Human Ecology

, Volume 44, Issue 4, pp 463–478

Ecosystem Services and Disservices for a Vulnerable Population: Findings from Urban Waterways and Wetlands in an American Desert City

  • Monica Palta
  • Margaret V. du Bray
  • Rhian Stotts
  • Amanda Wolf
  • Amber Wutich
Article

Abstract

Vulnerable human populations are exposed to social and biophysical stressors, but have limited capacity to mitigate them, and thus may access ecosystem services in unconventional ways. As a result of this access, they may also experience disservices (i.e., functions of ecosystems harmful to human wellbeing) in ways that are not well understood. We use a mixed-method socio-ecological approach to examine how persons experiencing homelessness in Phoenix, Arizona, access ecosystem services and encounter disservices in urban waterways. We find that urban waterways provide users with drinking and bathing water, and cooler, shaded areas, but potentially expose them to pathogens and legal persecution. The wetlands provide cultural services by affording a sense of place and safety; however, these locations can also be associated with restrictive ordinances and aggressive law enforcement. This study explores the role of ecosystem services and disservices in bridging the gap between biophysical and social vulnerability.

Keywords

Ecosystem services and disservices Vulnerability Urban waterways Urban marginality Phoenix Arizona USA 

Introduction

The concept of “ecosystem service” is often adopted to explain the goods and benefits environments provide to humans. Proponents of this approach argue that ecosystem services provide for human wellbeing at many scales and in a variety of landscapes (Costanza et al. 1997; de Groot et al. 2002; Boyd and Banzhaf 2007; Fisher et al. 2009). As a mark of the concept’s success, ecosystem services have been widely adopted as a guiding framework in ecological research and environmental management over the last two decades (Costanza and Folke 1997; Costanza et al. 1997; Godoy et al. 2000; UNEP 2008; Fisher et al. 2009; World Bank 2009). While the recent emphasis on ecosystem services improved the integration of human dimensions into environmental management (Loomis et al. 2014), this literature is not yet well-informed by a theoretical understanding of social vulnerability. In this paper, we use an urban ecological approach to advance understanding of ecosystem services as they relate to socially-vulnerable populations. To do so, we examine ecosystem services and disservices in a unique setting: urban waterways in the desert city of Phoenix, Arizona, USA. Using observational data, water quality monitoring, and ethnographic interviews, we examine how people experiencing homelessness—a highly marginalized and vulnerable human population—benefit (or not) from ecosystem services provided by urban waterways.

Urban Ecosystems: Services and Disservices

Scientists developed the concept of ecosystem services in the mid-1990s. As an effort to place certain, often monetary, values on the goods and services that fulfill human needs and wellbeing, ecosystem services have become prominent in arguments for the protection of certain biomes and species (de Groot et al. 2002; Boyd and Banzhaf 2007; Fisher et al. 2009). While ecosystem services may fall into a variety of categories, these benefits are typically categorized as: (1) provisioning services, such as a material resources (e.g., food and water), (2) regulating services, i.e., valuable ecosystem processes (e.g., purification or cooling of water or air), or (3) cultural services, i.e., nonmaterial environmental benefits (e.g., recreation and aesthetic appreciation) (Costanza et al. 1997; MA 2005; de Groot et al. 2002; NRC 2005). Supporting services such as nutrient and water cycling and primary production are necessary for the production of all other ecosystem services (MA 2005).

Much of what we do know about ecosystem services is derived from research on protected, “natural” ecosystems, rather than human-inhabited areas (Martin et al. 2012). Yet direct human interactions with the natural world are often most intensive in urban settings, where human modifications of the landscape have a profound effect on ecosystem functions (Bolund and Hunhammar 1999; Grimm et al. 2008), and in turn on the wellbeing of large human populations (Martin et al. 2012). In urban ecosystems, city planners often design landscape features for the purpose of performing specific ecological functions (Grimm and Redman 2004; Redman et al. 2004). Many of these landscape features can, however, provide additional unplanned ecosystem services. For instance, storm-water channels and retention ponds can provide unplanned regulating services by removing contaminants and nutrients from storm-water (Grimm et al. 2005; Roach and Grimm 2009). Urban areas can also support unplanned “accidental” ecosystems in abandoned or underutilized spaces. Although little is known about them and they are not designed to provide services, “accidental wetlands” have been shown to support nutrient (Palta et al. 2013, 2014) and contaminant (Qian et al. 2012; Feng et al.2013) removal, as well as diverse bird and plant communities (Gallagher et al. 2008; Hofer et al.2010; Palta et al.2013). Such research reveals that, in urban settings where humans interact in complex ways with ecosystems, there may be hidden or unplanned ecosystem services conferred by the built environment (Roach et al. 2008).

While the ecosystem services literature largely emphasizes the benefits ecosystems confer on humans, some recent studies—especially those that focus on ecosystems highly disrupted by human intervention—have argued for the importance of understanding both ecosystem services and disservices (Lyytimäki and Sipilä 2009; Ango et al. 2014; Baró et al. 2014). Ecosystem disservices can be defined as: “functions or properties of ecosystems that cause negative effects on human well-being or that are perceived as harmful, unpleasant or unwanted” (Lyytimäki 2013:418). For example, the same landscape management practices that regulate water quality can generate greenhouse gases, demonstrating why both ecosystem services and disservices must be taken into account in land management decisions (Burgin et al. 2013). We argue that an analytic framework that encompasses ecosystem services and disservices is a promising, but as-yet underutilized, approach for understanding social vulnerability in the context of urban ecosystems.

