Tag Archives: Marine species

Offshore turbines get approval of seals

Researchers tracking the movements of seals in the North Sea reveal that “artificial reefs” created by wind farms and pipelines are becoming attractive as foraging grounds on fishing expeditions. LONDON, 25 July, 2014 − Environmental campaigners and countryside conservators aren’t the only fans of those great arrays of turbines, generating renewable energy from the winds at sea. Grey and harbour seals in the North Sea are beginning to show a preference for offshore wind farms as well. Deborah Russell, research fellow at the University of St Andrews, Scotland, and colleagues tracked the movements of both the harbour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). There are an estimated 56,000 harbour seals in the North Sea and around 65,000 of the greys haul out on the British coast on the North Sea alone. Tagged specimens, with their movements tracked by GPS satellite systems as they surface to breathe, reveal a lot about the ecology of each species and their response to environmental change.

Distinct preference

The researchers report in the journal Current Biology that some of their tagged animals seemed to show a distinct preference for offshore wind farms and associated pipelines. Eleven harbour seals headed for two wind farms: one was Alpha Ventus, off northern Germany, and the other was Sheringham Shoal, off the North Norfolk coast, England. Some individuals regularly cruised the sites, and some even revealed a pattern of grid-like movements as they appeared to forage at individual turbines. Two seals in the Netherlands were tracked along sections of submarine pipeline, on fishing expeditions that lasted 10 days at a time.

A harbour seal with a GPS phone tag used to track movements Image: Current Biology, Russell et al
A harbour seal with a GPS phone tag Image: Current Biology, Russell et al

The guess is that the seals regarded the offshore structures as artificial reefs where crustaceans settle and fish congregate. Turbine blades can swirl at speeds of up to 280 kilometres an hour, and represent a danger to  birds and bats − one estimate is that such structures in the US account for 600,000 bat deaths a year. But marine creatures far below the circling blades seem to value a touch of freshly-planted, three-dimensional shelter in the muddy basin of a shallow sea. “I was shocked when I first saw the stunning grid pattern of a seal track around Sheringham Shoal,” Dr Russell said. “You could see that the individual appeared to travel in straight lines between turbines, as if he was checking them out for potential prey, and then stopping to forage at certain ones.”

Open questions

Only a small proportion of the tracked animals showed a preference for wind farms, and such structures still cover only a trifling area of the available coast. But the research leaves open a number of questions. One is whether, as wind farms add to the available habitat in the North Sea, they will increase the available fish and crustacean populations, or whether they simply attract the prey and make life easier for innovative predators. As offshore investment grows, such studies may help engineers to design farms that help both the consumer and the wild things in the offshore waters. The researchers say: “In this period of unprecedented development of the marine renewables industry, the number of apex predators encountering such structures is likely to increase. The ecological consequences may be dependent on whether such reefs constitute an increase or just a concentration of prey.” – Climate News Network

Researchers tracking the movements of seals in the North Sea reveal that “artificial reefs” created by wind farms and pipelines are becoming attractive as foraging grounds on fishing expeditions. LONDON, 25 July, 2014 − Environmental campaigners and countryside conservators aren’t the only fans of those great arrays of turbines, generating renewable energy from the winds at sea. Grey and harbour seals in the North Sea are beginning to show a preference for offshore wind farms as well. Deborah Russell, research fellow at the University of St Andrews, Scotland, and colleagues tracked the movements of both the harbour seal (Phoca vitulina) and the grey seal (Halichoerus grypus). There are an estimated 56,000 harbour seals in the North Sea and around 65,000 of the greys haul out on the British coast on the North Sea alone. Tagged specimens, with their movements tracked by GPS satellite systems as they surface to breathe, reveal a lot about the ecology of each species and their response to environmental change.

