Updated 8:29 p.m. ET
Environmental experts say the damage caused by the oil spill unfolding in the Gulf of Mexico may equal or even eclipse the 1989 Exxon Valdez spill off the southern coast of Alaska, the worst oil spill in U.S. history and one of the worst environmental disasters in decades.
Federal officials said Thursday that oil is gushing into the Gulf of Mexico, after a deep-water rig -- and the massive slick .
It remains unclear how much oil will flow into the Gulf before the flow can be cut off. The teams of state, federal and company officials charged with the cleanup have tried unsuccessfully to activate an underwater cutoff valve and now say they plan to dig a relief well half a mile away - a process that could take weeks or months. (BP, the company that leased the sunken rig, is currently leading the cleanup effort but has asked the military for assistance.)
According to the latest estimates, oil is flowing into the Gulf at the rate of 5,000 barrels - or 210,000 gallons - a day. At that rate, it would take nearly two months to equal the 11 million gallons unleashed by the Valdez, a 1,000-foot tanker that breached after crashing into a reef in Alaska's Prince William Sound.
But experts say that even if the current spill doesn't match the Valdez in terms of pure numbers, it could be more damaging because the marshlands of the Mississippi delta are home to numerous species of threatened and endangered birds and other animals.
"Late spring is the peak time for neo-tropical songbirds moving from the Yucatan Peninsula to make their first landfall in Louisiana. As many as 25 million birds a day transit the region during the period of northern migration," the Los Angeles Times 10 Animals Most At Risk from Gulf Oil Spill "It's quite possible this will end up being worse than the Valdez in terms of environmental impact since it seems like BP will be unable to cap the spill for months. In terms of total quantity of oil released, it seems this will probably fall short of Exxon Valdez. But because of the habitat, the environmental impact will be worse," John Hocevar, oceans campaign director for Greenpeace USA, told MSNBC Thursday.
Louisiana State Wildlife and Fisheries Secretary Robert Barham had said Thursday that oil could reach the Pass a Loutre wildlife area Friday night, Breton Sound on Saturday and the Chandeleur Islands on Sunday. In fact, as of around 8 p.m. Thursday oil was expected to reach Pass a Loutre within hours.
Lousiana Gov. Bobby Jindal has declared a state of emergency and the state has allowed a temporary shrimping season so that shrimpers can bring in their catches before a greater swath of gulf waters become contaminated.
David Kennedy of the National Oceanic and Atmospheric Administration told the Associated Press that efforts to manage the spill "are just mind-boggling."
The sinking of the Deepwater Horizon rig has re-ignited the debate over offshore drilling, reports CBS News correspondent Don Teague. In the Gulf alone, there are more than 3,500 oil and gas platforms with about 35,000 offshore workers. They produce more than 1.7 million barrels of oil per day, almost 30 percent of total domestic production.
Environmental groups say the disaster proves offshore drilling isn't worth the risk, Teague reports.
In a reversal of his stance on the topic, Florida Gov. Charlie Crist said Thursday after flying over the oil slick in the Gulf that he wouldfor his state.
Crist said the disaster proved that oil rigs are "the opposite of safe."
More on the rig explosion:
Government Vows Aggressive Action on Oil Spill
BP Exec: Size of Leak Won't Change our Response
Crews Start Burning Gulf Oil Slick
Fighting Oil with Fire
Oil Rig Cook Haunted by Nightmares Since Blast
Oil Spill Growing off Coast after Rig Explosion
Oil Spill Continues; Will Robot Fix Leak?
Man-Made Disaster in the Gulf
New Oil-Rig Safety Rules Eyed Before Blast
Map shows approximate locations where the oil spill has spread and where it is expected to spread Thursday