what is the real cause of rapid population growth in these days?

whether you believe it or not , the Hindu scriptures say that the total number of jiva (one unit of life) is constant on the earth and all exist in one form or the other. Since man has virtually destroyed the animal kingdom and also destroying the aqatic kingdom those units have to reborn as human beings only for survival. The proof of this is man now are more like predators than human beings

People having too many babies. Also, the bigger the population gets, the bigger it will continue to get because of more people on earth to have babies. People are staying alive and healthy for longer periods of time, as well, which means more people are being born, but less people are dying young now.