Nutrient cycle

A nutrient cycle is the model of how essential elements move between living organisms and their physical environment—cycling endlessly through cause and effect. These cycles are the planet's recycling system: nitrogen, phosphorus, carbon, and other nutrients are absorbed by life, released through decay and respiration, and absorbed again. Without them, Earth would be a graveyard of locked-away resources.

The most famous cycles are the Carbon cycle, Nitrogen cycle, and Phosphorus cycle. Each follows a similar rhythm: atoms are taken up by plants or microbes, passed through food chains, returned to soil or atmosphere via death and waste, then transformed by bacteria and chemistry back into usable forms. The timescales vary wildly—carbon cycles in years, while geological phosphorus cycling spans millennia.

These cycles are intimately connected to Ocean pollution, Ecosystems, and Climate. Human activities—fertilizer runoff, fossil fuel burning, industrial agriculture—have turbocharged some cycles, creating dead zones and atmospheric imbalances. Understanding nutrient cycles is essential for solving problems from eutrophication to climate change.

Nutrient cycles reveal a profound truth: there is no "away." Everything that leaves must return.

Related

Carbon cycle, Nitrogen cycle, Phosphorus cycle, Biogeochemical cycle, Ecosystems, Decomposition