Articles
Wetlands as Settings for
Human Health: Incorporating
Ecosystem Services and Health
Impact Assessment into Water
Resource Management
Pierre Horwitz and C. Max Finlayson
Reconsidering the relationship between human well-being and environmental quality is central for the management of wetlands and water
resources and for public health itself. We propose an integrated strategy involving three approaches. The first is to make assessments of the
ecosystem services provided by wetlands more routine. The second is to adopt the “settings” approach, most developed in health promotion,
wherein wetlands are one of the settings for human health and provide a context for health policies. Finally, a layered suite of health issues in
wetland settings is developed, including core requirements for human health (food and water); health risks from wetland exposures; and broader
social determinants of health in wetland settings, including livelihoods and lifestyles. Together, these strategies will allow wetland managers to
incorporate health impact assessment processes into their decisionmaking and to examine the health consequences of trade-offs that occur in
planning, investment, development, and decisionmaking outside their direct influence.
Keywords: healthy settings, ecosystem services, trade-offs, health impact assessment, wetland management
T
he consequences of increased interaction between people and wetland ecosystems have received more attention in
recent years, particularly in global assessments (UNESCO
2006, Falkenmark et al. 2007, Gordon et al. 2010, Vörösmarty et al. 2010), with an emphasis on the relationship
between ecosystems and human well-being (MA 2005a,
UNEP 2007). A common outcome of these assessments has
been a desire for wider recognition of the meaningful relationships that exist between the well-being of people and
the quality of their surroundings, including food and water
sources. For wetlands, in the broadest sense, this desire is
acute. Because people are producing more food globally and
extracting more water globally, wetlands continue to decline,
and their capacity to provide such benefits is diminishing.
At the same time, the public health and living standards of
many people have not improved and access to water and
sanitation remains problematic. Wetland ecosystems provide resources for people directly and indirectly, and these
benefits are taken for granted—even hidden—by the technologies that successfully provide water and sanitation, with
a persistent negative view of wetland ecosystems being held
by the public in general and the public-health profession in
particular. Despite the evidence that wetlands provide many
benefits for people, they are perceived as the source of vectors or waterborne infectious diseases, and they are thought
to pose a sanitation challenge for the safe disposal of human
excreta and to make access to health services more difficult for those populations living in and around them. The
“problem” for human health is therefore perceived to be the
wetlands, rather than the upstream factors that determine
disease occurrence. For inland wetlands (including swamps,
marshes, lakes, and rivers), the importance of developing
environmental management strategies that concurrently
support the maintenance of both the ecological character of
wetlands and human health has been recognized (Corvalan
et al. 2005, MA 2005b).
The desire to recognize a richer relationship between
wetland ecosystems and human health has come from a
realization that the causes of harm to human health and
well-being can be disguised by the time, spatial scale, and
socioeconomic and cultural distances between policymakers and those who suffer, particularly where environmental
BioScience 61: 678–688. ISSN 0006-3568, electronic ISSN 1525-3244. © 2011 by American Institute of Biological Sciences. All rights reserved. Request
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reprintinfo.asp. doi:10.1525/bio.2011.61.9.6
678 BioScience • September 2011 / Vol. 61 No. 9
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Articles
change is concerned (see, e.g., Butler 2008, referring to forest
clearance). In addition, it has become apparent that many
problems in which the environment is thought to adversely
affect human health cannot be solved by traditional health
approaches alone. Rather, broader approaches are needed,
often drawn on a wider scientific base, including ecological and social sciences (Corvalan et al. 2005, Boischio et al.
2009). This broad approach underlines the uncertainty and
complexity of the systems in question (Wilcox and Colwell 2005); the need to work across sectors of government
(WHO 2010a); and—above all—the need for awareness of
the interconnectedness, interdependencies, and reciprocal
relationships that exist between people and their environments (Parkes and Horwitz 2009).
The links between malaria and humans include land
ownership, land use, vector ecology, hydrology, and wetland
management (O’Sullivan et al. 2008). Furthermore, the
implications of climate change for reliable access to water
resources (Kundzewicz et al. 2007) are expansive for those
events for which predictions can be confidently made regarding increased human health exposures (e.g., floods, storms,
fires, droughts) and greater disease burden (e.g., diarrheal
and vector-borne diseases) (Confalioneri et al. 2007).
