggressive bluestem. Dense tall grass is not so positive a fate as some may think. The rank, tall grass will monopolize the light and nutrients much as buckthorn, a woody invasive, would. Not many other plants or animals can live in a "prairie" such as this.

Another approach includes mowing to reduce the goldenrod and sowing rare prairie seed. Then burns might more successfully help a diverse ecosystem to become established. The taller grasses would ultimately take their place among the many other prairie species. Such a diverse ecosystem provides habitat for a great many rare animals and plants. These are the sorts of options land that managers ponder when they read the landscape and make the work prescriptions that are gradually restoring health to our natural lands.

Photo of Spears Woods in Cook County by Mike MacDonald (www.ChicagoNature.com). Words by Stephen Packard.