Towards Solving the Beach Litter Problem: Ecosystem Service Assessments at North African Coasts

Abstract

Sandy beaches along the North African Mediterranean coast face significant challenges due to accumulating human-made debris (marine litter) and natural debris (beach wrack). Addressing these issues requires awareness of pollution and the ecological relevance of beach wrack, along with stakeholder involvement. This study quantifies beach litter pollution and identifies sources in Tunisia, Morocco, and Egypt, serving as a basis for ecosystem service assessments and further integration into the implementation of mitigation measures. High levels of plastic litter were found, ranging from 1565 to 7778 pieces per 100 m of beach length. Shoreline activities, tourism, and poor waste management were identified as the main sources of litter, with single-use plastics accounting for 41.1% of the debris. Further objectives include providing a list of suitable ecosystem services and developing management scenarios. Local stakeholders’ perceptions of the impact of marine litter and beach wrack on ecosystem services were assessed using a scenario approach and different formats (i.e., stakeholder workshop, interviews, teaching). Stakeholders highlighted the negative impact of marine litter on cultural services, while beach wrack was perceived positively for regulating and maintenance services. This approach enhances awareness, interest, and knowledge in data-scarce regions, serving as a valuable tool for stakeholder engagement, elicitation of stakeholder knowledge, and teaching (i.e., learning tool). Limitations include the subjectivity of the results, limited participant reach, and dependence on stakeholder knowledge. Integrating stakeholder-based ecosystem service assessments into measure planning and decision making is essential for effective litter management and beach conservation efforts.

1. Introduction

As transition zones between land and sea, sandy beaches occupy one-third of the world’s shoreline [1]. Beaches are highly dynamic and sensitive ecosystems that provide important ecological functions, such as natural coastal protection [2], habitat provision for endemic biological communities [3], and the processing and recycling of nutrients [4]. Additionally, as a hotspot for recreational activities and tourism, beaches are of high socio-economic importance and, in particular, serve as income generation sources in coastal areas [5]. Thus, beaches are constantly challenged by the need to balance human activities and preserve nature.

In the future, the main threats to beaches stem from socio-economic activities such as population growth, coastal urbanization, and the tourism industry [6]. For example, beach biodiversity is negatively impacted by trampling (from tourists) [7] and by ongoing marine litter pollution worldwide [8]. As climate change and sea level rise accelerate beach erosion, almost half of the sandy beaches globally are projected to face severe erosion by 2100 [9]. Consequently, beaches of major political interest are in a coastal squeeze and require sustainable management.

Beaches are accumulation hotspots for both human-made debris (i.e., marine litter) and natural debris (i.e., beach wrack). First, marine litter is defined as “any persistent, manufactured or processed solid material discarded, disposed of, or abandoned in the environment” and became a target of global political action because of its significant increase worldwide [10]. Second, beach wrack can be defined as all marine organic material transported by the sea and washed ashore composed of macrophyte debris (i.e., macroalgae, seagrass), animal remnants (i.e., seashells), and driftwood [11]. Terminologies used by other authors are “beach cast”, “beach debris”, and “flotsam” [12].

Studies show that both litter and beach wrack are perceived as a nuisance to beach users and cause high costs for municipalities. Krelling et al. [13] show that litter reduces the aesthetic view and attractiveness of beaches for tourists, causing severe income loss for local communities up to almost 40%. Similarly, despite studies highlighting important ecological functions of beach wrack, such as habitat provision and biodiversity [14] and natural coastal protection [15], Rotini et al. [16] found that people perceive beach wrack accumulation as a nuisance and even consider negative effects by the presence of seagrass banquettes.

Therefore, touristically used beaches are regularly cleaned from both litter and beach wrack. In Europe, beach cleaning costs for municipalities are on average around EUR 7000 per km per year but can increase up to EUR 82,000,000 per km per year in touristic areas [17]. In the Mediterranean Sea, cleaning costs (mainly beach wrack) vary from EUR 15,000 to EUR 130,000 per year and additionally around EUR 60 to EUR 80/m³ for the disposal of beach wrack [18]. Depending on the efficiency of cleaning methods (i.e., manual, mechanical), cleaning operations entail high costs and negative impacts on the ecosystem (i.e., loss of biodiversity and coastal protection function) [19], as the removal of marine litter unavoidably also involves the removal of beach wrack. To reduce cleaning costs and the ecosystem´s degradation, an increased awareness is required of both the ecological value of beach wrack as well as the implications of marine litter pollution on beach ecosystem services.

