The eco guide to the ocean | Lucy Siegle

Over the past 40 years, we have killed off 50% of marine life through overfishing, habitat destruction and climate change. But the international spotlight and a change in policy mean things are looking up

I do love to be beside the seaside, but I am finding it increasingly hard to look the ocean in the eye. Over the past four decades we have killed off 50% of marine life through overfishing, habitat destruction and climate change. We shovel 250,000 tonnes of plastic into the ocean every year, and all Pacific tropical reefs could be lost by 2050. The blue planet gets short shrift; while we've protected 15.4% of terrestrial ecosystems, just 3.4% of the world's oceans are marine protected areas.

Land lubbers need to make a splash as ocean conservationists to push these numbers up. We should take a cue from earlier campaigns. In the 60s, a stretch of Australian coastal shelf was slated to become a limestone quarry. If it hadn't been for a few campaigning environmentalists, it would have been lost forever. Today the site is known as the Great Barrier Reef.