Ecosystem Services and Disservices for Socially-Vulnerable Human Populations

While the ecosystem services concept resonates with many biophysical scientists, policymakers, and environmental advocates (Norgaard 2010), it receives a less enthusiastic response from some social scientists and critical scholars. Key criticisms of the ecosystem services concept include: it inappropriately monetizes ecosystem functions; it ignores non-monetary benefits provided by ecosystems; it defines human wellbeing too narrowly; and it may not fully account for trade-offs between different ecosystem functions (Bockstael et al. 2000; Kumar and Kumar 2008; Peterson et al. 2009; Norgaard 2010; Gómez-Baggethun and Ruiz-Pérez 2011; Wegner and Pascual 2011; Chan et al.2012). Kosoy and Corbera’s (2010) critique of schemes that offer payments for ecosystem services argues that ecosystem services are valued differently by multiple social groups (p. 1232). Further, inequities in power, access, and wealth undermine the ability of some groups to have their perspectives heard when it comes to valuing specific ecosystem services (pp. 1233–1234). Thus, the exclusion of socially-vulnerable groups may to some extent be built into the ecosystem services concept—particularly when ecosystem services are conceptualized in narrowly economic ways.

Urban environments provide an opportunity to bridge a disconnect between natural and social science approaches to the concept of ecosystem services. Natural sciences traditionally take an ecosystem approach, where humans are a part of the ecology governing an urban ecosystem and natural environments within a city are a point of departure (Grimm et al. 2008); social sciences tend to focus on social phenomena first, using behaviors, vulnerability and risk, or livelihoods to examine human-nature relationships (Lyytimäki et al. 2008). Since the properties and processes of urban ecosystems are a function of both human behavior patterns and the natural environment, both approaches are needed to explore the relevance of urban green space to urban dwellers (Lyytimäki et al. 2008), and more particularly to examine the relevance of green space to socially marginalized or vulnerable populations. Further, hydrologic ecosystem services, or terrestrial ecosystem services related to water (referred to here as “ecosystem services”) provide a unique opportunity for merging biophysical and socioeconomic evaluations of the environment al impact on human wellbeing (Brauman 2015). Our socio-ecological study of urban ecosystem services and disservices examines functions inherent to emergent “natural” urban environments, and simultaneously examines how those functions are connected to behaviors, values, or risks associated with human populations utilizing these environments.

Research on ecosystem services has focused largely on the biophysical vulnerabilities of ecosystems themselves (e.g., Schröter et al. 2005) rather than social vulnerability or socially-marginalized groups. These studies assess ecosystem exposure to stress or harm as a result of chronic or extreme environmental change (Adger 2000; Luers 2005; Smit and Wandel 2006; Turner 2010). Biophysical vulnerability is then used to assess social and environmental impacts on local populations (Liverman 1990; Adger 2006). This approach may be inadequate to develop a full understanding of integrated social and ecological responses because it does not account for social vulnerability.

Social vulnerability refers to “the degree to which different classes in society are differentially at risk” (Susman et al. 1984; Cutter et al. 2003). For the purposes of this paper, we define social vulnerability following Wisner et al. (2004:11) as “the characteristics of a person or group and their situation [that] influence their capacity to anticipate, cope with, resist and recover from the impact of a natural hazard.” Social vulnerability research demonstrates, for example, how social and structural inequities force people into inhabiting more risky (e.g., disaster-prone) environments and make it harder for them to tolerate environmental stressors (e.g., heat) even when they are equitably distributed (Handmer et al. 1999; Cutter et al.2000; Klinenberg 2003; Fraser 2003; Eakin and Luers 2006). Social vulnerability approaches have made vital contributions to a wide range of subfields, including hazards (Watts and Bohle 1993), entitlements (Sen 1995), disaster anthropology (Oliver-Smith 2002), climate change (Ribot 1995; O’Brien et al. 2007), and environmental history (Keller 2014). Despite its large influence and fruitful application across environmental studies, a social vulnerability approach has only rarely been applied to studies of ecosystem services. In the few cases where it has, researchers have been able to demonstrate how and why ecosystem services are distributed inequitably across human populations; for example, that poor and minority populations are more at risk from urban heat island effects and less likely to benefit from the temperature-regulating ecosystem services provided by urban green spaces (Harlan et al. 2006; Jenerette et al. 2007; Ruddell et al. 2010). Further, urban parks located near ethnic minority communities are smaller and more subject to social dis-amenities like crime than those in non-minority communities, thus compromising potential ecosystem services for socially-vulnerable groups (Boone et al. 2009; Cutts et al. 2009).

We argue that a more explicit focus on ecological services and disservices in unplanned urban environments is needed to further develop research on socially-vulnerable populations. Because socially-vulnerable populations may access or utilize ecosystems in unusual or unexpected ways, they may benefit (services) or be at risk (disservices) in ways that are not well understood and are quite different from the benefits and risks experienced by people in less-vulnerable groups. Our goal is to contribute to the rich tradition of research linking environmental phenomena to social vulnerability by examining a case study of ecosystem services and disservices provided by unplanned “accidental” waterways to a socially-vulnerable urban population.

Research Questions and Design

We examined interactions of a highly vulnerable population, people experiencing homelessness, with ecosystem services and disservices provided by urban waterways and wetlands in the desert city of Phoenix, Arizona, USA. Our research addresses two key questions. First, drawing on research in urban ecology, to what extent do urban waterways provide hidden or unplanned services (provisioning, regulating, and cultural) for a vulnerable population? Second, drawing on environmental research linked to social vulnerability, to what extent does the urban ecosystem also put vulnerable people at risk from ecosystem disservices (provisioning, regulating, and cultural)? We use a mixed-methods approach drawing on indirect observation, ethnographic methods (semi-structured interviewing, informal interviewing, participant-observation), and water quality monitoring.

