3. CLEAR WATER: HOW WE RESTORE OUR COASTAL WATERS

Up to the latter half of the 19th century, our waters were mostly crystal clear, thanks to the billions of native rock oysters, which can filter 200 litres of water a day, and to the abundant and rich beds of sea-grass. Industrialisation and dredging turned these waters pea-green and starved them of life. In this discussion, marine biologist Helen Scales and Charles Clover, writer and presenter of the award-winning documentary The End of the Line, look at how historic practices have transformed our coastline, but also offer hope for how the crisis in our oceans can be reversed, with benefits for both local communities and entire ecosystems.