Ducks & Resiliency

Ecologists increasingly mention “resiliency” and “regime change” when discussing wildlife populations and their habitats. What do these ideas signify and why are they becoming increasingly important to ducks and duck hunters?
ducks

The three of us who founded Madduck have a combined experience with duck hunting that exceeds 150 years in the field. This experience cuts across a very wide swath of time and geography. Our collective sense is that there is something fundamentally changing in the duck world that causes us to have great concern over diminishing waterfowl populations and the future of duck hunting.

For example, between 1960 and 2008 the human population more than doubled and economic growth increased in excess of seven-fold. These two phenomena resulted in activities that altered the landscape by fragmenting it and changing the activities conducted on it. The historical breeding, nesting and brood-rearing habitats of various waterfowl species have been significantly disturbed and in many cases altered irreversibly. The net result is a decrease in the abundance and quality of the natural resources required by waterfowl to sustain their historic population levels. As the natural resource base needed to allow our waterfowl to annually produce harvestable surpluses has become more fragile, the resilience of each duck species to flourish has been compromised.

I use the word “resilience” deliberately. It is defined as the “capacity of a system to absorb disturbance and reorganize while undergoing change so as to still retain essentially the same function, structure, identity and feedbacks.”  This concept is finding increasing acceptance among ecologists. (For those who want to further explore the concept in all its manifestations, and I encourage you to do so, consult the references and sources at the end of this article.)

ducks2Resiliency is particularly applicable to our waterfowl. Disturbances to waterfowl populations include habitat degradation (quality and quantity), weather cycles/changes, inherent population dynamics, and sport harvest. Most of these variables are beyond our control. Only the harvest variable gives us the ability and power to exert some control.

Unfortunately, the management of our waterfowl harvest has been built upon a model that uses average conditions and assumes that changes will be incremental and linear. What concerns this writer is that this is the same kind of modeling used for some of the world’s famous fisheries that have collapsed one after another. The fisheries harvest models had sustainability as their long term goal (sound familiar?). And yet for all the good intentions and so-called expert opinions, many fish populations have plummeted to historic lows such as the Pacific Coast salmon where commercial fishing has been suspended in an emergency effort to save the fish. ¹

At the intersection of ecology, economics and sociology, scientists today are finding natural systems considerably more complex, intricate and vulnerable than our assumptions, models and experts allow for. It is pure folly to assume there is, or can be, an “optimal sustainable state.” Yet, our waterfowl managers pursue this fabricated goal year in and year out. They try to optimize the elements of complex systems, even though the push for optimization (i.e. maximum sustainable harvest) greatly diminishes the resilience of our flocks by making them increasingly vulnerable to shocks and disturbances.

Could it be that the current system of waterfowl management is pushing us toward a “population threshold” for individual species that will cause a population to behave in a whole new way? Examples abound of thresholds being reached where species have undergone a fundamental behavioral change in response to a reduced population or altered environment. (Ecologists often describe this as “regime change.”). This new behavior is outside our realm of experience and knowledge. Black ducks, canvasbacks, pintails and scaup have undergone significant declines and it is doubtful that they will ever return to the levels that we at Madduck and many of our readers experienced when we first ventured out into the duck marshes. Could it be that our mallards and other species of ducks are destined to share the same fate?

This raises a key issue. Should we not err on the side of caution when setting harvest regulations so we don’t push more species across a threshold to a new regime? Should we not embrace a strategy of absolutely protecting the resilience of each and every species of duck so that they can absorb the increasing number of shocks and disturbances in the complex system that sustains them?

A specific case illustrates this concern. In California we have a well documented and discreet subpopulation of mallards that live their entire life in California and southern Oregon. This population provides a significant part of each season’s “bag” for California hunters. But two consecutive years of drought resulting in very poor reproductive success, coupled with excessively long seasons and bag limits, and an ever changing natural resource base, have diminished the ability of this particular population to sustain itself at historic levels. This is happening in spite of tremendous efforts over the last decade to restore, enhance and expand habitat dedicated to the ducks. An increasing number of field biologists and waterfowl scientists are sounding the alarm bell that this population may have been reduced this year below a threshold where a return to historic abundance may not be possible. A regime shift may be underway and the resilience of California mallards to respond could have been comprised, much like that of California salmon. Ecologists view it as probable that tiny incremental changes can trigger a large shift in some systems if a critical threshold is breached. The vexing problem is that nobody knows exactly where the critical population threshold level is. Suffice to say that in our lifetimes the resiliency of most – if not all — waterfowl populations have been diminished, with no guarantee of a rebound to historic numbers.

The resiliency message is simple. We need to be conservative and protective in managing our waterfowl so that we can pass on to the next generation the wonderful  heritage that we have enjoyed. Since we are only interim stewards of these waterfowl, we must not allow hunter opportunity and short-term pleasure to come at the expense of a long-term loss of resiliency. We have already done a miserable job of sustaining great numbers of black ducks, pintails, canvasbacks and scaup. Let’s not add other species to this list.

I leave you with a closing thought by Dr. Steven Carpenter of the University of Wisconsin: “Assuming that multiple regimes (for any population) are absent when they are actually present could lead to dangerous assumptions, such as the idea … that a harvested population cannot collapse.” ²

By:

Peter D. Stent

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¹Walker, Brian, Holling, C.S., Carpenter, Steven R., and Kinzig, Ann. 2004. Resilience, Adaptability and Transformability in Social-Ecological Systems. Ecology and Society 9(2): 5.

²Scheffer, Marten and Carpenter, Steven R. 2003. Catastrophic Regime Shifts in Ecosystems: Linking Theory to Observation. Trends in Ecology and Evolution Vol. 18 No. 12 December, 2003.

OTHER SOURCES OF INFORMATION:
Resilience Thinking: Sustaining Ecosystems and People in a Changing World. Brian Walker and David Salt. Island Press, 2006.

www.resalliance.org

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