2008-02-14

Almost half the world's 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 unprecedented effort to chart the changing ocean environment shows that Homo sapiens has exacted a much heavier toll on the seas than had previously been thought, through effects such as fishing, pollution and climate change.

The new world map, created by dividing the oceans in to kilometre squares, shows that 41 per cent have been affected strongly by 17 human activities, a much higher proportion than had been anticipated.

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

The ambitious project is the first to combine information on how various different human influences are affecting the oceans, examining a wide range of 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 today at the American Association for the Advancement of Science annual meeting in Boston, was produced by drawing up human impact scores for each marine square. A paper describing the map has also been published in the journal Science.

It included 17 types of human influence, each of which broadly fits one of four categories — climate change, pollution, fishing and shipping.

Climate change has had the greatest impact, particularly through rising sea temperatures and its effect of acidifying the oceans. Effects related to fishing are the next most important, especially damage to coral reefs from trawling and stock depletions caused by overfishing and bycatch.

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

“Clearly we can no longer just focus on fishing or coastal wetland loss or pollution as if they are separate effects,” said Andrew Rosenberg, 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 in many places around the globe.”

Beyond British waters, the worst affected regions 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 west Pacific.

The least-affected areas are mainly near the Poles, but these regions are at great risk of further damage through global warming.

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

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

“My hope is that our results serve as a wake-up call to better manage and protect our oceans rather than a reason to give up. Humans will always use the oceans for recreation, extraction of resources, and for commercial activity such as shipping. This is a good thing.

“Our goal — and really, our necessity — is to do this in a sustainable way so that our oceans remain in a healthy state and continue to provide us the resources we need and want.”

British scientists welcomed the study, though they 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 extort and exploit the goods and services marine ecosystems provide are shown in glorious technicolor in this paper, and as a nation we should be concerned.

“But before we all move to Peru, 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 (sometimes better than recording our marine habitats).

“It is also down to a legacy of historical pressures which we are now beginning to do something about - in particular by protecting our marine areas within a national regional and global context.”

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 on the sea around us is very significant and growing all the time.”

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 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 1km grid 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 or site marine reserves.”

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