It's fun letting bright helium balloons fly up into the sky,but they are not biodegradable and they can injure or kill wild animals. If they land in the sea.the turtles,dolphins and whales can mistake them for jellyfish,a favourite food,and swallow them.The balloons can get caught in their stomachs and kill them.If the balloons land in a tree,birds and small animals can get caught in the string.So help wildlife:don't release balloons outside.