Raine Island is a really small cay. It's located in the far northern section
of the Great Barrier Reef about 80 kilometres off the tip of Cape York.
Raine Island's one of the largest rookeries, in terms of the number of
turtles that come ashore every year, for green turtles in the world. The Raine
Island project has scientists involved from many
different disciplines and they are not only university scientists.
We have indigenous people with indigenous knowledge. We have government
scientists and scientists from other institutions, all
part of this larger project. The science disciplines, however, also vary so
we have disciplines including oceanography,
biology, physics, chemistry, social science... All of these
different disciplines have a role to play in terms of the Raine Island
project, the interventions that the government's
placing on the island and the science that's being done there
to try and understand the threats and also monitor the population.
The turtles in Raine Island, they've got a few problems. The first problem
is that the island is not supporting their nesting behaviour as well as it
used to, so we've got areas of the island where the
sand is too shallow for the turtles to dig their nests.
We've got areas of the island where the nests are vulnerable to the water table
rising or the over-topping of waves onto the island
and that's flooding the eggs. So rather than just watching that continue over
time, the decision was taken to try and do something about it
and the thing that was decided to do about it was to actually move sand
around on the island to lift up the parts of
the island that the turtles used for nesting
and rather than bringing sand from elsewhere, which could bring in a whole
lot of problems like pathogens or diseases that could be
harmful or could actually damage the reef and the corals around it,
the decision was to use natural processes much like what would happen in
big storms to transfer sediment from the beach back
up into those low areas where the turtles nest.
So we had to work out how much sand we could move, where we should move it from
and what times of the year we should move it at and
we did that by undertaking a whole range of analyses.
One of the things that was really critical to work out was
how long it would take the organisms on the reef flat, which actually
provide the sediment (the sediment is really just the bits and bobs
of all their skeletons) how long that would take to replenish the material
that we transferred from the beach back up onto the islands. And one of the
things that many people don't know is when you go to a coral cay
the sand that's on the beach, the sand that makes up the island isn't sand like
you would find down on the mainland beaches. It's not derived from rocks,
it is actually just the skeletal material bits and bobs of the skeletons
of all the organisms and plants and animals and corals
that live out there and on Raine Island one of the really important things
is that there's one particular organism, which many people know nothing about,
that provides about 50 per cent of the all of the sediment that's on the island
and without that sediment there's no turtles. So we had to work out how
much of that material gets produced in a year, how long it takes to go from where
it's being produced to the island and then we could work out
how much sand we could safely take from the beaches
before, you know, it either caused problems, which you didn't want to have
or before it would actually be able to recover from the sand that we've moved
away. What we've been able to do with the satellite tracking project is we can
tell now where the turtles are nesting on the
island. So we know that the turtles are nesting
on and using those places where the sand profiles have changed
and where the Queensland Government have placed their mitigation strategy. So we
know the turtles are using those new beach
areas that have been constructed. We also know that they're not only using
those areas but they're successfully laying eggs
into those areas and it's taking them less time to lay eggs into those
areas. In terms of the time spent on the beach,
which is good because it saves them energy.
The less energy a turtle takes to lay a clutch of eggs, the better.
So we know that, at least in that sense, those re-profiled or
new areas on the island are actually going to work.
Gradually we're going to see more hatchlings being produced from those
areas. Now this is a longer-term strategy, mitigation strategy, so it'll
take a number of years for it to produce
significantly more hatchlings but, season by season, we're showing gradual
progress in the number of hatchlings that are coming off the beach
and into the marine environment, which is a good thing.
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