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Article

Using Systems Thinking to Manage Tourist-Based Nutrient Pollution in Belizean Cayes

by
Daniel A. Delgado
1,
Martha M. McAlister
2,
W. Alex Webb
1,
Christine Prouty
3,
Sarina J. Ergas
1 and
Maya A. Trotz
1,*
1
Department of Civil and Environmental Engineering, University of South Florida, 4202 E Fowler Ave, Tampa, FL 33620, USA
2
Sierra Institute for Community and Environment, 4438 Main Street, Taylorsville, CA 95983, USA
3
Community and Practice, 615 E Street, NE, Washington, DC 20002, USA
*
Author to whom correspondence should be addressed.
Systems 2025, 13(7), 544; https://doi.org/10.3390/systems13070544
Submission received: 6 March 2025 / Revised: 26 June 2025 / Accepted: 2 July 2025 / Published: 4 July 2025
(This article belongs to the Special Issue Systems Thinking: Insights and Solutions to Complex Societal Challenges)
Browse Figures
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Abstract

Tourism offers many economic benefits but can have long-lasting ecological effects when improperly managed. Tourism can cause overwhelming pressure on wastewater treatment systems, as in Belize, where some of the over 400 small islands (cayes) that were once temporary sites for fishermen have become popular tourist destinations. An overabundance of nitrogen, in part as a result of incomplete wastewater treatment, threatens human health and ecosystem services. The tourism industry is a complex and dynamic industry with many sectors and stakeholders with conflicting goals. In this study, a systems thinking approach was adopted to study the dynamic interactions between stakeholders and the environment at Laughing Bird Caye National Park in Belize. The project centered on nutrient discharges from the caye’s onsite wastewater treatment system. An archetype analysis approach was applied to frame potential solutions to nutrient pollution and understand potential behaviors over time. “Out of control” and “Underachievement” were identified as system archetypes; “Shifting the Burden” and ‘‘Limits to Success’’ were used to model specific cases. Based on these results, upgrading of the wastewater treatment system should be performed concurrently with investments in the user experience of the toilets, education on the vulnerability of the treatment system and ecosystem, and controls on the number of daily tourists.