The relationship between biodiversity conservation and
poverty alleviation involves multiple sectors, such as those
involved in development, taxation and finance, and genetic
resources (Boersema et al. 2009). For all of these sectors, the
ramifications are that professionals engaged in wetland ecology and wetland management and those engaged in public
health need to develop skills to enter into a productive
dialogue if they are to find optimal solutions. Topics in this
dialogue might include the management of flora and fauna;
access to harvestable items, such as timber, fish, or edible
plants; and the nature of sediment, water regimes, and access
to water and water quality. Beyond these topics are the following ones: the presence of waterborne pollutants, human
sanitation, animal health, water-related diseases, and disease
emergence related to small and large dams. The dialogue will
then need to include catchment land use, livelihoods in or
around wetlands, property prices, patterns of human movement and transport, human nutrition and its relation to
wetlands, and wetlands as sources of beneficial drugs. Some
of these issues are relevant in the short-term future, others
in the long term; some are local, others regional or global;
and most are influenced by local economies, cultural factors, political structure, and gender- and age-related factors
in populations. Compounding factors will occur, such as the
impact of climate change on human health issues associated with wetlands and the consequences of fragmented
approaches by government (Flinders 2002), such as those
taken with water resource management and public health.
A framework will be useful to constrain this almost infinite list. In addition, it is inevitable that choices will need to
be made regarding conflicting outcomes that might be reasonably predicted and that might require a trade-off. Some
of the starkest current trade-offs are those between wetland
www.biosciencemag.org hydrology and human health. In this article, we provide a
strategy for making these trade-offs explicit. The article is
intended to serve as a guide for decisionmaking that more
richly encompasses the interaction between wetland ecology and management and human health. We then deal
with the inclusion of ecosystem services in the assessment
of the condition of wetland ecosystems and with how ecosystem services might be best recognized in a public-health
discourse.
The ecological character of wetlands and wetland
ecosystem services
There has been a modern tendency to assess the condition
of natural resources and the human well-being associated with those resources separately. For wetlands (in the
broadest sense of the word as it was originally defined by
the Ramsar Convention on Wetlands in 1971, which would
include, e.g., rivers, lakes, marshes, rice fields, coastal areas),
their condition was relevant to two concepts: the wise use of
wetlands and the maintenance of their ecological character.
Using the framework adopted by the Millennium Ecosystem
Assessment, the term wise use has since been equated to the
maintenance of ecosystem benefits or services to ensure the
long-term maintenance of both biodiversity and human
well-being; the term ecological character includes the combination of the ecosystem components, processes, and benefits
or services that characterize the wetland at a given point in
time (Ramsar Convention 2005).
Table 1 outlines the breadth of ecological character likely
to be included in a description of an assessment of a wetland,
including the physical, chemical, and biological components;
ecological processes; and an array of ecosystem services, such
as provisioning, regulating, cultural, or supporting services.
The categorization as ecological character provides a basis for
identifying key issues for management consideration and the
role of wetlands in supporting human well-being. It should
be emphasized that not all of the categories of information
in table 1 apply to all wetlands, and for some—hopefully
only a few wetlands—this categorization may not describe
them adequately. We note the caution expressed by Fisher
and colleagues (2009) toward attempts to come up with a
single or fundamental classification system, since ecological
character will also be determined by complexities introduced by biogeographic and social considerations that are
invariably difficult to identify.
Nevertheless, we use this construct to link human wellbeing with ecological character through the services that a
wetland provides so that human well-being is included in
wetland assessments (figure 1). We accept that human wellbeing is a broad notion that includes security, basic materials
for a good life, health, good social relations, and freedom
of choice and action (MA 2005a), where human health is “a
state of complete physical, mental, and social well-being and
not merely the absence of disease or infirmity” (WHO 2006,
p. 1). Health therefore becomes linked with the ecological
character of wetlands (figure 1).
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Table 1. A global scheme for describing the ecological character of wetlands.
Ecological components
Ecological processes
Ecosystem services
Geomorphic setting: in the landscape,
catchment, or river basin
Primary production (S)
Drinking water for humans or livestock (P)
Nutrient cycling (S)
Water for irrigated agriculture (P)
Carbon cycling
Water for industry (P)
Habitat types
Animal reproductive productivity
Groundwater replenishment (R)
Habitat connectivity
Vegetational productivity, pollination,
regeneration processes, succession,
role of fire, etc.
