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Almost half of the oceans have been badly damaged by humanity and no region has been left untouched, the first global map of Man’s impact on marine ecosystems has revealed.

The ambitious project to chart the changing ocean environment shows that Man has exacted a much heavier toll on the seas through fishing, pollution and climate change than had been thought.

The world map, which was created by dividing the oceans into kilometre squares, shows that 41 per cent have been affected strongly by 17 human activities, a much higher proportion than expected.

Some of the worst-affected marine areas are found around the British Isles. Parts of the North Sea, the Channel and the North Atlantic off the Irish and Scottish coasts have all been assessed as suffering very high ecological damage.

The map is the first to combine information on how different human influences are affecting the oceans. It examined indicators of environmental health, including coral reefs, fisheries, kelp forests and water quality.

Ben Halpern, of the US National Centre for Ecological Analysis and Synthesis (NCEAS), who led the study, said: “This project allows us to finally start to see the big picture of how humans are affecting the oceans. Our results show that when these and other individual impacts are summed up, the big picture looks much worse than I imagine most people expected. It was certainly a surprise to me.”

David Garrison, the biological oceanography programme director at the US National Science Foundation, which funded the initiative, said: “This research is a critically needed synthesis of the impact of human activity on ocean ecosystems. The effort is likely to be a model for assessing these impacts at local and regional scales.”

The map, which was presented at the annual meeting of the American Association for the Advancement of Science in Boston yesterday, was produced by drawing up human impact scores for each marine square. A paper describing the map has been published in the journal Science.

Each type of human influence fits one of four categories: climate change, pollution, fishing and shipping. Climate change has had the greatest impact, particularly though rising sea temperatures and its effect of acidifying the oceans. The effect of fishing is the next most important, especially the damage that has been caused to coral reefs from trawling and stock depletions from overfishing.

In many regions the effects of these are combined with pollution, particularly run-off of fertilisers from agricultural land and invasive alien species that are often introduced in the ballast tanks of ships.

“Clearly we can no longer just focus on fishing or coastal wetland loss or pollution as if they are separate effects,” said Andrew Rosenberg, a professor of natural resources at the University of New Hampshire, an indepedent scientist who was not involved with the study.

“These human impacts overlap in space and time and, in far too many cases, the magnitude is frighteningly high. The message for policymakers seems clear to me: conservation action that cuts across the whole set of human impacts is needed now.”

Beyond British waters the regions that are most affected are in the South and East China seas, the Caribbean, the East Coast of North America, the Mediterranean, the Red Sea, the Gulf, the Bering Sea and several parts of the western Pacific. The areas near the poles have been affected the least but these regions are at risk of damage through global warming.

“Unfortunately as polar ice sheets disappear with a warming global climate and human activities spread into these areas there is a great risk of rapid degradation of these relatively pristine ecosystems,” Carrie Kappel, of NCEAS, a principal investigator on the project, said.

Dr Halpern said that while the picture is grim it could be reversed by urgent action. “There is definitely room for hope,” he said. “With efforts to protect the chunks of the ocean that remain relatively pristine we have a good chance of preserving them.

“My hope is that our results serve as a wake-up call to better manage and protect our oceans. Humans will always use the oceans for recreation, extraction of resources and commercial activity such as shipping. This is a good thing. Our goal is to do this in a sustainable way so that our oceans remain in a healthy state and continue to provide us with the resources we need and want.”

British scientists welcomed the study but said that the poor scores for British waters could reflect better recording of environmental problems.

Emma Jackson, of the Marine Biological Association, said: “The unsustainable way in which we exploit the goods and services that marine eco-systems provide are shown in this paper and, as a nation, we should be concerned.

“But we should consider that the UK human impact hotspot, which Halpern and colleagues have highlighted, is partly due to the fact that we are fairly good at recording our human activities. It is also down to a legacy of historical pressures, which we are now beginning to do something about by protecting our marine areas.”

Professor John Shepherd, of the National Oceanography Centre in Southampton, said: “This is a bold attempt to make a global map of human impacts on the ocean. The high impact shown for UK waters is probably due to heavy fishing, intensive exploitation of oil and gas resources, shipping and tourism. Not all of these lead directly to ecosystem damage but there is no doubt that mankind’s impact is significant.”

Professor Chris Frid, of the University of Liverpool, said: “As the management of human impacts on the environment seeks to be more holistic and ecosystem-based it is critical that we have means of assessing the sites of human impacts.

“Spatial mapping of the ‘footprint’ of human impacts is a useful way of doing this as different impacts — fishing, oil exploration, aggregate dredging — can then be superimposed. The results confirm the fact that coastal seas close to populous and industrialised areas are most impacted.

“The major limitation of this approach is the pseudo-precision of the maps. The original scientists did not score the impact of each activity in each square but their responses were transferred by the authors to these grids and then aggregated.

“The resulting broad patterns will be correct but the detail in terms of footprint and intensity will be approximate and must not be used as the basis for management decisions, for example on where to allow development.”

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