The shift in thinking about how to manage national economies and economic systems in the 1980s was part of a broader revolution in intellectual thought. This is seen in ecology, where a shift in thinking about how to manage environments took place at the same time. Traditionally, the environment was viewed in determinist (structuralist) terms, as a system which was susceptible to management and manipulation. Ecosystems were thought to evolve through predictable stages, reaching a climax state. From the late 1980s, ecologists became increasingly convinced that ecosystems, like economic systems, are complex. They argued that while human intervention is often necessary, wherever possible it should be replaced with more natural controls, which can often fulfil policy aims as well if not better than deliberate intervention. Like economies, the best ecosystems are those which largely manage themselves.