Water purification,waste treatment or dilution (R)
Notable species interactions, including
grazing, predation, competition,
diseases and pathogens
Food for livestock (P)
Animal communities
Notable aspects concerning animal
and plant dispersal
Medicinal products (P)
Main species present
Notable aspects concerning migration
Soil: geology, substrates, soil biology
Pressures, vulnerabilities, and trends
concerning any of the above or
concerning ecosystem integrity
Climate: overview of prevailing climate type,
zone, and major features
Area, boundary, and dimensions: site shape,
boundaries, area, area of water or wet area,
length, width, depth
Plant communities, vegetation zones, and
structure
Water regime: water source, inflow or outflow,
evaporation, flooding frequency, seasonality and
duration, magnitude of flow or tidal regime, links
with groundwater
Food for humans (P)
Wood, reed, fiber, and peat (P)
Biological control agents for pests or diseases (R)
Other products and resources, including genetic material (P)
Flood control, flood storage (R)
Soil, sediment, and nutrient retention (R)
Connectivity of surface waters and of groundwater
Coastal shoreline and river bank stabilization and storm
protection (R)
Stratification and mixing regime
Other hydrological services (R)
Sediment regime
Local climate regulation, buffering of change (R)
Water turbidity and color
Carbon storage or sequestration (R)
Light and attenuation in water
Recreational hunting and fishing (C)
Water temperature
Water sports (C)
Water pH
Nature study pursuits (C)
Water salinity
Other recreation and tourism (C)
Dissolved oxygen in water
Educational values (C)
Dissolved or suspended nutrients in water
Cultural heritage (C)
Dissolved organic carbon
Contemporary cultural significance, including for arts and
creative inspiration and including existence values (C)
Redox potential of water and sediments
Water conductivity
Aesthetic and “sense of place” values (C)
Spiritual and religious values (C)
Important knowledge systems, importance for research (C)
Source: Ramsar Convention 2008, with minor changes.
C, cultural ecosystem service; P, provisioning ecosystem service; R, regulating ecosystem service; S, supporting ecosystem service; categorized according
to the Millennium Ecosystem Assessment (MA 2005a).
There are broader implications of this link for the
conservation objective of a wetland management agency
that adopts this construct. Since conservation equates to
the maintenance of ecological character, the conservation
imperative relates to protecting ecosystem services and
human well-being as much as it does to protecting, for
example, species biodiversity. This is a useful “olive branch”
to sectors in which it is perceived that natural resource
management agencies insufficiently consider the human
dimension.
680 BioScience • September 2011 / Vol. 61 No. 9
Healthy wetlands
Health is another way of describing the condition of an
entire entity or ecosystem. The term health might be applied
in a series of tiers: the health of an individual, the health
of a population, the health of an ecosystem, each nested
within the next tier. Health might also include the degree of
dysfunction, disease, or illness, and the health of one tier is
dependent, at least in part, on the health of the other tiers.
For wetlands, this term might apply as much to fish, a
species of zooplankton or macroalgae, or waterbirds as to
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Figure 1. Conceptual linkages: The Millennium Ecosystem
Assessment recognizes the links between ecosystem services
and human well-being (and thereby human health, too).
By including the concept of ecosystem services, the Ramsar
Convention’s definition of ecological character implicitly
now includes human well-being.
humans, or it might apply to the nested tiers themselves
or even to the landscape in which the wetland ecosystem
is embedded. The phrase healthy ecosystem acknowledges
that humans are an intrinsic part of ecosystems; of course,
humans are implicated in activities that degrade ecosystems,
but they can also be agents for their maintenance, construction, or restoration. The health of humans is in some way a
reflection of the health of the ecosystem in which they live or
on which they depend and vice versa. This reciprocity contradicts any psychological discontinuity between humans
and their environment, where nature is distinct from culture—an increasingly discussed dysfunction in Western
thinking and an impediment to rational policymaking (see
Plumwood 1990, Davidson-Hunt and Berkes 2004).
Various approaches have been used to measure the health
of an ecosystem. They range from a description of the
symptoms of ecosystem disruption to the use of indicators
of systemic attributes, the emergence of human or animal
disease or to qualitative principles.
The relationships among biodiversity loss, ecosystem
disruption, and disease transmission may be instrumental
indications of the health of an ecosystem. There are welldocumented cases of disease emergence associated with
land-use change, deforestation, or other forms of ecosystem
disruption, and global trends indicate that these cases are
increasing in frequency (Jones et al. 2008). Indeed, both
trade and intensive agriculture are known drivers of pathogen emergence and reemergence through host switching
and pathogen resistance to antimicrobial compounds. Biodiversity loss can increase disease transmission for important diseases associated with wetlands, such as malaria,
West Nile virus, and schistosomiasis (Keesing et al. 2010
and see the references cited therein). The incidence rates
of vector-mediated diseases and direct zoonoses have been
proposed as a bioindicator for underlying disturbances to
ecosystems (e.g., Cook et al. 2004) and, notionally, therefore,
its health. In a broader sense, aspects of animal and human
health can become an important indicator for the health of
www.biosciencemag.org an ecosystem, and vice versa, provided that there are clear
causal links between the two.
Measures of how the delivery of ecosystem services can
be enhanced, maintained, or disrupted provide sensitive
and useful indicators for the health or integrity of an ecosystem, and specific indicators for a full range of ecosystem
services can be examined accordingly (Scholes et al. 2010).
