Standing and surveying grassland in central Minnesota, I was picturing pioneers rolling by in their covered wagons making tracks through the expanses of prairie. But, Dr. Johannes Knops, an ecologist from the University of Nebraska, quickly drew a big red X through my image by telling me that this shag carpet of green and brown was not real prairie. “It’s way too uniform,” he continued, adding that the uniformity was in large part due to the nitrogen deposition on the soil as well as exotic species that had been introduced by human activity – from planting lawns to unwittingly carrying seeds on pant-legs. Real prairie is an eclectic patchwork of different plant communities, and it’s a sight you rarely see anymore. “Prairie is probably the most endangered ecosystem in the United States,” Dr. Knops told me, even more endangered than wetlands.
According to the DNR, 18 million acres of prairie covered Minnesota prior to European settlement, and this prairie belonged to the largest ecosystem in North America (stretching from Canada down to Mexico and from Indiana out to the Rockies). Now, less than 1% of Minnesota’s native prairie remains. However, there is a new piece growing, stealthily but surely, at the Science Museum of Minnesota in their Big Backyard. Though it is overshadowed right now by the river mini golf and will take at least another summer to reach its full height, the Science Museum’s new prairie exhibit has the potential to be, shall we say, a-maze-ing.
Pat Hamilton, the director of environmental science at the museum, told me in an interview that the idea for a prairie maze first came from Dr. David Tilman, an ecologist at the University of Minnesota. Dr. Tilman and his family had recently traveled to England where one of their favorite activities became winding their ways through complicated mazes made of shrubs and bushes. Why not take that principle of problem solving and fun and use it to communicate information about the Minnesota prairie to museum-goers at the Science Museum? The project of a “science park”, which became the Big Backyard, at the museum was already in the works, and what could be a better location for a prairie maze?

Some Minnesota grassland – this piece used to be an agricultural field.	The new prairie maze growing at the Science Museum of Minnesota

Mr. Hamilton explained to me that through its composition and informational graphic panels the maze will convey several stories. There will certainly be the story of the loss of native prairie and what a real prairie is. Then, there will be stories drawing from the research of several University of Minnesota professors including Dr. Tilman, Dr. Steve Polasky, and Dr. Donald Wyse. These will be stories about the importance of biodiversity for ecosystem productivity and the potential of converting biomass into biomass energy.
But, what does all that mean?
Let’s start with biodiversity: biodiversity is most simply a measure of how many different species live together in an ecosystem and how many different jobs they perform that help keep their ecosystem running. Because of the way we humans are changing the environment, many species are being lost and ecosystems are becoming less diverse. We rely on ecosystems to provide us with a great many services, from preventing erosion to absorbing greenhouse gases to decomposing waste, so what the results of these losses might be has become a critical question. Therefore, many ecologists have devoted themselves to studying biodiversity. Some of the most important biodiversity experiments in the world have been done, and continue to be done, in Minnesota at Cedar Creek Natural History Area.
Results from experiments at Cedar Creek along with results from experiments performed at several other research sites have drawn a connection between how diverse an ecosystem is and how productive it is. The studies have suggested that when an ecosystem contains more diversity, whether this is because it has a larger number of species or because the species there perform a wider variety of disparate jobs, then that ecosystem may be healthier, be better able to recover from disturbances (like fire or drought), be more resistant to invading exotic species, and be more reliable in the services with which it provides us.
Now, what about biomass energy? Perhaps you have heard about the use of corn to make ethanol for fueling cars. This is an example of biomass energy. It’s the use of biological materials - mostly leftovers from crops like the stalks, leaves, husks, and straw or leftovers from forest industry – to make energy including heat, steam, and electric power. There are two main methods for making biomass into energy. Either it can be broken down into sugars by heat and chemical enzymes and then processed (often fermented) to fuels and other products, or it can be heated with a limited amount of oxygen, which converts the biomass into gas or oil that can be burned. These two methods are called the sugar platform and the thermochemical platform respectively.
Using biomass energy is an exciting possibility for the future because it appears to be pretty sustainable. The Department of Energy is developing particular plants, fast growing (at least relatively) perennials like switchgrass, willows, and poplars, for use solely as energy crops. These crops require about one-tenth the amount of herbicides and pesticides required by agricultural crops. Plus, because they are perennials these plants can develop large root systems that can help improve soil quality and nutrient reserves as well as prevent erosion. Though burning biomass produces greenhouse gasses like burning coal does, the plants that make up the energy crops actually take in during their lifetimes the same amount of gas they release when they are burned (don’t forget that a plant needs carbon dioxide and nitrogen to photosynthesize). Other negatives dim the alluring green glow of biomass energy, the cost for example, but measures are being taken to reduce the negatives, and this is becoming a more and more viable form of energy. According to the U.S. Department of Energy, Energy Efficiency, and Renewable Energy, biomass currently supplies over 3% of America’s total energy consumption, which is a start, but there’s room to grow.

