If all second-order consumers are removed from an ecosystem, what is the most likely short-term effect?

Removing all second-order consumers, also known as secondary consumers, from an ecosystem disrupts the food chain and creates a significant impact on the populations of primary consumers (first-order consumers). In the short term, without the presence of these predators, first-order consumers, which typically feed on producers (like plants), have fewer checks on their population.

This absence of predation leads to an increase in the number of first-order consumers since they face reduced competition and predation pressures. As their populations grow, they may consume more producers (e.g., herbaceous plants), which could eventually affect the ecosystem's plant life. This is a direct illustration of how the removal of a trophic level affects the dynamics of the entire ecosystem, particularly influencing population growth rates at adjacent levels.

The other outcomes – such as a decrease in first-order consumers, a balanced ecosystem, or an increase in biodiversity – are less likely to happen directly after the removal of secondary consumers in the short term. Instead, the chain reaction initiated by the loss of these predators typically leads to an overabundance of first-order consumers.