Their Last Hope

In a near but distant future, the world is in ruins. The remaining 300 people are living underground. There is no chance of living in the outside world. Then the people find a way to live on Earth, but it it dangerous. They decided to send twenty 16 year olds to a small island that has borders that protected it from the dangers of the rest of the world. But the only way to do that was to make this island's environment change every day. If at least 15 people are still alive on the island after a year, then the rest of the people will join them. If not, the people that are still alive will have to stay there.......Forever.