A Place Apart
Cedar Creek Natural History Area
For more than 60 years, this ecological research site has been yielding insights into how the natural world works.
By Lansing Shepard
Cedar Bog Lake lies still under the late afternoon sun, a gray sheet of water rimmed by a skirt of wheat-colored reed-grass and cattails. Backing them are tamaracks just coming into leaf, a gossamer wall of the palest green through which can be seen the dark green of the cedar forest that encircles the lake. And on the horizon, massive white pines rise heaven-ward, their splayed crowns silhouetted against the sky. From somewhere overhead comes the quacking of a mallard.
For a moment, a visitor could almost believe this was someplace in the wilds of the Boundary Waters. But only for a moment, because a breeze carries the muffled growl of an 18-wheeler, and you remember you're only a few miles from Highway 65 and a mere 35 miles from downtown Minneapolis.
What is not illusion, however, is the importance of this little lake and its environs-9 square miles of forested wetlands, oak savanna, abandoned farm fields, and woodlots known as Cedar Creek Natural History Area. At this world-famous research station owned and operated by the University of Minnesota, ecologists have been studying how ecosystems work for more than 60 years. Their findings have deepened our understanding of biological diversity, climate change, and other worldwide environmental issues-with practical applications from the arctic tundra to Minnesota back yards.
Cedar Creek is a premier research site because it is located at the junction of three North American ecological landscapes. Within its boundaries, the northern evergreen forest, eastern broadleaf forest, and western tallgrass prairie meet.
Here one can see stands of hardwoods that predate European settlement, a white-cedar swamp and black-spruce peatlands that could have been plucked from northeastern Minnesota, and prairie openings and oak savanna that look much as they did 300 years ago.
"If you were trying to design an ecological laboratory, a place laid bare by glaciers, with uniform soil-in this case, sand-and destined over 10,000 years of ecological succession to contain these three ecosystems in a triple meeting place, Cedar Creek is what you'd come up with," says Clarence Lehman, Cedar Creek's associate director. "It makes for a place where you can do a lot of experimenting."
The possibilities of the place were evident as early as 1930, when William Cooper first spied it from the air. A professor of plant ecology at the university, Cooper was snapping pictures of farmland when he spotted what appeared to be a northern Minnesota white-cedar swamp amid oak woods and savanna. He knew instantly he was looking at something special.
"He saw this incredible diversity from the air all in one spot, and realized it was close to the university and what a resource it was," says David Tilman, ecology professor and director of Cedar Creek.
Subsequent investigations on the ground proved Cooper right. The Minnesota Academy of Science, which he helped incorporate, purchased Cedar Bog Lake and surrounding land. The academy then deeded the property to the university. University land purchases during the next 30 years rounded out the rest of the property.
Ecology on the Map
Modern ecology was essentially born at Cedar Creek Natural History Area in 1942. Until then, the study of organisms' relationships with their environment was mostly a descriptive exercise, looking at individual animal and plant species: what lived where, who was eating whom, who appeared to be competing with whom.
Enter Raymond Lindeman, an intense, young graduate student. Lindeman wondered if ecologists could study ecosystems in their entirety. Beginning in 1936, he decided to zero in on Cedar Bog Lake's food web and how nutrients and energy flowed through it.
For more than five years, Lindeman and his wife, Eleanor, collected samples of water, aquatic plants, phytoplankton, zooplankton, worms, insect larvae, crustaceans, and fish. He categorized the organisms based on how they obtained, used, and passed on nutrients and energy-the currency of ecosystems. He observed how processes varied from one part of the lake to another and over time. Then he produced a portrait of Cedar Bog Lake rendered entirely in terms of how energy moved through its constituent parts.
"He invented what we think of as ecosystem ecology," Tilman says. "He measured the efficiency of energy transfer between one trophic level to the next, and suggested that this was how other ecosystems functioned."
Lindeman's study not only set a new direction for the field of ecology as a whole, but it also launched a wave of investigations into nutrient and energy flows in other Cedar Creek ecosystems. The aim of this early work was to get a handle on just how much biomass (plant material) different habitats were producing across a given area and over a given amount of time. Looking at cornfields, old farm fields, cattail marshes, and other habitats, researchers collected the basic data that became the foundation for today's more complex investigations of how different ecological systems function.
In 1964 university scientists, spurred by recent investigations that had revealed the importance of fire to the maintenance of pine forests in northern Minnesota, decided to investigate the influence of fire on oak savanna. A once-widespread ecosystem intermediate between prairie and forest, oak savanna was known to have been historically maintained by fire.
