They are parts of an enormously complex system. And unless we can learn to see them within the system, we have no hope of anticipating the damage they may do. A system is a set of interrelated elements in which some sort of change is occurring, and even very simple systems can behave in unpredictable ways. No one has been able to do it thus far. The unpredictable dynamics of system behavior have inspired an entire mathematical science, variously known as complexity or systems theory.
Systems theory is useful for exploring several other sciences, including ecology.
It's also useful for exploring the ways in which we can be surprised. Suppose, for example, that you were a marine biologist studying Black Sea plankton in the early 1970s. Had you confined your observations solely to the plankton themselves, you would have had no basis for predicting the explosion of red tides that followed the closing of the Iron Gates. But that's not true. No ecologist could have put it better.