"The nightmare may be poised to repeat itself," the council said in a statement accompanying a report released Wednesday.

Algae blooms have been on the rise since the mid-1990s in parts of all of the Great Lakes except Lake Superior, whose icy waters are not as hospitable to the slimy aquatic plants.

The problem has worsened recently and is particularly severe on shallow, warm Lake Erie, experts said.

"It's very much the same story on our coast" on Lake Michigan, said John Berges, a biologist with the University of Wisconsin at Milwaukee's Great Lakes Water Institute.

Out-of-control algae look bad and smell worse but there are more serious dangers, the environmental council's report said.

Swimmers and pets who accidentally swallow algae-choked water can get sick. Algae blooms can reduce oxygen levels in the waters, causing fish kills. Some clumps are thick enough to block water intake pipes.

The surge four decades ago was blamed on excessive phosphorus, an essential plant nutrient. A single pound of phosphorus can stimulate growth of up to 500 pounds of algae, the report said.

Legislatures in Michigan and some neighboring states imposed limits on phosphate laundry detergents in the 1970s that were credited with significantly reducing the algae buildup.

But phosphorus continues flowing into the lakes from fertilizer runoff from farms and residential lawns, pet and livestock waste and leaky residential sewage systems, the report said.

Also, although Michigan was among the first states to virtually ban phosphorus in laundry soaps, it exempted dishwashing machine detergents -- a loophole the environmental council wants the state Legislature to close.

But Berges said he was skeptical that dishwashers are a primary culprit in the green slime's return.

A more likely cause -- and the reason the problem may be harder to solve this time -- is the arrival in the 1980s of two exotic species of mussels, the zebra mussel and its cousin, the quagga mussel, he said.

The mussels filter water, making it clearer, allowing sunlight to penetrate deep into the lakes, possibly enabling algae to thrive at greater depths than before, Berges said. The mussels also eat microscopic algae and excrete nutrient-rich wastes, he said.

Phosphorus levels are lower in the lakes than they were in the 1960s, increasing the likelihood the mussels are the leading cause of the algae's resurgence, he said.

The report recommends banning phosphorus in lawn fertilizer and dishwasher detergents, helping farmers and landowners create strips of natural vegetation along waterways to absorb excess phosphorus and patching up septic and municipal sewage systems.

"By looking at other stars that are currently at the state our Sun was in then, we can see that they are surrounded by a flattened disc of dust and gas," Wood says.

"We know that within about 10,000 years these formed into small bodies that were about 10 kilometres across."

Radioactive dating has shown that over the next 100,000 to one million years, those small "planetesimals" collided to form Moon-to-Mars sized planetary embryos.

Within 10 to 100 million years, larger planets had formed. "In the case of Earth, it was around 30 million years," Wood says.

Magma ocean

Early in its history, the Earth was probably covered in a sea of molten rock, hundreds of kilometres deep.

During the planet's development, this "magma ocean" reacted with metals in the planetesimals, extracting many of the most important and interesting elements, including gold, and eventually depositing them in the Earth's own iron-rich core.

To calculate how much gold was in the Earth's core Wood compared the composition of the Earth's crust with that of meteorites, which can be used to represent planetesimals.

He and other researchers have found that the meteorites had similar levels of all elements that would not normally dissolve in iron.

But they also noted that meteorites had higher levels of elements such as gold, platinum and nickel.

"This tells us that the Earth is chemically very similar to those meteorites, but the Earth's crust is depleted in all those elements that like to dissolve in iron," Wood says.

There's only one place those elements can have gone - the molten core.

"We can say that more than 99% of the Earth's gold is in the core," Wood says. "It's a nice image to think we could all step outside and be knee-deep in the stuff."

"The water is about one foot deep. The rivers are flowing above the danger level because of the rains upstream in India but so far there have been no reports of any casualties and communication links have not been cut," he said.

In the neighbouring Indian state of Assam flooding has forced nearly 500,000 people out of their homes and 16 people have died since the end of May.

Bangladesh, a low-lying delta nation which is criss-crossed by a network of 230 rivers, suffers regular floods with at least a fifth of the country inundated each year.

In July and August in 2004 flooding left more than 700 people dead and 38 percent of the country submerged, forcing millions to flee their homes.

The last Canadian outbreak occurred in November 2005 on the other side of the country, in British Columbia, and involved low-pathogenic H5N2 strain. In that case no birds actually showed signs of illness but 60,000 ducks and geese were culled nonetheless.

The Canadian Food Inspection Agency said there is no evidence that the latest bird flu case is the high-pathogen H5N1 strain that has spread to 48 countries so far since its resurgence in 2003.

If it is, it would be the first case in the Americas. The H5N1 strain has killed 129 people in nine countries since 2003, mostly in Asia.

"Just because the virus was there does not mean that's what killed the geese," said CFIA veterinarian Jim Clark.

"Ducks and geese are natural reservoirs for avian influenza viruses. The viruses exist quite nicely in their intestinal tract and cause absolutely no illness or death in the birds. That would be the situation in this case," he said.

A sample from the non-commercial flock of about 35 ducks, geese and chickens was brought to the Atlantic Veterinary College for testing after four goslings became sick on June 4, Clark said. The geese were not imported and there were no known links to Asia.

The CFIA has culled the entire backyard flock and is monitoring a 3 km (2 mile) zone around the property.

Prince Edward Island has only seven commercial chicken farms -- compared with over one thousand in top producer province Ontario -- and there are none within a 10 km (6 mile) radius of the affected farm, industry group Chicken Farmers of Canada said.

"We are alert but not alarmed, at this period in time," said Lisa Bishop-Spencer, a spokeswoman for the group. "We're going to wait for the results before we really react ... the fact that other birds appeared healthy is a very good sign in our eyes."

Not all H5 viruses are highly pathogenic and not all will cause severe disease in poultry.

Prince Edward Island's health officer, Dr. Lamont Sweet, told Reuters that the results of further bird flu tests were expected next week.

He downplayed any risk of transmission to humans but issued a warning nonetheless.

"People need to continue washing their hands carefully after handling poultry," Sweet said.

Canada, which has had numerous low pathogenic outbreaks, reported a case of H5N9 bird flu in 1966, which was highly pathogenic, and a case of high pathogenic H7N3 in 2004.

"It's going to be quite a fight not to lose them,'' said Kristy Bryner, a fire information officer.

Oak Creek Canyon, more than 90 miles north of Phoenix, contains a mix of homes, including upscale houses and mobile home parks, said Brenda Grey, a spokeswoman for Coconino County. It also contains hotels, resorts and stores scattered throughout the canyon.

Helge Zipprich, who lives in a mobile home in Oak Creek Canyon, said he and his three sons were in Sedona at the time of the evacuation so they didn't have time to get anything from their home. They arrived late Sunday at a Sedona evacuation shelter in Sedona with only their clothes.

Zipprich said the worst part was not knowing what's happening. "If the fire does spread and gets my home I wouldn't know,'' he said.

The fire ignited in a wooded area and quickly led to the evacuations in the Sedona subdivisions, including Cibola Hills, Rim Shadows, Painted Cliff, Shadow Rock Circle and Casa Contenta.

Evacuations followed in Oak Creek Canyon, a popular scenic area between Sedona and Flagstaff. The cause was under investigation. It was unclear how many people the evacuations included.

Melissa Wenzel, a spokeswoman for the Grand Canyon Chapter of the Red Cross, said about 50 people checked in at a shelter at a Sedona school. Only six were sleeping there as of early Monday. Only about two people checked in at a second shelter in Flagstaff on Sunday. She said other people were staying with friends or in hotels.