Acid rain is formed when sulfur and nitrogen oxides from human sources like power plants and vehicles react with water vapor in the air to form acids. These acids can damage ecosystems when deposited as rain, snow, or fog. The effects of acid rain include sterilized soil, decreased plant growth, and harmed aquatic life. While natural phenomena also produce acids, human industrial activity since the Industrial Revolution has increased acidifying emissions and spread the problem regionally. Treaties have aimed to reduce sulfur emissions to lessen acid rain's environmental effects.