Ecosystem health is a metaphor used to describe the condition of an ecosystem. Ecosystem condition can vary as a result of fire, flooding, drought, extinctions, invasive species, climate change, mining, overexploitation in fishing, farming or logging, chemical spills, and a host of other reasons. There is no universally accepted benchmark for a healthy ecosystem, rather the apparent health status of an ecosystem can vary depending upon which health metrics are employed in judging it and which societal aspirations are driving the assessment. Advocates of the health metaphor argue for its simplicity as a communication tool. "Policy-makers and the public need simple, understandable concepts like health." Critics worry that ecosystem health, a "value-laden construct", is often "passed off as science to unsuspecting policy makers and the public."
History of the concept
The health metaphor applied to the environment has been in use at least since the early 1800s and the great American conservationist Aldo Leopold (1887–1948) spoke metaphorically of land health, land sickness, mutilation, and violence when describing land use practices. The term "ecosystem management" has been in use at least since the 1950s. The term "ecosystem health" has become widespread in the ecological literature, as a general metaphor meaning something good, and as an environmental quality goal in field assessments of rivers, lakes, seas, and forests.
Recently however this metaphor has been subject of quantitative formulation using complex systems concepts such as criticality, meaning that a healthy ecosystem is in some sort of balance between adaptability (randomness) and robustness (order) . Nevertheless the universality of criticality is still under examination and is known as the Criticality Hypothesis, which states that systems in a dynamic regime shifting between order and disorder, attain the highest level of computational capabilities and achieve an optimal trade-off between robustness and flexibility. Recent results in cell and evolutionary biology, neuroscience and computer science have great interest in the criticality hypothesis, emphasizing its role as a viable candidate general law in the realm of adaptive complex systems (see  and references therein).
The term ecosystem health has been employed to embrace some suite of environmental goals deemed desirable. Edward Grumbine's highly cited paper "What is ecosystem management?" surveyed ecosystem management and ecosystem health literature and summarized frequently encountered goal statements:
- Conserving viable populations of native species
- Conserving ecosystem diversity
- Maintaining evolutionary and ecological processes
- Managing over long time frames to maintain evolutionary potential
- Accommodating human use and occupancy within these constraints
Grumbine describes each of these goals as a "value statement" and stresses the role of human values in setting ecosystem management goals.
It is the last goal mentioned in the survey, accommodating humans, that is most contentious. "We have observed that when groups of stakeholders work to define … visions, this leads to debate over whether to emphasize ecosystem health or human well-being … Whether the priority is ecosystems or people greatly influences stakeholders' assessment of desirable ecological and social states." and, for example, "For some, wolves are critical to ecosystem health and an essential part of nature, for others they are a symbol of government overreach threatening their livelihoods and cultural values."
Measuring ecosystem health requires extensive goal-driven environmental sampling. For example, a vision for ecosystem health of Lake Superior was developed by a public forum and a series of objectives were prepared for protection of habitat and maintenance of populations of some 70 indigenous fish species. A suite of 80 lake health indicators was developed for the Great Lakes Basin including monitoring native fish species, exotic species, water levels, phosphorus levels, toxic chemicals, phytoplankton, zooplankton, fish tissue contaminants, etc.
Some authors have attempted broad definitions of ecosystem health, such as benchmarking as healthy the historical ecosystem state "prior to the onset of anthropogenic stress." A difficulty is that the historical composition of many human-altered ecosystems is unknown or unknowable. Also, fossil and pollen records indicate that the species that occupy an ecosystem reshuffle through time, so it is difficult to identify one snapshot in time as optimum or "healthy.".
A commonly cited broad definition states that a healthy ecosystem has three attributes:
While this captures significant ecosystem properties, a generalization is elusive as those properties do not necessarily co-vary in nature. For example, there is not necessarily a clear or consistent relationship between productivity and species richness. Similarly, the relationship between resilience and diversity is complex, and ecosystem stability may depend upon one or a few species rather than overall diversity. And some undesirable ecosystems are highly productive.
