Assessing ecosystem health

Abstract

I recognize the importance of much of the material in Rapport et al.'s recent TREE article1xRapport, D.J., Constanza, R., and McMichael, A.J. Trends Ecol. Evol. 1998; 13: 397–402Abstract | Full Text | Full Text PDF | PubMed | Scopus (352)See all References1, but criticize the basic theme around which it is organized. There are problems with the concept of ecosystem health, and in particular with the assumption that it is both analagous with and contributory to human health.There are well known difficulties in producing a rigorous definition of human health, but the idea that all was well before civilization came along smacks too much of ‘noble savage’ mythology. Wild populations of animals are not normally free of parasites, and we must imagine ‘primitive’ humans as also living in a fluctuating equilibrium with disease organisms of all kinds. Also, a population living with endemic malaria would not be regarded as a healthy one in modern terms. We presumably wish to define ‘healthy’ in terms of what can be expected under modern conditions, rather than in some primitive state that could be described as more ‘natural’. The ecosystems visited by the early European settlers in Africa were probably reasonably healthy in their own terms. That did not stop them being called the white man's grave.This immediately raises problems when we talk about humans as part of a wider ecosystem. The health of that system includes the welfare of the malaria parasite, and there is logically a negative correlation between that and human health. This is the fallacy of supposedly holistic views that assume no fundamental conflicts of interest, and it is one of the basic problems of the Gaia hypothesis.Even if we leave humans out of it, the health of an ecosystem is still not a variable that can be defined in value-free terms. Rapport et al.'s example of the Ponderosa pine ecosystem includes some very clear value judgements: for instance, parasites of trees are an indication of poor ecosystem health whereas saprophytes signify good health. This is obviously being seen purely from the standpoint of trees and their human consumers, rather than from any more objective view of overall ecosystem health. The second problem with the ‘healthy ecosystem’ approach to the ‘services’ provided for humans is that mention is rarely made of the biggest of them all – the production of food. Highly productive agriculture always seems to involve ecosystems that by any definition are degraded. The biggest conservation dilemma is whether our population can continue to be fed (and clothed, housed and warmed) without destroying most of what is left of even passably ‘natural’ ecosystems in the process. The present catastrophic destruction of the Amazon forest ecosystem described in another TREE article2xLaurance, W.F. Trends Ecol. Evol. 1998; 13: 411–415Abstract | Full Text | Full Text PDF | PubMed | Scopus (126)See all References2 cannot be condoned, but would our objections be as easy to defend if there were a convincing scheme to replace it with productive and sustainable agriculture? Discussion of the global ecosystem as a holistic unity ignores these dilemmas completely. If the prime determinant of human health is adequate nutrition, it is unlikely to correlate with the measures of ecosystem health being proposed.None of this is to deny the importance of an ecological view of both agriculture and human illness, and much that is said by Rapport et al. is very valuable, but the ecology invoked needs to be focused and relevant to specific problems, and not encumbered by mystical ‘holistic’ terminology.