Researchers began by setting carefully controlled fires on prescribed tracts. They documented how plants and animals recovered, how nutrients within the system responded, and how biological diversity was affected. Now one of the longest--running controlled-burn experiments in the nation, the ongoing project has yielded information vital to restoration and management of remnant prairies throughout the United States.
On the Right Track
In 1957, when the Soviet Union sent Sputnik II into orbit carrying a dog monitored by a radio transmitter, a team of Cedar Creek researchers and university engineers recognized the technology could be used to track wildlife. The team designed collars and built receiving and data-storage equipment.
In 1958 the researchers began placing radio transmitters on rabbits, raccoons, squirrels, and other wildlife in the natural history area. New data about how wild animals were using habitat came streaming in, once again putting Cedar Creek in the headlines. From the late 1950s to the early '70s, Cedar Creek was world headquarters for radio telemetry use in wildlife research.
"Cedar Creek became the place to do radio telemetry," Tilman says. "Researchers from all over the world would come to Cedar Creek, develop the collars, and go off and study their animals. They wound up putting them on polar bears, fish, sea otters, and all kinds of animals."
The world spotlight again turned to Cedar Creek when the National Science Foundation began searching for sites where single ecosystems could be studied at many levels and over many decades. When the foundation launched its Long Term Ecological Research Network in 1980, Cedar Creek was ready.
"We saw this as an opportunity," says John Tester, retired ecology professor, who was then Cedar Creek's director. "NSF was interested in sites that had good research already going on. And here we had this big block of protected land with many kinds of habitats. We had already collected a lot of background information on it from all the animal work we'd done, so we had something substantial to build on. We said, 'What the heck, let's try.' "
In 1982 Cedar Creek joined just 11 other sites in the network. Since then, the network has been expanded to include more than two dozen sites across the globe.
Today, the NSF program at Cedar Creek is looking into some of the most profound impacts humans are having on the planet. Tilman ticks them off like the horsemen of the apocalypse: loss of biological diversity, changes in climate, spread of invasive species, changes in nutrient balances.
"How are all these things interacting?" he asks. "How are they affecting the way ecosystems function?"
To find out, researchers have designed their experiments to simulate some of those impacts. Researchers apply particular conditions to selected components of Cedar Creek's ecosystems, then they watch how species respond. Discoveries include solid evidence that the greater the diversity of plants in an ecosystem, the more productive and resilient that ecosystem will be. Greater biological diversity increases an ecosystem's ability to absorb pollutants, withstand the ravages of drought and disease, and capture carbon dioxide from the air. The latter is of particular importance because the buildup of carbon dioxide in the atmosphere is driving global climate change.
End of Natural History?
But perhaps Cedar Creek Natural History Area's most immediate concern is its own survival. The property is fast becoming an island in a sea of new housing.
Houses too close to the property's borders make it difficult to conduct the controlled burns needed to maintain its fire--dependent habitat. Houses, roads, streets, and lawn chemicals threaten to alter the quality and quantity of ground and surface water. In addition, development introduces pets and exotic plants that can compromise the integrity of native plant and animal communities. Damage from snowmobiles and all-terrain vehicles has already been documented in the preserve.
Cedar Creek Natural History Area is now working with Anoka and Isanti county parks departments as they craft open-space plans. Staff members have met with neighboring landowners and begun offering public tours and special events to show what is being done at Cedar Creek.
Hannah Texler, Department of Natural Resources regional plant ecologist, has been working with Lehman on a public education program. "We want to educate local landowners about what's on the university's property and the work that goes on here, as well as what good stewardship is," says Texler.
Cedar Creek could gain some protection if it had a buffer zone of open spaces around the property. But that would need the cooperation of local landowners and governments, as well as the university. Such a plan would likely require the use of voluntary conservation easements, zoning changes, and other strategies.
"Development is inevitable," says Texler. "But we can help to ensure that it's planned with sensitivity to this wonderful place."
Much will be riding on what actions will be taken over the next few years. That's why Cedar Creek has launched a campaign to raise more than $4 million for improvements at the natural history area. Tilman is leading the effort to secure individual gifts, grants, and government funds. Plans include restoring 950 acres of prairie and savanna, creating interpretive trails for hiking and cross-country skiing, and building a science and interpretive center. As part of outreach efforts, the center will showcase cost-effective, energy-efficient technologies.
Protection of this research area is -critical: Hidden somewhere in the forests, bogs, and prairies of Cedar Creek may be the insights humans will need to successfully negotiate environmental perils of the 21st century.
Editor's note: Cedar Creek is open for monthly public tours. Tours are currently scheduled for Aug. 13, Sept. 10, and Oct. 8. Call 763-434-5131 or see Cedar Creek Natural History Area.
Lansing Shepard, a freelance writer from Minneapolis, specializes in natural history, environmental affairs, and conservation biology.