"Resilience is not desirable per se. There can be highly resilient states of ecosystems which are very undesirable from some human perspectives , such as algal-dominated coral reefs." Ecological resilience is a "capacity" that varies depending upon which properties of the ecosystem are to be studied and depending upon what kinds of disturbances are considered and how they are to be quantified. Approaches to assessing it "face high uncertainties and still require a considerable amount of empirical and theoretical research."
Other authors have sought a numerical index of ecosystem health that would permit quantitative comparisons among ecosystems and within ecosystems over time. One such system employs ratings of the three properties mentioned above: Health = system vigor x system organization x system resilience. Ecologist Glenn Suter argues that such indices employ "nonsense units," the indices have "no meaning; they cannot be predicted, so they are not applicable to most regulatory problems; they have no diagnostic power; effects of one component are eclipsed by responses of other components, and the reason for a high or low index value is unknown."
Health metrics are determined by stakeholder goals, which drive ecosystem definition. An ecosystem is an abstraction. "Ecosystems cannot be identified or found in nature. Instead, they must be delimited by an observer. This can be done in many different ways for the same chunk of nature, depending on the specific perspectives of interest."
Ecosystem definition determines the acceptable range of variability (reference conditions) and determines measurement variables. The latter are used as indicators of ecosystem structure and function, and can be used as indicators of "health".
An indicator is a variable, such as a chemical or biological property, that when measured, is used to infer trends in another (unmeasured) environmental variable or cluster of unmeasured variables (the indicandum). For example, rising mortality rate of canaries in a coal mine is an indicator of rising carbon monoxide levels. Rising chlorophyll-a levels in a lake may signal eutrophication.
Ecosystem assessments employ two kinds of indicators, descriptive indicators and normative indicators. "Indicators can be used descriptively for a scientific purpose or normatively for a political purpose."
Used descriptively, high chlorophyll-a is an indicator of eutrophication, but it may also be used as an ecosystem health indicator. When used as a normative (health) indicator, it indicates a rank on a health scale, a rank that can vary widely depending on societal preferences as to what is desirable. A high chlorophyll-a level in a natural successional wetland might be viewed as healthy whereas a human-impacted wetland with the same indicator value may be judged unhealthy.
Estimation of ecosystem health has been criticized for intermingling the two types of environmental indicators. A health indicator is a normative indicator, and if conflated with descriptive indicators "implies that normative values can be measured objectively, which is certainly not true. Thus, implicit values are insinuated to the reader, a situation which has to be avoided."
It can be argued that the very act of selecting indicators of any kind is biased by the observer's perspective but separation of goals from descriptions has been advocated as a step toward transparency: "A separation of descriptive and normative indicators is essential from the perspective of the philosophy of science … Goals and values cannot be deduced directly from descriptions … a fact that is emphasized repeatedly in the literature of environmental ethics … Hence, we advise always specifying the definition of indicators and propose clearly distinguishing ecological indicators in science from policy indicators used for decision-making processes."
And integration of multiple, possibly conflicting, normative indicators into a single measure of "ecosystem health" is problematic. Using 56 indicators, "determining environmental status and assessing marine ecosystems health in an integrative way is still one of the grand challenges in marine ecosystems ecology, research and management"
Another issue with indicators is validity. Good indicators must have an independently validated high predictive value, that is high sensitivity (high probability of indicating a significant change in the indicandum) and high specificity (low probability of wrongly indicating a change). The reliability of various health metrics has been questioned and "what combination of measurements should be used to evaluate ecosystems is a matter of current scientific debate." Most attempts to identify ecological indicators have been correlative rather than derived from prospective testing of their predictive value and the selection process for many indicators has been based upon weak evidence or has been lacking in evidence.
In some cases no reliable indicators are known: "We found no examples of invertebrates successfully used in [forest] monitoring programs. Their richness and abundance ensure that they play significant roles in ecosystem function but thwart focus on a few key species." And, "Reviews of species-based monitoring approaches reveal that no single species, nor even a group of species, accurately reflects entire communities. Understanding the response of a single species may not provide reliable predictions about a group of species even when the group is comprised of a few very similar species."
Relationship to human health: the health paradox
A trade-off between human health and the "health" of nature has been termed the "health paradox" and it illuminates how human values drive perceptions of ecosystem health.
