Ecosystem health: more than a metaphor?

There is considerable discussion about the nature of the health metaphor as applied to ecosystems. One does not need to accept the analogy of ecosystem as 'organism' to reap insight into the diagnosis of ecosystem ills by applications of approaches pioneered in the health sciences. Ecosystem health can be assessed by the presence or absence of signs ecosystem distress, by direct measures of ecosystem resilience or counteractive capacity, and by evaluation of risks or threats from human activity and natural forces which may decrease the supply of ecological services. The focus of this essay is on what is and what is not implied by the ecosystem health metaphor. It also elaborates a research agenda for this emerging transdiciplinary science. One can argue that beyond the metaphor is the potential for systematic diagnosis of ecosystem ills, develop- ment of indicators of ecosystem health, development of early warning indicators of ecosystem dysfunction, development of diagnostic protocols and preventive strategies for maintaining ecological services