Research Setting: Phoenix, Arizona, USA

Phoenix, Arizona, is located in the southwestern United States, and is the sixth largest U.S. city (population: 4.3 million). Phoenix receives the bulk of its precipitation (annual average: 204 mm) during the summer monsoon season (July–September) and the winter rainy season (November–March). From June to September, the average high temperature is ≥37.8 °C (100 °F), the temperature at which the U.S. National Weather Service declares a heat warning. In July and August, average temperatures exceed 38 °C for 6.4 h a day (Baker et al. 2002). Climate change models project increases in heat and droughts for the southwestern US (IPCC 2007). These projected changes pose a number of problems in terms of the sustainability of future water supply (Ellis et al.2008) and the ability of human populations to mitigate heat stress and avoid fatalities (Baker et al. 2002). However, the presence of tree canopies, green spaces, and waterways can lower heat 5 °C–11 °C in Phoenix microclimates (Brazel et al. 2000).

One major river, the Salt River, runs through Phoenix, but this stretch of the river has no upstream perennial water source following the construction of six upstream dams. Sections of the Salt River have undergone planned restoration projects, designed to provide riparian habitat, flood control, and recreational and educational opportunities. Unlike these planned renewal projects, unplanned waterways are not intended for human use; they may be located on private or public land, and human access may be restricted by “no trespassing” warnings. Many of these waterways and wetlands are ephemeral and frequently dry up after major storm events; however, some stormwater outfalls flow perennially, fed by municipal water use (e.g., runoff from lawn irrigation and groundwater pumping) during dry periods. During summer monsoon and winter storms, runoff from paved surfaces enters pipe networks, increasing discharge in outfalls. Occasionally, large rain events will cause water to overtop Salt River dams upstream of Phoenix, producing upstream inputs in addition to stormwater inputs from pipes.

Like many U.S. cities, Phoenix is home to a large population experiencing homelessness. Among 100 large American metropolitan areas, Phoenix ranks 22nd in homeless population and 60th in rate of homelessness (Sermons and White 2011). Phoenix has an estimated 27,000+ people experiencing homelessness (ADES 2013), but Phoenix homeless shelters have a capacity to house only 17,000 people (Brinegar 2003; Phoenix Homeless Rising 2011). Of the 10,000+ people seeking refuge elsewhere, 43 %–45 % are estimated to be living on the streets, in parks, and other publically-accessible environments (Continuum of Care Regional Committee on Homelessness 2014). In a study of 25 US cities, Phoenix ranked third for highest unmet needs (United States Council of Mayors 2013). Additionally, like many U.S. cities, Phoenix has established laws that criminalize homelessness. Under the 2004 anti-camping ordinances (Section 23–30, Ord.No.G-3552,§1; Ord.No.G-4660,§§1,2), living on the street (including: sleeping, storing personal belongings, or preparing food in public areas) is illegal. Water fountains and bathrooms are often closed and locked at night, limiting access. While riverbed occupation falls under the anti-camping ordinance, the riverbed’s relative isolation and seclusion means that those occupying these areas are less likely to be disturbed (personal communication, Brent Babb, Project HOPE Director).

For people living outdoors in Phoenix, heat and potable water scarcity pose potentially serious public health risks. In Central Phoenix, where the Salt River bisects the city, heat-related hospitalization rates and heat vulnerability are high (Fig. 1; Chuang and Gober 2015). Of 136 heat-related deaths from 2000 to 2005 in Maricopa County (where Phoenix is located) 46 % occurred outdoors and 25 % of the dead were experiencing homelessness (Yip et al. 2008). The Phoenix Heat Relief Network provides valuable public hydration and cooling stations to people experiencing homelessness (Fig. 1), but the network does not have the capacity to deliver to all Phoenix’s homeless the 1–2 l of water per hour recommended for people outdoors in Phoenix’s summer (ADHS 2014). Additionally, the hydration and cooling stations are in operation primarily during weekdays, often for limited hours. People experiencing homelessness in Phoenix report seeking alternative sources of shade, refuge from the heat, and drinking water to support hydration when sufficient public services are absent (Sanchez 2011). Health risks associated with acute and chronic extreme temperatures can be mitigated through respites in the landscape that provide evaporative and vegetative cooling (evapotranspiration) (Jenerette et al. 2011). Based on models of evapotranspiration in Phoenix, some of the highest evapotranspiration levels are in the bed of the Salt River, while surrounding neighborhoods in the urban core have some of the lowest evapotranspiration levels (Jenerette et al. 2011).
Fig. 1

Study area within the Phoenix Metropolitan Area, USA. Black arrows indicate the stretch of river bed utilized for this study. Shown on the map are areas with the highest heat vulnerability and highest heat hospitalization rates in the City of Phoenix according to Chuang and Gober (2015). SD refers to the standard deviation of hospitalization rate within the study area utilized by Chuang and Gober (2015) (outlined in black). Blue icons are Phoenix Heat Relief Network locations (Emer. Hyd. = Emergency Hydration)

While Phoenix’s service providers are aware that the Salt River is a popular refuge for people experiencing homelessness (personal communication, Brent Babb, Project HOPE Director), the extent to which unplanned waterways and wetlands play a role in meeting the heat mitigation and water acquisition needs of this population is unknown. Based on initial research, we hypothesized that people experiencing homelessness may want to avoid shelters, which can be associated with psychological or physical harms (lack of privacy or amenities, physical danger from other patrons, restrictions on behaviors). In order to find shelter and water amenities outside the existing shelter system, these individuals may access hidden or less-utilized urban environments. Potential environmental services provided by urban waterways may be provision of more privacy, a cooler environment, avoidance of altercations with other people, and running water, but associated disservices may be exposure to disease (due to lower water quality) and persecution by police or land managers (due to the illegality of camping in the wetlands).

Research Methods

Site Selection

For 1 year (2012–2013), we monitored six perennially-flowing outfalls and associated wetland areas along the urbanized (28 km) stretch of the Salt River traversing the Phoenix Metropolitan Area (Fig. 1). Hundreds of stormwater outfalls exit Phoenix into the Salt, but less than a dozen flow year-round and sustain permanent wetland areas. During this time, we repeatedly collected observational data on human use and trash in outfalls and wetlands.

