Human activities are negatively impacting the environment in several key ways: 1) Carbon dioxide emissions from burning fossil fuels and deforestation are enhancing the greenhouse effect and causing global warming, droughts, and floods. 2) Unsustainable agricultural practices, overgrazing, and deforestation are contributing to desertification. 3) Water pollution from domestic, industrial, and agricultural waste is reducing water quality and causing eutrophication and algal blooms. 4) Construction of dams and depletion of aquifers are reducing water availability in some areas.