Despite federal claims that most of the oil in the Gulf of Mexico is gone, some independent scientists said Wednesday that they fear the amount of crude left from the massive BP spill will wreak environmental destruction.
Among the unanswered questions is how much damage the remaining oil will have on marine life and coastlines. John Hocevar, a marine biologist with Greenpeace in Washington, said the answer may not be known for a year or longer.
"And it's more than losing a year of baby fish," Hocevar told msnbc.com. "We will eventually lose habitat. We will lose entire islands. ... It will have serious impact on our population of whales in the Gulf, the sea turtles, and it goes on. This is something we will be facing for 10 years to come."
Hocevar was reacting to a federal report released earlier in the day indicating that nearly three-quarters of the spilled oil — more than 152 million gallons — has been collected at the well by a temporary containment cap, been cleaned up or chemically dispersed, or naturally deteriorated, evaporated or dissolved.
That would leave 53 million gallons still in the Gulf, an amount nearly five times the size of the 11 million-gallon Exxon Valdez spill, which caused massive environmental damage in Alaska in 1989.
The government report was based on daily operational reports, estimates by scientists and analyses by federal experts. The government acknowledged it made certain assumptions about how oil dissolves in water naturally over time.
"This is a shaky report. The more I read it, the less satisfied I am with the thoroughness of the presentation," Florida State University oceanography professor Ian MacDonald told The Associated Press. "There are sweeping assumptions here."
NOAA chief Jane Lubchenco acknowledged the numbers could be off by as much as 10 percent. One of the scientists who peer-reviewed the work and is mentioned in the report, Ed Overton of Louisiana State University, said he wasn't comfortable with NOAA's putting precise percentages of how much oil is left in the Gulf. What would be more accurate would be a much broader range of, say, 40 million to 60 million gallons, he said.
Still, Overton thought the report was mostly good work. He said the Gulf itself deserves much of the credit, describing the body of water in two words: "incredibly resilient."
The White House claimed only 26 percent of the oil remained in the Gulf, but that was based on a 206-million-gallon figure for the spill that included oil that spewed from the pipe but was captured by BP and never got into the Gulf. Using the 172 million gallons that got into the Gulf, 31 percent of the oil remains.
So what happened to the oil? Thank nature more than the federal government. Burning, skimming and chemically dispersing the spill got rid of 35 million gallons of oil, while natural processes of dispersion, evaporation and dissolving got rid of 84 million gallons, according to the report.
"Mother Nature is assisting here considerably," Lubchenco said. She cautioned that the oil that's left can harm wildlife for years or even decades to come, saying: "Diluted and out of sight doesn't necessarily mean benign."
Still, outside scientists said this was a just too-simple explanation for a complex oil that has confounded federal scientists at every turn.
"This is just way too neat," said Larry McKinney, director of the Texas A&M University research center on the Gulf of Mexico. "How can you even do this at this point? There's a lot of oil still floating out there."
McKinney said he most worried that this overly optimistic assessment would cost the government — and save BP — billions of dollars in the damage assessment process. McKinney, who has served as a state of Texas trustee in the process, said, "BP attorneys are placing this in plastic and putting this in frames."
White House energy adviser Carol Browner said, "We are going to continue to ensure BP is held accountable for damage they did."
MacDonald said the core of the idea here — that oil in water essentially has about a half-life of a week — makes sense, but what happened from there doesn't.
"There's some science here, but mostly, it's spin," he told The Associated Press. "And it breaks my heart to see them do it."
MacDonald pointed out that NOAA spent weeks sticking with its claim the BP well was spewing only 210,000 gallons a day. Now, after several revisions, the federal government said it really was 2.2 million gallons a day. So he has a hard time believing NOAA this time, he said.
'It's so bad'
Thousands of birds and other animals are known to have been damaged or killed by the spill. Efforts are still under way in Louisiana, Mississippi, Alabama and Florida to clean up more than 600 miles of oiled shoreline. As of last weekend, the government and BP collected 35,818 tons of oily debris from shorelines but more work remains to be done.
"There is no reason to exaggerate the impact, because it's so bad that we don't have to exaggerate," Hocevar said. "I stepped into an area that was the size of a football field and it had 50,000 dead crabs. This is an area that can no longer sustain life. You don't want to see 50,000 of anything dead."
Adding to the controversy are questions over the environmental impact of the nearly 2 million gallons of chemical dispersants used by BP to help break the oil into into droplets so huge slicks wouldn't tarnish shorelines and coat marine animals, and to encourage the oil to degrade more quickly.
Lawmakers in Washington pressed scientists Wednesday to explain what effects those chemicals will have on the Gulf's ecosystem.
Paul Anastas of the EPA's office of research and development acknowledged there are "environmental tradeoffs" to consider when using dispersants but said earlier this week that "dispersants were less toxic than oil or oil-dispersants mixture."
Residents, however, remain skeptical.
"These dispersants are confounding our detection efforts," said Susan McMillan, a 30-year Florida resident and the founder of a nonprofit group called Protect Our Waters, which organized in response to the spill.
McMillan told The Associated Press she is curious about who is testing Florida's waters for dispersant levels, if anyone, and whether the chemicals are dangerous to people and marine life.
"We never want our Gulf to be used in a giant Frankenstein experiment again," she said.
The Associated Press, Reuters contributed to this report.