1. Introduction

Tourism offers many economic benefits by creating jobs and stimulating local businesses [1]. This is especially true for small island economies around the world, such as Belize, Barbados, the Maldives, Vanuatu, and others [2,3]. However, when not properly managed, the tourism industry can cause long-lasting ecological impacts, including increased pollution, eutrophication, loss of biodiversity, and disruption of aquatic ecosystems [4,5,6,7]. The tourism industry can place overwhelming pressure on wastewater treatment systems, which are often designed to accommodate year-round populations [8,9]. This is often the case when the tourism industry grows faster than the wastewater infrastructure, such as in Belize, where some of the over 400 small islands, or cayes, that were once temporary sites for overnight fishing have become popular tourist destinations [10].
Improper wastewater treatment is one of the major sources of nutrient pollution [11,12]. Although nutrients, such as nitrogen and phosphorus, are essential for life, the excessive discharge of reactive nitrogen (such as ammonia, nitrite, and nitrate) results in eutrophication, which can lead to a drastic increase in algae populations. Some algae produce toxins that can cause rashes, stomach or liver illness, respiratory problems, and neurological effects in humans and wildlife [13]. Eutrophication can also result in the depletion of dissolved oxygen in aquatic ecosystems, making it uninhabitable for aquatic life. For these reasons, managing the nitrogen cycle is one of the 14 Engineering Grand Challenges for the 21st century and is one of the most important pollution issues facing humanity [14,15].
The tourism industry is a complex and dynamic industry, with many sectors and stakeholders (e.g., tour guides, park managers, maintenance workers, environmental management professions, and conservation groups) who can have conflicting goals ranging from increasing tourism revenue to ecological conservation [16]. Managing nutrient pollution in this context is a complex problem, highlighting the applicability of systems thinking. Systems thinking is a method of thinking that steps away from the linear “A” causes “B” model to consider the system creating the challenge and the cyclical, feedback interactions between actors and other elements [17]. Depending on the complexity of the system, many variables can be considered at once. One method to organize the conceptions of a system is through causal loop diagrams (CLDs), which can be used to map feedback relationships, with indications of direct or inverse causation.
Generic causal loop structures, more commonly known as system archetypes, can help to classify structures responsible for patterns of behavior over time, showing both intended actions and unintended reactions. They represent a system model or template that can represent a wide range of situations [18]. The generic archetypes were synthesized using qualitative and quantitative modeling efforts over several years by several analysts [19]. It is through these archetypes, in conjunction with the four levels of thinking model (events or symptoms, patterns of behaviors, systemic structures and mental models), that a deeper understanding of the context that creates the challenges or symptoms can be cultivated. This method allows for another important paradigm shift; that is, addressing systemic structures acting as the root of the problem instead of the superficial symptoms produced by the problem.
Several studies have used systems thinking to explore tourism-induced pollution and degradation of water resources and aquatic ecosystems [7,18,20,21,22]. Their work has assisted in identifying key factors that can minimize waste production and water pollution, such as implementing changes in tourist activity, infrastructure development and management, and waste disposal [20]. Pásková et al. [7] performed a systematic review of 68 articles relating to water pollution generated by tourism and found that system models were either focused on pollution of the environment or tourism, but rarely both. The authors identified environmental education and awareness as well as investments in environmental protection as conditions capable of intervening in tourism water-related pollution. Furthermore, Pásková et al. [7] found 16 studies containing CLDs, with only 2 published papers using a CLD and its associated archetype. To our knowledge, no prior study has used CLDs to explore the dynamics of wastewater management for a tourist-dedicated wastewater treatment system in an environmentally sensitive area.
The central research question of this study was as follows: what managerial support is needed for an onsite wastewater treatment system (OWTS) to effectively mitigate tourist-based nutrient pollution in a coastal region? This study addressed this question by analyzing how archetypical system failures mapped onto a case study. Then, the known behavior patterns for these archetypes and their fundamental solutions were translated to sustainable strategies for addressing the case study’s observed challenges. The site chosen was Laughing Bird Caye National Park (LBCNP), where wastewater treatment improvements on the caye have been proposed to reduce nutrient pollution. This strategy was explored while intentionally incorporating insights from stakeholders (park rangers, conservation groups, wastewater treatment developers, and environmental managers).
The first objective of this study was to understand the management challenges around tourism and nutrient pollution for LBCNP. A CLD was created using the literature, informal interviews with stakeholders, and site visits to LBCNP, a remote and environmentally sensitive island. The next objective was to use archetype analysis to find the most appropriate archetype or archetypes for the situation. Once the generic structures were identified, the CLDs and their corresponding behavior patterns were analyzed to evaluate potential solutions to tourism and wastewater management in the context of LBCNP. Though the focus of this study was on LBCNP, the results can be transferable to small island developing states or national parks where wastewater treatment systems are managed by multiple stakeholders and where tourist-related marine activities can harm environmentally sensitive areas. Moreover, Belize shares similar indicators for water stress due to tourism to many other small island developing states [23], indicating a high potential for transferable results.