Distinct preference

The researchers report in the journal Current Biology that some of their tagged animals seemed to show a distinct preference for offshore wind farms and associated pipelines. Eleven harbour seals headed for two wind farms: one was Alpha Ventus, off northern Germany, and the other was Sheringham Shoal, off the North Norfolk coast, England. Some individuals regularly cruised the sites, and some even revealed a pattern of grid-like movements as they appeared to forage at individual turbines. Two seals in the Netherlands were tracked along sections of submarine pipeline, on fishing expeditions that lasted 10 days at a time.

A harbour seal with a GPS phone tag used to track movements Image: Current Biology, Russell et al
A harbour seal with a GPS phone tag Image: Current Biology, Russell et al

The guess is that the seals regarded the offshore structures as artificial reefs where crustaceans settle and fish congregate. Turbine blades can swirl at speeds of up to 280 kilometres an hour, and represent a danger to  birds and bats − one estimate is that such structures in the US account for 600,000 bat deaths a year. But marine creatures far below the circling blades seem to value a touch of freshly-planted, three-dimensional shelter in the muddy basin of a shallow sea. “I was shocked when I first saw the stunning grid pattern of a seal track around Sheringham Shoal,” Dr Russell said. “You could see that the individual appeared to travel in straight lines between turbines, as if he was checking them out for potential prey, and then stopping to forage at certain ones.”

Open questions

Only a small proportion of the tracked animals showed a preference for wind farms, and such structures still cover only a trifling area of the available coast. But the research leaves open a number of questions. One is whether, as wind farms add to the available habitat in the North Sea, they will increase the available fish and crustacean populations, or whether they simply attract the prey and make life easier for innovative predators. As offshore investment grows, such studies may help engineers to design farms that help both the consumer and the wild things in the offshore waters. The researchers say: “In this period of unprecedented development of the marine renewables industry, the number of apex predators encountering such structures is likely to increase. The ecological consequences may be dependent on whether such reefs constitute an increase or just a concentration of prey.” – Climate News Network

Ocean damage 'is worse than thought'

FOR IMMEDIATE RELEASE
A new report says the world’s oceans are changing faster than previously thought, which could have dire consequences for both human and marine life.

LONDON, 3 October – Marine scientists say the state of the world’s oceans is deteriorating more rapidly than anyone had realised, and is worse than that described in last month’s UN climate report from the Intergovernmental Panel on Climate Change.

They say the rate, speed and impacts of ocean change are greater, faster and more imminent than previously thought – and they expect summertime Arctic sea ice cover will have disappeared in around 25 years.

Their review, produced by the International Programme on the State of the Ocean (IPSO)  and the International Union for the Conservation of Nature (IUCN) and published in the journal Marine Pollution Bulletin, agrees with the IPCC that the oceans are absorbing much of the warming caused by carbon dioxide and other greenhouse gases.

But it says the impact of this warming, when combined with other stresses, is far graver than previous estimates. The stresses include decreasing oxygen levels caused by climate change and nitrogen run-off, other forms of chemical pollution, and serious overfishing.

Professor Alex Rogers of the University of Oxford, IPSO’s scientific director, says: “The health of the ocean is spiralling downwards far more rapidly than we had thought. We are seeing greater change, happening faster, and the effects are more imminent than previously anticipated.”

The IUCN’s Professor Dan Laffoley says: “What these latest reports make absolutely clear is that deferring action will increase costs in the future and lead to even greater, perhaps irreversible, losses.”

Damaged molluscs found

The review says there is growing evidence that the oceans are losing oxygen. Predictions for ocean oxygen content suggest a decline of between 1% and 7% by 2100.

The loss is occurring in two ways: through the broad trend of decreasing oxygen levels in tropical oceans and areas of the North Pacific over the last 50 years, and because of the “dramatic” increase in coastal hypoxia (low oxygen) associated with eutrophication, when excessive nutrient levels cause blooms of algae and plankton.

The first is caused by global warming, the second by increased nutrient runoff from agriculture and sewage.

The authors are also concerned about the growing acidity of the oceans, which means “extremely serious consequences for ocean life, and in turn for food and coastal protection”. The Global Ocean Commission reported recently that acidification would make up to half of the Arctic Ocean uninhabitable for shelled animals by 2050.