We divided the study area into five sites; four sites are fed by one outfall, and one is fed by two outfalls). With the exception of Sites 3 and 4, which are located roughly 1 km apart, outfalls are located up to 28 km apart, and are generally separated by dry stretches of riverbed or manmade reservoirs (i.e., no easily traversable path is available between them along the riverbed).

Trash Data: Indirect Observation of Human Use

Given the difficulty of collecting data directly (via observation, participant-observation) or in self-reports (via interviewing) on illicit behaviors, we developed a protocol for indirectly observing human presence in and use of wetlands using trash. Indirect observation of human material culture, including trash, is a common method of analyzing human behavior when it cannot be directly observed (Hughes 1984; Bernard 2011).

We conducted one trash survey at four of the five study sites (1–2 sites per day) in June 2013; environmental variables related to potential ecosystem services were measured at each trash collection point (Fig. 2). We excluded Site 5 from indirect observation because it was the site of a permanent encampment where inhabitants regularly removed trash; as an alternative, we were able to collect interview data from the inhabitants.
Fig. 2

Transects and survey points used in June 2013 for quantification of trash items, degree of shade and privacy, vegetation, and air temperature measurements. Drawings not to scale

At each outfall, several transects (21–750 m long) were established both upstream and downstream of the outfall, parallel with outfalls and wetland areas (Fig. 2). Two or three observers together walked the full length of all transects and, every time evidence of human use (i.e., a trash item) was found, recorded the quantity and category of the trash item. As trash items can be swept into an area during floods, our observations were limited to items not in contact with water flow and indicative of onsite human use. Because some sites were located under highway overpasses, not all of the trash indicated onsite use; we took note of the location of trash items and factored the proximity of overpasses into the data collection (Fig. 2).

Trash items were categorized as indicating utilization of three types of ecosystem services: provisioning (running water, shelter), regulating (cool areas, areas promoting health and hygiene), and cultural (relaxation, enjoyment) (Table 2). Clothing items were considered separately, as they are a general indicator of human use or habitation, but do not provide conclusive evidence of type of wetland use or service. It is important to note, however, that clothing could be indicative of contact with the water, since we observed individuals washing clothes in the water.

Environmental Data Linked to Trash Observations: Quantification, Coding, Comparisons

At each point where trash items were found, we measured or ranked the following: air temperature (°C, measured with a handheld glass tube alcohol thermometer), shade (5 = 100 % coverage, 3 = 50 % coverage, 1 = 0 % coverage), privacy (5 = very, 3 = somewhat, 1 = not private), vegetation height and fullness (5 = high/full, 3 = medium, 1 = low/sparse). To assess shade, privacy, and vegetation, we visually surveyed a 4-m circumference (360° turn) around each point. For vegetation assessment, tall trees were considered “high”; smaller trees/bushes and tall reed plants (Typha) were considered “medium”; bare ground and ground cover plants were considered “low.” Privacy was assessed based on how visible the point was from all surrounding vantages (i.e., how obstructed the point was by overpasses, vegetation, or topography): “very” private meant that, while one was standing at a given point, one would not be visible from any cardinal direction or aerial view. “Somewhat” private meant no visibility from 1 to 3 cardinal directions or from an aerial view. “Not private” meant the point was highly visible from all directions and from above.

These measurements were made to assess the potential regulating and cultural services of heat mitigation, safety/privacy, and enjoyment of the environment at sites where human use was evident. At each site, at least one point was located away from outfall and wetland areas, and used as a point of comparison with point(s) near the water (Fig. 2). To provide an additional metric reflective of potential heat mitigation, we utilized water temperature data collected at multiple points (outfalls, wetlands) within all five sites during the summers (May–August) of 2012 and 2013. Submerging the human body in water temperatures below core body temperature (36.5–37.5 °C) facilitates cooling through convection, and exposure to air temperatures above 37.8 °C for more than 2 h can overwhelm the human body’s ability to maintain core temperature. Wetland water temperatures were compared to air temperatures measured at the same time, on the same date, at the NOAA gauge at Phoenix Sky Harbor International Airport, 3–13 km away from sampling points.

Ethnographic Research with People Experiencing Homelessness

We conducted participant-observation, informal interviews, and semi-structured interviews with people experiencing homelessness occupying three of the five study sites during 2012–2013. For the participant-observation, we visited the each of the five Salt River research sites 31 times over the course of the research, totaling 155 site visits. During each visit, we inhabited the site and observed the ways in which others used the landscape. We also documented conversations among those making use of the area. During these visits, we conducted—when possible—informal interviews about a range of topics, including the social environment on the Salt River, the availability of water and refuge outside of the river, and the suitability of the river environment for human habitation. We conducted 10 informal interviews with five respondents over the fieldwork period.

After establishing through the participant-observation and informal interviewing that people inhabit the riverbed and use the water, we developed a semi-structured interview protocol focused on human uses of the Salt River waterways and wetlands. In September–October 2012 and June 2013, we conducted interviews with seven people experiencing homeless (six male, one female) who we encountered in the wetlands. Our ability to formally recruit respondents for interviews was hindered by the illicit nature of their occupation of the Salt River environment. While small, our sample size for the semi-structured interviews meets the minimum number of interviews needed to detect themes in qualitative data (Guest et al. 2006). Respondents were all between 40 and 70 years old and experienced long-term homelessness. Given our own observations and a 2013 Morrison Institute for Public Policy study finding that the average person experiencing homelessness in Arizona is a childless white male in his mid-40s (Hedberg and Hart 2013), we believe our sample is reasonably representative of the demographics of the population inhabiting the Salt River.

