Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
Steve Packard hiked down railroad tracks for two miles one winter searching for the last piece of a puzzle that had him spending hours poring through old books and journals that mentioned some unusual grassland plants that actually grew in the woods. As he approached what today is known as the Middlefork Savanna in Lake Forest, Illinois, he began to see large bur oak trees scattered here and there, spreading their long arms onto grasses! These grasses were not growing in a prairie but beneath the oaks. As Packard got closer he then found yellow lady's slippers, prairie white-fringed orchid, purple milkweed, and other plants that would not be found in a dense woods.
What the Chicago region director for the National Audubon Society discovered was a remnant of one of the most globally imperiled ecosystems - the Midwestern oak savanna. This one was a black soil savanna, so named for its rich, fertile soil. "There was a misconception that savanna is merely a transition between forest and prairie," says Packard. "When we looked harder, we found a lot of plants unlikely to be in a dark forest or a prairie, plants like yellow gerardia and false foxglove, which need oaks for their survival. You'll never find these in a prairie or deep woods."
Since that miraculous day at least 10 years ago, Packard has embarked on a crusade to save and restore these oak savannas. He is joined by others across the country who are working in their neck of the woods to help reclaim a rapidly declining ecosystem that points to the very roots of human beginning - the savanna.
Beauty and Wonder
The Midwestern oak savanna is one of seven types of savannas in North America including mesquite, southwestern oak, California oak, juniper, ponderosa pine, and longleaf pine. Some are more endangered than others. But what they all have in common are trees, grasses, and the need for fire to sustain them.
"All savannas (in North America) are fire-dependent," says Packard, co-editor of The Tallgrass Restoration Handbook. "They become dense stands of invasive trees and shrubs in the absence of fire. Essentially none of the original plants or animals can live or reproduce in that dense shade."
So many reasons exist as to why the savannas should be saved - within them may lie the undiscovered cure for a particular cancer, says Guy McPherson, author of Ecology and Management of North American Savannas. If humans lose the savannas before they understand and explore the plants and animals that live within these ecosystems, he says, "We will lose all hope that we'd ever find out what we've lost." And, McPherson hastens to add, we would lose "astonishing beauty and wonder."
Savannas occur on one-third of the world's land surface, and today some 50 million hectares or 123.5 million acres of savanna, from pristine to degraded, grow in North America. That's just a mere fraction of what was once here, says McPherson.
The term savanna comes from an extinct group of Arawak Indians who lived in the Greater Antilles. The word meant treeless plain. "But today savanna means grasslands with scattered woody plants as the overstory," says McPherson, professor of natural resources and ecology and evolutionary biology at the University of Arizona in Tucson.
"Generally, it's more than 1 percent and less than 30 percent of these overstory trees," says McPherson, "but that's debatable." The greatest threat to these ecosystems is urban development and agricultural practices, which includes raising cattle, logging trees, and growing food, says McPherson. Fires set by lightning and indigenous cultures encouraged savannas to thrive by helping maintain the grasslands, keeping shrubs at bay, and helping dominant savanna trees to regenerate. However, the suppression of fire as well as intensive overgrazing and other practices are causing many plant and insect species in savannas to disappear faster than they can even be discovered.
Only the beginning
Restoration of savannas is young. It's only been a few decades in which land managers, scientists, and others began recognizing the Midwestern oak savanna and the longleaf pine savanna, among other types of savanna. "Each of these savanna types is truly distinct," McPherson says. "There's no silver bullet to save all of them. You have to go to each site and ask what did it look like historically."
Mesquite and southwestern oak savannas are probably faring the best of the seven different types of savannas, says McPherson. The 20-foot-tall mesquite trees have little commercial value and the grasses growing there seem to be somewhat resilient to livestock grazing. The southwestern oak savanna, found mostly in Arizona, New Mexico, and Mexico and dominated by Emory oak (Quercus emoryi), is less impacted than other types of savannas because the soils beneath it are not as good for growing (for example, Midwestern savannas and prairies have much more fertile soil).
Some of these savannas do need restoration. For example, The Nature Conservancy owns the Mule Shoe Preserve in Arizona, which contains juniper as well as mesquite savannas. This region has been heavily grazed by cattle. About 20 years ago, The Nature Conservancy purchased the grazing permit from this area and began restoration, removing the cattle and allowing natural fires to occur as well as beginning a prescribed burning regimen. "It's taken 20 years and they are slowly making a dent," says McPherson. In some parts of the reserve, he says, "You can walk through the landscape and get lost in it. It's dead quiet. You can walk among blue grama grasses and black grama grasses, and especially after a wet winter, colorful poppies and lupines blooming." Under disturbance this savanna community often changes to a juniper-pinyon pine woodland and eventually a closed canopy forest.
Ponderosa, longleaf, and Midwestern oak savannas require even more attention since so much historic acreage of these ecosystems has been lost. For example, perhaps only 10 percent of the historical ponderosa pine (Pinus ponderosa) savanna is left, says McPherson.