Professor Rogers told the Climate News Network: “At high latitudes pH levels are decreasing faster than anywhere else because water temperatures are lower, and the water is becoming more acidic. Last year, for the first time, molluscs called sea butterflies were caught with corroded shells.”

When atmospheric CO2 concentrations reach 450-500 parts per million (ppm) coral reefs will be eroded faster than they can grow, and some species will become extinct. Projections are for concentrations to reach that level by 2030-2050: in May they passed 400 ppm for the first time since measurements began in 1958.

Methane a concern

With the ocean bearing the brunt of warming in the climate system, the review says, the impacts of continued warming until 2050 include reduced seasonal ice zones and increasing stratification of ocean layers, leading to oxygen depletion.

It also expects increased releases from the Arctic seabed of methane, a greenhouse gas at least 20 times more effective than carbon dioxide in trapping heat in the atmosphere (the releases were not not considered by the IPCC); and more low oxygen problems.

Another stress identified is overfishing. Contrary to claims, the review says, and despite some improvements, fisheries management is still failing to halt the decline of key species and damage to ecosystems. In 2012 the UN’s Food and Agriculture Organisation said 70% of world fish populations were unsustainably exploited.

The scientists say world governments must urgently reduce global CO2 emissions to limit temperature rise to under 2°C – something which would mean limiting all greenhouse gas emissions to 450 ppm.

They say current targets for carbon emission reductions are not enough to ensure coral reef survival and to counter other biological effects of acidification, especially as there is a time lag of several decades between atmospheric CO2 emissions and the detection of dissolved oceanic CO2.

Potential knock-on effects of climate change, such as methane release from melting permafrost, and coral dieback, mean the consequences for human and ocean life could be even worse than presently calculated. The scientists also urge better fisheries management and an effective global infrastructure for high seas governance. – Climate News Network

FOR IMMEDIATE RELEASE
A new report says the world’s oceans are changing faster than previously thought, which could have dire consequences for both human and marine life.

LONDON, 3 October – Marine scientists say the state of the world’s oceans is deteriorating more rapidly than anyone had realised, and is worse than that described in last month’s UN climate report from the Intergovernmental Panel on Climate Change.

They say the rate, speed and impacts of ocean change are greater, faster and more imminent than previously thought – and they expect summertime Arctic sea ice cover will have disappeared in around 25 years.

Their review, produced by the International Programme on the State of the Ocean (IPSO)  and the International Union for the Conservation of Nature (IUCN) and published in the journal Marine Pollution Bulletin, agrees with the IPCC that the oceans are absorbing much of the warming caused by carbon dioxide and other greenhouse gases.

But it says the impact of this warming, when combined with other stresses, is far graver than previous estimates. The stresses include decreasing oxygen levels caused by climate change and nitrogen run-off, other forms of chemical pollution, and serious overfishing.

Professor Alex Rogers of the University of Oxford, IPSO’s scientific director, says: “The health of the ocean is spiralling downwards far more rapidly than we had thought. We are seeing greater change, happening faster, and the effects are more imminent than previously anticipated.”

The IUCN’s Professor Dan Laffoley says: “What these latest reports make absolutely clear is that deferring action will increase costs in the future and lead to even greater, perhaps irreversible, losses.”

Damaged molluscs found

The review says there is growing evidence that the oceans are losing oxygen. Predictions for ocean oxygen content suggest a decline of between 1% and 7% by 2100.

The loss is occurring in two ways: through the broad trend of decreasing oxygen levels in tropical oceans and areas of the North Pacific over the last 50 years, and because of the “dramatic” increase in coastal hypoxia (low oxygen) associated with eutrophication, when excessive nutrient levels cause blooms of algae and plankton.

The first is caused by global warming, the second by increased nutrient runoff from agriculture and sewage.

The authors are also concerned about the growing acidity of the oceans, which means “extremely serious consequences for ocean life, and in turn for food and coastal protection”. The Global Ocean Commission reported recently that acidification would make up to half of the Arctic Ocean uninhabitable for shelled animals by 2050.