1.1. Site Description

Laughing Bird Caye National Park (LBCNP) is a 1.8-acre caye located 11 miles off the coast of Belize (N 16° 26.5848′, W 088° 11.8707′). About a third of the caye is a bird sanctuary and is off limits to visitors. For the last decade, Fragments of Hope Ltd. (FoH), a community-based organization in Belize, has led coral restoration efforts at LBCNP. FoH’s efforts have resulted in coral cover increasing from 6% to 60% [24]. The restored critically endangered acroporid corals around LBCNP attract schools of parrot fish, sharks, rays, lobsters, crabs, and hundreds of other marine species. These efforts have made LBCNP one of the most successful coral reef restoration projects, attracting tourists for snorkeling, leisure activities around the caye, and picnicking. Park records show average visitation of around 28 visitors per day, with a high of 38 visitors in the slow season and 120 visitors in the peak season between 2014 and 2023.
There are four structures on the caye, consisting of a ranger station with a kitchen on the ground floor and sleeping quarters on the second floor, a canopy for the lunch area, a souvenir shop, and a facility housing two separate toilets. In 2015, FoH raised the alarm that macroalgae mats were observed on the coral around the caye, close to the toilet facilities. With algae functioning as bioindicators for high nutrient loads, actions were taken to improve the OWTS. In 2017, FoH supported renovations to the septic system after initial meetings with researchers from the University of South Florida and EcoFriendly Solutions, the company that constructed the wastewater treatment systems at LBCNP. Response actions by the Southern Environmental Association (SEA), co-manager of the caye, included moving the toilets to another part of the caye due to erosion and increasing the capacity of the OWTS. The changes did not include adding the treatment steps needed for advanced biological nitrogen removal (BNR), such as aerobic and anaerobic zones and reactive media materials. Although there are several examples of OWTSs in the surrounding cayes, the treatments are not configured for BNR.
An important factor for the OWTS on LBCNP is that seawater is used for toilet flushing. A large barrel in each restroom is filled each day with seawater by the park rangers. People using the toilet then use a pitcher to fill the toilet tank and flush the toilet. This practice results in saline wastewater. As the salinity of wastewater increases, BNR becomes more difficult, because most of the microorganisms involved in BNR are not adapted to high-salt environments. High salt concentrations can make it difficult for these microorganisms to perform their metabolic processes and maintain their osmotic pressure, potentially resulting in bacterial plasmolysis [25,26,27]. High salt concentrations can also reduce enzyme activity, thereby reducing nitrogen removal efficiency [28]. Microbial deflocculation due to increased salinity can result in sludge with poor settling ability [29].
Saline wastewater is not unique to LBCNP. Silk Caye, located a few miles from LBCNP, is another popular tourist destination where seawater is used for toilet flushing. Globally, coastal cities and nations such as the Marshall Islands, Kiribati, and Avalon, California, are using seawater for toilet flushing to ease stress on freshwater sources [30]. In Hong Kong, the SANI® process provides one of the few examples of BNR in saline domestic wastewater treatment [31,32]. Pilot-scale tests of the SANI® process focused on centralized wastewater treatment versus a decentralized OWTS. The SANI® process requires electricity and chemical dosing, which makes it less suitable for LBCNP. Passive BNR OWTSs that rely on gravity-driven flows though porous media materials, eliminating the need for electricity or chemical addition, have been used in domestic wastewater treatment [33]. Prior research has shown that passive BNR can be successfully applied to saline wastewater [34].

1.2. Problem Articulation

Tourism is vital to the local economy and the co-managers of the area, SEA and the Forest Department of Belize. Though LBCNP is a popular attraction for snorkeling due to its coral ecosystem, that same activity increases pollution around the caye. The most evident form of pollution at LBCNP, aside from plastic waste that is brought in by the currents, is nutrient pollution. Overgrown algae mats are a bioindicator that nutrient concentrations are too high, endangering the coral ecosystem. Actions are needed to reduce the nutrient levels around the caye. Improving the OWTS to incorporate nitrogen removal has the potential to help in reducing nutrient pollution. For this intervention to be successful, visitors must use the toilets appropriately and park managers must follow proper maintenance practices. Education on what cannot be flushed down the toilets (such as wet wipes and chemical disinfectants) and removal of solids every three to five years must be performed. Ignoring one or both requirements will cause the OWTS to fill with solids, clog the plumbing, or kill the bacteria that treat the wastewater, all of which result in OWTS failure. LBCNP’s distance from the shore makes maintenance difficult, and upkeep requires the cooperation of the park rangers, tour guides, and the tourists visiting the park.
The concern is that improvements to the OWTS will not adequately address the nutrient load issue, and the environmental impact will return to its current state or worsen over time. Though a system model could incorporate all of these actors and challenges, once mapped comprehensively, it is useful to reduce the model to a subset of interactions to capture the intended and unintended behaviors in an OWTS intervention. For this reason, the authors wanted to create a CLD that captured the behaviors observed at LBCNP and anticipate how the intervention could fail following improvements to the OWTS.

