There is a positive relationship between vegetation and climate particularly rainfall and temperature. The intensity of rainfall is high in the extreme south giving rise to mangrove swamp forests. The rainfall decreases towards the north till when the rainfall is low in extreme north, e.g Borno area. The decrease in rainfall also accounts for the decrease in the thickness of the vegetaton from rain forest to grassland. In other words, the heavier the rainfall the thicker the vegetation will be. Hence south with heavy rainfall results in rainforest while the north with little rainfall results in grassland or savanna.