COLOGISTS USED TO BELIEVE that the systems they studied tended toward balance. Over the course of the 20th century, though, they realized that disturbance is not a detour but a destination. Humans can do terrible harm to ecosystems, of course, but disturbance itself is not necessarily a problem; in most ecosystems, the only steady state is a state of upheaval. Relationships between and among species, while indispensable and often enduring, are in constant flux, subject to small and large disruptions. The vaunted “balance of nature” is more or less a mirage.