Another set of indicators might be measures of how healthy
ecosystems retain their vigor (i.e., their productivity), their
resilience (i.e., their capacity to recover from disturbance),
and their organization (i.e., their diversity and the nature of
the interactions within them) (Rapport et al. 1998). In this
way, a claim that an ecosystem is “healthy” means thinking
about the behavior of a system, making judgments on the
desirability of an ecological character, and being much more
explicit about the health of the components of the ecosystem
(including humans).
At any level of organization, it might also be argued that
the behaviors of a system can be desirable and acceptable
if the organization of the system is flexible and adaptive
at scales compatible with the temporal and spatial scales
of critical ecosystem functions. This is consistent with the
Ramsar Convention’s concept of the “wise use” of wetlands
and with efforts aimed at detecting, reporting, and responding to change in ecological character. The reasoning is that
wise use entails the establishment of institutional processes
for wetland management to describe ecological character
and to develop a management plan (to include objectives
for particular uses of the wetland and limits of acceptable
change) that is then implemented and monitored and for
which responses are determined accordingly, including
interventions to restore particular features of the wetland
when that is necessary (see Ramsar Convention 2008).
Recognizing wetland ecosystem services in
public health
Numerous examples can be used to show the link between
ecological character and human health. A change in climate
or hydrological regime, including a change in precipitation or
a change in the volume or seasonal presence of surface water,
may cause a change in the population numbers of vectors and
may alter the rates of human exposure to pathogens (Lafferty
2009), as may changes to the trophic structure of a wetland
as a result of overpredation (Stauffer et al. 2006). Changes
in nutrient cycles and trophic status can lead to toxic algal
blooms (Fristachi et al. 2008), and changes in hydrological
regimes can mobilize chemicals that are toxic to humans or
agricultural products (e.g., arsenic from groundwater extraction; Harvey et al. 2002). Land degradation and declining
productivity in wetland ecosystems can have direct or indirect
health consequences for people whose livelihoods depend
on them (e.g., Béné and Friend 2009). In each case, wetland
management must be involved in the intervention scenarios.
Despite the abundance of evidence for these links, the contributions that an ecosystem’s full range of services make to
human health have rarely—if ever—been documented.
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As was shown in the Millennium Ecosystem Assessment
(MA), the links between broad categories of ecosystem services
and the components of human well-being can be mediated
by socioeconomic factors, and the strength of the links and
the extent of the mediation can vary, depending on the type
of ecosystem and the geographical region (MA 2005a). For
example, a significant benefit will accrue for humans living
in areas in which soils have a high assimilatory capacity for
pollutants, through the service of water filtration and purification. This service can be mediated strongly if economic
conditions enable access to technologies for sanitation and
reliable drinking water or to parts of the landscape where this
service is enhanced.
If the capacity for socioeconomic mediation is uneven
between ecological services and human well-being, the
unevenness is exacerbated by the humans’ degree of dependence on the services and the choices people make in and
near wetlands. Some groups of people are more dependent
on ecosystem services, and the effects of these services’ degradation can be shown to be immediate and direct, sometimes
reinforced in a cyclical manner (Butler and Oluoch-Kosura
2006). In other instances, people supplement their livelihoods and incomes and enrich their lifestyles through wetland ecosystem services, which thereby indirectly determine
human health by contributing to other forms of well-being
(e.g., providing security, basic materials for a good life and
for good social relations). Exposure to harmful health effects
from (insufficient) access to wetland ecosystem services is
not equally distributed among groups of humans. There will
be different priorities for safeguarding the health of wetland
communities in poor and rich countries and differences in
the vulnerability of wetland communities, depending on the
local population’s socioeconomic status.
This unequal distribution of health-damaging
experiences is not in any sense a “natural” phenomenon but is the result of a toxic combination of poor social policies and programmes,
unfair economic arrangements, and bad politics.
Together, the structural determinants and
conditions of daily life constitute the social
determinants of health.
(WHO 2008, p. 1)
Again, the consequence for wetland management is clear:
Wetland managers are required to help with interventions
and to engage with those groups that seek to address the
determinants of health.
Health determinants in wetland settings
The links among ecosystem services, human health, and
their determinants resonate with the Ottawa Charter for
Health Promotion (WHO 1986), which identified five major
strategies for promoting health: (1) building healthy public
policy, (2) creating supportive environments, (3) strengthening community action, (4) developing personal skills, and
682 BioScience • September 2011 / Vol. 61 No. 9
(5) reorienting health services. The central tenet was that
“health is created and lived by people within the settings of
their everyday life: where they learn, work, play, and love,”
(WHO 1986, p. 2) establishing the healthy-settings approach
to health promotion, where people actively use and shape the
environment and thus create or solve problems relating to
health. Recently, and built on the work of Falkenmark and
Folke (2002), among others, there has been a suggestion that
watersheds or water catchments can be considered settings
on the basis that doing so reconnects health promotion with
the ecosystem context (Parkes and Horwitz 2009, Bunch et al.
