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Banding Together for Waterfowl

Conservation: Renovating Greentree Reservoirs

Careful management is required to maintain the productivity of these classic waterfowl habitats
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By Jody Pagan

After graduating from college I spent nine months working on a wildlife habitat mapping project. At the completion of the project, I received a certificate of merit that included a quote from the great Aldo Leopold: "The key to intelligent tinkering is to keep all the parts." Leopold's words are especially relevant to those working in wetland restoration.

In the case of the Mississippi Alluvial Valley (MAV), a crucial wintering area for mallards and many other waterfowl species, we did not save all the parts. Of the 24 million acres of seasonally flooded bottomland hardwood forest that once existed across this region, less than 5 million acres remain. In eastern Arkansas alone, more than 72 percent of this important waterfowl habitat has been cleared and drained. 

Much of the remaining bottomland hardwood forest in the MAV is found in fragmented blocks. Many of these isolated tracts have been developed into "greentree reservoirs" for waterfowl hunting. A greentree reservoir is defined as a stand of bottomland hardwood forest that is equipped with a levee system, water-control structures, and in some cases wells and pumps. Managed on both public and private land, greentree reservoirs are flooded in late fall, when oaks and other trees are dormant, to provide crucial wintering habitat for waterfowl. Duck hunters from all over the world travel to Arkansas to hunt mallards in the flooded timber, something all waterfowlers should experience at least once.  

Pioneered during the 1930s, early management of greentree reservoirs was fairly simple. Managers would flood impoundments to full pool by opening day, and then drain the impoundments the day after the close of duck season. A standard practice was to start pumping on October 1 or earlier. In the MAV, October is the driest month of the year. While early flooding was not good for the trees, it did offer much-needed habitat for mallards and other dabbling ducks. During dry years, the hunting was phenomenal in these artificially flooded forests. Over time, however, the productivity of many greentree reservoirs declined as the long-term effects of early flooding took a toll on timber health and habitat quality. 

Of particular concern to managers is the health of red oaks, which can produce bumper crops of acorns that provide food for mallards and other dabbling ducks. For decades researchers struggled to determine how to keep red oaks alive in greentree reservoirs. Studies were conducted to better understand forest health and natural flooding regimes, identify management problems, and develop corrective measures. The most notable research was led by Dr. Leigh Fredrickson of the University of Missouri. By the late 1990s, this research made clear that flooding before the first frost as well as long-duration flooding can cause a catastrophic collapse of the red oak component in greentree reservoirs. 

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