Professor Rogers told the Climate News Network: “At high latitudes pH levels are decreasing faster than anywhere else because water temperatures are lower, and the water is becoming more acidic. Last year, for the first time, molluscs called sea butterflies were caught with corroded shells.”

When atmospheric CO2 concentrations reach 450-500 parts per million (ppm) coral reefs will be eroded faster than they can grow, and some species will become extinct. Projections are for concentrations to reach that level by 2030-2050: in May they passed 400 ppm for the first time since measurements began in 1958.

Methane a concern

With the ocean bearing the brunt of warming in the climate system, the review says, the impacts of continued warming until 2050 include reduced seasonal ice zones and increasing stratification of ocean layers, leading to oxygen depletion.

It also expects increased releases from the Arctic seabed of methane, a greenhouse gas at least 20 times more effective than carbon dioxide in trapping heat in the atmosphere (the releases were not not considered by the IPCC); and more low oxygen problems.

Another stress identified is overfishing. Contrary to claims, the review says, and despite some improvements, fisheries management is still failing to halt the decline of key species and damage to ecosystems. In 2012 the UN’s Food and Agriculture Organisation said 70% of world fish populations were unsustainably exploited.

The scientists say world governments must urgently reduce global CO2 emissions to limit temperature rise to under 2°C – something which would mean limiting all greenhouse gas emissions to 450 ppm.

They say current targets for carbon emission reductions are not enough to ensure coral reef survival and to counter other biological effects of acidification, especially as there is a time lag of several decades between atmospheric CO2 emissions and the detection of dissolved oceanic CO2.

Potential knock-on effects of climate change, such as methane release from melting permafrost, and coral dieback, mean the consequences for human and ocean life could be even worse than presently calculated. The scientists also urge better fisheries management and an effective global infrastructure for high seas governance. – Climate News Network

Ocean damage ‘is worse than thought’

FOR IMMEDIATE RELEASE A new report says the world’s oceans are changing faster than previously thought, which could have dire consequences for both human and marine life. LONDON, 3 October – Marine scientists say the state of the world’s oceans is deteriorating more rapidly than anyone had realised, and is worse than that described in last month’s UN climate report from the Intergovernmental Panel on Climate Change. They say the rate, speed and impacts of ocean change are greater, faster and more imminent than previously thought – and they expect summertime Arctic sea ice cover will have disappeared in around 25 years. Their review, produced by the International Programme on the State of the Ocean (IPSO)  and the International Union for the Conservation of Nature (IUCN) and published in the journal Marine Pollution Bulletin, agrees with the IPCC that the oceans are absorbing much of the warming caused by carbon dioxide and other greenhouse gases. But it says the impact of this warming, when combined with other stresses, is far graver than previous estimates. The stresses include decreasing oxygen levels caused by climate change and nitrogen run-off, other forms of chemical pollution, and serious overfishing. Professor Alex Rogers of the University of Oxford, IPSO’s scientific director, says: “The health of the ocean is spiralling downwards far more rapidly than we had thought. We are seeing greater change, happening faster, and the effects are more imminent than previously anticipated.” The IUCN’s Professor Dan Laffoley says: “What these latest reports make absolutely clear is that deferring action will increase costs in the future and lead to even greater, perhaps irreversible, losses.”

Damaged molluscs found

The review says there is growing evidence that the oceans are losing oxygen. Predictions for ocean oxygen content suggest a decline of between 1% and 7% by 2100. The loss is occurring in two ways: through the broad trend of decreasing oxygen levels in tropical oceans and areas of the North Pacific over the last 50 years, and because of the “dramatic” increase in coastal hypoxia (low oxygen) associated with eutrophication, when excessive nutrient levels cause blooms of algae and plankton. The first is caused by global warming, the second by increased nutrient runoff from agriculture and sewage. The authors are also concerned about the growing acidity of the oceans, which means “extremely serious consequences for ocean life, and in turn for food and coastal protection”. The Global Ocean Commission reported recently that acidification would make up to half of the Arctic Ocean uninhabitable for shelled animals by 2050. Professor Rogers told the Climate News Network: “At high latitudes pH levels are decreasing faster than anywhere else because water temperatures are lower, and the water is becoming more acidic. Last year, for the first time, molluscs called sea butterflies were caught with corroded shells.” When atmospheric CO2 concentrations reach 450-500 parts per million (ppm) coral reefs will be eroded faster than they can grow, and some species will become extinct. Projections are for concentrations to reach that level by 2030-2050: in May they passed 400 ppm for the first time since measurements began in 1958.

