Above: The global marine Living Planet Index (LPI) shows a decline of 49 per cent between 1970 and 2012. This is based on trends in 5,829 populations of 1,234 species. Below: The index for Scrombidae (tuna, mackerel, bonito) declined 74 per cent between 1970 and 2010. Graphic: WWF / ZSL

By Fiona Harvey
15 September 2015

(The Guardian) – Tuna and mackerel populations have suffered a “catastrophic” decline of nearly three quarters in the last 40 years, according to new research.

WWF and the Zoological Society of London found that numbers of the scombridae family of fish, which also includes bonito, fell by 74% between 1970 and 2012, outstripping a decline of 49% for 1,234 ocean species over the same period.

The conservation charity warned that we face losing species critical to human food security, unless drastic action is taken to halt overfishing and other threats to marine life.

Louise Heaps, chief advisor on marine policy at WWF UK, said: “This is catastrophic. We are destroying vital food sources, and the ecology of our oceans.”

Attention in recent years has focused on species such as bluefin tuna, now on the verge of extinction in the Pacific, but other close relatives commonly found on restaurant menus or in tins, such as yellowtail tuna and albacore, are now also becoming increasingly scarce. Only skipjack, also often tinned, is showing “a surprising degree of resilience”, according to Heaps, one of the authors of the Living Blue Planet report [pdf] published on Wednesday.

Other species suffering major declines include sea cucumbers, a luxury food in Asia, which have fallen 98% in number in the Galapagos and 94% in in the Egyptian Red Sea. Populations of endangered leatherback turtles, which can be seen in UK waters, have plummeted.

Overfishing is not the only culprit behind a halving of marine species since 1970. Pollution, including plastic detritus which can build up in the digestive systems of fish; the loss of key habitats such as coastal mangrove swamps; and climate change are also taking a heavy toll, with the oceans becoming more acidic as a result of the carbon dioxide we are pouring into the atmosphere.

“I am terrified about acidification,” Heaps told the Guardian. “That situation is looking very bleak. We were taught in the 1980s that the solution to pollution is dilution, but that suggests the oceans have an infinite capacity to absorb our pollution. That is not true, and we have reached the capacity now.” [more]

Tuna and mackerel populations suffer catastrophic 74% decline, research shows


Cover of the 'Living Blue Plant Report 2015'. Graphic: WWF

15 September 2015 (WWF) – A new report on the health of the ocean finds that the marine vertebrate population has declined by 49 percent between 1970 and 2012.

WWF’s Living Blue Planet Report tracks 5,829 populations of 1,234 mammal, bird, reptile, and fish species through a marine living planet index. The evidence, analyzed by researchers at the Zoological Society of London, paints a troubling picture. In addition to the plummeting number of marine vertebrate species, populations of locally and commercially fished fish species have fallen by half, with some of the most important species experiencing even greater declines.

These findings coincide with the growing decline of marine habitats, where the deforestation rate of mangroves exceeds even the loss of forests by 3-5 times; coral reefs could be lost across the globe by 2050; and almost one-third of all seagrasses have been lost.

Global climate is one of the major drivers causing the ocean to change more rapidly than at any other point in millions of years. The oceans store huge quantities of energy and heat, but as the climate responds to increasing carbon emissions, the exchange intensifies. This may result in extreme weather events, changing ocean currents, rising sea temperatures, and increasing acidity levels—all of which aggravate the negative impacts of overfishing and other major threats such as habitat degradation and pollution.

Finding solutions for saving oceans

Though the challenge seems immense, it’s possible for governments, businesses, communities and consumers to secure a living ocean. To reverse the downward trend we need to preserve the oceans natural capital; produce better; consume more wisely; and ensure sustainable financing and governance.

Our ocean needs a strong global climate deal and work is already underway as President Obama and leaders of the Arctic nations recently pledged to work together to boost strong action on climate change. But more needs to be done to prioritize ocean and coastal habitat health.

Speak up for oceans! Together we can make a difference by halting the depletion of the ocean and restoring damaged ecosystems for species and people.

Read the Living Planet Report 2014.

An Uncertain Future for Our Living Blue Planet

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