Human health has benefited by sacrificing the "health" of wild ecosystems, such as dismantling and damming of wild valleys, destruction of mosquito-bearing wetlands, diversion of water for irrigation, conversion of wilderness to farmland, timber removal, and extirpation of tigers, whales, ferrets, and wolves.
There has been an acrimonious schism among conservationists and resource managers over the question of whether to "ratchet back human domination of the biosphere" or whether to embrace it. These two perspectives have been characterized as utilitarian vs protectionist.
The utilitarian view treats human health and well-being as criteria of ecosystem health. For example, destruction of wetlands to control malaria mosquitoes "resulted in an improvement in ecosystem health." The protectionist view treats humans as an invasive species: "If there was ever a species that qualified as an invasive pest, it is Homo sapiens,"
Proponents of the utilitarian view argue that "healthy ecosystems are characterized by their capability to sustain healthy human populations," and "healthy ecosystems must be economically viable," as it is "unhealthy" ecosystems that are likely to result in increases in contamination, infectious diseases, fires, floods, crop failures and fishery collapse.
Protectionists argue that privileging of human health is a conflict of interest as humans have demolished massive numbers of ecosystems to maintain their welfare, also disease and parasitism are historically normal in pre-industrial nature. Diseases and parasites promote ecosystem functioning, driving biodiversity and productivity, and parasites may constitute a significant fraction of ecosystem biomass.
The very choice of the word "health" applied to ecology has been questioned as lacking in neutrality in a BioScience article on responsible use of scientific language: "Some conservationists fear that these terms could endorse human domination of the planet … and could exacerbate the shifting cognitive baseline whereby humans tend to become accustomed to new and often degraded ecosystems and thus forget the nature of the past."
Criticism of the concept and proposed alternatives
Criticism of ecosystem health largely targets the failure of proponents to explicitly distinguish the normative dimension from the descriptive dimension, and has included the following:
- Ecosystem health is in the eye of the beholder. It is an economic, political or ethical judgement rather than a scientific measure of environmental quality. Health ratings are shaped by the goals and preferences of environmental stakeholders. "At the core of debates over the utility of ecosystem health is a struggle over which societal preferences will take precedence."
- Health is a metaphor, not a property of an ecosystem. Health is an abstraction. It implies "good", an optimum condition, but in nature ecosystems are ever-changing transitory assemblages with no identifiable optimum.
- Use of human health and well-being as a criterion of ecosystem health introduces an arrogance and a conflict of interest into environmental assessment, as human population growth has caused much environmental damage.
- Ecosystem health masquerades as an operational goal because environmental managers "may be reluctant to define their goals clearly."
- It is a vague concept. "Currently there are many, often contradictory, definitions of ecosystem health," that "are open to so much abuse and misuse that they represent a threat to the environment."
- "There are in general no clear definitions of what proponents of the concept mean by 'ecosystem'."
- The public can be deceived by the term ecosystem health which may camouflage the ramifications of a policy goal and be employed to pejoratively rank policy choices. "The most pervasive misuse of ecosystem health and similar normative notions is insertion of personal values under the guise of 'scientific' impartiality."
Alternatives have been proposed for the term ecosystem health, including more neutral language such as ecosystem status, ecosystem prognosis, and ecosystem sustainability. Another alternative to the use of a health metaphor is to "express exactly and clearly the public policy and the management objective", to employ habitat descriptors and real properties of ecosystems. An example of a policy statement is "The maintenance of viable natural populations of wildlife and ecological functions always takes precedence over any human use of wildlife." An example of a goal is "Maintain viable populations of all native species in situ." An example of a management objective is "Maintain self-sustaining populations of lake whitefish within the range of abundance observed during 1990-99."
Kurt Jax presented an ecosystem assessment format that avoids imposing a preconceived notion of normality, that avoids the muddling of normative and descriptive, and that gives serious attention to ecosystem definition. (1) Societal purposes for the ecosystem are negotiated by stakeholders, (2) a functioning ecosystem is defined with emphasis on phenomena relevant to stakeholder goals, (3) benchmark reference conditions and permissible variation of the system are established, (4) measurement variables are chosen for use as indicators, and (5) the time scale and spatial scale of assessment are decided.