2011). One of the strengths of this proposal is that it explicitly
puts ecosystem into the parlance of public health, something
that has been perceived to be missing from the healthysettings agenda. Another strength is that it brings water to the
foreground as human society’s principal natural resource. We
note here Strang’s (2005) description of the particular qualities of water as one of two important “universalities” that generate cross-cultural themes of meaning that persist over time
and we also draw attention to Barbar’s (2007) idea of “water
currency.” Furthermore, human health can be seen as commencing with the basic right to sufficient water for health and
well-being. (In July 2010, the United Nations General Assembly formally recognized the right to water and sanitation with
a resolution acknowledging that clean drinking water and
sanitation are integral to the realization of all human rights.
Commentators argue that although it is nonbinding and a
long way from a treaty on the right to water and sanitation,
the resolution is still a welcome step in the right direction.)
Wetlands conform to the construction of settings for health
promotion, since they are normally identified as having physical boundaries and since a range of people have designated
and defined roles around common meanings and values of
water. An organizational structure also exists in the water
resource and wetland management sectors, in which health
determinants and health inequalities can be addressed.
Health issues in a wetland setting
So far, we have argued that ecosystem services are provided
in wetland settings in which determinants of human health
exist. Wetland ecosystems and the services they provide, and
the ways in which they affect human health and well-being,
can be outlined as follows.
Contributors to hydration and safe water. The principal supply
of renewable freshwater for human use comes from an array
of inland wetlands, including lakes, rivers, swamps, and
shallow groundwater aquifers, and they play a major role in
treating and detoxifying a variety of waste products.
Contributors to nutrition. Many of the world’s major food
items—core requirements for human health—come from
wetland ecosystems or are irrigated by water from wetland
ecosystems. Rice—a staple food item for almost half the
world’s population—is grown in a wide range of environments, mostly wetland ecosystems. Inland fisheries and
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aquaculture contribute about 25% of the world’s production
of fish. Wetland ecosystems also have a role in maintaining dietary diversity, which contributes to a multidimensional agenda focused on nutritional and health status,
sociocultural traditions, income generation, and biodiversity
conservation.
by understanding the family and community situations by
listening to their stories, hopes, and wishes, and then by acting
according to them, within a context of local and traditional
knowledge, government requirements, and market forces.
Sites of exposure to pollution or toxicants. Human health can be
affected by acute or chronic exposure to toxicants, through
the media of water, wetland sediments, or even air when
sediments become desiccated and airborne or are burned.
These exposures result where ecosystem services have been
eroded—principally, when the hydrological services that
maintain biological, geological, and chemical processes are distorted by human activities—in particular, the overextraction
of water. Drainage and diversions of water are the two
activities responsible for the majority of such changes.
settings, their different behaviors and activities will be a
proximal determinant of their health. Lifestyle factors are
related to the ecosystem services—particularly, leisure, recreation, sporting activities, education, and cultural heritage
(including the spiritual significance of water)—and provide
for both physical and mental health, given human affinities
for wetlands and watercourses.
Sites of exposure to infectious diseases. Wetlands are loci for
communicable disease; microorganisms (the pathogens)
are transmitted through water, people, animals as vectors,
surfaces, foods, sediments, or air—any or all of which can
be associated with wetlands. Poor-quality (unsafe) water,
inadequate sanitation, and insufficient hygiene are the major
risk factors for diarrheal disease, which is the second-leading
contributor to the global burden of disease (WHO 2010b,
WHO–UNICEF 2010). An important share of the total burden of disease worldwide could be prevented by improvements related to drinking water, sanitation, hygiene, and
water resource management. Infectious diseases associated
with wetlands have profoundly influenced the discipline of
public health, and this influence is probably the source of
the erroneous oversimplification that wetlands are bad for
human health.
Settings for mental health and psychosocial well-being. Wetlands, in their myriad forms, become embedded in the
human psyche through a “sense of place” (the meanings
that people assign to a place through the process of living
in it, comprising the cognitive, emotional and behavioral
dimensions of identifying with, attaching to, and depending on a place; Tucker et al. 2006). Changes to wetlands, to
their products, or to their ability to deliver a livelihood or to
become a source of toxic exposure or disease can influence
a person’s mental health (Higginbotham et al. 2007). These
potentialities are increasingly recognized as being part of
the wetland manager’s and the public-health practitioner’s
spheres of prevention and intervention (Tucker et al. 2006).
