Dec 04, 2001
an online newsletter for and by NOAA employees
NOAA Satellite Imagery Goes to Work in Field
Wetland Loss Averages “One Football Field Every 45 Minutes”
Most of us don’t known it but two narrow lanes cutting through the marshes of south Louisiana are vital to our daily lives. As Louisiana Highway 1, the slim road is a lifeline to about 17 percent of America’s natural gas and about 16 percent of our crude oil. Highway 1 helps ensure our transportation and comfort. It is also a significant contributor to the $17 billion in coastal and offshore Louisiana oil and gas that help bolster America’s economy every year.
But just as in so many other parts of the world – NOAA scientists report 20 percent – severe drought has wreaked havoc in the wetlands surrounding Highway 1 as well as along the rest of Louisiana’s coast. While the impact of drought has been page one in many parts of the world – active fires in our country, intensified food shortages in Kenya, extreme dryness in Asia’s crop-producing region -- the devastation around Highway 1 is still a largely unreported story.
Highway 1 is the only route in and out of Port Fouchon on the Gulf of Mexico. "The entire country depends on access to Fourchon," said U.S. Rep. Billy Tauzin of Louisiana. Historically Highway 1 has been buffered from flooding by coastal marshes or wetlands. When Hurricane Andrew struck in 1995, surrounding land sheltered Highway 1 and Port Fourchon. But today much of that same area is water, with no protection from floods. Other Louisiana ports and resources crucial to the nation’s economy are faced with the same threat.
Suffering from three years of drought and other yet-to-be determined causes, hundreds of thousands of coastal Louisiana wetlands either died or were severely harmed last year. “Travelers on Highway 1 watched as large areas of coastal marshes turned brown and started to die. Seeing it firsthand makes it very easy to appreciate the dangers of having open water in place of healthy coastal wetlands,” said Tim Osborne, program manager for NOAA’s National Ocean Service in Louisiana.
Working with other federal agencies and the State of Louisiana, NOAA is moving ahead to identify both causes and long-term effects of this major coastal marsh die-off known as “Brown Marsh.” Brown Marsh refers to the rapid and unusual browning of Louisiana’s intertidal smooth cordgrass, the most abundant plant in the state’s saline marsh zone. Under normal circumstances the plant thrives in saltwater but the prolonged drought along with other factors can interact to stress smooth cordgrass beyond its ability to recover. A number of possibilities for the Brown Marsh dieback, the most extensive in recent history, are now being evaluated.
Perhaps the most devastating impact has been on the very rich salt marshes and fragile habitat of the Barataria-Terrebonne National Estuary. On the west bank of the Mississippi, New Orleans stretches into the estuary, which has been the site of over 400,000 productive acres of wetland since 1932. In terms of hurricane protection alone, each Barataria-Terrebonne wetland acre yields $1,500 in benefits. Each one-mile loss amounts to an estimated annual average of over $5 million in property damage. Already Brown Marsh has either moderately or severely impacted 250,000 acres of Barataria-Terrebonne’s wetlands. Kerry St. Pe, the estuary’s program director, said that while the impact has not yet been fully quantified, the fear is that the areas most seriously affected will erode away because of vegetation loss. “Vegetation is what holds the sediment together,” he said. “Once marshes revert to open water, the sediments must be replaced by humans, a difficult and expensive process.”
Over-all Louisiana is home to over 40 percent of the nation’s coastal wetlands. Eighty percent of the nation’s wetland loss occurs in the state, where coastal communities also depend on healthy wetlands for commercial and recreational fishing and to safeguard the coast for waterways and shipping. Seventy-five miles from New Orleans, Highway 1’s entrance to Port Fourchon is also the single hurricane escape road for residents of nearby Grand Isle and about fifty percent of the 13,000 people working offshore each day.
Yet Louisiana’s wetland loss may well be the worst in the nation and among the most severe in the world. “No state in the nation is losing wetlands faster than Louisiana -- at the average rate of one football field every 45 minutes,” Kerry St. Pe said. In a hurricane year, shoreline retreat can amount to over 100 feet each year. With 60 to 70 percent of the state’s residents living within 50 miles of the coast, wetland loss must be effectively addressed. Louisiana now losses 25 to 35 square miles or 20,000 to 25,000 acres of coastal wetlands each year.
In addition to the drought that caused Brown Marsh, Mississippi River dredging, oil and gas drilling, subsidence or sinking, hurricanes and sediment reduction all contribute to yearly wetlands losses. With NOAA as a key player, a joint federal-state partnership under the Coastal Wetlands Planning Protection and Restoration Act was formed to address Louisiana’s wetlands losses. But the Brown Marsh phenomenon required additional attention.
Along with NOAA and other federal agencies and the state, researchers and environmental planners are now collaboratively addressing the extraordinary wetland impact. Louisiana universities, local parishes and major landowners are key to the effort. Earlier this year, Congress provided $3 million through NOAA to the Louisiana Department of Natural Resources to initiate and monitor a number of pilot restoration projects. The Barataria-Terrebonne National Estuary convened a scientific technical committee to coordinate the response effort.
As a critical aspect of the response, NOAA collaborated with Louisiana’s Department of Natural Resources, U.S. Geological Survey, the University of New Orleans and others to introduce the use of LANDSAT satellite imagery to seek out and monitor Brown Marsh, which has been observed along Louisiana’s entire coast. The same team is now managing this response.
Less expensive than aerial photography, LANDSAT provides multiple color imagery, providing data that can be classified and used to produce maps. The maps can reflect satellite data indicating plant health, with color anywhere from a healthy deep red to a lifeless brown.
In applying imagery from outer space to on-site field work, NOAA and its partners visited a large number of sites harmed by Brown Marsh as well as healthy marshes to ensure that imagery was identifying the correct sites. By working together, remote sensing specialists and field staff learned from each other about those areas that were hardest hit and how satellite imagery could be used to accurately pinpoint them. Over the next two years, Tim Osborn will be working closely with NOAA Fisheries’ John Foret to advance this effort. Roger Zimmerman, also of NOAA Fisheries, is among NOAA staff also actively engaged in countering the effects of Brown Marsh.
This year and last, occasional healthy smooth cordgrass have been collected from brown lifeless sites, grown in nurseries, and replanted in a pilot effort to restore healthy vegetation to dead areas. The question of why some marsh areas and plants have survived and how they differ from those that died is one area of investigation in the die-back study effort. This year, with the passing of drought, there is improvement in coastal areas. Many are beginning to recover. In time, the continuing collaborative effort to study Brown Marsh’s causes, effects and potential remedies is expected to yield long-term protection for the nation, Louisiana’s coastal communities, fresh water sources and vital transportation routes. Highway 1 is prominent in this picture.
Web site - http://lacoast.gov/