Consenting procedures were approved under Arizona State University IRB# 1305009270. Due to the sensitivity of the research topic, data were collected in field notes (rather than audio or video recordings). Field notes from semi-structured interviews, informal interviews, and participant-observation were coded to identify key themes (Ryan and Bernard 2003) related to ecosystem services and disservices (provisioning, regulating, cultural) provided by the Salt River waterways and unplanned wetlands. Our use of mixed-methods ethnographic approaches allows us to crosscheck themes elicited from semi-structured interviews against the analysis of structured indirect observation (trash) data and themes elicited from unstructured informal interview and participant-observation data.

Water Quality Monitoring

To assess potential risks or benefits associated with exposure to water in unplanned waterways and wetlands along the Salt River, we collected water quality data from the Salt River at all five sites during the summers (May–August) of 2012 and 2013. We collected water samples for pathogen analysis during baseflow (pre-monsoon season, late May–early July) and immediately following storm events (monsoon season, mid-July–mid-August). Because urban runoff can differ substantially in source, quality, and wetland retention time between these two seasons, we separated the two seasons in our assessment of wetland pathogen removal capacity and the risks and benefits of human contact with runoff.

Within 12 h of water collection, we analyzed water for total coliform and Escherichia coli (E. coli) concentrations using methods modified from (ISO 9308–1:2014). 500 μL of each sample was plated on selective media (Brilliance® by Oxoid Ltd.) and incubated at 70 °C for 20 h. Plates were counted for total number of colonies following incubation; plates with greater than 200 colonies were considered to have too many colonies to count and excluded from data analysis. We used water samples collected within approximately five meters of where indirect (trash) or direct (people present) use of water was observed.

E. coli concentrations were compared against Environmental Protection Agency standards for bathing and drinking water. For recreational waters (lightly used full body contact), the EPA recommends that measurements of cfu per 100 mL recorded at a site during any 30-day period should have a geometric mean of 126 cfu/100 mL or less, and that there should not be greater than a 10 % excursion frequency of those measurements from 410 cfu/100 within the same 30-day period. These criteria “are designed to protect primary contact recreation, including swimming, bathing… and similar water contact activities where a high degree of bodily contact with the water, immersion and ingestion are likely” (EPA 2012). The estimated illness rate under compliance with these recommendations is 36/1000 (EPA 1986, 2001). In Arizona, the single sample E. coli maximum for full body contact is 235 cfu/100 mL, and 576 cfu/100 mL for partial body contact (EPA 2003). While the E. coli data serve to demonstrate the harms posed by drinking from or bathing in waterways, it is important to note that E. coli is an indicator bacteria and not necessarily pathogenic; direct measurements of pathogens, including viruses, Cryptospiridium, Giardia, and Legionella would be ideal for confirming the actual risk posed from consumption of or bodily contact with the water.

Results

Provisioning Services and Disservices

The semi-structured interviews indicate people use the wetlands for provisioning services that they may not be able to access elsewhere, particularly bathing (Table 1). Several respondents said that although shelters have bathing facilities and they did take advantage of them, they are available at only limited times. Two of those who mentioned bathing in shelters were observed bathing in the wetlands. While one indicated that it was their first time there, the other stated that he regularly bathed there. One of the respondents stated that he first sought the area as a place to cool off and would often put his feet in the water, which eventually led to his bathing there. Respondents also mentioned using outfall water for other activities requiring running water such as washing clothes (Table 1). Researchers found toothbrushes, towels, and soap, indicating the use of wetlands for personal hygiene (Figs. 3 and 4, Table 2).
Table 1

Relevant excerpts from field notes collected 2012–2013 from interview participants

Respondent ID

Themes Detected from Interviews

Services

Disservices

Provisioning

Regulating

Cultural

Provisioning

Regulating

Cultural

1

Shade, cooling

Relaxation, beauty of place

Personal safety concerns, restrictive law enforcement

2

Bathing

Shade, cooling

Peace of mind, beauty of place

Water safety concerns

Health hazards (mosquitoes)

3

Bathing, willingness to drink

4

Bathing, drinking, clothes washing

Connection to environment

Bitter taste to water

Personal safety concerns

5

Shade

Connection to environment

Water safety concerns

6

Relaxation

Water safety concerns

7

Bathing

Water safety concerns

Fig. 3

Bathing products found at sites 1 (a), 2 (b), 3 (c), and 4 (d). Items in image (c) are deodorant (left) and a shaving razor (right). Items in image (d) are a shaving razor (left) and a tube of toothpaste (right)

Fig. 4

Temperatures recorded in Phoenix air (NOAA gauge GHCND:USW00023183, Phoenix Sky Harbor International Airport) and in water at study sites in the Salt River during May–August in 2012 and 2013. Dotted line represents a 1:1 relationship between air and water temperature. Dashed line represents the best-fit relationship between air and water temperature data (R2 = 0.170); the ratio of air:water temperature of the best-fit line is shown above the line. Shaded areas are the range of air temperatures in which the U.S. National Weather Service declares a heat advisory (i.e., air temperature ≥ 37.8 °C)

Table 2

Results of trash survey conducted at four of the five study sites in June 2013. Number of items per survey site is the combined number of trash items in each service category across all points where trash was encountered at a given site (see Fig. 2). Percent of survey points with trash item type is the total number of points across all sites (25 total) that had at least one instance of a trash item falling within a given service category

Service Category

Items Falling into Category

Number of items per survey site

Percent of survey points with trash item type (out of 25 total)

Provisioning/Regulating

Bathing/Hygiene: Razors; rags/towels; tissues/toilet paper; oral care; bathing/body products

7–61

100 %

Provisioning/Regulating

Habitation: tent structures; camping; campfire; bedding; backpacks/bags

4–78

68 %

Cultural

Relaxation/Enjoyment: food waste; bottles/cups; cigarettes

138– ~500

72 %

Only one respondent indicated that he had drunk the water, although he stated that because of its bitter taste he sought drinking water elsewhere. The female respondent, who was relatively new to using the wetlands, indicated that she would be willing to drink the water there. Another respondent specifically stated that he did not drink the water because he was aware of contamination. Respondents cited public restrooms and the soda fountains at fast food restaurants and convenience stores as common locations to get water. A large portion of the trash documented in the wetland areas consisted of bottles and cups. Based on our interviews, it appears that the majority of these receptacles are from users bringing beverages in from other areas. However, based on our observations we believe that respondents may have consumed the water but were reluctant to admit to this.

