Bottom-up cascades

A bottom-up trophic cascade occurs due to a disturbance in the balance of primary-producers in an ecosystem.

By removing primary-producers from the food web, the food for most of the trophic levels disappears, meaning the number of primary consumers will decline, as well as anyone feeding on the primary consumers.

By adding primary-producers to the food web, they might outcompete other primary-producers by removing nutrients or blocking the energy-source, but in theory, more food means more consumers.

When the main food source disappears most primary producers who rely on this food source disappear as well, those who mainly eat these disappear as well until the ecosystem becomes scarce.

This cascade will ultimately impact the apex predators, all due to a change at the primary producing level.