A 300 kilogram polar bear is on the loose.

What the helicopter's going to do, there's a nice flat open area behind here, we're going to

try and push him across.

It's a race to get to the bear before the bear gets to people.

In the air and on the ground, a Polar Bear Alert team zeroes in, armed with tranquilliser guns

It's a dangerous task -- there's a fear the panicked bear could turn and attack. We're

told to move, fast. Get back in the vehicle right now.

But finally, reluctantly, it goes down for the count. Yeah. The dart

Does it take a while to go down this one? Yeah. The dart

went low in the leg, so it didn't implode quite as quickly. In recent years, the Bear

Alert team has found more and more bears coming closer and closer to town.

When they come this close to Churchill, this is a big attraction for them because of smell and they root around

in the dump looking for food. Sheer Hunger? Sheer hunger. The polar bears of Churchill

are turning up hungrier each year.

The Cree Indians call the Polar Bear 'Wapusk' -- White Bear --

and that's the name of the vast national park in which they live, here on Hudson Bay,

in Canada. Thousands of visitors flock to this region every year for just a glimpse

of this majestic animal -- but there's now a belief, the very existence of the polar

bear in this wilderness is under threat. Lunn: Polar bears are really giving us a warning

signal that there is something going on and it's not just polar bears that are in trouble,

it could be an entire ecosystem, the entire arctic marine ecosystem.

Getting ready to

take to the air -- a research team from the Canadian Wildlife Service. For nearly 40 years,

scientists have studied the polar bears of Wapusk National Park, building an incredibly

detailed database. I made some blood kits -- there's more blood kits... Dr Nick Lunn,

on the right, has spent twenty years of his life studying the bears. Now a world authority

on the mammal -- he's deeply worried by what he sees.

The bears in this population over

the past two decades, which is sort of our best data set, is declining and that's consistent

for adult males and consistent for adult females with cubs. Each autumn Dr Lunn and his team

come to the park to carry out tests on the bears.Over the past 20 years are losing condition.

They're coming ashore lighter and lighter.

Knocked cold, the bear wakes hours later with

the equivalent of a hangover. The tests are done now while the bears are on shore during

the summer and autumn months. Winter is spent on the ice hunting their favourite prey, seals

and they're only forced ashore to fast when the winter ice melts. What troubles Dr Lunn

is his discovery the bears are being forced ashore earlier each year because the ice is

melting sooner.The air temperature in springtime since about 1950 when they first started recording,

looking at this stuff, has been warming at about .2 to .3 degrees Celsius per decade.

So over the past five decades that's an increase of anywhere from sort of 1 to 1 and a half

degrees Celsius warming trend. And this might require some help. I'm not that strong. What

we're seeing now is the break-up of sea ice here on Hudson Bay is occurring about one

and a half to two weeks earlier now in the early 2000's than it did in the early 1980's.

For the bears of Wapusk, the early break up of ice has had a dramatic effect.There's a

little bit of vegetation in his teeth. Historically, those last weeks of feeding before the ice

melts are when the bears find the bulk of their prey -- newborn seal pups. Well I feel

strongly that what's basically happening here is the bears are at the critical feeding time

just before they're coming ashore, they're, they have reduced access to seals so they're

simply just not able to put on as much fat in the springtime prior to being forced ashore,

as they used to. You can put your hands here and feel -- you can feel the vertebrae -- yep,

not a lot of fat on the ribs. For each week the bears come ashore earlier, they arrive

10 kilos lighter -- a critical loss of weight for a polar bear about to start a long fast.

Yeah he's below average and he's got another two, two and a half months to go. So by the

time he heads back out on the sea ice, he's going to be pretty hungry. Today the adult

males are 30 to 40 kilograms lighter than they were just 15 years ago. The greatest

fear is the weight loss may already be affecting females and their ability to produce cubs

-- and that the cubs that are born are not surviving.Well at some point in time this

population will probably become unviable -- it just will not be able to sustain itself here

and you'll probably lose this population or certainly major segments of it.

Wapusk National Park is alive with the animals of the tundra.

But scientists believe temperatures are rising

in Hudson Bay and throughout the Arctic, faster than anywhere else in the world. Mankind,

they argue, is causing it -- with decades of pollution and greenhouse gases.I think

the rapid rate at which this is occurring, to me sends some sort of alarm that this isn't

something natural. Usually natural events don't tend to be as dramatic and rapid as

they seem to be -- as our data seems to suggest they are. Dr Lunn's theory has powerful support.

At NASA, new satellite surveillance research reveals the thickest Arctic ice -- called

perennial ice -- is disappearing at an alarming rate. It's retreating and it's retreating

at a rapid rate of nine percent per decade. So that's quite substantial in terms of rate

of decline -- and if you project that, you might lose all that multi-year ice cover within

this century.

Neither is his prediction the worst case scenario. There's a belief that

less ice means less reflection of the sun's heat -- and the growing body of water will

get warmer and warmer -- speeding up the ice melt. Some modelling efforts have projected

we lose the ice totally in fifty years. If true, the change in climate may allow some

animals to inhabit areas previously too cold. But it may also mean the loss of other species,

like the polar bear.There are a number of species that depend on the ice above and below.