2. Materials and Methods

2.1. Field Observations and Informal Interviews

Field observations and informal interviews with stakeholders began in June of 2019 and continued until August of 2023. In 2019, a visual inspection inside each step of the wastewater treatment train at LBCNP and informal interviews with FoH, park rangers, and EcoFriendly Solutions were conducted to understand the amount of wastewater generated on LBCNP and practices for OWTS operation and maintenance. Also discussed during these meetings were the water quality sampling and analysis needed to evaluate the OWTS performance. Site visits to LBCNP included observations of the number of visitors to the caye and their behavior once on the caye, including frequency of toilet use and other practices that may increase anthropogenic nutrient pollution, such as disposal of food waste. The research team also visited OWTSs throughout the Belizean cayes, including Silk, Hatchet, Little Water, Ray, Tobacco, Mosquito, Carrie Bow, and Moho Caye.
In June 2022 and 2023, pH and dissolved oxygen were measured at each step of the treatment train using a Hydrolab Quanta Multimeter probe, (Hydrolab, AB, Canada). In June 2022, samples were collected and sent to the Belize Brewing Company, LTD Water and Waste Laboratory. Total nitrogen was measured using the persulfate digestion method, ammonia was measured using the salicylate probe method, nitrite was measured through diazotization, nitrate was measured with cadmium reduction, and phosphate was measured using the PhosVer Orthophosphate method. In June 2023, triplicate samples were collected and sent to the University of Belize Hummingbird Analytical Lab. Total nitrogen was measured using Hach method 10072 (Hatch Company, Loveland, CO, USA), nitrate was measured using Hach method 8039 (Hatch Company, Loveland, CO, USA), ammonia was measured using Hach method 10031 (Hatch Company, Loveland, CO, USA), and phosphate was measured using Hach method 8178 (Hatch Company, Loveland, CO, USA).
A visit to EcoFriendly Solutions headquarters and tours of four of their mainland OWTSs throughout Belize were conducted in June 2023, along with accompanying their maintenance team to service the system on LBCNP.
Data gathered from 2019 to 2023 were presented to SEA, LBCNP rangers, FoH, and EcoFriendly solutions during semi-structured informal follow-up interviews. Water sampling results and information related to the current wastewater treatment system on LBCNP, the OWTS’s operation and maintenance, BNR, and potential OWTS renovations were presented at this time. In February and April 2025, the results from this study, including the CLDs and recommendations to support OWTS renovations, were presented to SEA and EcoFriendly Solutions. All participants interviewed were Belizean or long-term residents of Placencia, Belize.

2.2. Archetype Analysis

When selecting a systems approach, it is recommended to base methodological decisions on the stated objectives of the study [35]. Archetype analysis was chosen as an appropriate systems approach due to the complexity of characteristics that stand out in the articulated problem, including the potential for detrimental unintended consequences in a sensitive ecosystem. Archetype analysis also allows for modeling behaviors in the absence of numerical data. Furthermore, expressing problems and potential solutions as CLDs can be an effective tool for stakeholder engagement.
In 2019, a CLD was constructed to conceptualize the interactions that produced the observed challenges evidenced by field data [10]. Notable components and drivers related to the environment, human health, and socioeconomic factors were included. Causal relationships between components were connected with arrows and the nature of the relationships (inverse or direct) was denoted with plus and minus signs.
The CLD from [10] was then reduced to a generic archetype. When Wolstenholme [19] reduced the list of known archetypes to four completely generic archetypes, he noted that actions for change can be condensed down to actions that attempt to improve the achievement of an organization by initiating reinforcing feedback effects and those that attempt to control an organization by introducing balancing feedback effects. Likewise, reactions can be reduced to one of these two categories. These driving factors were used to identify the appropriate generic archetypes and validate semi-generic archetypes—those rooted in the local context of the system being modeled. Variables were reduced to include control actions or actions to achieve an intended outcome (renovations to the wastewater treatment system), the intended consequence, and potential unintended consequences. The semi-generic archetypes were then used to predict potential patterns or behaviors over time.

3. Results

3.1. Analytical Results

For both laboratories used in 2022 and 2023, the analytical methods used for total nitrogen and ammonia experience known salt and organic interferences, leading to unreliable results. Taking this into consideration, the results shown in Table 1 should be considered initial estimates.
The nitrogen concentrations appear reasonable considering that a domestic OWTS would have a concentration of about 70 mg/L N but is diluted by other wastewater containing little nitrogen, including from showers, sinks, and washing machines. In 2022, nitrogen concentrations changed little throughout the OWTS, but in 2023, there appeared to be a decrease in nitrogen level by 48% and ammonia level by 32% between the water entering the OWTS and the influent to stage three of the treatment train. Some of this decrease could be due to BNR; however, while servicing the system in 2023, precipitate was found coating the inlet pipes and media in stage three of the OWTS. A sample was sent to the University of South Florida for X-ray diffraction analysis, revealing its composition to be mostly struvite, along with sulfur, sodium chloride, gypsum, and newberyite. Struvite is a crystalline mineral made of magnesium, ammonium, and phosphate. The formation of struvite decreases the aqueous nutrient concentration but makes system maintenance more difficult and can ultimately clog up the OWTS.
The OWTS discharges into a plastic-lined plant bed where total nitrogen ranges from 50 to 100 mg/L and ammonia level ranges from 30 to 40 mg/L-N. Though there appears to be a large decrease in nitrogen, these concentrations are similar to nitrogen concentrations entering a wastewater treatment process, and therefore more treatment is needed.

