As sea levels rise, tough decisions are going to have to be taken about the flood defences of coastal Britain. How realistic will it be to continue to maintain them in future? In this programme, Qasa Alom asks whether we are facing up to this yet, and visits two places where the effects are already being felt. At Cwm Ivy on the Gower peninsula in South Wales, he visits a nature reserve where the decision has already been made to let the sea take back land which was originally claimed from it centuries ago. He walks along the sea wall which once kept the waves at bay, but which is now being left to gradually crumble away. The result is a landscape very different from the pasture and rough grazing which was here a few years ago. It's now being transformed into saltmarsh - a rarer and more valuable environmental habitat. It was a move which took careful consideration even for a nature reserve, but it's a much harder and more complicated decision when people's homes are involved. Qasa also visits the coastal village of Fairbourne in North Wales, which was earmarked for "decommissioning" almost a decade ago. He finds out what this could mean, asks whether it will really happen, and learns what the uncertainty of being labelled "the UK's first climate change refugees" has meant for the village's residents. Producer: Emma Campbell