Methane a concern

With the ocean bearing the brunt of warming in the climate system, the review says, the impacts of continued warming until 2050 include reduced seasonal ice zones and increasing stratification of ocean layers, leading to oxygen depletion. It also expects increased releases from the Arctic seabed of methane, a greenhouse gas at least 20 times more effective than carbon dioxide in trapping heat in the atmosphere (the releases were not not considered by the IPCC); and more low oxygen problems. Another stress identified is overfishing. Contrary to claims, the review says, and despite some improvements, fisheries management is still failing to halt the decline of key species and damage to ecosystems. In 2012 the UN’s Food and Agriculture Organisation said 70% of world fish populations were unsustainably exploited. The scientists say world governments must urgently reduce global CO2 emissions to limit temperature rise to under 2°C – something which would mean limiting all greenhouse gas emissions to 450 ppm. They say current targets for carbon emission reductions are not enough to ensure coral reef survival and to counter other biological effects of acidification, especially as there is a time lag of several decades between atmospheric CO2 emissions and the detection of dissolved oceanic CO2. Potential knock-on effects of climate change, such as methane release from melting permafrost, and coral dieback, mean the consequences for human and ocean life could be even worse than presently calculated. The scientists also urge better fisheries management and an effective global infrastructure for high seas governance. – Climate News Network

FOR IMMEDIATE RELEASE A new report says the world’s oceans are changing faster than previously thought, which could have dire consequences for both human and marine life. LONDON, 3 October – Marine scientists say the state of the world’s oceans is deteriorating more rapidly than anyone had realised, and is worse than that described in last month’s UN climate report from the Intergovernmental Panel on Climate Change. They say the rate, speed and impacts of ocean change are greater, faster and more imminent than previously thought – and they expect summertime Arctic sea ice cover will have disappeared in around 25 years. Their review, produced by the International Programme on the State of the Ocean (IPSO)  and the International Union for the Conservation of Nature (IUCN) and published in the journal Marine Pollution Bulletin, agrees with the IPCC that the oceans are absorbing much of the warming caused by carbon dioxide and other greenhouse gases. But it says the impact of this warming, when combined with other stresses, is far graver than previous estimates. The stresses include decreasing oxygen levels caused by climate change and nitrogen run-off, other forms of chemical pollution, and serious overfishing. Professor Alex Rogers of the University of Oxford, IPSO’s scientific director, says: “The health of the ocean is spiralling downwards far more rapidly than we had thought. We are seeing greater change, happening faster, and the effects are more imminent than previously anticipated.” The IUCN’s Professor Dan Laffoley says: “What these latest reports make absolutely clear is that deferring action will increase costs in the future and lead to even greater, perhaps irreversible, losses.”

Damaged molluscs found

The review says there is growing evidence that the oceans are losing oxygen. Predictions for ocean oxygen content suggest a decline of between 1% and 7% by 2100. The loss is occurring in two ways: through the broad trend of decreasing oxygen levels in tropical oceans and areas of the North Pacific over the last 50 years, and because of the “dramatic” increase in coastal hypoxia (low oxygen) associated with eutrophication, when excessive nutrient levels cause blooms of algae and plankton. The first is caused by global warming, the second by increased nutrient runoff from agriculture and sewage. The authors are also concerned about the growing acidity of the oceans, which means “extremely serious consequences for ocean life, and in turn for food and coastal protection”. The Global Ocean Commission reported recently that acidification would make up to half of the Arctic Ocean uninhabitable for shelled animals by 2050. Professor Rogers told the Climate News Network: “At high latitudes pH levels are decreasing faster than anywhere else because water temperatures are lower, and the water is becoming more acidic. Last year, for the first time, molluscs called sea butterflies were caught with corroded shells.” When atmospheric CO2 concentrations reach 450-500 parts per million (ppm) coral reefs will be eroded faster than they can grow, and some species will become extinct. Projections are for concentrations to reach that level by 2030-2050: in May they passed 400 ppm for the first time since measurements began in 1958.