So if we're losing polar bears we're also probably having effects on those populations

and we may lose more than just bear species, we may lose the whole arctic marine eco-system.

But just as scientists are sounding the alarm, sceptics are calling for caution.

For Churchill,

a town dependent on eco tourism, losing the polar bears would be disastrous. Many don't

want to believe what the scientists are saying, for fear of what it will do to tourism -- and

the town.

We're not travelling in the smoothest town in the world. Merv Gunter is a former

banker turned tourism operator. It's our livelihood. Like this is our company, Tundra Buggy Tours,

we've invested in these over the last fifteen years. My wife and I, my son, are all involved

with the business. The polar bear business is the key part of what we do. It's probably

95 percent of our total revenue for our business. The height of the polar bear season lasts

just six weeks -- and it's enough to sustain a town -- a province -- all year round.Churchill

actually creates a spin-off benefit of about 130 to 160 million dollars for our province

-- the big impact is here locally in town. It's businessmen like Merv who challenge claims

the bears may be headed for extinction. I don't see a decreasing number of bears, I

sense a larger number of bears. I talk to our drivers and our guides and I ask how things

are going and what's going on out there and I mean there's days you don't see a lot of

bears -- that's just normal. But an overall reaction to it is, there seems to be all the

bears that we used to have and more. His greatest fear is an attempt to limit access to the

bears, based on scientific results that are not yet conclusive. The concern that bothers

me the most is people over-reacting, becoming alarmist, basing a conclusion on little fact

and more assumption and more emotion and that's not valid.

There's support for Merv from an

unexpected quarter. That is wonderful news. Thanks a lot. We've had many, many sightings.

So far this year, this year was a little unusual, it was the earliest the ice has ever broken

up, the earliest we've ever had bears come out to and in and around Churchill and actually

stay. Local conservation supervisor, Richard Romaniuk believes the abundant number of bears

near town is a good sign. We're now thinking that the bear population has actually increased.

We're considering it to be stable at 1200 bears, but realistically it could be closer

to 1400 or 1600. We're not seeing a reduction in the number of bears. So is the population

crashing at this present time? The answer is No. You're getting reports of many, many

more bears, for instance, in and around town than you had before. You just haven't seen

that before. Some people say that's an indication that the population is expanding -- that there's

just many, many more bears. An alternative hypothesis is that there are just many more

bears that are hungry, that are going in search of food, you know, and are attracted by the

sights and sounds of Churchill. The answer lies in greater research -- but there are

already signs 300 km further north that Dr Lunn may be right.

North of Churchill is the

territory of Nunavut and the town of Arviat -- where most inhabitants are indigenous Inuit.

The local language is Inuktutut - and on Sundays, that includes hymns and the Bible.

This community

has lived off the land for centuries -- and the key to that existence has always been

the seal.

Former church pastor, Jimmy Muckpah is also one of Arviat's most respected seal hunters.

We're out on the water today in the hunt for ringed seals-- a favourite with both

polar bears and Inuit hunters. The reason I'm doing this is that the seals normally

The reason I'm doing this is that the seals normally

come to investigate the scraping sound.

Not a seal in sight. In fact, conservationists

now believe there will be fewer seals in the future, because global warming is killing them.

We consider the ringed seal an indicator species because it's the most numerous mammal

in the arctic and it's very dependent on the sea ice, so if there's going to be a loss

of sea ice, that will be one of the first marine mammals to show these changes.

And from the past collections of seals that our data has provided us...

Canadian Fisheries officer Steve Ferguson has secured the consent of Arviat elders for hunters to

help his research. There's something bad happening in that spring, all the seal pups are dying.

When the ringed seals are caught, their organs will be bagged and sent for examination. A

picture will grow of the age, condition and reproduction of the seals -- all clues to

the fate of their missing young.

The indication now is that the snow may be a very important

characteristic -- that the amount of snow fall is important to protect the pups; the

females have their young underneath these little snow dens and if there's not enough

snow for them, they may be exposed to the cold or to predators like polar bears or arctic foxes.

For the

Inuit, it may mean the survival of a species that has contributed to their own survival.

I can speak about this because the seals have been part of my diet since I was a child.

That includes using them as clothing as well as feeding from them. I had so much seal skin

clothing as a child. Now, my daughters, my grandchildren and my wife can hunt seals in

the traditional way, through seal holes in the ice. The hunters that live in these communities

depend on the seals and other marine mammals for food, it's culturally important to them

as well as economically important. So we want to ensure that they have that lifestyle

through the climate changes. There are times when even the best hunters come home empty-handed.

There are times when even the best hunters come home empty-handed.

No seals today for Jimmy Muckpah. As he heads home, the land behind him is littered with

stone pillars called inukshuk, signposts that guide Inuit across this barren place. If Nick

Lunn is right, the polar bear itself is an Inukshuk, pointing the way to a devastating

loss affecting us all.I just see them as a very charismatic species, very intelligent,

very smart. For me, to think we may lose that is a sense of sort of sadness, I guess. If

I figure I may be working on a species that may no longer be around, down the road, it's

sort of like working on the dodo or some other species that have gone extinct in recent times.