An analysis of satellite imagery of the Gulf Coast shows that Hurricane Katrina destroyed an estimated 320 million trees in Mississippi and Louisiana, an unprecedented loss of forest land that will reshape the region for generations, Louisiana researchers report Friday.
The death of the trees from wind damage and soaking in salt water for long periods ultimately will release about 367 million tons of carbon dioxide as they decompose -- about the same amount of carbon that is absorbed by all U.S. forests in a year, according to the study published in the journal Science.
Considered on the scale of global climate change, Katrina's impact is small. But as a one-time event, its infusion of carbon is significant.
"This is a one-shot massive hit to these systems, where you see this enormous impact," said Jason Neff, a professor of geosciences at the University of Colorado at Boulder.
Most of the lost trees in the Gulf region stood 70 to 100 feet tall and will not grow back for decades, if ever, experts said.
Hurricane Katrina, which made landfall in August 2005 with winds that reached 125 mph, damaged 5 million acres of forests, 80 percent of them in Mississippi, according to the U.S. Forest Service. By comparison, the 1980 eruption of Mt. St. Helens in Washington state wiped out 150,000 acres of forest.
"In some areas of southeast Louisiana and southeast Mississippi, it was 100 percent damage," said Wayne Hagan, owner of Timberland Management Services of Louisiana in Clinton.
Biologist Jeffrey Q. Chambers of Tulane University and his colleagues said the deforested land, once covered with native species such as longleaf pine, oak and cypress, is being taken over by invasive species that are changing the area's ecology. One of the most prolific, the Chinese tallow, oozes a milky, toxic sap that creates an inhospitable environment for insects, birds and small animals.
The trees that are growing back represent only a fraction of those destroyed, and they are surrounded by large quantities of decomposing lumber. Combined with the drought that is punishing the South, that is the recipe for a devastating forest fire, said James L. Cummins, executive director of the Mississippi Fish and Wildlife Foundation.
"If we have significant fires, all of those young trees are going to be toast," he said.
The images from the satellite's spectrometers enabled them to distinguish live trees from dead ones and from other vegetation. That data was then verified by analyzing selected tracts on the ground, Chambers said.
"I was amazed," he said. "I didn't expect that much damage."
The extent of losses was highly dependent on the type of tree in the hurricane's path. Only about 10 percent of stands of the loblolly pine, favored by commercial timber growers, survived the assault.
In contrast, more than 90 percent of native longleaf pine stands escaped damage. But the acreage of longleaf pine is only about 2 percent of what it was a century ago, Cummins said.
The only timber stands that survived were ones planted within the past 20 years, Hagan said. Those trees were planted in close proximity, so they were able to support each other through the high winds. "One tree leans on another," he said.
Experts said that they expected that most of the lost forest land never will be replanted.
The federal government earmarked $504 million for tree replacement, but the program typically provides only half the cost of replanting, along with a small stipend -- as low as a net of $100 per acre in some areas -- to keep the trees growing for a decade.
Owners struggling to rebuild their homes and businesses in the wake of Katrina weren't able to make up the difference, Hagan said, and many sold their land to people who used it for residential construction.
To date, only about $70 million of the government funds have been disbursed and no more than 100,000 acres have been replanted, Cummins said.
Forestry advocates are pressing landowners to tap into those funds. More forest recovery money will become available in the spring, Box said.
"It's a major push here, and it's still ongoing," she said.
Staff writer Alan Zarembo contributed to this report.