The pathogen indicator data collected at the wetlands in areas with documented direct or indirect use generally validates the concerns of respondents about contamination (Table 3). During the pre-monsoon season, E. coli concentrations exceeded drinking water standards (i.e., 0 cfu/100 mL) in 21–88 % of measurements, and during the monsoon season, E. coli concentrations exceeded drinking water standards in 60–100 % of measurements (Table 3). Three sites met bathing requirements during one out of two 30-day periods monitored in either 2012 or 2013 (Table 3). Although every site had occasional measurements of 0 cfu/100 mL, mean and maximum values at all sites were often many orders of magnitude higher than EPA drinking and bathing standards, particularly during the monsoon season (Table 3). Site 3 met Arizona standards for single sample full body E. coli contact during the pre-monsoon period in 2013, and Site 4 met criteria for partial body contact during the pre-monsoon period in 2013.
Table 3

Concentrations of Escherichia coli (E. coli) at the five study sites, and number of measurements exceeding drinking and bathing standards. Concentrations are reported in colony-forming units (cfu) per 100 ml (mL). Combined percent exceedences and mean values of E. coli concentrations that meet EPA bathing standards at a given site within a 30-day period are indicated in boldface and underlined (3 total)

 

Season

Percent Exceedence

E. coli concentration (cfu/100 mL)

Drinkinga

Bathingb

2012

2013

2012–13

2012

2013

Min

Max

(Mean)

Min

Max

(Mean)

Site 1

Pre-monsoon

29 %

40 %

 

0

1000

(2.9 × 102)

   

Monsoon

60 %

33 %

 

0

2800

(8.0 × 102)

   

Site 2

Pre-monsoon

44 %

10 %

50 %

0

1200

(2.0 × 102)

0

1200

(5.0 × 102)

Monsoon

100 %

83 %

100 %

400

13,000

(4.1 × 104)

500

70,000

(2.1 × 104)

Site 3

Pre-monsoon

21 %

20 %

0 %

0

1400

(4.0 × 102)

0

0

(0)

Monsoon

80 %

50 %

67 %

200

240,000

(6.4 × 104)

0

1400,000

(4.0 × 105)

Site 4

Pre-monsoon

53 %

0  %

20 %

0

400

(2.0 × 102)

0

600

(2.0 × 102)

Monsoon

83 %

33 %

75 %

200

180,000

(5.9 × 104)

100

60,000

(2.1 × 104)

Site 5

Pre-monsoon

88 %

78 %

75 %

0

14,000

(4.8 × 103)

4

27,000

(5.6 × 103)

Monsoon

100 %

100 %

100 %

600

1000,000

(1.8 × 105)

1000

400,000

(5.3 × 104)

aThe EPA standard for drinking water is 0 cfu per 100 mL

bFor recreational waters (lightly used full body contact), the EPA recommends that measurements of cfu per 100 mL recorded at a site during any 30-day period should have a geometric mean of 126 cfu/100 mL or less, and that there should not be greater than a 10 % excursion frequency of those measurements from 410 cfu/100 within the same 30-day period

EPA drinking and bathing standards for E. coli are very clearly not met during the monsoon season, and the areas that are accessed by individuals for water use are likely posing a risk to their health during this season. Water in the outfalls should not be ingested (either through tooth-brushing or drinking) at any time. Bathing and wading, however, is likely safe during the pre-monsoon period at some sites. Because high temperatures and heat waves can characterize the pre-monsoon season, the wetlands and outfalls may provide a safe regulation service during these times.

Regulating Services and Disservices

Shade and temperature data indicate that these ecosystems provide regulating, cooling services from evaporative cooling or shade or both; these areas therefore may be an integral strategy for vulnerable populations, particularly during the hottest months of the year. We recorded higher temperatures and less vegetation cover farther away from the water (Table 4). Air temperatures recorded by NOAA gauges in Phoenix were in all cases higher than air temperatures recorded near the water during our surveys (Table 4). Degree of shade was in some cases higher away from the water; in the case of Sites 2 and 4, this was due to the presence of a bridge shadow at the point away from the water (Fig. 2). Temperatures in the water of outfalls and wetlands were lower than air temperatures measured at the same time by the Phoenix airport NOAA gauge, with the exception of approximately six measurements (out of 160 total) that either matched air temperature or were slightly higher (Fig. 3). Water temperatures never exceeded 35 °C, even when air temperature was equal to or greater than 37.8 °C (Fig. 3). A best-fit line demonstrated that water temperature increased by only 1 °C for every 3 °C increase in air temperature (Fig. 3), demonstrating the temperature buffering capacity of the water.
Table 4

Environmental data from trash survey points visited in June 2013. Variables were measured at each point where trash was observed. Sites located more than 1 m away from an outfall or wetland patch were classified as being “away from the water” (AW) vs. “near the water” (NW). Average temperatures recorded at NOAA gages in either Phoenix or Tempe during trash surveys are shown parenthetically. Shade, privacy, and vegetation were ranked on a scale of 1–5. Average values are shown ± one standard error of the mean

 

Location

Temperature (°C)

Shade

Privacy

Vegetation

Site 1

NW (average)

39 ± 1.2

3.8 ± 0.5

4.6 ± 0.4

4.6 ± 0.4

AW (average)

42 ± 1.5 (41)

1.7 ± 0.7

3.0 ± 1.2

2.7 ± 0.3

Site 2

NW

35

4.0

3.0

3.0

AW (average)

35 ± 0.7 (39)

5.0 ± 0.0

1.7 ± 0.7

1.7 ± 0.7

Site 3

NW (average)

29 ± 0.5

4.1 ± 0.4

4.4 ± 0.4

5.0 ± 0.0

AW

36 (38)

2.0

1.0

3.0

Site 4

NW (average)

34 ± 0.6

3.8 ± 0.5

3.0 ± 0.0

3.3 ± 0.5

AW

40 (39)

5.0

1.0

2.5

Most respondents mentioned the shade and cooler temperatures in the area as a reason for being there. One of the individuals interviewed said that he found the area accidentally, and said that he now regularly goes to the area to cool off, especially in the mornings when the shade is more expansive. Several respondents indicated that shade and cooling via water contact were services they accessed at the wetlands. Researchers observed bedding in numerous locations near the water, suggesting that people are taking advantage of the cooler temperatures there.

