TORONTO: Walrus counting from space: How many tusked beasts do you see?

TORONTO: A new project aims to get a
better idea of the number of walruses on Earth by counting them from space.

Volunteers
are being sought to search through thousands of satellite images to see how
many of the tusked animals they can spot.

Scientists
need improved population data as they try to asses how this polar keystone
species will be affected by climate change.

Walruses
are heavily dependent on sea-ice, which has been in sharp retreat.

The
marine mammals will haul out on to the floes, to use them as a platform on
which to rest and raise their young, and as a base from which to launch
foraging trips.

A walrus
will drop to the seabed to hunt in the muds for clams and other invertebrates,
such as snails, soft shell crabs and shrimp.

All this
is being made more difficult as the extent of the seasonal sea-ice declines.

“We’re seeing about a 13%
loss in summer sea-ice per decade,” said Rod Downie, chief polar adviser
at environmental campaign group WWF.

“One
of the implications of not having the sea-ice to haul out on is that we’re
increasingly seeing walruses spend longer on land. And that comes with a number
of impacts, which include overcrowding with the potential for calves to be
crushed in stampedes. This happens. But also for local food sources to be
depleted,” he told BBC News.

WWF is running the “Walrus From Space” project jointly with the British Antarctic Survey,
which has expertise in satellite surveys of polar wildlife.

BAS has
long counted penguins from orbit, and is also now tracking seals, albatross,
and even whales under the water.

“It’s
only recently that satellites have had high enough resolution to allow us to
count walruses accurately,” said BAS remote-sensing specialist Peter
Fretwell.

“We’ll
be using Maxar’s WorldView satellite which has a resolution where each pixel is
only about 30cm on the ground. That’s about the size of an A4 sheet of paper
and we can easily count individual animals at that resolution.”

Volunteers
are being directed to an online portal where they’ll be shown images and asked,
in the first instance, merely to state whether or not the view contains one or
more of the tusked pinnipeds.

A second
phase, once all “empty” pictures have been excluded, will then ask
the volunteers to put a dot on every walrus they see.

The
survey, which will run for at least five years, is concentrating on the
Atlantic sub-species, and a somewhat isolated group of animals in the Laptev
Sea area.

Today’s estimate is that these
mammals in total probably number around 30,000. The project hopefully will
narrow the uncertainties.

Surveys
of this kind naturally come with some caveats. For example, the type of
satellite being used can’t see the Earth’s surface when it’s cloudy; and
walruses aren’t static, they move around. But such confounding factors are all
taken into account by the methodologies and models used to build population
data-sets.

And, of
course, they’re underpinned by the knowledge of indigenous communities who live
side-by-side with the walruses.

The
Walrus From Space project is receiving funding support from the People’s
Postcode Lottery, the Royal Bank of Canada and directly from WWF supporters.

The goal
is to recruit more than 500,000 citizen scientists over the next five years.
Early volunteers have included cub scouts, who’ve been testing the counting
portal ahead of its live launch.

Phoebe
Overton, from the 1st Molesey scout group in Surrey, acknowledged it was tricky
to identify the walruses even with the super-sharp pictures.

“It’s
quite hard because there are rusty barrels and rocks that look really
similar,” she said.

But
Charlotte Guise, from the nearby 9th Walton-on-Thames group, added, “it’s
fun to see the way they live and how many there are, and they are kind of
really cool creatures”.

There is
no plan at the moment for the project to try to count the Pacific sub-species
of walrus, which may number some 200,000 individuals. Again, this estimate is
uncertain.

“Whilst
the Pacific walruses are a lot more numerous, Atlantic walruses are probably
spread out over a larger area,” Dr Downie said. “And if you include
both Atlantic and Laptev, then you’re talking about a vast area with many more
haul-out sites. So, we’re focussing on them, but there’ll be other research
groups in the Arctic working on the Pacific sub-species.”