Population.control.?

i am writing a persuasive speech where i basically want to make the cl aware of the consequences of having multiple children. global warming, epidemics,depletion of food and resources etc...I dont want gov't control i just want ppl to feel persuaded that having more than 2 children is not a good idea and that adoption is a great alternative if you want more. What would be the listeners reason for caring/listening?? what would be a good opening attenion getter?? any ideas or input on any of this would be greatly appreciated..THANK YOU