Both litter and beach wrack are the main management issues in the Mediterranean Sea. The Mediterranean Sea is one of the most heavily impacted areas globally by marine litter [20]. Additionally, beach wrack can accumulate up to 2.5 m in height, building so-called “banquettes” (mainly from seagrass) [21]. However, as the Mediterranean Sea attracts approximately one-third of global tourism each year [10], clean beaches and high bathing quality are of pivotal importance. In particular, North African countries of the Southern Mediterranean Sea are generally underrepresented in the literature on tourism, which is one of the main economic sectors. While tourism is also among the primary causes of waste generation and litter pollution, municipalities are often lacking financial means for appropriate management [22].

Can assessing the problem of litter and beach wrack from a socio-economic–ecological perspective contribute to sustainable beach management? Using such an interdisciplinary perspective, the concept of ecosystem services (ESs) is a holistic and anthropocentric approach that arouse out of the need for nature conservation increasing in interest in science and politics since the 1990s. ESs are defined as the benefits to humans provided by natural ecosystems either directly or indirectly [23] divided into provisioning (i.e., food), regulating and maintenance (i.e., coastal protection), and cultural services (i.e., tourism). There has been an increase in ES studies in the Northern Mediterranean Sea. For example, Drius et al. [24] provide an ES-based framework to address the challenges of sustainable coastal tourism in Italy. Another study assesses the ES specifically provided by reed and seagrass debris, offering implications for management [25]. In Spain, Herrera et al. [26] found through interviews with the general public that marine debris can significantly decrease coastal ES provision. Interdisciplinary studies on the Southern Mediterranean Sea (North African countries) are largely lacking, as supported by Wangai et al. [27], stating that in Africa, most ES research concentrates on the sub-Saharan region.

Solving problems with litter and beach wrack on North African beaches requires, first, an awareness of the pollution problem and the ecological relevance of beach wrack, and second, the involvement of local stakeholders, which is essential for developing and implementing solutions. The first objective of this study is to quantify beach litter pollution and identify the main pollution sources of sandy beaches in Egypt, Tunisia, and Morocco. To combine the pollution status with the ES approach, further objectives are (a) to provide a list of ESs that generally enable ES assessments of North African sandy beaches; (b) to develop beach management scenarios of different pollution levels (including litter and beach wrack) that allow for comparative assessments; (c) to test different ES assessment methods involving local stakeholder groups and literature data; and (d) to compile the local relevance of the ES and the scenario impact on ES provision as perceived by stakeholders. The last two objectives are to provide an overview of mitigation measures for litter management and to provide an approach that integrates the ES concept to support measure implementation and decision making.

2. Materials and Methods

2.1. North African Beaches in Morocco, Tunisia, and Egypt

This study focuses on the sandy beaches of North African countries bordering the Mediterranean Sea, specifically Morocco (including the Atlantic coast), Tunisia, and Egypt (Figure 1). The primary management issues of sandy beaches worldwide are marine litter pollution due to increasing pressure from tourism [20], high amounts of beach wrack accumulation [21], and increasing coastal erosion [9].

In Morocco, the Mediterranean coast has a length of 350 km out of the total 2500 km shoreline [28]. The Atlantic coast of Morocco exhibits low cliffs and beaches that span over 20 km, constituting of approximately 30% of the coastline [28]. The majority of the Mediterranean coast in Morocco consists of mountains, featuring sandy and pebbled beaches along broad embayments, accounting for approximately 25% of its total length [28]. The tourism sector in Morocco accounts for up to 7.1% of the gross domestic product with 12.9 million international tourist arrivals in 2019 [29]. An increasing trend of tourist arrivals for the years 2022 to 2024 was reported by the country´s Ministry of Tourism, Handicrafts, and Social and Solidarity Economy. A study by Mghili et al. [30] found an average of 0.20 ± 0.098 litter pieces/m² along five Moroccan Mediterranean beaches.