Ecological health has been used as a medical term in reference to human allergy and multiple chemical sensitivity and as a public health term for programs to modify health risks (diabetes, obesity, smoking, etc.). Human health itself, when viewed in its broadest sense, is viewed as having ecological foundations. It is also an urban planning term in reference to "green" cities (composting, recycling), and has been used loosely with regard to various environmental issues, and as the condition of human-disturbed environmental sites. Ecosystem integrity implies a condition of an ecosystem exposed to a minimum of human influence. Ecohealth is the relationship of human health to the environment, including the effect of climate change, wars, food production, urbanization, and ecosystem structure and function. Ecosystem management and ecosystem-based management refer to the sustainable management of ecosystems and in some cases may employ the terms ecosystem health or ecosystem integrity as a goal.
- Rapport, David (1998). "Defining ecosystem health." Pages 18-33 in Rapport, D.J. (ed.) (1998). Ecosystem Health. Blackwell Scientific.
- Rapport, David J. (1992). "Evaluating ecosystem health." Journal of aquatic ecosystem health 1:15-24
- Palmer, Margaret A. and Catherine M. Febria (2012). "The heartbeat of ecosystems." Science 336:1393-1394.
- Meyer, Judy L. (1997). "Stream health: incorporating the human dimension to advance stream ecology." Journal of the North American Benthological Society 16:439^447
- Lackey, Robert T. (2007). "Science, scientists, and policy advocacy." Conservation Biology. 21(1): 12-17.
- Anon (1816). "Rural economy, agricultur " Encyclopaedia Perthensis Volume 19, 391-497. Edinburgh: John Brown.
- Anon (1839). "On the culture of potatoes". Framer's Magazine, 2(5):337-338.
- Leopold, Aldo (1946). "The land health concept and conservation." Pages 218-226 in Callicott, J. Baird, and Eric T.Freyfogle. (1999) For the Health of the Land. Washington DC: Island Press.
- Lutz, H.J. (1957). "Applications of ecology in forest management." Ecology 38:46-64.
- Jax, Kurt. (2010). Ecosystem Functioning. Cambridge University Press
- Davies, P.E. et al. (2010). "The Sustainable Rivers Audit: assessing river ecosystem health in the Murray–Darling Basin, Australia." Marine and Freshwater Research 61:764–777.
- Xu, F, ZF Yang, B. Chen, and Y.W. Zhao. (2012). "Ecosystem Health Assessment of Baiyangdian Lake Based on Thermodynamic Indicators." Procedia Environmental Sciences 12: 2402–2413.
- HELCOM (2010). Ecosystem health of the Baltic Sea 2003–2007 HELCOM Initial Holistic Assessment.Balt. Sea Environ. Proc. No. 122.
- Covington, W. Wallace et al. (1997) "Restoring Ecosystem Health in Ponderosa Pine Forests of the Southwest." Journal of Forestry 95:23-29.
- Ramírez-Carrillo, Elvia; López-Corona, Oliver; Toledo-Roy, Juan C.; Lovett, Jon C.; León-González, Fernando de; Osorio-Olvera, Luis; Equihua, Julian; Robredo, Everardo; Frank, Alejandro (2018-07-16). "Assessing sustainability in North America's ecosystems using criticality and information theory". PLOS ONE. 13 (7): e0200382. doi:10.1371/journal.pone.0200382. ISSN 1932-6203.
- Roli, Andrea; Villani, Marco; Filisetti, Alessandro; Serra, Roberto (2017-11-17). "Dynamical Criticality: Overview and Open Questions". Journal of Systems Science and Complexity. 31 (3): 647–663. doi:10.1007/s11424-017-6117-5. ISSN 1009-6124.
- Slocombe, D. Scott (1998). "Defining Goals and Criteria for Ecosystem-Based Management." Environmental Management 22:483–493
- Grumbine, R. Edward (1994). "What is ecosystem management?" Conservation Biology 8:27-38
- Leslie, heather M. and Karen L. McLeod (2007). "Confronting the challenges of implementing marine ecosystem-based management." Frontiers of Ecology and the Environment 5:540-548.
