Wetland Smörgåsbord

What a vista! Timber in the distance, emergent plants (“reeds”) on the water’s edge, a Muskrat (Ondatra zibethicus) mound, and plenty of waterfowl—how many species can you find?

Big Marsh in Butler County is aptly named: it is indeed large. This site is an Iowa DNR holding, and in total the property contains 6700 acres (2700 hectares) with 25% being covered in wetland, so perhaps 1700 ac (700 ha) as wetland. Surely, one of the biggest wetlands in the State! It has been pieced together over decades, with significant changes in attitude of the landowners over this time. The neighbors seem to see the project differently now, in part due to a growing realization that the Cedar River presents an ever-increasing flood threat to adjacent low lands. A recent “growth spurt” with sizable land acquisition has therefore presented challenges for the conservation professionals involved. You can read more about the history and management of the site at the DNR web page.

In any case, with all that space, you’d expect a variety of habitats and landscape features…and you would be correct! The property is associated with the West Fork of the Cedar River, and I saw plenty of floodplain habitat. Some of the low areas (lowest or closest to streams) were floodplain forest, and other areas were recently farmed—with a few still farmed (crops grown in so-called food plots for wildlife). I found ponds of various areas and depths, prairies and old fields, and of course, marsh.

The most obvious feature I noticed on my recent visit was waterfowl, and lots of it. A large area of open water near the east end of the site (running parallel to State Highway 14) is formed by a sizable dam, presumably creating permanent deep(ish) open water. A boat ramp off the parking area gives easy access, and videos on-line show the site being explored by canoeists. They’re likely to get closer to the birds than I could, although I still saw many, and not just in the “lake,” but in the outflow swale, nearby ponds, and even roadside ditches. I was delighted to watch the coots and ducks churn the water as they took flight and landed again.

In addition to a home for all the wildlife, this site serves important other functions. It ameliorates flooding in downstream areas, something we should all keep in mind in Iowa and elsewhere. I’ve written about it already, for example at sites such as Maskunky Marsh in Mahaska County, or Mount Sterling Marsh in Van Buren County. And let’s keep in mind, Big Marsh provides recreation opportunities: the canoeists mentioned previously, birders, hunters, and others. During my visit I watched a man exercising his bird dog, practicing the techniques they’ll use during hunting. And just off-site is a bird dog kennel—this must be a popular spot.

So, we have a smorgasbord of functions and activities laid out before us. Big Marsh is so very large, both human and other organisms are likely to find something worth a visit, any time of year, year after year. Frankly, this is not what I’m used to! Most of Iowa’s wetlands are small and isolated. I wander Iowa looking at tiny, sometimes quite ephemeral systems. Such wetlands are important, but it’s fun to think about what a super-sized system like this one does ecologically. Is bigger, better? What are the ecological functions of this wetland as a 1000-area-piece, as opposed to creating 1000 individual 1-unit-area smaller pieces, spread around Iowa (something like 10 per County)? Would the total waterfowl production, or turtle population, or flood prevention, or Nitrogen removal, or any other “ecosystem service” of interest be diminished by splitting up a wetland and spreading it around? Is there a synergism in a large system, with it doing something that the same wetland area could not, when split up into small pieces? This is a basic question in landscape ecology (not just wetlands ecology), and we should consider it further in future posts. Let’s “bank” that for now. In the meantime, let me take a lesson from these old Coots, and take off! See you next week…

American Coots (Fulica americana) running on water, preparing for takeoff…

Author: Paul Weihe

Associate Professor of Biology at Central College, traditional author (Textbook of Limnology, Cole & Weihe, 5th ed.; Waveland Press), and now...blogger!

One thought on “Wetland Smörgåsbord”

  1. Very interesting questions. My amateur assumption would be that these larger wetland complexes can provide ecological functions and services for both humans and wildlife that little isolated wetlands cannot.

    As the owner of a very small wetland complex, I am happy and grateful that little isolated wetlands can do as much good as they do, which is a lot. But it’s clear just from your post and photos that a 7,000-acre wetland complex can provide many more big diverse benefits than little wetlands, including sizeable havens for diving ducks.

    I think the questions in this post also bring up the question of wetland wishful thinking. It would be very handy for us Iowans if the small deep isolated CREP wetlands that can lower farm nitrate pollution could provide all the other functions that wetlands can provide. But the ecological evidence indicates otherwise.

    One large contiguous marsh complex can provide ecological services for wildlife and humans that two dozen small isolated CREP wetlands cannot, even if the latter contain the same total amount of surface water. And the very shallow temporary sheetwater wetlands that appear on Iowa cropland every spring are vital for migrating shorebirds, which are declining and need all the help they can get. Those shorebirds cannot just use small deep CREP wetlands instead.

    Any drainage-improvement proposal that would essentially replace shallow temporary sheetwater in Iowa with deep CREP wetlands, and such proposals are being made, should be considered with great caution. Shorebirds certainly don’t have the political clout of nitrate concerns in this state. But shorebirds are amazing beautiful animals with incredibly long migrations, and they are an important part of the heritage of humankind and our planet. They matter.

    Liked by 1 person

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