Ecosystems around the world are the result of the co-evolution of organisms over millions of years. Organisms in these ecosystems are adapted to their environment and to each other, and are interconnected through complex linkages – the exchange of energy and matter, pollination, dispersal, predation, competition, cooperation. All of this goes into the making of healthy ecosystems, which are dynamic but resilient, able to persist and bounce back from disturbance. The arrival of alien invasive species into such ecosystems can be a disruptive force. Invasive alien species can change ecosystem composition, affect the interactions between species, affect people who are dependent on services from natural ecosystems and also affect ecosystem resilience.  Let’s explore the answers to how and why this happens with our expert guests today.