- Myers, Andrew (2015). Which wolf, which trap? Socially constructing wolves and trapping in western Montana. Scholar Works, University of Montana, Oral Presentations.
- Horns, W.H., et al. (2003). Fish-community objectives for Lake Superior. Great Lakes Fish. Commission Special Publication. 03-01. 78 pages.
- Shear, Harvey et al. (2003). "The development and implementation of indicators of ecosystem health in the Great Lakes Basin." Journal of Environmental Monitoring and Assessment 88:119–152
- Rapport, David J. and • Luisa Maffi (2011). "Eco-cultural health, global health, and sustainability." Ecological Research 26:1039-1049
- Wicklum, D. and Ronald W. Davies (1995). "Ecosystem health and integrity?" Canadian Journal of Botany 73:997-1000.
- Adler, Peter et al. (2011). "Productivity is a poor predictor of plant species richness." Science 333:1750-1752.
- Ives, Anthony R. and Stephen R. Carpenter (2007). "Stability and Diversity of Ecosystems." Science 317:58-62.
- Asanova, Umut (2002). "Philosophy of ecological ethics education, considering the Issyk-Kul Lake reediation mechanisms." Jean Klerkx and Beishen Imanakanov (2002). Lake Issk-Kul: Its natural Environment Springer Science
- Costanza, R. 1992. "Toward an operational definition of ecosystem health." Pp 239-256 in Costanza, R., B. Norton, and B. Haskell. Ecosystem health. New Goals for Environmental Management. Washington DC: Island Press.
- Suter, Glenn W. (1993). "A critique of ecosystem health concepts and indexes." Environmental toxicology and chemistry 12:1533-1539.
- Jax, Kurt (2007). "Can we define ecosystems? On the confusion between definition and description of ecological concepts." Acta Biotheor 55:341–355
- O'Neill, Robert V. (2001). "Is it time to bury the ecosystem concept? (with full military honors, of course!)" Ecology 82:3275–3284
- Wright, David A. and Pamela Welbourne (2002) Environmental Toxicology. Cambridge University Press.
- Heink, Ulrich and Ingo Kowarik (2010) "What are indicators? On the definition of indicators in ecology and environmental planning." Ecological Indicators 10:584–593
- Costanza, Robert, and Michael Mageau (1999). "What is a healthy ecosystem?" Aquatic Ecology 33: 105–115
- Carolan, Michael (2006). "The values and vulnerabilities of metaphors within the environmental sciences." Society and Natural Resources 19:921–930
- Jax, Kurt (2005). "Function and 'functioning' in ecology: what does it mean?" Oikos 111:3
- Borja A, et al. (2014). "Tales from a thousand and one ways to integrate marine ecosystem components when assessing the environmental status." Frontiers in Marine Science. 1:72
- Woodward, Guy, et al. (2012). Continental-wide effects of nutrient pollution on stream ecosystem functioning. Science, 336:1448-1440.
- Barton, Philip S. et al. (2015). "Learning from clinical medicine to improve the use of surrogates in ecology." Oikos 124:391-398.
- Ahmed A.H. et al. (2016). "How do ecologists select and use indicator species to monitor ecological change? Insights from 14 years of publication in Ecological Indicators." Ecological Indicators 60:223-230.
- Kremsater, Laurie L. and Fred L. Bunnell (2009). "Sustaining forest-dwelling species." Pages 173-218 in Bunnell, Fred L. and Glen B. Dunsworth (2009). Forestry and Biodiversity. Learning how to Sustain Biodiversity in Managed Forests. UBC Press.
- C. Max Finlayson and Pierre Horwitz (2015). "Wetlands as settings for human health – the benefits and the paradox." Pages 1-13 in Finlayson, C.M. et al. 2015. Wetlands and Human Health. Springer
- Tallis, Heather and & Jane Lubchenco (2014) "Working together: A call for inclusive conservation." Nature 515, 27–28
- Tudela, Sergi and Katherine Short (2005). "Paradigm shifts, gaps, inertia, and political agendas in ecosystem-based fisheries management." Marine Ecology Progress Series 300:282-286.
