With the help of NASA satellite data, a research team has estimated that Hurricane Katrina killed or severely damaged 320 million large trees in Gulf Coast forests, which weakened the role the forests play in storing carbon from the atmosphere. The damage has led to these forests releasing large quantities of carbon dioxide into the atmosphere.

The August 2005 hurricane affected five million acres of forest across Mississippi, Louisiana and Alabama, with damage ranging from downed trees, snapped trunks and broken limbs to stripped leaves.

Young growing forests play a vital role in removing carbon dioxide, a greenhouse gas, from the atmosphere by photosynthesis, and are thus important in slowing a warming climate. An event that kills a great number of trees can temporarily reduce photosynthesis, the process by which carbon is stored in plants. More importantly, all the dead wood will be consumed by decomposers, resulting in a large carbon dioxide release to the atmosphere as the ecosystem exhales it as forest waste product. The team’s findings were published Nov. 15 in the journal Science.

After Hurricane Katrina, the Federal Emergency Management Agency (FEMA) provided 120,000 trailers to victims and relief workers. Residents soon began complaining of sore throats, burning eyes and noses and trouble breathing.

The cause? High levels of formaldehyde.

Formaldehyde is an industrial chemical that is bonded to nasal cancer, respiratory problems and even leukemia. Scientists believe that the fumes resulted from cheap wood and poor ventilation. Whatever the cause, the government banned the trailers from being used for long term housing. The fumes and health risks were too high.

But the trailers, which cost FEMA $130 million a year to maintain and store, recently found a new market. According to the New York Times, they are being bought by hundreds of contracting companies, dozens of which are in Louisiana, and by individuals in public auctions. Some buyers said they were unaware of the health risks.