Modern medical advances mean that people in developed countries are now living much longer lives than in the past.
As the number of people increases, so does the demand for food, water and other resources. Techniques developed to farm food and produce items that people want to use, from clothes and cars to computers, mean that the Earth’s resources are rapidly being used up. The harmful emissions produced by factories and vehicles cause environmental damage, such as climate change. You can get redirected here to learn the causes of overpopulation.
In a particular place, over population can also be caused by an influx of people forced into the area due to war, famine or other disasters making their previous home uninhabitable.
Climate Change is causing an increase in the number of hurricanes and floods and is likely to cause many more people to become displaced in the future. Overcrowding leads to further demand for limited resources and this, in turn, can lead to more conflict and warfare.
As humans seek out more resources, they take over land that was once the habitat of other species leading to huge biodiversity loss. Present extinction rates may be as high as 140,000 species lost every year due to humans over fishing and taking over large areas of land (such as tropical rainforests) to use for farming food and fuel crops.
Sir David Attenborough has stated that the level of human population has a knock-on effect on all other environmental problems. In 2013, he called humanity "a plague on the Earth" and suggested that limiting population growth would be necessary to control it.