Respondents reported that they use the water to cool off, but responses also indicated that they are being discouraged from using this water, or feel that it is not appropriate. Our observations at the wetlands indicate that individuals experiencing homelessness were using the water to bathe, but several individuals additionally noted that they would get in the water as a cooling mechanism. One informant noted that several of his friends use the water to cool off by dipping their feet in, but that he had once seen a Park Ranger ask them to remove their feet from the water. While this respondent noted that others use the wetlands for cooling off, he did not use the wetlands in this way because he viewed the water as “meant for replenishing the environment” and not for human use.

Thus, while water in Salt River outfalls and wetlands is potentially very harmful if consumed or used for oral hygiene, it may be safely used for cooling at certain times (Table 4). Additionally, as water moves downstream, the counts of E. coli often decline, which suggests a water purification service provided by the wetlands (Fig. 5). During the monsoon season, Sites 2, 3, 4, and 5 demonstrated microbial removal between upstream and downstream points in over 50 % of sampling days, with Sites 2 and 3 demonstrating removal in 100 % of sampling days during the monsoon season. Removal occurred during a lower percentage of sampling days during the pre-monsoon, but all sites except Site 5 still demonstrated a decline in E. coli concentrations through the wetland 50 % or more of the time (Fig. 5). The wetlands at Sites 1 and 5 in some seasons demonstrated an increase on more occasions than they provided a service in terms of E. coli removal (Fig. 5). It is important to note, however, that an increase in E. coli can be due to waste contributions from warm-blooded animals living in the river (i.e., it may not reflect an increase in human pathogens), and a decrease in E. coli does not necessarily reflect a decline in other, more robust pathogens.
Fig. 5

Percent of pre-monsoon (black) and monsoon (gray) sampling dates where wetlands provided removal (regulating service) of Escherichia coli (E. coli). Measurements of E. coli in cfu/100 mL were taken in upstream (i.e., in the outfall) and downstream (i.e., in the wetland area) locations. Wetlands provided a service if E. coli concentrations decreased along the wetland flowpath. Instances where E. coli concentrations did not change between upstream and downstream locations, including when concentrations at upstream and downstream locations were both 0 cfu/100 mL, are not included in the percentages

Cultural Services and Disservices

In addition to providing cooling shade at the wetlands for our respondents, vegetation also provided a degree of protection from law enforcement and other perceived dangers. For some respondents trying to avoid the shelter system due to its lack of safety or privacy, the visual obstruction of vegetation provided a sense of security and privacy, allowing them to bathe and relax away from the city environment. Privacy and vegetation rankings were generally higher at points closer to the water (Table 4).

It is important to note that accessing these wetlands is illegal, as they are often the property of the state or federal government. If individuals experiencing homelessness are discovered by Park Rangers at these sites, they could be prosecuted. One of our informants reported being threatened with arrest for occupying the wetlands, and sees Park Rangers as a major deterrent from wetland use by people experiencing homelessness. Additionally, two of our respondents suggested that safety was a concern at the wetlands. While they did not elaborate about the nature of their concerns beyond theft of property, it is important to note that respondents using the wetlands are aware of simultaneous feelings of higher security and the potential legal security risks, particularly at night.

Aside from the privacy, respondents observed that the wetland ecosystems provided them with peaceful surroundings in which to relax and enjoy the beauty of nature. For example, one respondent who did not directly interact with the water discussed his enjoyment of the natural setting and noted that the sound of the water was relaxing and the visual beauty was soothing. Respondents were observed reading and napping in the wetland ecosystem, and said that the area provided a quiet respite from the city, where the shelters are located.

Additional observations of cookware suggest that homeless individuals may be using the wetlands as a secure place to cook food. Because food sharing is illegal in public, the wetlands may be providing an area where individuals can safely prepare and share food, a cultural service, as well as access to the water, a provisioning service. Heating of food and water also means these provisions are safer to consume. If cooking is more possible in these environments than elsewhere in the city, they may be facilitating better food hygiene, a regulating service.

Discussion

The goal of this paper is to introduce a social vulnerability approach to research on ecosystem services and disservices. While the importance of ecosystem service studies is well-established among natural scientists, policymakers, and environmental advocates, the approach is subject to two important critiques. First, an ecosystem services approach places too great an emphasis on the monetary value of services that ecosystems provide. While an ecosystem services framework encompasses provisioning, regulating, and cultural services, the third category—cultural—often proves difficult to quantify and, in practice, is often ignored (Chan et al.2012). Relatedly, the valuation of services may not pay sufficient attention to the unique needs and unconventional ecosystem uses of members of socially vulnerable groups (Kosoy and Corbera 2010). Second, an ecosystem services approach does not direct sufficient attention to ecosystem disservices—that is, ways in which ecosystem functions can be harmful to humans. Lyytimäki et al. (2008) and Lyytimäki and Sipilä (2009) have proposed a reframing of the ecosystem services concept to include both services and disservices, and this approach has begun to be widely adopted (Burgin et al. 2013; Lyytimäki 2013; Ango et al. 2014). The research presented here focuses on how one user group—people experiencing homelessness—makes use of unmanaged and unplanned “accidental” urban wetlands to illustrate the analytic value of human social structure (specifically, social vulnerability) and ecosystem disservices to the larger discussion of ecosystem services.

