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Fish Perish as Climate Change Disrupts Ocean Systems

MONACO, February 22, 2008 (ENS) – Climate change is threatening the world’s fish populations, already stressed by pollution, alien infestations and over-exploitation, warns a new report by the United Nations Environment Programme, UNEP.

The worst impacts are concentrated in 10 to 15 percent of the oceans, a far greater area than previously believed. These locations are “concurrent with today’s most important fishing grounds,” the report documents, including the 7.5 percent of the oceans that are the most economically valuable fishing areas of the world.

The findings come in a rapid response report entitled “In Dead Water,” which for the first time maps the multiple impacts of these stressors on the seas and oceans.


Tuna encircled in a net
(Photo courtesy NOAA)

The work of UNEP scientists in collaboration with universities and institutes in Europe and the United States, the report was presented today during the final day of UNEP’s Governing Council/Global Ministerial Environment Forum in Monaco. At least 100 environment ministers and other officials from 138 countries attended the three day meeting.

Dr. Christian Nellemann, head of the rapid response team that compiled the report, said, “We are already seeing evidence from a number of studies that increasing sea temperatures are causing changes in the distribution of marine life.”

“We are getting more and more alarming signals of dramatic changes in the oceans,” said Dr. Nellemann. “It is like turning a big tanker around. Our ability to change course and reduce emissions in the near future will be paramount to success.”

Some of these ocean changes are documented in the Continuous Plankton Recorder survey of the Northeast Atlantic.

Warmer water species of tiny animals called copepods have moved northward by around 1,000 kilometers during the second half of the 20th century, with the patterns continuing into the 21st century, the survey shows.

“Further evidence of this warming signal is seen in the appearance of a Pacific planktonic plant in the Northwest Atlantic for the first time in 800,000 years by transfer across the top of Canada due to the rapid melting of the Arctic in 1998,” said Dr. Nellemann.


A fishing boat full of anchoveta off the coast of Peru, 1999. (Photo by Jose Cort courtesy NOAA)

The report shows that at least 75 percent of the world’s key fishing grounds may be affected by changes in the circulation of ocean water as climate change interferes with the ocean’s natural pumping systems. These natural pumps bring nutrients to fisheries and keep them healthy by flushing out wastes and pollution.

Higher sea surface temperatures over the coming decades also threaten to bleach and kill up to 80 percent of the world’s coral reefs, which provide natural sea defenses, nurseries for fish, and income from the tourist industry for local communities.

There also is growing concern that the atmospheric concentration of carbon dioxide, CO2, is steadily rising, and oceans directly assimilate CO2. As ocean concentration of CO2 increases, the oceans automatically become more acidic.

This, in turn, may interfere with the ability of shellfish to form their shells and corals to form their structures due to a lack of calcium and also is likely to affect tiny creatures at the base of the food chain.

Dead zones, ocean areas low in oxygen, are increasing as a result of pollution from urban and agriculture areas. There are an estimated 200 temporary or permanent dead zones up from around 150 in 2003, the UNEP report shows.

In addition to the climate stress, fishing pressure is relentless.

Up to 80 percent of the world’s primary fish catch species are exploited beyond or close to their harvesting capacity, according to the report. Advances in technology, alongside subsidies, means the world’s fishing capacity is 2.5 times bigger that that needed to sustainably harvest fisheries.

Bottom trawling is among the most damaging and unsustainable of fishing practices.


Fisherman in the Western Indian Ocean hauls
in his catch. 1986. (Photo by Jose
Cort courtesy NOAA)

Alien invasive species, which can out-compete and dislodge native ones, are increasingly associated with the polluted, over-harvested and damaged fishing grounds. The report shows that the concentration of alien species matches the world’s major shipping routes.

Dr. Stefan Hain, of UNEP’s World Conservation Monitoring Centre, said it is critical that these existing stresses are also addressed in order to conserve fish stocks and coral reefs in a warming world.

“Coral reefs recovering faster are generally those living in marine protected areas and coastal waters where the levels of pollution, dredging and other kinds of human-induced disturbance are considered low,” he said.

The UNEP report comes in wake of findings issued last week by a team led by the National Center for Ecological Analysis and Synthesis which estimates that over 40 percent of the world’s oceans have been heavily impacted by humans and that only four percent remain relatively pristine.

“Climate change threatens coastal infrastructure, food and water supplies and the health of people across the world,” said UNEP Executive Director Achim Steiner. “It is clear from this report and others that it will add significantly to pressures on fish stocks.”

“This is as much a development and economic issue as it is an environmental one,” he said. “Millions of people, including many in developing countries, derive their livelihoods from fishing, while around 2.6 billion people get their protein from seafood.”

The new UNEP report draws on a wide range of new and emerging science including the latest assessment report of the Intergovernmental Panel on Climate Change – the 2,000 plus panel of scientists established by UNEP and the World Meteorological Organization.

Other contributions have come from organizations and institutions including the University of Plymouth, the Norwegian Institute for Nature Research, the University of British Columbia, the Institute of Zoology, Princeton University, the University of Barcelona and the Sustainable Europe Research Institute.

The report, “In Dead Water: Merging of climate change with pollution, over-harvest, and infestations in the world’s fishing grounds,” is online at: www.unep.org

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