First, u start with address, and then,say the following:-
1. We may protect the ozone layer, by not using vehicles to go to the nearby places.
2. By using public transport vehicles like buses, etc...
3.Ozone layer is depleted by the emissions of more and more greenhouse gases. So, the emissions of these gases should be controlled.
4.The ozone layer is the layer which protects us for the harmful UV rays of the sun.So, it is our duty to protect the ozone. The government must allocate a separate field for non-polluting vehicles.,  etc...
Thus, I conclude my speech by saying that,
Protect our defender.
We must reduce the usage of vehicles, and can use cycles for nearby places, and public transports. This should be just a speech. It should be a life-turning moment. We should take care of our fragile planet, by following any way,
Thank you for giving me this opportunity to speak.