Things can also go awry when a species is added; for example, when the introduction of a nonnative fish leads to a massive reduction in the local elk population. Because of a fish? The earth’s ecosystems, it seems, are a bit too complex for us to compartmentalize them and draw up simple rules of cause and effect. Even conservation measures can have unexpected results. Who knew, for example, that recovering crane populations in Europe would affect the production of Iberian ham?