Ecological healthecosystem's pending loss of carrying capacity, ability to perform nature's services, or pending ecocide due to cumulative causes such as pollution. The term health is used to be reminiscent of human environmental health concerns, which are often closely related (but as a part of medicine not ecology). As with ecocide, that term assumes that ecosystems can be said to be alive (see also Gaia philosophy on this issue). While the term integrity or damage seems to take no position on this, it does assume that there is a definition of integrity that can be said to apply to ecosystems. The more political term ecological wisdom refers not only to recognition of a level of health, integrity or potential damage, but also, to a decision to do nothing (more) to harm that ecosystem or its dependents.
Measures of ecological health, like measures of the more specific principle of biodiversity, tend to be specific to an ecoregion or even to an ecosystem. Dependencies between species vary so much as to be difficult to express abstractly. However, there are a few universal symptoms of poor health or damage to system integrity:
- buildup of waste material and the proliferation of simpler life forms (bacteria, insects) that thrive on it - but no consequent population growth in those species that normally prey on them.
- loss of keystone species, often a top predator, causing smaller carnivores to proliferate, very often overstressing herbivore populations.
- many deaths due to disease rather than predation, climate, or food scarcity.
- migration of whole species into or out of a region, contrary to established or historical patterns
- proliferation of a bioinvader or even a monoculture where previously a more biodiverse species range existed.
Ecotage is another tactic thought to be effective by some in protecting the health of ecosystems, but this is hotly disputed. In general, low confrontation and much attention to political virtues is thought to be important to maintaining ecological health, as it is far faster and simpler to destroy an ecosystem than protect it - thus wars on behalf of ecosystem integrity may simply lead to more rapid despoliation and loss due to competition. See scorched earth and Easter Island Syndrome.
Deforestation and the loss of deep-sea coral reef habitat are two issues that prompt deep investigation of what makes for ecological health, and fuels a great many debates. The role of clearcuts, tree farms and trawler nets is often portrayed as negative in the extreme, held akin to the role of weapons on human life.