3.2. Informal Interviews and Field Results

During initial interviews in 2019, EcoFriendly Solutions brought up their concern that not all park rangers were performing regular upkeep of the OWTS. These concerns were echoed in the 2023 follow-up interviews with SEA and EcoFriendly Solutions.
In June 2022, 67% of visitors were observed visiting the toilet facility over the four-hour study on LBCNP; however, park rangers estimated that over the course of the day, most visitors used the toilets. This observation, along with the experience of using the toilet facilities and conversations with other researchers that visited LBCNP, led to the hypothesis that some visitors were urinating in the water while snorkeling. In June 2023, informal interviews with SEA and park rangers revealed that low employee retention may result in some park rangers not maintaining the toilet facilities and OWTS. The park ranger did insist that, in general, most of the rangers were performing EcoFriendly Solutions’ suggested OWTS upkeep. SEA also expressed their willingness to carry out a science-based intervention.
The CLDs in this study were presented to SEA and EcoFriendly Solutions in 2025. Both groups agreed with the layout of the CLD and potential outcomes. During these meetings, SEA elaborated on how carrying capacity is calculated, revenue collection, and how they perceived the tradeoffs between tourists and environmental conservation, with conservation being their main objective. SEA also addressed their concern that the results of the archetype analysis could be misinterpreted as promoting more visitors, causing additional risk to the environment. EcoFriendly Solutions reiterated their concern about park rangers’ regular upkeep of the toilet facilities and OWTS and how the upkeep should be part of the job description if SEA wants all park rangers to perform this regularly. These findings are sumarized in Table 2, showing the takeaways that were used in developing the CLDs.

3.3. Archetype Analysis

Using archetype analysis, “Out of Control” and “Underachievement” were chosen as the most appropriate generic archetypes based on actions for change.

3.3.1. Shifting the Burden

In an “Out of Control” archetype, Figure 1A, a control action attempts to address a problem by introducing balancing feedback. For this achetype, it is usually the control action and not the outcome that can lead to a worsening of the problem [19]. For LBCNP, the problem in need of control is nutrient load causing environmental degradation. The control action would be to improve the wastewater treatment system, and therefore reduce the enviornmental impact from visitors.
Improving the OWTS may give the impression that there is less need to limit visitors to the caye. The system reaction might be to increase the carrying capacity at LBCNP or provide a loosening in enforcement on allowable daily visitors. By increasing the allowable number of daily visitors, there would be an increased nutrient load to both the OWTS and to the surrounding environment from other tourist activities. There is usually a time delay between when a pollution source begins to overwhelm an ecosystem and when those affects visiably degrade an environment.
Furthermore, when the OWTS is performing well and preserving the enviornment, the caye may become a more popular tourist destination, attracting more visitors. The attraction of a pristine environment may increase visitors, who would then use the toilets, and increase wastewater loads. Wastewater treatment systems are sized and designed to allow for a certain peak and average use. Regardless of the technology, if users increase past the peak system design, the system would be undersized and the treatment time would be too short to adequately remove pollutants. In this case, the intended consequence loop is a balancing loop and the unintended consequence loop is a reinforcing loop, spiraling the problem “out of control.”
For this case, “Shifting the Burden” was the most appropriate of the “Out of Control” manifestations (Figure 1B). In the “Shifting the Burden” archetype, a balancing intended consequence is created by a fix to control the problem or problem symptom and divert attention away from a more fundamental solution. Here, the fundamental solution to reducing the impact to the ecosystem from nutrient pollution would be to reduce or limit the allowable number of daily visitors to the caye. Figure 1B represents the CLD that isolates behaviors at LBCNP and does not incorporate the tradeoffs outside the model, such as how visitor fees support management and tourists support livelihoods, making the proposed fundamental solution less appealing. Recent improvements and maintenance to the OWTS at LBCNP were funded by outside sources, another reason why “visitor fees” were not incorporated into the CLD. Instead, wastewater system improvements would be a symptomatic fix and would take on the burden of reducing nutrient load to the environment while allowing toursim to continue.
Over time, the symptomatic fix could make the problem symptom worse and make the fundamental solution more difficult to enact (Figure 2). Given the context of a tourist-based economy versus environmental conservation, both a fundamental solution of limits on allowable daily visitors and symptomatic fix of wastewater system improvements should be applied.

