Biogeochemical cycle
A biogeochemical cycle is the movement and transformation of elements or compounds through living organisms, rocks, water, air, and chemical reactions.
What a biogeochemical cycle is
A biogeochemical cycle is a pathway by which matter moves through biology, geology, and chemistry. The term brings together living organisms, rocks and sediments, water, air, soils, and the reactions that transform substances from one form to another.
Matter cycles, energy flows
Ecosystems need a steady supply of elements, but Earth does not receive a fresh delivery of carbon, nitrogen, phosphorus, sulfur, or water every day. Matter is reused and redistributed. Energy, by contrast, mostly flows through systems from sunlight or chemical sources and eventually dissipates as heat.
Reservoirs and fluxes
A reservoir is a place or form where matter is stored, such as the atmosphere, ocean, soil organic matter, living biomass, rocks, or sediments. A flux is a movement between reservoirs, such as photosynthesis, respiration, weathering, runoff, burial, volcanic release, or microbial transformation.
Fast and slow pathways
Some cycling happens quickly. Carbon can move from air to leaves and back through respiration within a season. Other cycling is slow: phosphorus can remain in rocks or sediments for long periods before weathering or uplift makes it available again.
Biology changes chemistry
Organisms do more than ride along inside cycles. Plants fix carbon, microbes transform nitrogen and sulfur, animals move nutrients through food webs, and decomposers return elements from dead matter to soils and waters. Life actively changes the chemical form and location of elements.
Geology sets the long frame
Rocks, sediments, volcanoes, plate tectonics, erosion, and mineral weathering give many cycles their long-timescale structure. Some nutrients enter ecosystems mainly when minerals break down, while burial can remove material from short-term circulation for thousands to millions of years.
Human changes
Fertilizer production, fossil fuel burning, mining, land clearing, dams, agriculture, wastewater, and climate change have altered many biogeochemical cycles. These changes can increase greenhouse gases, nutrient pollution, acid deposition, soil depletion, or algal blooms.
Why it matters
Biogeochemical cycles explain how Earth keeps life supplied with matter while also showing how human activity can push systems out of balance. They connect crop fertility, climate, ocean chemistry, drinking water, ecosystem services, pollution, and the deep history of the planet.