If I get a chance to create something for the World , it will be a robotic DUST CLEANER! It will work on the biggest problem that mankind is facing and fighting with, AIR POLLUTION. And hence, is going to be the bestest friend of trees.
The dust cleaner will be of green, tree shape robotic machine with two big bulging eyes and a wide mouth on its face. There will be hundreds of tiny eco friendly jet boosters on each sides of it. Root type dangling would help it to fly. When it will reach to skyscraper height , it will open up its big mouth and suck all the dust, smoke and pollutant from air. After, working to capacity and reaching to its target, it would land at a place and clean all its content and release fresh , clean air into the sky by opening its mouth.
It will work and look similar to a green aerial plant, giving greenery and beauty to the world and making it a better place to live in.