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After floods, Overton Bottoms went from crop fields to wildlife habitat

Wednesday, August 7, 2013 | 6:00 a.m. CDT; updated 9:28 a.m. CDT, Thursday, August 8, 2013
The U.S. Fish and Wildlife Refuge established the Big Muddy National River Refuge in the Missouri River flood plains between St. Louis and Kansas City after the flood of 1993. In the years after refuge’s creation, the Fish and Wildlife Service studied the natural processes at work.

COLUMBIA — In the Overton Bottoms, a parking lot serves as a starting point for visitors to the Big Muddy Fish and Wildlife Refuge that covers the Missouri River bottoms adjacent to Interstate 70.

The parking lot is where a farm once stood. In Google Earth, sliding the timescale tab back to the earliest aerial photo available, April 1, 1995, shows the life someone once made here: a house, a barn, a couple sheds, a couple grain bins and a couple pecan trees.

Today, the pecans are all that remain. U.S. Fish and Wildlife Service biologist Wedge Watkins points them out. He said people often come here to gather pecans in the fall.

"That’s a significant use in a good pecan year," Watkins said. Mushroom foragers, deer hunters and anglers are other frequent users, he said.

Over the past 20 years, tens of thousands of acres of Missouri River bottomlands have made the same metamorphosis as Overton Bottoms. Where corn and soybeans once grew, different kinds of plant communities have sprouted after the floods of 1993 and 1995.

The floods set in motion a series of changes that transformed these crop fields into public conservation lands. The first of the changes were human — the transfer of property to state and federal government agencies from willing sellers and the decisions those agencies made about how to use the land.

"It was a time to kind of consider what we really want to do with all our flood plains," Big Muddy National Wildlife Refuge manager Tom Bell said of the 1993 flood and the years after. "It was a time of change."

Since then, mechanical processes of flood and drought, with the help of tenacious organisms — plants, insects, birds and mammals — have done more to alter the appearance of these conservation lands than any human actions.

Birth of the Big Muddy

During the record flooding in 1993, Bell was refuge manager at Port Louisa National Wildlife Refuge on the Mississippi River near Wapello, Iowa. During the flood, he flew over several major Midwestern rivers in an airplane and saw the extent of the flooding.

The confluence of the Missouri River near St. Louis "looked like an ocean," he said. "The Illinois River, the Missouri River and the Mississippi River all came together and just spread out over everything. It was literally bluff-to-bluff water."

The 1993 flood was the largest and most significant in American history, according to presentation by NOAA hydrologist Lee Larson at the 1996 conference of the International Association of Hydrological Sciences.

Floodwaters completely inundated 75 towns, spilled over more than 1,000 levees and covered more than 15 million acres of farmland, Larson stated.

Areas prone to damage, such as bottomlands with levees close to the river or surrounded by sharp river bends, received greater damage than in previous floods, Bell said.

"Big piles of sand, great big scour holes, things that would be very expensive to repair but weren’t necessarily all bad for wildlife, either," he said.

The damage provided the political will and opportunity to start establishing more wildlife refuges in the floodplains, Bell said.

"There was a move at that time to establish wildlife refuges where there was appropriate habitat, where there were willing sellers," Bell said.

The Big Muddy National Wildlife Refuge, a string of 15 refuge units in the Missouri River flood plain between Kansas City and St. Louis, grew out of this movement. The U.S. Fish and Wildlife Service established the refuge in 1994 and made its first land purchase in 1995. Today, the service owns or manages 16,775  acres along the Missouri River. The Army Corps of Engineers will transfer another 853 acres to the service within the next month, Bell said.

The idea for this refuge had been around for some time, Bell said.

"The Big Muddy National Wildlife Refuge didn’t just spring out of the '93 flood," he said. "There had been talk of a refuge along the Missouri River going back probably into the early '60s."

The Missouri Department of Conservation also began purchasing more land along the river. Conservation department spokesman Jim Low said the department now owns or manages more than 23,000 acres in the flood plain it did not have access to before the 1993 flood.

Other government entities that own conservation land in the flood plain include the Army Corps of Engineers, with about 16,000 acres, and the Missouri Department of Natural Resources, with about 2,000.

Getting the land was the first step in creating the refuges and conservation areas Missouri has today. Natural processes of ecological succession, migration and colonization then began to work on the land.

Dog-hair stands and weedy fields

Bell became manager of the Big Muddy in 1999, four years after the service made its first land purchase. He described how many of the old farm fields had changed since flooding in 1993 and again in 1995.

"A lot of the places that we had acquired, the state had acquired or the Corps of Engineers had acquired had grown up in what we commonly refer to as dog-hair stands of willow and cottonwood," Bell said.

A few of these stands still remain in the Overton Bottoms. Watkins pointed them out during a visit there on a muggy July morning. He said thousands of acres of the little trees had sprouted three to five years after the floods.

The trees are green and flexible, about a finger’s width in diameter and densely packed. They stand close together, criss-crossing each other, preventing easy passage but allowing green-tinted light to filter through.

Other areas were more open with weedy, herbaceous vegetation. Plants such as smartweed, milkweed and Johnson grass took hold there. These areas are also still present in Overton Bottoms. Interstate 70 bisects one of these open, weedy areas after crossing the Missouri River near Rocheport.

