The diversity of species and genes in ecological communities affects the functioning of these communities. These ecological effects of biodiversity in turn are affected by both climate change through enhanced greenhouse gases, aerosols and loss of land cover and biological diversity causing a rapid loss of biodiversity and extinctions of species and local populations. The modern rate of extinction is sometimes considered a mass extinction with current species extinction rates on the order of 100 to 1000 times as high as in the past. The two main areas where the effect of biodiversity on ecosystem function have been studied are the relationship between diversity and productivity and the relationship between diversity and community stability.