March 17, 2010

A Matter of State

Anacostia mud flatMarsh or mudflat? Clear water and underwater grasses or brown turbid water and blooms of harmful algae?  Comb jellies or or stinging sea nettles? Each ecological “state” has persisted in the Chesapeake Bay to varying degrees, in varying locations, at various points in history.

As humans, we have clear preferences for one state over another. The activities that we associate with the Bay –– fishing, boating, swimming –– all rely on our favorite spot being in a particular state at a particular time.  Our efforts to restore the Bay hinge on a human desire to shape the state of the Bay’s ecology.

But ecological systems have a momentum of their own.

Picture a roller coaster. Once the cars crest the top of a hill, there’s little that can stop a rapid descent to the bottom.  Without an engine, the cars will rock up and down the inclines, ultimately settling in a trough.  Climbing the hill to recovery takes momentum in one direction –– a concerted push, sustained over time, until feedbacks kick in like an engine to give the uphill climb a boost.

Restoration is our human attempt to push an ecosystem into a preferred state of health.  But this is no easy task. At Kingman Marsh in the Anacostia River, diverse groups, including scientists, government, and non-governmental organizations, have come together to return a freshwater marsh to a part of the river that had “flipped” into a mudflat state after decades of environmental insult (see Marsh in the City).  This is a massive undertaking, a huge push more than a decade in the making. It required substantial dredging, followed by the planting of some 700,000 new plants –– at a cost of $6 million.

But in the case of Kingman Marsh, the uphill push of restoration efforts has faced a strong downhill counterforce.  A hungry flock of resident Canada geese seems determined to eat every last palatable shoot from the marsh, pushing the area toward a persistent state of mudflat. Because of this, the fate of the whole restoration effort hangs in the balance.

In other parts of the Bay, the return to a desirable state has come more decisively. Take Gunston Cove for example. In this tidal embayment of the Potomac River, once dominated by noxious algal blooms, clear waters have returned. It took a while.  For decades, the Blue Plains Sewage Treatment Plant had discharged large amounts of phosphorus into the river, causing eutrophication — the result of too many nutrients.  But even after treatment upgrades reduced the discharge of phosphorus, the waters saw little change.  Not until some two decades later, did Gunston Cove suddenly experience a rapid improvement –– presumably reflecting the time that phosphorus “lagged” behind in the system.

Late last fall, as I struggled to trudge, with borrowed hip waders, through the thick ooze of Kingman Marsh, I marveled at the uphill struggle underway to restore marshland to a small part of this ruined river. I was doing my best to keep pace with U.S. Geological Survey biologist Cairn Krafft as she surveyed the extensive damage done to the marsh by Canada geese. The devastation was pretty incredible. In the battle between the states of marsh and mudflat, the geese seem determined to make mud prevail.

How can we use ideas about ecological states to inform restoration efforts? How can we encourage ecological systems to work for us, not to fight our best intentions?

Here’s where it seems to me that lessons from history can provide valuable insights. By looking to the past, we can see how and where ecological states have flipped before, and where they would be likely to flip in the future. Such an effort would require the diverse expertise of different disciplines.  We need scientists analyzing long-term data sets for evidence of changes in state –– data reflecting trends in fisheries, water quality, and more. We need modelers and statisticians to work on understanding transitions from one state to another, where thresholds for recovery might help set a regime change in motion. And we need synthetic thinkers to help translate from the academic realm to decisions on the ground.

It’s a steep hill to climb, but the potential gains for restoring the Bay are worth it.  Aren’t they?

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