Restoring Fields to “Old-Growth Grassland” May Bolster Climate Resiliency

A scattering of unplowed gems tucked between farm fields, suburban sprawl and brushy woodland: that is what remains of the original prairies of Illinois, less than .01 percent of what was once an unbroken flowering landscape. Today, these remnant prairies are some of the most biodiverse places in the state, harboring Illinois threatened species like hoary puccoon (Lithospermum canescens) and the elusive grasshopper sparrow (Ammodramus savannarum). While restoration ecologists have been working for decades to expand prairie habitat by spreading seed, conducting prescribed burns, and battling invasive plants, it has long been thought that once lost, the biodiversity of a remnant prairie is nearly impossible to reclaim. In the face of a changing climate, ecologists are scrambling to find ways to reconstruct these remnants — often called “old-growth grasslands” — before biodiversity loss accelerates.

From Soybeans to Prairie in Six Years

At Dixon Waterfowl Refuge, the task is especially urgent, as endangered species, such as the upland sandpiper, depend on high quality prairie habitat there. Sandpipers and other grassland denizens have cause for celebration though, as just last month, researchers working at the waterfowl refuge laid out a blueprint for the complete reconstruction of a remnant prairie. Working with the nonprofit group The Wetlands Initiative, ecologists Bill Sluis, Katherine Kucera and Gary Sullivan turned an herbicide-laden soybean field into a prairie in only 6 years. Running against the prevailing wisdom of what is possible in a restoration, their test plots are home to 82 different species of plants — the same level of biodiversity as nearby remnant prairies. Seed mixes commonly used on restoration sites elsewhere are composed of just 30 species and often lean heavily on dominant grasses, such as big bluestem.

Finding seed for 82 different plant species was no walk in the park, and the ecologists often found themselves disappointed when some species refused to sprout during the first few years of the project.

“There were some seeds I had to go collect by hand,” recalled Bill Sluis, the first author of the case study. “Some I had to propagate first, and that can take a couple years. “If it didn’t come up from seed, then we used plugs.”

Perseverance got them to their 82-plant target. Old-growth grasslands have existed for thousands of years, maintained through frequent fires by Indigenous tribes such as the Illini. Over the ages, different conditions within the prairie favored certain plants, with some sensitive plants needing a very specific amount of moisture to germinate. That variation in plant preferences is the reason that restoring sites to old-growth levels could be a key bastion of biodiversity as the climate heads toward uncharted territory.

“You’ve got high spots, you’ve got depressions, you’ve got slough areas that have water that collects, areas where soil is sandy, where it is clingy,” explained Gary Sullivan, a co-author on the case study who serves as the Restoration Program Director for the Wetlands Initiative. “Across the whole landscape you’ve got this mosaic of different conditions, and species that are going to be able to respond to changes are found in these different micro-habitats.”

As the climate warms, researchers expect droughts, floods and other extreme weather events to become more common in the Midwest. But for a prairie with 82 species of plants, a drought is no big deal. Sullivan revealed that plants — while not as mobile as animals — can move across the landscape as conditions change. With 82 species flinging seeds across the prairie, thousands of those seeds will lie dormant, waiting for the perfect conditions in their little patch of soil. Plants that prefer wet feet, like swamp milkweed or marsh marigold, will sprout closer to water sources in drought conditions, while further up a hill, the dusty seeds of little bluestem quickly colonize arid real estate.

Sullivan argues that high biodiversity and long-term thinking will help prairie restoration sites survive a changing climate: “If you’ve planned not just to get the restoration done, but to manage it going forward…then those areas are going to be more resilient to whatever kinds of disturbances or impacts they’re going to have, which climate is going to be a big one.”

At Dixon Waterfowl Refuge, where the research took place, wetlands are the lynchpin of a successful prairie ecosystem. Healthy wetlands provide valuable habitat for migrating birds, and they also act as a buffer to extreme climate events, absorbing and storing water in flood years, and sustaining moisture through long periods of drought. The Wetlands Initiative manages a total of 3,000 acres at the site, which was named in 2012 as a Wetland of International Importance. While only a slim fraction of the 3,000 acres of lakeshore, savanna and prairie at the site have been restored to old-growth standards of biodiversity, rare plants are already sneaking out beyond the borders of the research test plots.

Some Plants are a Challenge to Introduce

Most aggressive are clonal plants that, once established, can reproduce asexually, sending out shoots through the soil. These plants include prairie standby species, such as Indian grass, but also plants that are thought to be partially parasitic, such as wood betony (Pedicularis canadensisi), and arguably one of the best-named plants in the world, bastard toadflax (Comandra umbellate).

“Making sure you have a lot of these plants is important in terms of how the community develops, as these hemi-parasites have a positive impact on diversity by suppressing the more aggressive plants,” Sullivan said.

Unfortunately, as key as these hemi-parasites may be for the prairie ecosystem, their seed can be prohibitively expensive, with bastard toadflax all but impossible to find at commercial nurseries. Some flowers, such as hoary puccoon, make collecting seeds on-site a challenge: the seeds of hoary puccoon launch from the stem of the plant at unpredictable times. Sluis, Kucera and Sullivan resorted to transplanting a few puccoon plants into their restored plots, a strategy not replicable by many private landowners, or those restoring sites on a much larger scale. It’s one thing to prove that a landscape can be fully restored. It’s another task entirely to dedicate the time and money to accomplish it.

For the Wetlands Initiative researchers, the point of their project was not to shame other restoration ecologists into shelling out thousands of dollars on rare plants. Instead, they hope to show that recreating an ecosystem that developed over thousands of years is possible, and that it can be done in a few years. They are hopeful that as the field of restoration ecology continues to evolve, the full range of native species will eventually become accessible to the backyard restorationist.

Faced with more and more erratic climate patterns, 82 plant species might just be the magic number to ensure that the Prairie State continues to bloom.

Reference

Sluis, William & Kucera, Katherine & Sullivan, Gary. (2025). Establishing the plant component of a tallgrass prairie restoration using a remnant reference ecosystem model: A case study. Ecological Solutions and Evidence. 6. 10.1002/2688-8319.70014.