Places where people derive their livelihood. Addressing wetland
management as if people’s lives, their livelihoods, and their
lifestyles depended on it will undoubtedly help improve
human health. Livelihoods comprise the capabilities, assets,
and activities necessary to make a living. A wetland manager
and a health service provider should seek to sustain the family
and community livelihood in the context of the wetland, first
www.biosciencemag.org Places that enrich people’s lives, enable them to cope, and allow
them to help others. For those people who live in wetland
Places that help absorb the damage of natural disasters. Climate
externalities such as floods, severe storms, drought, and fire
and geological externalities such as earthquakes and tsunamis
can magnify any of these exposures; in fact, because most
people live in or near wetlands, the conditions of the wetlands
and their ability to absorb external forces will determine, to
a large extent, the degree to which human health is affected.
The disease burden following major disaster events include
psychosocial issues, infectious diseases, physical injury, and
systemic chronic illness. The pathways to such disease events
may be direct or indirect and include a spectrum of community members, including those directly injured; rescuers;
people who have lost property, belongings, or the capacity to
sustain a livelihood; families of those injured; and from there,
the more general population (Cook et al. 2008).
Sites where medicinal and other products can be derived. Health
benefits will accrue to societies in general and individuals
in particular, because the products of wetlands can be used
for pharmaceutical or other medicinal purposes. Wetlandassociated animals, fungi, bacteria, and lower plants (algae),
some of them living in extreme conditions, provide the most
productive sources of new natural products. The medicinal
qualities of these are good examples of the continued value
of traditional knowledge to health care today.
Proximal and distal influences
These wetland ecosystem consequences for human health
are shown together in figure 2 in the form of layers, inspired
by Barton and Grant’s (2006) determinants of health and
well-being in our neighborhoods and Syme and colleagues’
(2008) “sphere of needs” of water. As with the emphases
in these other conceptual approaches, all of these features
influence one another according to the circumstances;
what is proximal and distal can become causally connected. Figure 2 shows three examples. Drawing acidic
groundwater water for domestic or horticulture results in
personal exposures. Nutrient enrichment also exposes residents to hazards, as well as to nuisances such as unpleasant
odors, and makes recreational and other uses of the wetland
problematic. Disasters or extreme events can profoundly
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as has been outlined in recent
global assessments (Covich et al.
2004, Corvalan et al. 2005, MA
2005b, UNESCO 2006, UNEP
2007).
In the same assessments, the
many direct and indirect consequences for people when wetlands have been disrupted have
also been outlined, and the results
are degraded or lost ecosystem
services through the many drivers of change that have been
widely documented elsewhere.
Under these circumstances, there
is no question that human wellbeing in general—and human
health in particular—will be
compromised with wetland degradation (2 2 in figure 3; see
also supplementary table S1,
available online at http://dx.doi.
org/10.1525/bio.2011.61.9.6).
Figure 2. Influences on wetlands as settings for human health, showing the proximal
However, it is erroneous to
factors of provisioning ecosystem services (food and water requirements); personal
think that this relationship is as
exposures and risks; and more distally, the broader social determinants of health.
simple as the 11 or 2 2 linearThree examples of cross-cutting are shown, and for each example the extent of the
ity; there are two other conceivinfluence is diagrammatically represented by the widths of the “stream” (see the text
able situations in the relationship.
for further elaboration).
First, analogous to RaudeseppHearne and colleagues’ (2010)
“environmentalist’s paradox,”
degraded
ecosystem
services
can provide benefits to people
and unpredictably integrate social determinants and perin
such
a
way
that
there
are
positive
health outcomes (21
sonal exposures and can make the provisioning of hazardin
figure 3).
Numerous
examples
exist,
and three are given
free food and water difficult.
here: (1) the application of DDT (dichlorodiphenyltrichloroethane) to wetlands, or their drainage, for malaria control
A social ecology of health in a wetland setting
(which entails the loss of supporting and regulating services
At first, it might seem that what we have been arguing here
of the wetland in order to decrease malarial infection rates);
(equating healthy wetlands to healthy people) is a simple
linear relationship in which human health declines when
ecosystem services are disrupted and in which human health
improves so long as ecosystem services are maintained or
enhanced, but the truth is more complicated.
A “double dividend” (11 in figure 3) arises when we
consider ecosystem services provided by wetlands that
support a range of health benefits for people. These might
include the provision of freshwater and food items that have
a direct link with human health, as well as other services
that support wider economic productivity, poverty alleviation, and increased food security and are a potential source
of new natural products. In addition, many wetlands have
a well-known insurance value for many people, reducing
their vulnerability to extreme events, such as floods, whereas
others, such as peatlands, play an important role in carbon
sequestration. In this respect, wetland ecosystem services
make tangible contributions to human health and improve
Figure 3. Four relationships possible when considering the
the lives of many people at local, regional, and global scales,
condition of ecosystem services and human health.
