As well as having interlocking components, ecosystems also connect with each other. For example, during a flood, a river ecosystem might expand to take in the surrounding land. Conversely, during a drought, a river might reduce or evaporate entirely, so that land vegetation and animals now inhabit what was once a water-based ecology.
Even when they are stable, elements of different ecosystems are constantly moving to other ecosystems and back again. For example, air always moves across ecosystems, as does water. But so do some plants, animals and other organisms. A disaster for one ecosystem usually has a ripple effect on other systems, so we can think of the Earth as one giant ecosystem.
Although ecosystems are generally resilient, they can suffer irreparable damage, causing what is known as an ecological collapse. In the past this has happened due to the domino effects of natural phenomena such as volcanoes and asteroids. Scientists speculate that 305 million years ago the Carboniferous rainforest collapse, which led to the extinction of many plant and animal species, may have been at least partly caused by climate change.