What do the green stripes on the Nigerian flag represent?

I am so happy a question was about my country Nigeria, however my reservation is that though the natural wealth could be translated as Agriculture, but the green stands for our rich agricultural disposition, reason being that most ethnicity in Nigeria boast of agriculture as thier major occupation. so I would have preferred to see agriculture instead of natural wealth. it took me few secs, but I went with natural wealth because it was the closest possible answer to agriculture.