Half the World's Marine Life Lost in 40 Years: WWF

The global populations of some marine mammals, fish, birds and reptiles have declined by almost 50 percent in just four decades, according to a new report published on Wednesday by the World Wildlife Fund (WWF) in collaboration with the Zoological Society of London.

In the 2015 Living Blue Planet Report the WWF warns that the world's commercial fish stocks have been significantly affected by overfishing, climate change and pollution, and highlights that some of the most important species utilized by humans have been hit the hardest. The fish family which includes tuna and mackerel, for instance, has seen a decline of 74 percent between 1970 and 2010.

One in four species of sharks, rays and skates are now at threat of extinction, a problem which is again attributed to overfishing, while 29 percent of marine fisheries are overfished, according to the report.

Aside from the dwindling fish populations, the report also found that marine habitats were under threat. Half of the world's corals and seagrasses have already been destroyed, with the report saying that if temperatures continue to rise as they are now, coral reefs would cease to exist by 2050. Worldwide, mangroves decreased by 20 percent between 1980 and 2005.

The report addressed the problem of rubbish, and specifically plastic, in the world's oceans. 8 million tons of plastic waste is dumped every year into the oceans and it's estimated that there are currently more than 5 trillion plastic pieces in the sea, collectively weighing over 250,000 tons.

Writing in the introduction to the report, Marco Lambertini, the director general of WWF International, said it's obvious where to place the blame. "The picture is now clearer than ever: humanity is collectively mismanaging the ocean to the brink of collapse."

"The situation is urgent and the moment to act is at hand," he continued. "...The pace of change in the ocean tells us there's no time to waste. These changes are happening in our lifetime. We can and we must correct course now."

However, Lambertini also highlighted the ocean's ability to recover from its current situation if solutions are found quickly and key habitats are protected. "The ocean has another great advantage. It is a dynamic, interconnected global ecosystem that can bounce back relatively quickly if the pressures are dealt with effectively."