Washington: A team of the world’s leading marine scientists has warned that life in the world’s oceans faces far greater change and risk of large-scale extinctions today than at any previous time in human history.
The researchers from Australia, the US, Canada, Germany, Panama, Norway and the UK have compared events which drove massive extinctions of sea life in the past with what is observed to be taking place in the seas and oceans globally today.
Three of the five largest extinctions of the past 500 million years were associated with global warming and acidification of the oceans – trends which also apply today, the scientists said.
Other extinctions were driven by loss of oxygen from seawaters, pollution, habitat loss and pressure from human hunting and fishing – or a combination of these factors.
“Currently, the Earth is again in a period of increased extinctions and extinction risks, this time mainly caused by human factors,” the scientists stated.
While the data is harder to collect at sea than on land, the evidence points strongly to similar pressures now being felt by sea life as for land animals and plants.
The researchers conducted an extensive search of the historical and fossil records to establish the main causes of previous marine extinctions – and the risk of their recurring today.
Marine extinction events vary greatly. In the ‘Great Death’ of the Permian 250 million years ago, for example, an estimated 95 per cent of marine species died out due to a combination of warming, acidification, loss of oxygen and habitat. Scientists have traced the tragedy in the chemistry of ocean sediments laid down at the time, and abrupt loss of many sea animals from the fossil record.
“We are seeing the signature of all those drivers today – plus the added drivers of human overexploitation and pollution from chemicals, plastics and nutrients,” said co-author Professor John Pandolfi, of the ARC Centre of Excellence for Coral Reef Studies and The University of Queensland, an authority on the fate of coral reefs in previous mass extinction events.
The researchers wrote the paper out of their concern that the oceans appear to be on the brink of another major extinction event.
“There may be still time to act. If we understand what drives ocean extinction, we can also understand what we need to do to prevent or minimise it,” Prof. Pandolfi added.
Their findings appeared in the online edition of Trends in Ecology and Evolution (TREE).