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How does the ozone layer protect life on Earth from ultraviolet radiation?

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Wispy cirrus clouds stretch across a bright blue sky above trees and a river at Pinawa Dam Provincial Park in Manitoba, Canada, with sunlight illuminating the scene. — Atmosphere The atmospheres of planets in the solar system are composed of various gases, particulates, and liquids. They are also dynamic places that redistribute heat and other forms of energy. On Earth, the atmosphere provides critical ingredients for living things. Here, feathery cirrus clouds drift across the deep blue sky over Pinawa Dam Provincial Park, near Pinawa, Manitoba, Canada.

The ozone layer acts as a critical protective shield for life on Earth by absorbing the most harmful ultraviolet (UV) radiation emitted by the Sun. Located primarily in the stratosphere, this region contains high concentrations of ozone (O₃) molecules that effectively block nearly all solar radiation with wavelengths shorter than 290 nanometers.123

By filtering out these high-energy wavelengths, the ozone layer prevents lethal levels of UV radiation from reaching the surface. This screening process is essential because intense UV exposure can damage DNA, cause skin cancer, and harm the immune system in humans, while also proving lethal to various organisms, including marine plankton and other foundational species in the food chain.24153

The formation of this layer was a pivotal development in Earth's history, as it allowed life to safely transition from the oceans to land. Today, protecting the ozone layer remains a global priority, as its depletion—often caused by human-released chemicals like chlorofluorocarbons—increases the amount of hazardous UV radiation reaching the surface, threatening both human health and global ecosystems.126