Tunisia´s coastline has a total length of 1270 km, including 525 km of sandy beaches [31]. With 9.5 million tourist arrivals in 2019 [32], the tourism sector accounts for up to 8.1% of the national GDP [33]. A study on marine litter pollution [34] found an average of 3.09 litter pieces/m² ± 2.29 in Monastir.

In Egypt, the Mediterranean coast covers approximately 1000 km and is characterized by salt marshes, mud flats, lagoons, and sand dunes, as well as rocky beaches [35]. Despite low tidal effects and low wave energy, Hereher [35] found that one-third of the 1000 km coastline is highly vulnerable to rising sea levels. With 9.8 million international tourist arrivals in 2019, before the COVID-19 pandemic, tourism accounted for up to 15% of Egypt’s gross domestic product [36]. Hassan et al. [37] found an average of 7.20 plastic pieces/m² ± 1.03 in Alexandria.

2.2. Beach Litter Sampling

The collection of macro-litter (>2.5 cm) is based on the beach litter monitoring method described in the UNEP Mediterranean Action Plan [20]. However, due to high pollution and time constraints, the average beach length investigated was 60 m instead of 100 m. A total of 16 beach litter surveys were conducted between November 2021 and January 2023 on Mediterranean beaches at or near the study sites (Figure 1). Litter analysis was carried out using the “Joint List of Litter” by Fleet et al. [38]. The pollution was calculated in litter pieces/m² and extrapolated to pieces of litter/100 m of beach length. The Clean Coast Index by Alkalay et al. [39] was applied to assess beach cleanliness. The assessment of litter sources followed the method by Tudor and Williams [40], using the potential sources described in Vlachogianni et al. [41].

Despite the significance of factors such as tides, wind direction, wind speed, and proximity to rivers influencing beach pollution levels, this study focused solely on quantifying these levels and identifying potential sources. The overarching aim was to raise awareness of the pollution status and emphasize its importance for effective management strategies.

2.3. Ecosystem Service Assessment

The ES assessment approach applied in this study is based on Inácio et al. [42] and was adapted and applied to Baltic beaches by Robbe et al. [43]. The innovation of the application presented here is the regional focus (i.e., North Africa) on areas with low data availability and a lack of socio-economic studies. The approach consists of three main steps (Figure 2). First, a suitable set of ESs was selected based on experts (here, the authors) and the literature. Second, the beach scenarios that are subject to the ES assessments were developed based on experts (here, the authors) and the literature. Third, the ES assessment was carried out by different stakeholder groups, as well as by a literature-based approach using the selected list of ESs and the developed scenarios.

2.3.1. Selection of Sandy Beach ESs (Step 1)

To provide a set of ESs that generally enables an assessment of North African sandy beaches, 22 services were selected based on field experience and the literature. For this, the Common International Classification of Ecosystem Services (CICES V.5.1 in Haines-Young and Potschin-Young [44]) was used with adaptations by Müller et al. [45], Barbier et al. [5], and Defeo et al. [6]. At the class level, services are usually valid for sandy beaches globally [6]. However, the service descriptions and examples were modified according to the respective socio-ecological context of the study sites in order to guarantee applicability and understandability for local stakeholders. The main selection criteria of services were the relevance for sandy beach ecosystems and the study sites. The selected list fairly represents each service category by at least 6 services, including provisioning (27%), regulating and maintenance (41%), and cultural services (32%). For the full list of services and respective descriptions, see Appendix A.

2.3.2. Scenario Development (Step 2)

To allow comparative assessments by local stakeholders, three hypothetical but realistic scenarios of sandy beaches were developed, representative of North African beaches in Morocco, Tunisia, and Egypt that are touristically used and managed (Figure 3). The development of contrasting beach pollution scenarios is based on field experience and sampling data. To compare a potentially desired and clean beach (Baseline Scenario) to different pollution levels of beaches, the scenarios were divided into the state of litter pollution in Scenario 1 (i.e., meso- and macro-litter above 0.5 cm) and beach wrack accumulation in Scenario 2, and both are the main management issues in the Mediterranean Sea [46]. To visualize the Baseline Scenario, the current state of Plage Bouficha in Yasmine Hammamet (Tunisia), as of 11 November 2021, was utilized, with visual litter removed. For Scenario 1, litter accumulation was incorporated into the Baseline Scenario, as observed at Plage Ghiran in Ras Angela (Tunisia) on 23 November 2021. For Scenario 2, beach wrack accumulation observed at Plage Sidi Salem in Bizerte (Tunisia) on 22 November 2021 was added to the Baseline Scenario. The original photos can be found in Appendix A (Figure A1).