684 BioScience • September 2011 / Vol. 61 No. 9
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Articles
(2) conversion of a wetland into a reservoir (which results
in the loss of regulating services of the wetland in order to
provide water for humans during times of seasonal drought
or for irrigation for food); and (3) controlling water flows
in rivers as flood mitigation strategies (which leads to the
loss of regulating services in order to alleviate loss of life or
property).
Second, as was pointed out by Corvalan and colleagues
(2005), maintained or enhanced ecosystem services can have
problematic consequences for human well-being (12 in
figure 3), and again, numerous examples exist. Here are two:
(1) Urban wetlands protected for nature conservation (with
the protection designed to support and regulate ecosystem
services) can also support the presence of mosquitoes and
other vectors, and in so doing, they can expose humans to
vector-borne diseases (see Malan et al. 2009), and (2) the
presence of large woody debris in rivers (which regulates
services, slows down water flows, and contributes to the
trophic web as a supporting service) is an occupational and
recreational hazard for swimming or boating and may even
lead to a loss of life.
In addition, the four views in figure 3 still greatly oversimplify the relationship. In any wetland ecosystem, on balance,
some ecosystem services will be maintained, some enhanced,
and some degraded. Likewise, there will always be poor
health outcomes for some people, and some will benefit.
Furthermore, if the ecosystem services and health outcomes
happen to be causally linked, the situation can be complex
and layered, displaced in space and time, and dependent on
a number of modifying forces. For example, climate changes
can place stresses on agricultural production or on the
integrity of coral reefs and coastal fisheries, which, through
a chain of links related to changes in harvested volumes,
food quality, food storage, and food distribution, might lead
to malnutrition or related ailments. Similarly, deforestation
may change human population demographics and may alter
local and regional climates, potentially affecting disease vector distributions and, therefore, disease patterns over time.
Food security might link to any or all of the following: water
quality, household income, plant genetic resources, and fisheries management.
These causal chains are often important and complex.
They imply that trade-offs among benefits will occur when
wetlands are developed or otherwise altered in order to
promote or favor one or a few services over others (Nelson
et al. 2009, Gordon et al. 2010) and, equally, when particular
health outcomes occur when others are possible.
The wetlands of the Gnangara groundwater system in the
northern metropolitan area of the Australian city of Perth
provide an illustrative example. Decisions that have led to
the (over-) use of groundwater for domestic urban purposes and market gardens have also enhanced provisioning
services (providing water for direct consumption and for
the production of vegetables), which thereby yields health
benefits associated with hydration, nutrition, and livelihood.
In the process, however, hydrological regimes have changed,
www.biosciencemag.org and regulating services (e.g., the maintenance of anaerobic
saturated sediments and their biogeochemical processes)
have been degraded, which results in the exposure of
humans to the ill effects of drying and burning wetland sediments (Blake et al. 2009) or to acidic metal-rich plumes from
wetland sediments (Hinwood et al. 2006). Surface waters can
enhance mosquito breeding in either acidic environments
(see Ljung et al. 2009) or urban wetlands constructed for the
dual role of landscape aesthetics and to treat groundwater
(see Russell 1999), each of which might be problematic for
human health because of the occurrence of arboviruses,
such as the Ross River virus. All four quadrants of figure 3
can be filled under this scenario. If water use from the
groundwater system is allowed knowingly, as it has been, this
represents a trade-off scenario: One set of ecosystem services
is traded for another, and one set of human health outcomes
is traded for another. Despite the real and emergent potential for these human exposures, human health has not been
addressed in sustainability strategies for the groundwater
system (Bekesi et al. 2009).
Careful assessments of the direct benefits and of the
potential direct and indirect losses, including harm to
human health, are required in the management of water
resources and wetlands. Where such assessments are undertaken, it will be possible to demonstrate where compromises
and trade-offs exist between services and beneficiaries—
something that is rarely done in wetland management.
Health impact assessments for negotiating
ecosystem services trade-offs
We acknowledge, as do others (e.g., Campbell et al. 2010),
that recognizing trade-offs is no simple matter, because
a trade-off perceived by one stakeholder may not be recognized by another. So undertaking a process by which
the trade-offs and their consequences are fairly negotiated
becomes the central concern: The representation of marginalized stakeholders, increased transparency of information,
and engagement with the core pursuits of other sectors will
be key components of such a process. We perceive two areas
around which trade-offs need to be negotiated: valuation of
ecosystem services and the human health consequences of
intervention (or of the lack of intervention).