Harvesting switchgrass as an energy crop (photo by Warren Gretz, courtesy of NREL Clean Energy Basics webpage )	A biomass powerplant (photo courtesy of the U.S. Department of Energy & EREN)

Dr. Shawn Schottler, a researcher at the St. Croix Watershed, put together the seed mixes used for planting the prairie maze. In designing the mixes he drew from six different “planting themes” he said. One theme is aptly designated as “very tall,” those towering grasses that reach up over the average person’s head. The very tall parts will hopefully really make you feel like you are inside a maze and can’t see which direction you might next be heading. Other parts are planted with as much diversity as possible – the maze contains over 60 plant species total – to illustrate the relationship between diversity and productivity. This vibrant abundance will be contrasted by parts that have the structure of the plant communities currently planted by many government agencies in grassland areas. These plantings are very low in diversity and show, in Dr. Schottler’s words, “what a prairie is not.”

The diverse abundance of natural prairie (photo courtesy of Prairie Restoration, Inc.)

The planting theme of biomass energy consists of only switchgrass (Panicum virgatum), one of the government recommended energy crops. At the end of each growing season, this grass, along with the rest of the maze plants, will be clipped and then burned at a nearby power plant in St. Paul. This technique of co-firing is another possibility for using biomass energy. Burning between 5% and 15% biomass along with conventional coal is known to reduce carbon dioxide emissions, sulfur dioxide emissions, and possibly some nitrogen oxide emissions.
Another theme is designed to showcase some of the more rare and unusual native prairie plants. And, the final theme Dr. Schottler likes to call “the railroad special.” These parts are planted to look like the true, old prairie. In nature, pieces of real prairie can still sometimes be found on land remnants, often by railroad tracks. “That’s all that’s left,” Dr. Schottler sighed as he described it.
The prairie maze will be full of information for interpretation, and the maze structure should be perfect for highlighting the discrete types of plantings and themes that are there. It provides the opportunity to make the transitions - between diverse and simple, natural and unnatural - very stark and salient. It’s just up to the museum visitor to make it all the way through the maze to discover everything that is there. “Right now is just the basic infrastructure,” Mr. Hamilton reported. Right now the maze has several solutions, but the plan is to have gates that close off certain passages and make it possible to vary the solution, so it may be different from visit to visit.
The fact that the maze is composed of plants, living organisms with their own quirks and habits, presents some challenges for the exhibit that both Mr. Hamilton and Dr. Schottler said they recognized. Certain species may drop seeds and start to conquer areas where they weren’t originally planted, for example. And, because the maze has a uniform soil type, there will most likely be particular species that thrive on the soil while others don’t do as well. In a sense, the maze will, itself, be an experiment in biodiversity, prairie restoration, and renewable energy. “I think it’s going to be a very dynamic exhibit,” said Mr. Hamilton. “It’s going to be a very interesting challenge…not easy to predict. The composition of the maze will probably change over time.”

With the maintenance that it will likely require, Dr. Schottler thinks the maze “boils down to being a garden rather than a prairie.” But he believes that this is really quite all right. It will still be an extraordinarily valuable teaching tool, for thousands of people visit the Science Museum while almost nobody visits the remaining pieces of real prairie. They just drive by. Dr. Schottler figures that some people will find it easy to like the prairie maze and others won’t; they’ll just say it’s weeds. “Our job,” he said, “is to teach people that those weeds are special.”


These “weeds” are special.