3.3.2. Limits to Success

In the “Underachievement” archetype, Figure 3A, an action is taken in an attempt to improve the achievement of the organization by initiating reinforcing feedback. The system reaction from Figure 1, representing visitors to LBCNP, was incorporated into the outcome for the second archetype. The action to achieve an intended outcome was the same as the control action from the previous archetype, wastewater system improvements.
Site visits to LBCNP, which included the inspection and use of the toilets, revealed a potential system reaction, namely that visitors may be inclined to urinate in the water if the only action taken is to improve the wastewater treatment system and no effort is made to improve the bathrooms. Up to 90% of nitrogen in urine and feces comes from urine [37], so this practice could have a significant effect on nutrient load in the local environment.
Human-oriented renovations to the system should address issues that would encourage tourists to use the toilets and avoid urinating in the water. A variable “investment in toilet” was introduced to the CLD, creating a reinforcing loop for the solution archetype, Figure 3B. Visitor education on nutrient pollution was added as a second reinforcing loop for a solution archetype. “Limits to Success”, a special case of the “Underachievement” archetype, best described the situation [19]. In “Limits to Success,” the intended consequence loop is a reinforcing loop created by an effort (wastewater system improvements) to improve the performance within one sector of an organization (ecosystem health). These efforts are counterbalanced by a limiting action (tourists urinating in water) encountered in some other part of the organization.
The archetype behavior over time adapted from Kim and Lannon [36] is shown in Figure 4. The anticipated behaviors show that improvements to the wastewater treatment system will initially have a positive impact on ecosystem health. Over time, however, these efforts will have diminishing returns as the limiting action creates a slowdown and eventual decline in ecosystem health, regardless of how much effort is given to improve the OWTS.

4. Discussion

High salinity interferes with many water quality analyses, including those used to measure nutrients throughout the OWTS at LBCNP. The nutrient concentrations appear reasonable given the source of the wastewater. As such, the nutrient levels present in this research are estimates. The water quality analysis comprised a go, no go test to assess whether any action should be taken to improve the wastewater treatment system. Additionally, these results provided data to help quantify the problem and communicate its extent with stakeholders, while also creating a baseline for pre- and post-intervention comparison. The nutrient concentrations were high enough to warrant further action. Before any improvements to the OWTS were implemented, the research team wanted to know what is needed to ensure that the OWTS is a sustainable treatment system.
From an engineering standpoint, improper design, siting, and maintenance are the obvious reasons why an OWTS might fail. For OWTS, the main challenge comes from a lack of maintenance [38]. A concern is that interventions that only focus on renovations to the wastewater treatment system could be a temporary fix if the OWTS is not properly used and maintained. The perception that maintenance is not needed while the wastewater treatment system is operating efficiently could result in OWTS failure and the reduction in or elimination of the wastewater treatment system’s ability to remove nitrogen. A maintenance schedule from the OWTS providers could help to prevent this failure.
By modeling feedback dynamics (visualized with CLDs), additional context and foresight is gained that can assist in making a fix more sustainable and reduce the potential for unintended consequences. In this study, the first CLD analyzed was “Shifting the Burden”. From that analysis, it was suggested that a symptomatic fix could make the problem symptom worse and make the fundamental solution more difficult to enact. Given the context of a tourist-based economy versus environmental conservation, both a fundamental solution of limits on allowable daily visitor numbers and a symptomatic fix of wastewater system improvements should be applied, thereby preserving tourism and reducing the impact on the ecosystem. By using the park data on daily visitor numbers and deciding on an appropriate OWTS technolgy, a nutrient load carrying capacity can be calculated for the caye.
When the CLD was presented to SEA, they mentioned that improvements to the wastewater treatment system would not likely change the perceived need to limit visitors to LBCNP and that carrying capacity would predominantly be based on land area per visitor. They did, however, mention that this would be helpful in evaluating the carrying capacity of a nearby caye, Silk Caye. Silk Caye receives more visitors than LBCNP and they were already considering using both a symptomatic fix (improving the wastewater treatment system) and a fundamental fix (initiating a lottery system to limit the number of visitors) in this location.
Though the findings suggested both improving the OWTS and limiting visitors to LBCNP, SEA managers worried that the results of the archetype analysis could be misinterpreted as promoting an increased number of visitors, causing additional risk to the environment. For the people managing LBCNP, the visitor revenue is appreciated, but SEA’s primary goal is to conserve the natural ecosystem.
The importance of education and human-oriented design was apparent in a “Limits to Success” archetype depicting a wastewater treatment fix for LBCNP. Similarly, Pásková et al. [7] identified environmental education and awareness as well as investments in environmental protection as conditions capable of intervening in tourism-driven water-related pollution. This could be accomplished by having park rangers provide information on nitrogen pollution, such as its sources (urine) and the impact it can have on the environment, when they welcome visitors to the park and brief them on the rules. Another suggestion is to have signage with that information near the lunch area and toilet facilities and to thank visitors for their help in preserving the environment for generations to come.
Although the authors emphasized the importance of educating visitors, education of the park rangers could also increase the sustainability of the system. Prouty et al. [39] found that households with higher educational levels tended to spend more of their budgeted funds on OWTS operation and maintenance costs. Interviews and participatory observations from that study indicated a lack of awareness on the effects of reporting an inaccurate number of system users or inconsistent and poor operation and maintenance practices and the future costs incurred due to system failure.
These findings were presented to EcoFriendly Solutions. While they agreed with the conclusions, they added that not all park rangers are as proactive in maintaining the toilet facilities and OWTS. They suggested that any required upkeep should be part of the park ranger job description to prevent any lack of regular upkeep. Minimizing any additional burden on park rangers would be a consideration for any OWTS renovations and a reason why a passive wastewater treatment system is preferred.
Over the last eight years, maintenance to the OWTS has often been funded by non-government sources. It is recommended that SEA either increase the cost for park visitors to allow for funds to be set aside for maintenance or that they make changes to receive government assistance in maintaining the park.
It should be noted that CLDs are the investigators’ representation of reality, and bias or oversight of the true dynamic relationships involved can easily occur. Participatory processes such as interviews, participatory modeling, and model reviews with stakeholders can reduce these biases and make a CLD more situated in its problem context [40]. These processes were practiced throughout this work, including during the validation of results.