The plants grow knee- to head-high and tug at the legs of a visitor. Even though the areas might look similar to how they looked immediately after the flood to the untrained eye, Watkins said the plant communities differ year to year.

Bell and Watkins have a hypothesis for why some areas grew into dog-hair stands and others became weedy fields. It had to do with the timing of the floodwaters, they said.

When the floodwaters receded, fluffy, white willow and cottonwood seeds floated on the wind from the older trees along the river’s edges. Where they landed on dry ground, they sprouted and grew into the thick dog-hair stands.

Sometimes the seeds landed on areas where standing water remained. By the time this water evaporated, their seeding phase had ended, leaving the ground open for colonization by herbaceous plants.

To put it simply, Missouri River flood plain land circa 2000 fell into three categories: dog-hair stands, weedy fields and old trees. Many of the old trees lining the river existed before the floods.

Dog-hair stand cottonwoods grew fast and thinned themselves, Bell said. The taller ones would cast shade on the smaller ones, which would die. Tree diversity also changed. Bell said as the stands thinned, he started seeing more diversity in tree species: white mulberry, maples, sycamores, pecans, occasional oaks and even some cedars.

In the years after refuge’s creation, the Fish and Wildlife Service studied the natural processes at work. They also added more land; hired staff; improved roads, boundary signs, parking lots and other infrastructure; and kept out invasive species.

As the service’s biologists watched the refuge mature, they learned more about the animals using the new habitat on the flood plains.

Food webs grow

Bell said the animals that most surprised him in their use of the refuge were migratory birds, which started showing up in the stands of cottonwood and willows.

"I was weaned on the need for old-growth timber for a lot of migratory birds because it’s in short supply," Bell said.

Around 2000, Bell recruited a team of skilled birders to conduct a three-year inventory of bird species on the refuge. He found that perching birds, or songbirds, took to the dog-hair tree stands with enthusiasm.

"Those trees start to bud out in the spring and you get these little tiny leaves. You get a blossom of caterpillars, of larval insects of all kinds," he said. "There’s lots of them and those birds key in on that."

Turkeys arrived within the first few years after the refuge’s creation, and they also took to the dog-hair stands.

"Surprisingly, even when the forest was really thick, we got turkeys right away, too," he said.

Other birds started growing in population as well, he said, including wading birds, such as herons, and raptors, such as red-tailed hawks.

Amphibian surveys revealed growing populations of toad, frogs and salamanders. Mammals also started showing up.

"We knew we’d get deer. We got deer right away," Bell said.

Around 2005, Bell said he noticed an explosion of small rodents, including a whole lot of hispid cotton rats.

"That was the year we started noticing lots and lots of bobcats," he said. "So much food that bobcat numbers just really jumped up."

Last year, he caught a glimpse of a badger on a trail cam at Overton Bottoms. He’s still waiting to find out if apex predators, bears and mountain lions, start to move in.

Overall, Bell said he is pleased with how former fields have become wildlife havens.

"It’s diversifying. It’s kind of healing itself, in terms of how quickly you get that stuff back," he said. "That’s gratifying."

Letting nature take its course

These days, Fish and Wildlife is working closely with the Corps to create shallow-water habitat to help restore three endangered species on the river: the pallid sturgeon, piping plover and the interior least tern.

They still conduct inventory and monitoring studies. On the drive out to Overton Bottoms, Watkins explained that they were in the middle of a study on pollinators, especially bees. He said this summer they had found some species of bees that are new to Missouri.

"That’s not because we’re great scientists; it’s because bees are poorly studied," Watkins said.

Their method involves setting out brightly colored plastic cups filled with soapy water. Attracted by the bright colors, the bees move in for a landing and fall in. The soap eliminates the water’s surface tension. For a few species, they have to use a net, he said.

Bell said service biologists spend about half their time on the refuge killing invasive species, such as Johnson grass, garlic mustard, Japanese hops, bush honeysuckle and kudzu.

"In some places where we eliminate stuff like that, we don’t have to do much," Bell said. "We’ll pull garlic mustard under the canopy. We don’t have to go back and plant something. We let nature take its course."

Prairie cordgrass is one native species being planted in the refuge. A few hundred feet from the parking lot with the pecan trees, Watkins pointed out some stands of prairie cordgrass reaching head height.

"Any of this restoration work, especially in wet environments, you get pretty quick results," Watkins said.

Overton Bottoms floods frequently. Watkins pulled aside some of the grass and weeds blanketing the ground, revealing about six inches of cracked silt that had accumulated during the floods last spring.

Watkins described floods as a curse and a blessing. The disturbance resets the system, leaving opportunities for new plant communities to form. But they also leave the ground open to colonization by invasive species.

In late August, the Fish and Wildlife Service plans to release a final draft of its 15-year management plan to the public, Bell said. The plan involves allowing natural succession to occur without letting invasive plants take control.

After decades of agriculture, nature has fully reclaimed Overton Bottoms, along with tens of thousands of acres of other conservation land on the Missouri River. The floods and the cycles of rebirth that come after demonstrate how the river and its flood plains change constantly. With a little human guidance, these lands can come to resemble wilderness again.

"We want to have to do the least amount of manipulation as possible and still restore natural communities," Watkins said.

Supervising editor is John Schneller.


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