By Robert K. Kaufmann and Cutler J. ClevelandThe world's first web-based textbook on environmental science. Learn more


Life Depends on the Sun

April 20, 2013, 3:50 pm
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The Sun underpins life on Earth in innumerable ways. The Sun powers photosynthesis, the conversion of light energy to chemical energy and its subsequent storage in the bonds of sugar.

This process occurs in plants and some algae that use only solar radiation, carbon dioxide (CO2), and water (H2O) to make sugar. Photosynthesis is arguably the most important energy conversion process on Earth because the chemical energy it yields is the base of food chains that sustain the overwhelming majority of other life forms.

The Sun drives many of planet's biogeochemical cycles, including the water cycle, the carbon cycle, and the nitrogen cycle. These material cycles provide nutrients for plants, clean water for human use, and otherwise support the array of environmental services that sustain life. These physical processes strongly influence the course of evolution and the distribution and abundance of life.

Fossil fuels—oil, natural gas, coal, oil sands—are derived from the Sun. These fuels are the lifeblood of industrial civilization, accounting for about 85% of global energy use. The formation of oil and natural gas began hundreds of millions ago with the life and then death of marine phytoplankton, bacteria, and other organisms. Their organic material was ultimately buried deep in the Earth's crust under low oxygen conditions where extreme temperature and pressure transformed them into the fuels we know them as today. Coal formation was favored in certain coastal swamps and bogs whee plant material accumulated after a drop in sea level to form large, thick layers of organic matte rich in cellulose and lignin, materials characteristic of higher plants. This material was ultimatl buried and transformed into coal deposits.

Thus, whether it is solar radiation warming your face today, or that which produced a diatom 300 million years ago, the Sun is the ultimate source of life on the planet.


  • What is photosynthesis?, Center for Bioenergy & Photosynthesis, Arizona State University, Accessed 18 March 2008.
  • How fossil fuels were formed, U.S. Department of Energy, Accessed 18 March 2008.


Cleveland, C. (2013). Life Depends on the Sun. Retrieved from