How do flowers help the earth?

Interesting question, other than edible flowers? Assuming you mean flowers in general they are a source of food for beneficial insects which in turn reduces the need to use insecticides, also they are a source of pollen for bees which supply honey. Honey has many uses in food products and also has anti-bacterial properites. Also worth mentioning is the work bees do pollinating ffod crops so any additional source of food for the hive cannot be all bad.