The Ten Percent Rule

Food webs follow a fundamental rule: only about ten percent of energy transfers from one level to the next. Grass captures solar energy. Grasshoppers keep ten percent of that. Birds eating grasshoppers keep ten percent again. This is why large predators are always rare.

The energy pyramid shows why ecosystems need vast bases of producers to support a few top predators. Damage the base through habitat loss or pollution, and the effects ripple upward through every level above.