- Noss, Redd et al. (2013). "Humanity's domination of nature is part of the problem: a response to Kareiva and Marvier." BioScience 63:241-242
- Nijhius, Michelle (2014). "Bridging the conservation divide." New Yorker, December 9.
- Su, Meirong et al. (2010)."Urban ecosystem health assessment: A review." Science of the Total Environment 408:2425–2434
- Rapport, David J. (1998). "Some distinctions worth making." Ecosystem Health 4:193-194.
- Rapport, David (1998). "Dimensions of ecosystem health." Pages 34-40 in Rapport, D.J. (ed.) (1998). Ecosystem Health. Blackwell Scientific.
- Wilkins, D.A. (1999). "Assessing ecosystem health." Trends in Ecology and Evolution 14:70
- Hudson, Peter J., Andrew P. Dobson and Kevin D. Lafferty (2006). "Is a healthy ecosystem one that is rich in parasites?" Trends in Ecology and Evolution 21:381-385.
- Kuris, Armand M. et al. (2008). "Ecosystem energetic implications of parasite and free-living biomass in three estuaries." Nature 454:515-518.
- Kueffer, Christoph and Brendon M. H. Larson (2014). "Responsible Use of Language in Scientific Writing and Science Communication." BioScience 64(8): 719–724.
- Lancaster, Jill (2000). "The Ridiculous Notion of Assessing Ecological Health and Identifying the Useful Concepts Underneath."Human and Ecological Risk Assessment 6: 213-222
- Carolan, Michael S. (2006). "Science, Expertise, and the Democratization of the Decision-Making Process." Society and Natural Resources 19:661–668
- Lackey, Robert T. (2003). "Appropriate use of ecosystem health and normative science in ecological policy" Pages. 175-186 in: Rapport, David J. et al. (2003) Managing for Healthy Ecosystems Boca Raton, Florida: Lewis Publishers, , 1510 pages.
- Calow, P. (1992)." Can ecosystems be healthy? Critical consideration of concepts." Journal of Aquatic Ecosystem Health 1:1-5.
- Stanley, Thomas R. Jr. (1995). "Ecosystem management and the arrogance of humanism." Conservation Biology 9:255-262
- Lackey, Robert T. (2001). "Values, Policy, and Ecosystem Health." BioScience 51(6):437-443
- Duarte, Carlos M. et al. (2015). "Paradigms in the recovery of estuarine and coastal ecosystems." Estuaries and Coasts 38:1202-1212
- Link, Jason S. (2002) "What Does Ecosystem-Based Fisheries Management Mean?" Fisheries 27:18-21
- Schrecker, Ted (1995) Synthesis of Discussion.pp 118-125 in Hodge, Tony et al. Pathways to Sustainability: Assessing Our Progress. Ottawa: National Round Table on the Environment and the Economy.
- Anon (1995). Wildlife policy for Prince Edward Island. Government of Prince Edward Island, 18 pages.
- McCormick, Gail (2001). Living with multiple chemical sensitivity. North Carolina: McFarland and Company, 296 pages.
- "Implementing the ecological approach in tobacco control programs: results of a case study." Evaluation and Program Planning 27: 409–421
- Richard, Lucie et al. (2004).
- White, Franklin; Stallones, Lorann; Last, John M. (2013). Global Public Health: Ecological Foundations. Oxford University Press. ISBN 978-0-19-975190-7.
- Register, Richard (2006). Ecocities. Rebuilding cities in balance with nature. Gabriola Island: New Society publishers. 373 pages.
- KARR, J. R., (1996). "Ecological integrity and ecological health are not the same." Pp. 97-109, In: Schulz, P. (ed.) Engineering Within Ecological Constraints Washington, D.C.: National Academy Press.
- Dakubo, Crescentia Y. (2010). Ecosystems and human health, a critical approach to ecohealth research and practice. New York: Springer, 233 pages.
- Leech, Susan., Alan Wiensczyk, and Jennifer Turner. (2009). "Ecosystem management: A practitioners' guide." BC Journal of Ecosystems and Management 10:1–12.