- Scientists and engineers, politicians and environmentalists are talking about restoring and re-creating hundreds of square miles of wetlands along America's Gulf coast, which many contend would have saved New Orleans and the region from much of Katrina's wrath.
- When European settlers first arrived in what would become the United States, there were an estimated 220 million acres of wetlands
- Some two centuries later, the total wetland area in the United States has been cut in half to less than 103 million acres,
- Natural phenomena are partly to blame: erosion, subsidence, rising sea levels, drought, hurricanes and other storms. But the damage done pales in comparison to human-induced causes: drainage, dredging, stream channelization, the dumping of fill material, damming, levees, logging, mining, construction, runoff, air and water pollutants, changes in nutrient levels, the release of toxic chemicals, the introduction of invasive, nonnative species and farming.
- Twenty-two states have lost more than half of their original wetlands; six have lost more than 85 percent. California is down to just 5 percent of what it once had.
There's a news photo, taken a month after Hurricane Katrina, that depicts a storm-tossed Chevy lying upside down beside a marsh near Venice, La. Beyond the car and some open water, a row of somewhat scraggly trees – a remnant of what was once a much-larger and more robust wetland – strips across the horizon.
But in the wake of an unforgettably destructive hurricane season, scientists and engineers, politicians and environmentalists are talking about restoring and re-creating hundreds of square miles of wetlands along America's Gulf coast, which many contend would have saved New Orleans and the region from much of Katrina's wrath.
The talk is insistent, sincere and old. Scientists have been attempting to restore – and create – wetlands for decades, from the Tijuana River estuary to the Florida Everglades to Casco Bay in Maine. The results have been mixed at best. There have been many failures. Restoration researchers say they've learned a lot from those failures about how to build a healthy, functional wetland, but clearly nature still does a much, much better job.
People are better at the other end: destroying wetlands. When European settlers first arrived in what would become the United States, there were an estimated 220 million acres of wetlands, a word that encompasses a surprisingly diverse array of ecosystems, from coastal salt marshes and riparian habitat to cypress swamps, forest bogs and prairie potholes.
Some two centuries later, the total wetland area in the United States has been cut in half to less than 103 million acres, according to the U.S. Geological Survey.
Natural phenomena are partly to blame: erosion, subsidence, rising sea levels, drought, hurricanes and other storms. But the damage done pales in comparison to human-induced causes: drainage, dredging, stream channelization, the dumping of fill material, damming, levees, logging, mining, construction, runoff, air and water pollutants, changes in nutrient levels, the release of toxic chemicals, the introduction of invasive, nonnative species and farming.
Twenty-two states have lost more than half of their original wetlands; six have lost more than 85 percent. California is down to just 5 percent of what it once had.
Losses were greatest in the 1950s through 1970s when public policies broadly encouraged the elimination of wetlands in favor of economic development. Then came the realization, emboldened by a growing database of research, that wetlands were and are valuable in their own right.
They are the Earth's kidneys, filtering and cleansing water systems. They are home and hearth to thousands of species of birds and fish, particularly as a safe haven for reproduction. Their presence helps moderate temperatures, cooling days and warming nights.
In 1997, a team of ecologists, economists and geographers attempted to establish the monetary value of nature. Their answer: $33 trillion, of which wetlands accounted for $14.9 trillion, or 45 percent.
Part of that value, as residents of Louisiana will tell you, is protective. In coastal areas, wetlands buffer the effects of hurricanes and other destructive storms. They do this in two ways.
No. 1: They block storm surge. The rule of thumb is that every mile of marsh reduces the height of a storm surge by 1 foot. A Danish study published in October found that in areas of India where coastal mangrove forests remained, damage from last year's deadly tsunami was significantly less than in areas where the trees had been removed for commercial development.
The mangroves are like a bumper on a car. They take the brunt of the wave. It trashes the forest, said John Pernetta, a project director for the United Nations Environment Program, but reduces damage to infrastructure behind.
Computer models suggest 30 mangrove trees per 120 square yards in a 109-yard belt can reduce a large tsunami's power by more than 90 percent.
A number of Asian nations have announced plans to replant the lost mangrove forests. The Sumatran government, for example, says it will replant thousands of acres of mangroves in the northern province of Aceh, where more than 110,000 people were killed in the tsunami.
