We are one world on this planet - all our action affect our entire planet. The damage we do to one tiny island on the other side of this planet may change the world of or next neighborhood.
And since much of our modern products, food and gadgets are made from resources, materials or labor from other continents - all their pollution affects us as well. Hence We have reason to care for all planet, for the world, wellbeing and happiness of the humans on the other side of our planet as well.