N atural resources such as forests and fisheries are complex. Yet ecosystems are much more complicated than the models discussed in previous chapters in Part VI. Managed ecosystems called “agriculture,” “aquaculture,” and “silviculture” are purposefully simplified for ease of management and for human enjoyment. The natural ecosystems (on which managed systems are inevitably dependent) are several orders of magnitude more complex than managed systems; many vital functions are derived from them, and thus the future of the human race depends on preserving them (see Chapter 22). Chapter 26 touched on this dependence in the discussion of wetland restoration.