the king has hosted a reception at buckingham palace as part of a drive to raise billions of pounds to protect nature. the event is being attended by politicians from around the world, business leaders and philantropists as our environment correspondent jonah fisher reports. and they ve come from the high arctic. for the last a0 years, dave paynter has been watching bewick swans winter at slimbridge. smaller than the mute swans that live here full time, each of them has a unique bill design. it s a fingerprint. we know every swan as an individual, and that s an incredibly valuable conservation tool. this year, 137 came to slimbridge. dave says in the 80s there were more than three times as many. the results of the destruction of wetland habitats, he says, and global warming, shifting their migration routes. some studies suggest that wildlife populations may have fallen by as much as two thirds in the last 50 years. in some areas we ve won a few battles but when we look at the war, we