No. 2: Coastal wetlands act like giant sponges, soaking up storm water, which, in turn, reduces the chance of flooding. According to American Rivers, an environmental group, a single acre of wetland, saturated to a depth of one foot, retains more than 330,000 gallons of water – enough to flood 13 average-sized homes thigh deep.
Louisiana has long been the poster child of wetlands loss. Between 1932 and 2000, almost 2,000 square miles of wetlands were eliminated, an average of 34 square miles annually. In recent years, that rate has been reduced but still stands at about 25 square miles of wetland destroyed each year. If the current rate of loss is not slowed, researchers estimate an additional 800,000 acres of wetlands will disappear by 2040.
Earlier this month, a committee of the National Research Council (part of the National Academies of Science) issued a public assessment of a plan developed in 2004 by the state of Louisiana and the U.S. Army Corps of Engineers to begin to restore and protect the state's coast and wetlands.
The analysis was restrained and cautiously optimistic. Four of the five restoration projects proposed were "scientifically sound," but the NRC declared that the plan fell short of the "the type of integrated, large-scale effort needed for such a massive undertaking."
"It's a start," said Robert Dean, committee chairman of the NRC report and a professor of civil and coastal engineering at the University of Florida, "and we recommend that the work move forward with the understanding that long-range programs need to be developed."
To be fair, the Louisiana/Army Corps plan – called the Louisiana Coastal Area (LCA) study – was never intended to be a grand solution. Its goals were purposefully limited by time and funding to five projects that could theoretically be accomplished within the next five to 10 years.
These projects focused on repairing and restoring specific sections of Louisiana's coast and infrastructure, such as restoring shoreline along Barataria Basin, diverting the Hope Canal and mitigating environmental damage caused by the Mississippi River Gulf Outlet (MRGO), a large navigation channel.
Restoring a wetland is like putting together a billion-piece jigsaw puzzle with only the vaguest notion of what the big picture looks like. They are extraordinarily complicated, perhaps the most dynamic ecosystems on Earth. Ecologists struggle to even quantify the variables that determine whether a wetland is functional and healthy.
Take the issue of water, arguably the single most important and defining factor in all wetlands. For any preservation or restoration scheme to work, scientists must assess and understand how much water is present in a particular wetland, how it behaves, the purposes it serves. Is it primarily surface water or ground? What's the source: rain, river, sea? How does it move? Where does it go? How much is present at any particular time?
AdvertisementFor example, the MRGO was built by the U.S. Army Corps of Engineers in the 1960s as a major shortcut for oceangoing vessels traveling between the Gulf of Mexico and the port of New Orleans. The 76-mile-long channel required the dredging of more than 290 million cubic yards of earth, 60 million more than were excavated for the Panama Canal.
One result of the MRGO has been a massive intrusion of Gulf seawater deep into the surrounding wetland. Increased water salinity has wiped out more than 5,000 acres of cypress forest and decimated once-flourishing populations of alligators, fish, birds and muskrats. It's estimated that MRGO has destroyed more than 27,300 acres of wetland.
Local scientists are now trying to stop and reverse some of the damage by funneling part of New Orlean's storm water and treated sewage back into the remaining marsh. If all goes as planned, the "fresh" wastewater will push back the saltwater intrusion and provide needed sediment and nutrients for plants and animals.
But water poses just one set of questions and problems. What about local topography, the slope of the land? How much lies above the water? What is the soil quality? What kinds of plants live there? What animal species? How do they all interact?
Actual restoration is an educated guessing game, said Joy Zedler, a professor of botany at the University of Wisconsin in Madison who has spent more than 30 years studying and restoring wetlands, in particular the Tijuana River estuary south of San Diego.
"There are so many working parts, and conditions are always changing," she said. "There are always surprises you didn't predict."
One of Zedler's projects while she worked at San Diego State University was restoring the Sweetwater Marsh south of downtown San Diego for two endangered species of birds – the clapper rail and the least tern – and one endangered plant called bird's beak.
Previous efforts to create suitable habitat involved transplanting Spartina cordgrass from nearby wetlands. But the transplants failed. The grass refused to grow tall enough to provide adequate nesting sites. Researchers eventually discovered that the marsh's sandy soil lacked sufficient nutrients, so fertilizer was added to encourage grass growth.
