Charting Progress – an integrated assessment of the state of UK seas found that, while much of the open sea is not affected by pollution from monitored contaminants, in some areas fishing, diffuse pollution and the invasion of non-native species is having an effect. Rising sea temperatures and increased acidification caused by climate change are compounding these problems.

It shows severe depletion in numbers of certain species around British waters.

The extent to which global warming is having an effect can be seen most closely in plankton movements. Warm water plankton in the North Sea are migrating northwards while cold-water plankton are moving even further north as seawater temperature rises.

Plankton are at the start of almost all marine food chains, so their movement is likely to impact on the animals that feed upon them. Equally, important is the way plankton act as a biological pump – using the carbon dioxide from the atmosphere as their food source for growth, in turn producing more food for animals higher up the chain, such as fish.

Howard Dalton, Defra’s Chief Scientific Adviser said the shift in plankton species was surprisingly large compared to movements of plants or bird on land. “By understanding the movement of plankton we are much better able to handle our fish resources,” he said.

Speaking at the launch of the report, Environment Minister Elliot Morley said: “Today’s report suggests that asking new questions of our marine environment requires a new approach. This new approach will hopefully give us the answers we are looking for and help us plan for the long term. But, what I can say with certainty is that we are having an adverse affect on our marine life and climate change is clearly evident in our seas.”

Mr Morley said that government was now looking at a number of measures to combat the decline in marine species and needed an integrated approach to persuade the fishing industry itself of the benefits of minimising its impact on the environment.

One measure being considered is ‘closed zones’ of the sea where no fishing at all can take place. These zones may be closed only on a seasonal or temporary basis, such as when full of growing, juvenile fish, or on a permanent basis to allow stocks to prosper and build up in severely depleted areas.

These closed zones could well be more effective than quotas or new regulations, Mr Morley said.

By David Hopkins

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