5. Conclusions

In this study, a systems thinking approach was adopted to assist in understanding the dynamic interactions between stakeholders of an OWTS for a popular tourist destination in an environmentally sensitive area. Water quality samples throughout the OWTS justified taking further action to improve the OWTS. The goal was to understand what managerial support is needed for a wastewater treatment system to effectively mitigate tourist-based nutrient pollution in a coastal region before any renovations to the OWTS occurred. The supporting actions were concluded through CLDs and stakeholder interviews.
It was concluded that sustainable wastewater management would require additional changes in policy, education, and infrastructure. Policy actions included the collection of additional funding budgeted towards OWTS operation and maintenance, controls on the number of visitors allowed at LBCNP, and making regular upkeep of the toilet facilities part of the job description for park rangers. Education included educating visitors on the ecological harm of urinating in the water and educating visitors and facility managers on the future costs of improper operation and maintenance of the OWTS. Infrastructure improvements included renovations to the wastewater treatment system and improving the toilet facilities. Though the focus of this study is on LBCNP, the results can be transferable to small island developing states or national parks where tourist-related marine activities can harm environmentally sensitive areas.

Author Contributions

Conceptualization, D.A.D. and M.M.M.; methodology, D.A.D. and M.M.M.; investigation, D.A.D. and M.A.T.; writing—original draft preparation, D.A.D.; writing—review and editing, D.A.D., M.M.M., W.A.W., C.P., S.J.E. and M.A.T.; visualization, D.A.D.; supervision, S.J.E. and M.A.T.; project administration, M.A.T.; funding acquisition, M.A.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Science Foundation, grant numbers 2209284 and 1735320, the US Department of Education, grant number P200A180047, Alfred P. Foundation Award-G-2017-9717, and the Florida Education Fund McKnight Dissertation Fellowship.

Data Availability Statement

The original contributions presented in this study are included in this article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The leadership and staff of Fragments of Hope Ltd., the Southern Environmental Association, and EcoFriendly Solutions provided logistical support, data, and input.

Conflicts of Interest

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Abbreviations

The following abbreviations are used in this manuscript:
BNRBiological nitrogen removal
CLDCausal loop diagram
FoHFragments of Hope
LBCNPLaughing Bird Caye National Park
OWTSOnsite wastewater treatment system
SEASouthern Environmental Association

