During the 1980s and 1990s, Earth's natural vegetation productivity increased by 6%. As explained in the journal Bioscience and the journal Geophysical Research Letters, this greening of the Earth was caused by warmer temperatures, longer growing seasons, more rainfall in certain areas, and more atmospheric carbon dioxide, which is a vital ingredient for plant photosynthesis. Along with this rise in natural vegetation productivity, atmospheric CO2 increased by 10%, global population increased by 45%, and apparent food consumption per person increased by 15% worldwide and 25% in developing countries.