Our research demonstrates that human social structures and inequalities shape the unique ways in which different people—especially those in socially vulnerable groups—understand and make use of ecosystem services. Vulnerability drives people experiencing homelessness to make use of ecosystems in unconventional ways, including for cooling and water provisioning, which are not generally understood or acknowledged in the wider discussion of ecosystem services provided by urban wetlands (Brauman 2015; Zedler and Kercher 2005). Living in a desert city requires people to have adequate access to water and cooling resources in order to survive. However, various aspects of the social structure in Phoenix—including the absence of adequate housing for people experiencing homelessness, the insufficiency and inaccessibility of public potable water sources, and the criminalization of camping, food sharing, and cooking in public— exacerbate the vulnerability of people experiencing homelessness to health risks related to heat and water scarcity. Previous research taking a social vulnerability approach to ecosystem services has shown that such services are inequitably distributed in ways that are related to social structure and inequalities (Boone et al. 2009; Harlan et al. 2006, 2013). Our research contributes by showing that vulnerable groups may not simply get less access to desirable services, but in fact use ecosystems to create new and unanticipated services in unconventional ways that are invisible to average users and resource managers. More research is needed to investigate whether this trend can be found across a wider range of socially-vulnerable groups (e.g., low-income, racial/ethnic minorities, women, children).

A second contribution our research makes is to demonstrate the importance of including disservices an ecosystem service approach, especially when the research focuses on vulnerable communities. Most research on ecosystem services focuses on valuation of the positive contributions ecosystem functions can make to human wellbeing (Costanza et al. 1997; de Groot et al. 2002; MA 2005; NRC 2005). As Lyytimäki et al. (2008) Lyytimäki and Sipilä (2009), and Lyytimäki (2013) have argued, however, it is also important to acknowledge—and assess the potential cost of—the negative ways in which ecosystem functions can affect people. When users are socially vulnerable and making unconventional and unregulated uses of ecosystems, as our findings indicate, the likelihood of experiencing serious disservices (and of incurring serious health risks) is potentially much higher. We found that people experiencing homelessness in Phoenix made unconventional use of wetlands for the purposes of cooling, water provisioning, seeking refuge from authorities and other dangers, and pleasure. Yet the enjoyment of these unplanned ecosystem services—particularly cooling and water provisioning—put users at high risk of experiencing ecosystem disservices related to water contamination and, to a lesser extent, legal prosecution and other threats to their safety. Further, the service of water quality improvement (i.e., removal of E. coli) demonstrated by the wetlands did not generally outweigh the disservice of high E. coli loading in excess of bathing standards from the pipes. The latter finding demonstrates the importance of simultaneously examining both services and disservices in environmental valuations. Our findings regarding the presence of ecosystem disservices fit with well-established trends in the larger literature on social vulnerability and environmental risk (Susman et al. 1984; Cutter et al. 2003; Eakin and Luers 2006). Additional research documents the ways in which socially vulnerable groups experience greater risks related to, for instance, “natural” disasters (Watts and Bohle 1993; Sen 1995; Cutter 2000; Oliver-Smith 2002; Fraser 2003; Wisner et al. 2004) and other environmental stressors (Ribot 1995; Handmer et al. 1999; Klinenberg 2003). We argue that an ecosystem service and disservice approach can enrich this large and influential field of research by providing analytic tools incorporating a social vulnerability approach to examine a wider range of positive and negative ecosystem functions. Future research might focus on ecosystem services and disservices for vulnerable groups in a wider range of ecosystems (e.g., forest, coastal) and environments (e.g., suburban, peri-urban).

Conclusion

The wetland systems in the bed of the Salt River, fed by what is essentially wasted water from the urban environment, may be providing a critical cool refuge and water access point for a particularly vulnerable social group in Phoenix. Given that these wetlands and waterways are not actively maintained and managed, the city of Phoenix and other cities supporting “accidental” systems should be encouraged to evaluate the potential low-cost benefits associated with such environments, and consider how these services might best be taken advantage of by urban populations, particularly those who are socially vulnerable. Our measurements and qualitative assessments indicate that urban outfalls and wetlands may be providing services to people experiencing homelessness in Phoenix, but the extent to which wetlands provide a net benefit vs. harm varied according to site, season, and particular service. While these ecosystems provide heat mitigation, running water, privacy, and enjoyment, they may also pose serious health risks to individuals coming in contact with the water through drinking or bathing. Our findings indicate that vulnerable populations are accessing ecosystem services in unusual ways, and that ecosystems are simultaneously providing both valuable services and disservices that exacerbate the vulnerability of already vulnerable populations.

Acknowledgments

The authors wish to thank Otto Schwake, Amada Hernandez, Andrew Bishop, and Julianna Gwiszcz for assistance with data collection and sample analysis, and Morteza Abbeszadegan for provision of analytical facilities and materials. This material is based upon work supported by the National Science Foundation awards BCS-1026865(Central Arizona-Phoenix Long-Term Ecological Research) and SES-0951366 (Decision Center for a Desert City II: Urban Climate Adaptation).

Copyright information

© Springer Science+Business Media New York 2016

Authors and Affiliations

  • Monica Palta
    • 1
  • Margaret V. du Bray
    • 2
  • Rhian Stotts
    • 2
  • Amanda Wolf
    • 3
  • Amber Wutich
    • 2
  1. 1.School of Earth and Space ExplorationArizona State UniversityTempeUSA
  2. 2.School of Human Evolution and Social ChangeArizona State UniversityTempeUSA
  3. 3.School of Life SciencesArizona State UniversityTempeUSA

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