page_title: Hurricane Katrina
section_title: Environmental effects
hierarchical_section_title: Hurricane Katrina / Aftermath / Environmental effects
caption_attribution_description: Two images of the w:Chandeleur Islands off the coast of Louisiana, USA. The left image is from 2004 and the right is from 2005, after Hurricane Katrina.
context_page_description: Hurricane Katrina was a large Category 5 Atlantic hurricane which caused over 1,800 deaths and $125 billion in damage in August 2005, particularly in the city of New Orleans and the surrounding areas. It was at the time the costliest tropical cyclone on record, and is now tied with 2017's Hurricane Harvey. The storm was the twelfth tropical cyclone, the fifth hurricane, and the third major hurricane of the 2005 Atlantic hurricane season, as well as the fourth-most intense Atlantic hurricane on record to make landfall in the contiguous United States.
  Katrina originated on August 23, 2005 as a tropical depression from the merger of a tropical wave and the remnants of Tropical Depression Ten. Early the following day, the depression intensified into a tropical storm as it headed generally westward toward Florida, strengthening into a hurricane two hours before making landfall at Hallandale Beach on August 25. After briefly weakening to tropical storm strength over southern Florida, Katrina emerged into the Gulf of Mexico on August 26 and began to rapidly intensify.
context_section_description: Katrina also had a profound impact on the environment. The storm surge caused substantial beach erosion, in some cases completely devastating coastal areas. In Dauphin Island (a barrier island), approximately 90 mi (140 km) to the east of the point where the hurricane made landfall, the sand that comprised the island was transported across the island into the Mississippi Sound, pushing the island towards land. The storm surge and waves from Katrina also severely damaged the Chandeleur Islands, which had been affected by Hurricane Ivan the previous year. The US Geological Survey has estimated 217 sq mi (560 km²) of land was transformed to water by the hurricanes Katrina and Rita. Before the storm, subsidence and erosion caused loss of land in the Louisiana wetlands and bayous. This, along with the canals built in the area, let Katrina keep more of its intensity when it struck. The lands that were lost were breeding grounds for marine mammals, brown pelicans, turtles, and fish, and migratory species such as redhead ducks. Overall, about 20% of the local marshes were permanently overrun by water as a result of the storm.
  The damage from Katrina forced the closure of 16 National Wildlife Refuges. Breton National Wildlife Refuge lost half its area in the storm. As a result, the hurricane affected the habitats of sea turtles, Mississippi sandhill cranes, Red-cockaded woodpeckers, and Alabama Beach mice.
  Katrina also produced massive tree loss along the Gulf Coast, particularly in Louisiana's Pearl River Basin and among bottomland hardwood forests. Before the storm, the standard mortality rate for the area's trees was 1.9%, but this interval increased to 20.5% by the end of 2006. Delayed mortality as an effect of the storm continued with rates up to 5% until 2011. This significant loss in biomass caused greater decay and an increase in carbon emissions. For example, by 2006 the decreased biomass in bottomland hardwood forests contributed an amount of carbon which equated to roughly 140% of the net annual U.S. carbon sink in forest trees.
  The storm caused oil spills from 44 facilities throughout southeastern Louisiana, which resulted in over 7 million US gallons (26,000 m³) of oil being leaked. Some spills were only a few hundred gallons and most were contained on-site, though some oil entered the ecosystem and residential areas. After a spill at the Murphy Oil refinery, for example, 1,800 homes were oiled in the towns of Chalmette and Meraux. Unlike Hurricane Ivan, no offshore oil spills were officially reported after Hurricane Katrina. However, Skytruth reported some signs of surface oil in the Gulf of Mexico.
  Finally, as part of the cleanup effort, the flood waters that covered New Orleans were pumped into Lake Pontchartrain, a process that took 43 days to complete. These residual waters contained a mix of raw sewage, bacteria, heavy metals, pesticides, toxic chemicals, and oil, which sparked fears in the scientific community of massive numbers of fish dying.
caption: The Chandeleur Islands, before Katrina (left) and after (right), showing the impact of the storm along coastal areas.
exif: {}