Methane a concern

With the ocean bearing the brunt of warming in the climate system, the review says, the impacts of continued warming until 2050 include reduced seasonal ice zones and increasing stratification of ocean layers, leading to oxygen depletion. It also expects increased releases from the Arctic seabed of methane, a greenhouse gas at least 20 times more effective than carbon dioxide in trapping heat in the atmosphere (the releases were not not considered by the IPCC); and more low oxygen problems. Another stress identified is overfishing. Contrary to claims, the review says, and despite some improvements, fisheries management is still failing to halt the decline of key species and damage to ecosystems. In 2012 the UN’s Food and Agriculture Organisation said 70% of world fish populations were unsustainably exploited. The scientists say world governments must urgently reduce global CO2 emissions to limit temperature rise to under 2°C – something which would mean limiting all greenhouse gas emissions to 450 ppm. They say current targets for carbon emission reductions are not enough to ensure coral reef survival and to counter other biological effects of acidification, especially as there is a time lag of several decades between atmospheric CO2 emissions and the detection of dissolved oceanic CO2. Potential knock-on effects of climate change, such as methane release from melting permafrost, and coral dieback, mean the consequences for human and ocean life could be even worse than presently calculated. The scientists also urge better fisheries management and an effective global infrastructure for high seas governance. – Climate News Network

Rising CO2 'could devastate seas'

EMBARGOED until 0900 GMT on Thursday 29 August
The world’s marine species are liable to face 100,000 years of change, scientists say, unless greenhouse gas emissions are radically reduced.

LONDON, 29 August – Think of the Eocene geological epoch, more than 50 million years ago. Carbon dioxide concentrations exceeded 800 parts per million. Tropical oceans were at 35°C, nearing body temperature; polar oceans were 12°C, which is the temperature of the waters off San Francisco.

There was no Arctic ice. The coral reefs had all but perished. There were no reef fish and the seabed was paved with the remains of foraminifera, a tiny shellfish.

The ocean food web was dominated by minute picoplankton rather than the more substantial diatoms that are the basis of life today: these were creatures just too small to nourish the fish that would then become prey for today’s sharks, tuna, whales, seals and even seabirds.

The message is that cold is good for big creatures. The trade winds around 50 million years ago were feeble, the oceans were poorly ventilated, with huge zones in which oxygen was sparse or non-existent, and sea levels were high.

Then 56 million years ago came a crisis called the Paleocene-Eocene Thermal Maximum: it lasted 200,000 years and temperatures – already high – soared by at least 5° and perhaps 9°C. Ecosystems were disrupted, but extinctions were few: the sea’s animals managed by moving north or south.

Richard Norris of Scripps Institution of Oceanography at the University of California San Diego and colleagues want to use the Eocene 50 million years ago as a model for future possibilities. They point out in the journal Science that carbon dioxide levels passed the 400 parts per million mark in May 2013 and that if the world carries on burning fossil fuels at the present rate, then the conditions of the greenhouse world of 50 million years ago could be here in just 80 years.

And their message is: what happened once before could happen again. The seabed could become a disposal ground for featureless rubble, the acidification of the oceans could eliminate the coral reefs and leave the continental shelves smeared instead with red clay, and the food web on land and sea could start to alter. The lesson of the Paleocene-Eocene Thermal Maximum is that major ecological changes could endure a very long time.

A mere millennium of change?

