1. The ozone layer: This layer in Earth's stratosphere protects us from harmful ultraviolet (UV) radiation from the sun. UV radiation can cause skin cancer, cataracts, and other health problems. The ozone layer is being depleted by human activities, such as the release of chlorofluorocarbons (CFCs) and other ozone-depleting substances.

2. The rainforests: Rainforests are home to an enormous amount of biodiversity, including many plant and animal species that are found nowhere else on Earth. Rainforests also play a vital role in the global climate system, helping to regulate temperature and humidity and providing a source of rainfall. Rainforests are being destroyed by human activities, such as deforestation for logging, agriculture, and development.

3. The oceans: The oceans cover over 70% of the Earth's surface and are home to a vast array of marine life. The oceans also play a vital role in the global climate system, helping to regulate temperature and humidity and providing a source of food for humans and other animals. The oceans are being threatened by human activities, such as overfishing, pollution, and climate change.