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Systems 13 00544 g001
Figure 1. (A) “Out of Control” archetype and (B) “Shifting the Burden” specific case causal loop diagram for Laughing Bird Caye National Park. Dashed lines represent solution links. “B” denotes balancing loops, “R” denotes reinforcing loops, (+) denotes direct relation, (−) denotes inverse relation.
Figure 1. (A) “Out of Control” archetype and (B) “Shifting the Burden” specific case causal loop diagram for Laughing Bird Caye National Park. Dashed lines represent solution links. “B” denotes balancing loops, “R” denotes reinforcing loops, (+) denotes direct relation, (−) denotes inverse relation.
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Figure 2. “Shifting the Burden” behavior over time at Laughing Bird Caye National Park. Adapted from [36].
Figure 2. “Shifting the Burden” behavior over time at Laughing Bird Caye National Park. Adapted from [36].
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Figure 3. (A) “Underachievement” archetype and (B) “Limits to Success” specific case causal loop diagram for Laughing Bird Caye National Park. Dashed lines represent solution links. “B” denotes balancing loops, “R” denotes reinforcing loops, (+) denotes direct relation, (−) denotes inverse relation.
Figure 3. (A) “Underachievement” archetype and (B) “Limits to Success” specific case causal loop diagram for Laughing Bird Caye National Park. Dashed lines represent solution links. “B” denotes balancing loops, “R” denotes reinforcing loops, (+) denotes direct relation, (−) denotes inverse relation.
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Figure 4. “Limits to Success” behavior over time at Laughing Bird Caye National Park. Adapted from [36].
Figure 4. “Limits to Success” behavior over time at Laughing Bird Caye National Park. Adapted from [36].
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Table 1. Estimated nutrient concentrations of total nitrogen (TN), ammonia (NH3+), nitrate (NO3−), and phosphate (PO43−) in milligrams per liter for the onsite wastewater treatment system at Laughing Bird Caye National Park in June 2022 and June 2023. NH3 and NO3− measurements are expressed in milligrams per liter as nitrogen. Means and standard deviations (SD) are shown for the June 2023 samples when triplicates were measured.
Table 1. Estimated nutrient concentrations of total nitrogen (TN), ammonia (NH3+), nitrate (NO3−), and phosphate (PO43−) in milligrams per liter for the onsite wastewater treatment system at Laughing Bird Caye National Park in June 2022 and June 2023. NH3 and NO3− measurements are expressed in milligrams per liter as nitrogen. Means and standard deviations (SD) are shown for the June 2023 samples when triplicates were measured.
June 2022
TNNH3+NO3−PO43−
System Influent49437620133
Stage 3 Influent499337157
Stage 3 Effluent493924
June 2023
TNSDNH3+SDNO3−SDPO43−SD
System Influent537313.929447.12614.51010.9
Stage 3 Influent28043.6199152.119742.05818.3
Stage 3 Effluent10737.13327.610.282.2
Table 2. Findings from informal interviews and site visits to LBCNP from 2019 to 2023.
Table 2. Findings from informal interviews and site visits to LBCNP from 2019 to 2023.
YearActionsTakeaways
2019Interviews with FoH, park rangers, and EcoFriendly SolutionsLack of regular upkeep of OWTS. Park rangers’ understanding of OWTS upkeep.
2022Site visitVisitors urinating in water.
2023Interview with SEA managemen and EcoFriendly SolutionsPark ranger turnover and inconsistent OWTS upkeep.
Need for science-based intervention.
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MDPI and ACS Style

Delgado, D.A.; McAlister, M.M.; Webb, W.A.; Prouty, C.; Ergas, S.J.; Trotz, M.A. Using Systems Thinking to Manage Tourist-Based Nutrient Pollution in Belizean Cayes. Systems 2025, 13, 544. https://doi.org/10.3390/systems13070544

AMA Style

Delgado DA, McAlister MM, Webb WA, Prouty C, Ergas SJ, Trotz MA. Using Systems Thinking to Manage Tourist-Based Nutrient Pollution in Belizean Cayes. Systems. 2025; 13(7):544. https://doi.org/10.3390/systems13070544

Chicago/Turabian Style

Delgado, Daniel A., Martha M. McAlister, W. Alex Webb, Christine Prouty, Sarina J. Ergas, and Maya A. Trotz. 2025. "Using Systems Thinking to Manage Tourist-Based Nutrient Pollution in Belizean Cayes" Systems 13, no. 7: 544. https://doi.org/10.3390/systems13070544

APA Style

Delgado, D. A., McAlister, M. M., Webb, W. A., Prouty, C., Ergas, S. J., & Trotz, M. A. (2025). Using Systems Thinking to Manage Tourist-Based Nutrient Pollution in Belizean Cayes. Systems, 13(7), 544. https://doi.org/10.3390/systems13070544

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