WASHINGTON – New satellite imaging has revealed that Hurricanes Katrina and Rita produced the largest single forestry disaster on record in America – an essentially unreported ecological catastrophe that killed or severely damaged some 320 million trees in Mississippi and Louisiana.

The die-off, caused initially by wind and later by the weeks-long pooling of stagnant water, was so massive that researchers say it will add significantly to the greenhouse gas buildup – ultimately putting as much carbon from dying vegetation into the air as the rest of the American forest takes out in a year of photosynthesis.

In addition, the downing of so many trees has opened vast and sometimes fragile tracts of land to several aggressive and fast-growing exotic species that are already squeezing out far more environmentally productive native species.

Efforts to limit the damage have been handicapped by the ineffectiveness of a $504 million federal program to Gulf Coastland owners to replant and fight the invasive species. Congress appropriated the money in 2005 and added to it in 2007, but officials involved with the emergency conservation program say that only about $70 million has been processed or dispensed so far. Local advocates say onerous bureaucratic hurdles and low compensation rates are major reasons why.

“This is the worst environmental disaster in the United States since the Exxon Valdez accident … and the greatest forest destruction in modern times,” said James Cummins, executive director of the nonprofit environmental group Wildlife Mississippi and a board member of the Mississippi Forestry Commission.

Bengt “Skip” Hyberg, a U.S. Department of Agriculture Farm Service Agency economist and policy analyst, said changes were made in the program this year to make it more attractive to landowners

The U.S. Forest Service and Farm Service Agency had made estimates of the forest damage from two 2005 hurricanes, but they have generally focused on economic losses – $2 billion, or 5.5 billion board feet, worth of timber.

The new assessment of trees killed or severely damaged comes from a study to be released Friday in the journal Science, written primarily by researchers at Tulane University in New Orleans who studied images from two NASA satellites.

Lead author Jeffrey Chambers said the team used a before-and-after method perfected by researchers who study logging in the Amazon basin to assess the damage, which occurred over an area the size of Maine. The satellite images identified green vegetation before the storm and wood, dead vegetation and surface litter after the storm. The team then visited the areas of greatest damage to make their overall assessment.

“I was amazed at the quantitative impact of the storm,” Chambers said. Of the 320 million trees harmed, he said, about two-thirds soon died.

Chambers was even more surprised when his team calculated the amount of carbon that will be released into the atmosphere as the trees and other storm-damaged vegetation decomposes.

The total came out to be about 1.1 billion tons, which is equal to the amount of carbon that all the trees in the United States capture and take out of the atmosphere in a year.

Much of the forest damage occurred in Mississippi on land often owned in small parcels by individuals. Larry Payne, director for cooperative forestry for the Forest Service, said the congressional effort to begin restoring the forest was largely aimed at helping out those small landowners, who often used their timber land as a bank account. The program was created as an emergency add-on to the popular federal Conservation Reserve Program, which pays landowners “rent” for returning marginal or environmentally sensitive land to more natural conditions.

“Congress wanted to get money back into the hands of these people, and that was the top priority,” he said. But Payne and Hyberg said the Gulf Coast landowners were subject to most of the restrictions and compensation rates as Conservation Reserve participants around the nation, and that worked against efforts to jump-start reforestation in areas damaged by Katrina and Rita.

For instance, the rental rates are based on the quality of the soil, which is generally sandy and not considered especially valuable agriculturally in the affected area. In addition, a landowner who lost 35 percent of his stand had to promise to not cut trees on any of his property for 10 years in order to join the program. In an effort to get more participation, some of those restrictions were loosened this year.

The complexities of applying for help were so great that a nonprofit, national landowners’ group, working with conservation groups in the Gulf area, put together a Web site that walks potential applicants through the process.

“We knew how ineffectual USDA was on the delivery side, and we knew how important it was environmentally and financially that the area get some help on restoration, so we made the web site,” said Amon Eno, executive director of the Private Landowner Network. “It still may be that nobody in their right mind would apply for that program, but at least they can do it more easily now.”

Officials said that a Mississippi tax credit program for forest land owners has apparently been more widely used and effective.

Hurricane Katrina came ashore along the Pearl River, which divides Mississippi and Louisiana and is ecologically very rich and diverse. The Chambers study, as well as the work of local conservationist such as Cummins, found that native species like longleaf pine, live oak, and cypress did much better in surviving the hurricane than other species planted primarily for logging, such as loblolly and slash pine.

But the native deciduous forests were severely damaged in some areas, and the young, slow-growing oaks and maples are already being squeezed out by Chinese tallow trees – an ornamental plant imported for landscaping more than a century ago. It thrives in disturbed land, and foresters and environmentalists say it is running wild in the Katrina-damaged area. The tree produces a milky, toxic sap that keeps insects away, which in turn makes an inhospitable environment for birds and small mammals.

In pine forests, the suddenly open spaces are also being taken over by other invasive species, especially cogon grass. The aggressive Japanese grass was initially imported as packing material for oranges, but it has gotten into the environment and also squeezes out more productive native species.

“People are very concerned about the invasives – you hear that everywhere that Katrina went,” said Richard Martin, director for conservation services at the Nature Conservancy in Louisiana. “As the Chinese tallow and other invasives take over, they form a dense canopy that makes it hard for the oak and maple to grow well. Those trees will win out in the end, but it will take hundreds of years rather than a much quicker response if the invasives weren’t there.”

The slow pace of the reforestation has disappointed many conservationists, but so too has the government’s failure to encourage the planting of longleaf pine – a sturdy native species that once dominated 40 million acres in the Southeast but is now down to 1 million acres. Cummins said he wished that incentives would be offered to plant longleaf pine, but that “the opportunity has been lost for now.”

While much of the federal money available to plant new trees is going to owners of timber plots, urban “forests” often fared even worse than trees in more natural settings. According to Edward Macie, regional urban forester for Forest Service southern region, about 75 percent of trees in New Orleans died due to the storm. In some towns along the Mississippi coast, he said, not a tree remained standing.

AP-NY-11-15-07 1518EST