Page 51 - BBC Wildlife Volume 36 #11
P. 51
WILD NEWS
CONSERVATION REPORT RED LIST
STATUS
Greenturtle ENDANGERED
This month, the conservation spotlight
falls on a megaherbivore and its diet.
Where does it live? native seagrasses, the turtles are giving
The Green Turtle (Chelonia mydas) is a Halophila a competitive edge and helping
sea turtle that lives in the waters of the it spread to new areas. The invasion is
Atlantic salmon are
Caribbean. Its name comes from the happening faster in grazed regions.
starting to return to
colour of its body fat, resulting from the the Elan River.
adults’ diet of seagrass and algae. Can it be stopped?
Halophila is mainly a problem in tropical RIVER ECOLOGY
What’s the problem? waters. In the Mediterranean, it cannot
A seagrass from the Red Sea, introduced compete with the native seagrasses Gravel aids
to the eastern Caribbean in 2002, has adapted to cooler conditions. We can’t
already spread halfway across the region. do much to stop it spreading. But we river recovery
Halophila stipulacea is replacing the native can create conditions in which the
seagrass, which provides food and shelter native seagrasses flourish by addressing n August, juvenile Atlantic salmon
for many other organisms. Between 2011 local environmental problems such as Iwere spotted in the Elan River in
and 2017, Halophila spread from six to pollution, dredging and water clarity. mid-Wales for the first time in more
20 per cent of our monitoring sites on than 40 years. It’s an important step
Bonaire Island, while native seagrass Can the turtles adapt? in the recovery of the river, which had
declined by 33 per cent. The turtles may be able to switch diets gradually been depleted of aquatic life
from seagrass to algae, although that’s following the construction of the Elan
Why is that bad news for turtles? not straightforward because they carry a Valley dams in 1904. Gravel has played
Halophila is far less nutritious than the specialist cast of gut microbes that help a huge role in this turnaround.
native seagrasses, and is largely ignored them digest seagrass in particular. Our The recent discovery comes in the
by grazing green turtles. They’ll only eat it concern is that this invasion is happening wake of a three-year initiative by the
if there’s nothing else available, and then faster than they can adapt. S Blackman Wye and Usk Foundation, along with
they have to put more effort into grazing partners Dwr Cymru Welsh Water and
to meet their nutritional needs. This leads DR MARJOLIJN JA CHRISTIANEN Natural Resources Wales, to restore the
to slower growth rates and delayed sexual is assistant professor at Wageningen ecology of 7km of this tributary of the
maturity, which is significant in this slow- University in the Netherlands. Wye, near the dams. These structures
developing species. had prevented riverbed gravel flowing
FIND OUT MORE Journal of Ecology: down to the lower Elan, while existing
Turtlesaremakingmattersworse? https://besjournals.onlinelibrary.wiley. sediment had been washed away,
Yes. By preferentially grazing on the com/doi/10.1111/1365-2745.13021 leaving little habitat to support life.
Under the initiative, 2,300 tonnes of
new gravel have been deposited in the
The green turtle’s native river over the past two years, with regular
seagrass diet has given
a non-native seagrass top-ups planned. Initial surveys in 2017
a competitive edge. revealed invertebrates in the gravelled
area, while adult salmon were detected
Sa mon: L nda P tk n/2020VISION/NPL; turtle: Laura Dinraths/Shutterstock
spawning there last winter. Salmon and
brown trout fry were spotted near Elan
village in August – the first time they’ve
been seen there since the 1970s.
Tony Harrington, director of
environment at Dwr Cymru Welsh
Water, says: “We are delighted with the
results of this project. This is a great
example of where our funding to restore
a habitat has delivered real ecological
improvements.” C Vaughan
FIND OUT MORE Gravelling
the Elan: wyeuskfoundation.org
November 2018 BBC Wildlife 51
