http://news.independent.co.uk/uk/environment/story.jsp?story=454828
The Independent (U.K.),
Oct. 19, 2003
North Sea Undergoing
"Ecological Meltdown" Due to Warming
North Sea faces collapse of its ecosystem
Fish stocks and sea
bird numbers plummet as soaring water
temperatures kill off vital plankton
By Richard Sadler and Geoffrey Lean
The North Sea is undergoing
"ecological meltdown" as a result of
global warming, according to startling new research. Scientists
say that they are witnessing "a collapse in the system",
with
devastating implications for fisheries and wildlife.
Record sea temperatures
are killing off the plankton on
which all life in the sea depends, because they underpin
the entire marine food chain. Fish stocks and sea bird
populations have slumped.
Scientists at the Sir
Alistair Hardy Foundation for Ocean
Science in Plymouth, which has been monitoring plankton in
the North Sea for over 70 years, say that an unprecedented
heating of the waters has driven the cold-water species of
this microscopic but vital food hundreds of miles to the north.
They have been replaced by smaller, warm-water species that
are less nutritious.
"A regime shift
has taken place and the whole ecology of the
North Sea has changed quite dramatically", says Dr Chris
Reid,
the foundation's director. "We are seeing a collapse in the
system as we knew it. Catches of salmon and cod are already
down and we are getting smaller fish.
"We are seeing
visual evidence of climate change on a
large-scale ecosystem. We are likely to see even greater
warming, with temperatures becoming more like those off
the Atlantic coast of Spain or further south, bringing
a complete change of ecology.
"Some of the colder-water
fish species that people like
to have with chips are at the southern limit of their range,
and if the warming trend continues, cod are likely to become
extinct in the North Sea in the next few decades."
This year stocks of
young cod were at their lowest for 20 years.
The numbers of wild salmon have almost halved over the past
two decades and this year the numbers returning to British
rivers to spawn fell to a record low. Meanwhile, warm-water
fish such as red mullet, horse mackerel, pilchards and squid
are becoming increasingly common.
Overfishing has played
a part in the decline, but scientists
have been surprised to see that stocks have not made their
expected recovery after severe cuts in fishing quotas.
They say that continued warming will effect all forms of
marine life, including seabirds and dolphins.
Research by the Royal
Society for the Protection of Birds
has established that seabird colonies off the Yorkshire
coast and the Shetlands this year suffered their worst
breeding season since records began, with many simply
abandoning nesting sites.
The society puts it
down to a record slump in sand eels,
which normally breed in their millions, providing the staple
diet for many seabirds and large fish. The eels depend on
the plankton that are now being pushed out by the warming
waters.
The survey concentrated
on kittiwakes, but other species
that feed on the eels, including puffins and razorbills,
are also known to be seriously affected. Dr Euan Dunn of
the RSPB said last week: "We know that sand eel populations
fluctuate and you do get bad years. But there is a suggestion
that we are getting a series of bad years, and that suggests
something more sinister is happening."
He too pointed the
finger at global warming and added:
"Everything points to the conclusion that there are major
ecological changes going on in the North Sea."
Plankton
Microscopic creatures
found in their billions in every
square foot of sea. As the base of the marine food chain,
they are vital to young cod, salmon and sand eels.
As North Sea temperatures have risen, cold-water plankton
have moved hundreds of miles to the north, disrupting
ecology. Warmer-water species tend to be smaller and
less nutritious.
Crustaceans
Crab and lobster fisheries
are thriving in the warmer water
around the UK and on warm-water plankton which have taken
the place of cold-water species.
Sea birds
An RSPB survey this
summer shows east coast colonies of
kittiwakes, guillemots, puffins and razorbills had the
worst breeding season on record. Nest counts in east
Yorkshire and Shetlands show kittiwakes not laying or
hatching eggs because of a severe shortage of their
favourite food - sand eels. Some colonies have even
been abandoned.
Seals
Populations of common
seal were hit in the late Eighties
by viral infection. Numbers had almost recovered when
they were hit by a second outbreak last winter. Both
viral outbreaks coincided with influxes of warm Atlantic
water into the North Sea, and some scientists believe
that two events might be linked.
Salmon
Numbers estimated to
have almost halved in 20 years,
and this year adults returning to UK rivers fell to a
new low. Studies show salmon are highly dependent on
plankton on their journey to feeding grounds in the
north Atlantic.
Mediterranean
fish
As seas have warmed,
large numbers of Mediterranean
species, such as red mullet, squid and sardine, have
moved into UK waters. Red mullet, popular in Spain and
France, are now being caught commercially in the
North Sea. In the Channel there are emerging sardine
fisheries.
Sand eels
Make up between a third
and half of the weight of
all fish in the North Sea. Caught in huge quantities
by Danish factory ships, which turn them into food
pellets for pigs and fish. This summer, the Danish
fleet caught only 300,000 tonnes out of its
950,000-tonne quota - a record low.
Cod
Stocks of young cod
this year at their lowest for
20 years. Waters around the UK are the southern limit
of their range. The International Council for the
Exploration of the Seas says numbers are lower than
previously thought, and has called for a ban on cod
fishing in the North Sea and Irish Sea.
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