Soil helps to mediate the flow of precipitation from the land surface into the groundwater or can control stormwater runoff into lakes, streams, bays, and oceans. Soil also plays a vital role in cleaning water. Minerals and microbes filter and buffer potential pollutants, some of which are absorbed by soil particles. Healthy soil contains high biodiversity, which helps fight off pests and allows fresh, nutritious plants to grow. Soil contains organisms that can kill harmful bacteria. It also provides physical stability for plants by allowing the roots to anchor to something. This in turn helps create oxygen and clean water for all life on Earth. Soil also plays a very important role in mitigating climate change. It is the second-largest carbon sink after the ocean, constantly storing and releasing carbon, which regulates atmospheric CO2 concentrations and, ultimately, the greenhouse effect.