And it did, but the fertilizer also spurred the growth of pickleweed, a less desirable marsh plant that outgrew the cordgrass, leaving the birds with still no suitable place to nest.
In the early 1990s, Oregon scientists tried restoring a coastal marsh that had been diked off from tidal action to create pastureland in the Salmon River estuary. They presumed that, once re-exposed to ocean tides, the land would soon return to its original wetland state.
Ten years later, it looked nothing at all like the surrounding, untouched wetlands. Absent water for all those years, the land had subsided. More water flooded it, changing the kinds of plants and animals that would live there. It was a kind of wetland, but not like the wetland originally lost. Scientists now estimate it will take nature 50 years or more to build up sediments and return the land to what it once was.
Subsidence is merely one kind of glitch in restoration. Researchers have had to learn through trial and error (euphemistically called adaptive restoration) which species of plants are good colonizers – that is, which ones will move into a restored area naturally – and which must be hand-seeded and painstakingly nurtured. Similarly, some plants have proved to be strong competitors, able to hold their own, while others quickly succumb to problems like soil compaction or invasive species. How restored vegetation fares is a strong determinant of whether birds and other animals will return and thrive. Plans to replant lost mangrove forests in Indonesia, for example, have drawn criticism because they oversimplify nature. Alfredo Quarto, executive director of the Mangrove Action Project, a U.S.-based environmental group, said similar mangrove restoration projects in Thailand resulted in "plantation-style" forests that harmed biodiversity and eventually failed. The mangroves, he said, were often planted in places where they didn't naturally grow and died after a few years.
Indonesian government ecologists say they realize mangroves are only part of the solution, and promise to plant other kinds of trees, such as pine.
Likewise, Greg Stone, a professor of coastal geology at Louisiana State University, says future efforts to repair the Gulf Coast's swamps and bayous will not be sufficient or successful unless the coast's barrier islands – long, narrow strips of sand forming islands that protect inland areas from ocean waves and storms – are also restored.
"The islands are like the first layer of armor," he said. "We've allowed them to be eroded away over the years. We've probably lost three to five years of land in just this one hurricane season. If we're going to restore and preserve coastal wetlands, I think we've got to think first about how to restore the barrier islands that protect the coast."
Small steps, big needs
A handful of small-scale projects have begun to hydraulically pump sand and sediment onto existing barrier islands with some success, but Stone says this effort needs to be massively expanded.
Which means spending money, a lot of it. No one can yet say exactly how much will be needed to repair and restore the Gulf coast's barrier islands and wetlands. The current estimate, developed before Katrina, is roughly $14 billion, but some estimates have doubled the amount. The Louisiana Coastal Area plan, in fact, isn't even funded. Though the Bush Administration supports a plan to spend $2 billion over 10 years on the most promising restoration projects, Congress has yet to authorize any funding.
Even when the money comes, success won't immediately follow. Wetland restoration takes time, said Zedler and others. Real success is measured in decades, a fact that has frequently doomed projects where funding was mandated for only a few years.
Zedler cites an example:
Several years ago, an effort was made to create wetland habitat near the San Diego River for the least Bell's vireo, an endangered migratory bird. Millions of dollars were spent diverting the river into this new habitat.
Then a winter flood destroyed the diversion levee. The river returned to its old route; the restored wetland withered away.
"It turned out that the breached berm that shunted the water was built in the wrong place, but by then all of the project obligations and liability had passed. Nobody was responsible for the project anymore. Everybody just walked away from a wetland that had no water."
That happens a lot. From California to Louisiana, the idea of wetland restoration has become widely accepted and supported. Everybody's in favor of restoring their neighbor's wetland, said Dan Walker, Louisiana Coastal Area study director. They can understand the long-term benefits. But when it's their property or immediate economic interests that may be affected, people balk, and things get complicated.
"There are always competing and conflicting interests. What we're trying to do is get everybody on the same map."
No one, of course, believes wetlands restoration and creation will ever resemble what was lost. Louisiana environmentalists say their ultimate goal is to simply slow the ongoing erosion of their state. Something is better than nothing, whether it's looking out over a coastal lagoon in North County or across a bayou toward the Gulf and, inevitably, another incoming hurricane.