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A young Brown Pelican balances on boom still strung around the island where it was hatched and grew up. Melanie Driscoll/���Ϲ���

Since the provisional capping of the Macondo well July 15, images of oil-soaked birds have begun to fade from newspapers and TV screens. Indeed, it appears that for birds, the risk of direct contact with oil is decreasing as escaped oil continues breaking down in the environment.
 
But oil persists on islands, in marshes and on beaches across the northern Gulf Coast. According to the federal government’s own figures, 659 miles of Gulf Coast shoreline are still oiled – 133 miles moderately to heavily so and 526 miles with “light to trace oil impacts.”

Six hundred and fifty miles is the distance between Atlanta and Baltimore.

Last week in Louisiana, and I observed oil-saturated sand – often buried under a layer of clean sand – on islands including Grand Isle and Raccoon Island.

Melanie Driscoll examines oil-saturated sand on Grand Isle, La. David J. Ringer/���Ϲ���

Describing the experience on Raccoon Island, Melanie wrote:

“I scraped the flat side of my gloved hand across the sand, and, half an inch down, the sand turned black. […] I scraped down once, twice, and a third time, and kept pulling up oiled sand.  I was near the water’s edge, and the hole I was digging quickly filled with oily water.”
 
Much of the oil that has soaked into Gulf Coast beaches and marshes will remain untouched by cleanup crews. That government figure of 659 miles will not dwindle to zero as the response drags on. Oil will stay in the environment and will continue to affect birds and other wildlife.

Oil oozes up from underneath the sand on a Grand Isle, La., beach, threatening birds and other wildlife. David J. Ringer/���Ϲ���

Birds may come into contact with the oil if it is exposed by tides, if it leaches out into the environment or as they probe with sensitive bills into oily sand. Sand-dwelling invertebrates, on which birds and other organisms feed, will certainly be killed or affected by buried oil, and history tells us that those effects can persist for years.

In 1969, a barge called the Florida disgorged 189,000 gallons of fuel oil on Cape Cod, Massachusetts. A decades later showed that although marshes looked healthy, oil remained in their soils, that bacteria had consumed the easily digestible components but left the rest (think of this as eating the sugar cubes but ignoring the carrots and broccoli), and that although the volume of residual oil is small relative to what was spilled, it continues to affect animals and the integrity of the marsh.

Fiddler crabs in particular dig misshapen burrows when they encounter oil, and they display other abnormal behaviors and appear to have a lower survival rate. And the burrows fiddler crabs dig – or would dig if they could – contribute to the health of the marsh vegetation, which holds the whole system together.

As people face the realization that oil from the BP Deepwater Horizon disaster will remain in the environment for years, many react with rage and blame. How dare BP and the government pull out before every last grain of sand is scrubbed clean? Outrage! Atrocity!

And it truly is a terrible thing. But to remove millions of cubic feet of oiled sand (some of which would be put in plastic bags and taken to landfills) would also be catastrophic. Efforts to clean sand and other components of the environment can have damaging effects that persist for years, as scientists .

There is no right answer, and that's something no one wants to hear.

Of course, I’ve been talking about oil that reached shore; effects on the marine environment remain largely unknown as scientists grapple with heretofore unexamined (and in many cases unimagined) complexities. Birds may still come into contact with oily waters, and populations of marine organisms from algae to fish will continue to be affected in unknown ways for an unknown period of time. If the effects are serious enough, they could extend up the food chain to birds and other organisms.

And so, as thousands of young Brown Pelicans and other birds leave their nests and seek a new place in the world, they face an uncertain future, though maybe – just maybe – one that looks a little brighter than it did two months ago.

A juvenile Brown Pelican tries out its wings, balancing on boom near Queen Bess Island in Barataria Bay, Louisiana. Melanie Driscoll/���Ϲ���