Misc challenges

This document discusses several environmental and social issues: deforestation is caused by population growth and urbanization which destroys natural habitat and the ozone layer; emitting chlorofluorocarbons causes loss of the ozone layer which removes ultraviolet protection from the sun; emitting carbon dioxide contributes to the greenhouse effect and climate change; sulfur emissions from factories cause acid rain which destroys forests and biodiversity; technological and biological advances enable weapons that could lead to war or fall into the wrong hands; and population growth, war, and natural disasters can exacerbate hunger and starvation.