If wetlands play an important role in sustaining human
health and well-being and if wetlands continue to be lost
and degraded at rates more rapid than are other ecosystems
(MA 2005b), it is possible that something is wrong with the
way we are negotiating these sorts of trade-offs. This incorrect approach is largely attributed to policy decisions that
fail to internalize the values of wetland ecosystem services in
a manner that supports their retention or rehabilitation. In
many cases, the tangible and financial benefits arising from
wetland degradation or conversion are taken into account
when such decisions are made; however, the substantial
value arising from wetland ecosystem services, which are
not traded into formal markets and do not generate cash
flows, are not. Incomplete knowledge of the value of these
September 2011 / Vol. 61 No. 9 • BioScience 685
Articles
services can lead to perverse incentive systems that favor the
degradation and conversion of wetlands without considering the consequent loss of human welfare or the impacts on
human health. The quantification and valuation of wetland
ecosystem services in a way that makes them comparable
in value to the returns derived from alternative uses can
facilitate improved policy- and decisionmaking (Turner
et al. 2000).
Human health issues will always add another dimension to management decisions. A couple of key questions
for wetland managers would be what the human health
consequences of intervening for wetland management will
be and how we would intervene to improve human health
itself. Some of the key approaches, tools, and instruments
likely to be used by the health sector to respond to such
questions should be understood and used by wetland managers. Monitoring, surveillance and intervention, burden-ofdisease assessments, health impact assessments (HIAs), risk
assessments, and community and stakeholder engagement
are commonly used approaches, and in general structure,
the human health versions of these approaches might be
similar to their environmental equivalents. Their focus will,
however, be different; it will be important for these instruments and approaches to be developed for use by wetland
managers.
For wetland management, the four types of HIAs proposed by Harris-Roxas and Harris (2010) will be useful
in different circumstances. A mandated HIA would be
done to meet a regulatory or statutory requirement, a
decision-support HIA would be done voluntarily with the
goal of improving decisionmaking and implementation,
an advocacy HIA would be conducted by local organizations or groups seeking to influence decisionmaking and
implementation, and community-led HIAs could be done
in which potentially affected communities could examine
issues or proposals that would have consequences for their
health.
Regarding HIAs and trade-offs, Birley (2002) identified
the need to know how to use HIAs within the broader
context of economic appraisal structure and proposed a
framework that associated health determinants with five
forms of capital in relation to rural development. Table S1
extends this concept for wetlands, relating the classes of
health requirements, consequences, and determinants
associated with wetlands, and the relevant ecosystem
services for each as a way of incorporating wetland
valuation in the assessment. Evidence for how health
can be positively or negatively influenced according to
these ecosystem services can then be expounded for the
wetland in question. Such an approach concurs with the
call by Krieger and colleagues (2010) for the broadening
of HIAs beyond the social determinants of health and
into the domains of housing, water, sanitation, transport,
and communication. In doing so, this approach would
also appeal to private industrial corporations and major
financial institutions.
686 BioScience • September 2011 / Vol. 61 No. 9
Conclusions
We note that a comprehensive and specific assessment of
wetland ecosystem services and benefits for human health
has not hitherto been undertaken. Prior to the impetus
provided by recent global assessments (e.g., MA 2005a,
UNESCO 2006, UNEP 2007), there was a greater emphasis on describing the adverse effects on human health of
wetland degradation than on describing the benefits of
maintaining healthy ecosystems. As a consequence, there is
less information about the benefits for human health from
wetland ecosystem services.
We have therefore sought to provide a strategy for collecting further information and teasing apart the relationships
between wetlands and human health. This was done by
providing a joined-up account and by adopting constructs
from ecosystem management, ecological economics, public
health, epidemiology, and health promotion. We summarized
an accepted global framework for describing a wetland’s
ecological character and described how it should include the
services that wetlands provide to human welfare. We made
a case for bringing wetland ecosystems to the foreground as
the settings and context in which health determinants can
be addressed. We outlined nine ecosystem indicators of the
consequences for human health in wetland settings that can
be used as an analytical checklist: (1) contributors to hydration and safe water; (2) contributors to nutrition; (3) sites of
exposure to pollution or toxicants; (4) sites of exposure to
infectious diseases; (5) settings for mental health and psychosocial well-being; (6) places from which people derive their
livelihood; (7) places that enrich people’s lives, enable them
to cope, and enable them to help others; (8) sites of physical
hazards; and (9) sites from which medicinal and other products can be derived. Finally, we demonstrated the utility of
HIAs for the integration of these constructs. Together, these
indicators provide a strategy that will allow the trade-offs that
exist between sets of ecosystem services and different health
outcomes to be evaluated and the sociopolitical mechanisms
that support them to be taken into account.
Acknowledgments
The authors benefited from discussion with members of
the Scientific and Technical Review Panel of the Ramsar
Convention on Wetlands. Tim Nichols provided valuable
support with graphic design.
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Pierre Horwitz ([email protected]) is a professor in the School of Natural
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