Updated

The attacks of Sept. 11 have renewed the debate over drilling for oil in Alaska, with Republicans insisting on the need to be more self-reliant and Democrats criticizing their plan to open up the Arctic National Wildlife Refuge to achieve that self-reliance. To make their case, members on both sides of the aisle are using neighboring Prudhoe Bay as an example of the plusses and minuses of drilling in Alaska.

Environmentalists claim Prudhoe Bay, along the Arctic coast and west of the ANWR, has become a major industrial complex that has polluted the tundra, fouled the air and disturbed the wildlife. They argue the same thing will happen in ANWR if oil drilling is permitted.

Pro-development forces, on the other hand, point out that caribou and other wild animals are often seen wandering freely in the oil fields, and that the industry is now more environmentally friendly than ever.

There's truth to both arguments.

Prudhoe Bay, the flat coastal plain where mountains rise 100 to 150 miles from the sea, occupies the home range of the central Arctic caribou herd, which has grown to a record 27,000 animals. The population figures are used by developers to argue that 25 years of oil drilling has done no harm to the herd.

Drilling opponents don't dispute the numbers – or the fact that caribou sometimes linger in the oil fields – but they say studies show that the caribou have been displaced from their favorite calving grounds along the coast, and instead give birth in areas dozens of miles inland, a situation that could become a major problem for caribou in the ANWR who will have a much narrower 20-40 mile wide coastal plain.

For the porcupine herd of caribou, whose numbers reach nearly 130,000, that smaller coastal plain – reduced in size by drilling – means fewer places to birth.

"It could force caribou into areas that are very different, have much poorer forage and much higher numbers of predators," said Ken Whitten, a biologist at the University of Alaska at Fairbanks.

Then there's something called a "footprint." That's the amount of surface area occupied by oil production facilities.  In Prudhoe Bay, the footprint is about 9,000 acres spread across 1,000 square miles of tundra.

Oil industry experts say that footprint is getting smaller – wells that once occupied 65 acres of gravel pads built on top of the tundra now require only nine acres – and that's good for the ANWR's prospects.

"Oil development on the north slope has 30 years of research behind it and we've gotten to a point now where the footprint that we leave in development areas is very small," said Kim Duke, a spokeswoman for Arctic Power.

Oil experts also point to the technology behind the drilling. At Phillips Petroleum's new state-of-the-art "alpine" facility, drilling bits sunk into the ground in one spot can be maneuvered at different angles underground to find pockets of oil miles away, without disturbing the surface.

And now, instead of miles of gravel roads, facilities are being connected by ice roads built on top of the tundra during the long winter, leaving no trace behind when the snow is gone for three months each year.

That doesn't do much for environmentalists, who say there isn't enough surface water in ANWR to make all the needed ice roads.

And if the case of the caribou is not enough to sway opinions, there's also the case of the Gwitch'in Indians, who say the caribou are essential to their survival.

Part three of this series will look at the discord between two small bands of Native Americans whose lives are uniquely intertwined with the fate of the ANWR.