Paradoxically, the approaching greenhouse world will not be because of an arbitrary change in planetary conditions, as it was last time; it will be a consequence of advanced industrial human society.

The scale of this consequence, however, will be quite disproportionate. Small bands of humans roamed the planet as scavengers and hunter-gatherers for 250,000 years in an “icehouse” world. They invented agriculture only 10,000 years ago, and started using fossil fuels in systematic ways only 200 years ago: the past 200 years, however, seem set to make a world of difference to the blue planet.

If greenhouse emissions are dramatically curtailed, then the oceans will still change, but the period of change may last only a thousand years or so, say the authors. If emissions continue to increase, then the consequences could be very long-lasting.

“Although the future ocean will begin to resemble the past greenhouse world, it will retain elements of the present “icehouse” world long into the future”, Norris and colleagues warn.

“Changing temperatures and ocean acidification, together with rising sea level and shifts in ocean productivity, will keep marine ecosystems in a state of continuous change for 100,000 years.” – Climate News Network

EMBARGOED until 0900 GMT on Thursday 29 August
The world’s marine species are liable to face 100,000 years of change, scientists say, unless greenhouse gas emissions are radically reduced.

LONDON, 29 August – Think of the Eocene geological epoch, more than 50 million years ago. Carbon dioxide concentrations exceeded 800 parts per million. Tropical oceans were at 35°C, nearing body temperature; polar oceans were 12°C, which is the temperature of the waters off San Francisco.

There was no Arctic ice. The coral reefs had all but perished. There were no reef fish and the seabed was paved with the remains of foraminifera, a tiny shellfish.

The ocean food web was dominated by minute picoplankton rather than the more substantial diatoms that are the basis of life today: these were creatures just too small to nourish the fish that would then become prey for today’s sharks, tuna, whales, seals and even seabirds.

The message is that cold is good for big creatures. The trade winds around 50 million years ago were feeble, the oceans were poorly ventilated, with huge zones in which oxygen was sparse or non-existent, and sea levels were high.

Then 56 million years ago came a crisis called the Paleocene-Eocene Thermal Maximum: it lasted 200,000 years and temperatures – already high – soared by at least 5° and perhaps 9°C. Ecosystems were disrupted, but extinctions were few: the sea’s animals managed by moving north or south.

Richard Norris of Scripps Institution of Oceanography at the University of California San Diego and colleagues want to use the Eocene 50 million years ago as a model for future possibilities. They point out in the journal Science that carbon dioxide levels passed the 400 parts per million mark in May 2013 and that if the world carries on burning fossil fuels at the present rate, then the conditions of the greenhouse world of 50 million years ago could be here in just 80 years.

And their message is: what happened once before could happen again. The seabed could become a disposal ground for featureless rubble, the acidification of the oceans could eliminate the coral reefs and leave the continental shelves smeared instead with red clay, and the food web on land and sea could start to alter. The lesson of the Paleocene-Eocene Thermal Maximum is that major ecological changes could endure a very long time.

A mere millennium of change?

Paradoxically, the approaching greenhouse world will not be because of an arbitrary change in planetary conditions, as it was last time; it will be a consequence of advanced industrial human society.

The scale of this consequence, however, will be quite disproportionate. Small bands of humans roamed the planet as scavengers and hunter-gatherers for 250,000 years in an “icehouse” world. They invented agriculture only 10,000 years ago, and started using fossil fuels in systematic ways only 200 years ago: the past 200 years, however, seem set to make a world of difference to the blue planet.

If greenhouse emissions are dramatically curtailed, then the oceans will still change, but the period of change may last only a thousand years or so, say the authors. If emissions continue to increase, then the consequences could be very long-lasting.

“Although the future ocean will begin to resemble the past greenhouse world, it will retain elements of the present “icehouse” world long into the future”, Norris and colleagues warn.

“Changing temperatures and ocean acidification, together with rising sea level and shifts in ocean productivity, will keep marine ecosystems in a state of continuous change for 100,000 years.” – Climate News Network