An ecosystem engineer is an organism that significantly alters its environment, impacting other species and ecosystem processes. Examples include beavers, which create wetlands by damming rivers, and corals that build reefs providing habitats for diverse marine life. By modifying physical landscapes, ecosystem engineers can enhance biodiversity, improve resource availability, and influence nutrient cycling. Their actions are pivotal in maintaining ecological balance, highlighting the intricate relationships among species within ecosystems and the importance of preserving these organisms for ecosystem health.