Answer:
Climate Change
Step-by-step explanation:
Climate change affected all regions in the world, but it's not yet at the point where it make a specific place become inhabitable.
It's started with ecocide, European traders started to cut down the trees that exist in the Easter Island. Making a lot of animals lost their habitat. This includes animals that's usually a natural enemy for the rats (such as wild cats, or snakes)
This led to rat outbreaks that made it impossible for the people in Eastern Island to conduct a proper agricultural activities. Not only that, these rats also spread various type of diseases (such as salmonella)