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New Focus On Flooding Could Help Duck Habitat

Sometimes it can be too wet even for ducks.

The Arkansas Game and Fish Commission’s Greentree reservoirs, originally envisioned as an ideal way to impound water and provide valuable duck habitat, are getting a second look when it comes to the way their waters are managed.

The reservoirs, created in the 1930s as a response to bottomland hardwood forest reduction, use a system of levees in and around the timber stand to trap water. The forests have historically provided winter habitat for ducks and other wildlife because the hydrological patterns of rainfall and flooding coincided with duck migrations.

But as bottomland hardwoods declined from 19-25 million acres prior to European settlement to today’s 5-8 million acres, early conservationists and hunters saw the value in these wetland habitats.

GTRs were first constructed with the prevailing belief that flooding dormant bottomland was an acceptable imitation of natural flooding. But, as they were mostly built for the recreational purpose of hunting, management decisions regarding the timing and depth of flooding were based mainly on providing maximum hunting opportunities.

The years of unnatural flooding are reducing the periods of favorable growing conditions and promoting a shift in vegetation toward more water-tolerant woody species, which increases problems with stress, insects and disease and, among other things, reduces the food supply for ducks.

Results of a 2014 AGFC assessment further strengthen the body of evidence indicating that decades of GTR management have resulted in a water-stressed and damaged red oak forest within GTRs, along with a trend toward increases in the prevalence of more water-tolerant species in the canopy and, in particular, the regeneration layer.

Clearly, consistently flooding impoundments before full tree dormancy and holding water beyond when trees break dormancy is problematic to the sustainability of a healthy forest with the greatest potential to provide long-term, high-quality waterfowl habitat and hunting opportunity.

The combination of negative external and internal hydrologic influences through the years leaves the future health and sustainability of these forested systems in question.

External influences include widespread changes within the watersheds surrounding wildlife management areas — especially land clearing and drainage projects resulting in increased frequency and magnitude of flows into WMAs — with the cumulative impact of these various changes being GTRs becoming “wetter” over time.

Internal negative influences include suboptimal infrastructure design, the loss of topographic variation within GTRs (leading to reduced flow and drainage capacity) and the overall increase in the duration of soil saturation.

The primary objective of GTR management has been to replace the natural flooding regime of a bottomland hardwood forest with a more reliable flooding regime in order to consistently provide habitat for migrating waterfowl and subsequently provide waterfowl hunting opportunities.

However, current understanding of bottomland ecology clearly dictates this management objective must be adapted to include long-term forest health as a primary consideration.

The managed wetlands found in GTRs offer an opportunity to compensate for past losses and provide critical habitat functions well into the future, but only if goals focus on long-term habitat sustainability through management objectives guided by an understanding of forest ecology.

Improving and maintaining the quality of waterfowl habitat on AGFC lands, including GTRs, must play a pivotal role in maintaining wintering duck populations and waterfowl hunting opportunity for the long term.

Thus, no decision about management of these exceptionally popular duck hunting areas can be evaluated without consideration of the duck hunters who use them. However, the Commission’s primary responsibility is the long-term sustainability of these unique habitat remnants, so striking a balance among management objectives will be a key task in future management planning.