Ecological systems at both population and community scales are recognized increasingly as being more open than previously thought. In coastal marine systems, physical oceanographic processes affecting larval stages are as, or more important than, biological interactions affecting adults. In terrestrial systems, the membership in ecological communities is controlled by geologic transport processes as much as by species interactions. Hence ecological science has become increasingly an earth science, and less a biological science. The differences between marine and terrestrial ecosystems imply that terrestrial systems are more localized functionally than marine systems; more likely to suffer extinction from habitat loss; and less likely to recover upon removal of stress. In addition, damage to a marine system is more likely to be felt further from the source of stress than it would in a terrestrial system. Finally, harvesting strategies at sea should react to continuous environmental monitoring whereas on land, demographically based strategies of harvest can suffice.