• Baseline Scenario (Figure 3a) shows a “clean(ed)” beach without marine litter or beach wrack. It represents a common beach for the Southern Mediterranean Sea by active management (i.e., regular cleaning operations). Moderate beach vegetation was assumed.
• Scenario 1 (Figure 3b) shows high amounts of marine litter, i.e., around 2500 macro litter items per 100 m, but no beach wrack accumulation. Accumulation includes marine litter washed ashore from the sea, as well as litter from human activities on the beach. Entanglements of the moderate beach vegetation, as well as floating litter in nearshore waters, were assumed.
• Scenario 2 (Figure 3c) represents a beach with moderate to high amounts of beach wrack accumulation (50–75% coverage of the whole beach area) without marine litter. Beach wrack accumulation was defined as landed organic material, including sea grass and algae, as well as the remains of dead animals, such as crabs and seashells, stones, and wood pieces. Floating algae in the nearshore waters and birds feeding on landed beach wrack were assumed.

Scenario visualizations provided the foundation for the ES assessments conducted by stakeholders. Detailed scenario descriptions and visualizations were provided to stakeholders within a slideshow and an additional paper-based document.

2.3.3. Scenario-Based ES Assessment by Stakeholders (Step 3.a)

The ES assessment was carried out first by stakeholders and later complemented by a literature-based assessment (performed by the authors). To test different methods for the stakeholder-based ES assessment, group workshops (i.e., in person and hybrid) and individual in-person interviews (

Table 1. List of ES assessments carried out using the scenario approach with stakeholders.

Date	Location	Assessment Format	No. of Stakeholders	Stakeholders
1: 20 June 2022	Tunis (Tunisia)	Stakeholder workshop	19	Local: science (53%), municipalities (42%), government (10%), consulting (5%)
2: 10 January– 10 February 2023	Tangier, Essaouira, Agadir, and Marrakesh (Morocco)	Stakeholder interviews	7	Local: government (57%), NGOs (14%), science (29%)
3: 31 March 2022	Alexandria (Egypt)	Teaching/lecture (group workshop)	5	Local graduate students/science (100%)
4: 16 November 2023	Online (Germany)	Teaching/lecture (group workshop)	12	International graduate students/science (100%)

) were carried out using a spreadsheet-based scenario assessment. The group workshops covered an introduction to the methodology (i.e., ES assessments), topics (i.e., marine litter and beach wrack), scenario descriptions (ca. 30 min), individual assessment time (30–60 min), and a discussion of the results (60–120 min). Paper-based assessment sheets and detailed scenario descriptions were provided in English and French. Individual stakeholder interviews lasted an average of 60 min, including an introduction, written assessment, and oral discussion. First, stakeholders assessed the “Relative Importance (RI)” of each service perceived at their local sandy beach in general (independent from scenarios) and relative to the overall ES provision. A non-linear scoring scheme was used, ranging from 0 (not important), 1 (low), 2 (moderate), 4 (high), to 8 (very high importance) and based on previous studies. Second, the stakeholders were asked to assess the impact (or relative change) of the Baseline Scenario compared to Scenarios 1 and 2. A scoring scheme was employed ranging from a high (−/+3), moderate (−/+2), to low (−/+1) decrease or increase in service provision. As a starting point for discussions, stakeholders were asked for their reasons behind their outliers or extreme values (i.e., very low or high). This was performed to identify under- or overestimations, misunderstandings, or misconceptions. Services with higher standard deviations (SD > 1.5), either for RI values or impact scores indicate, needed clarification. To analyze the SD of the RI values, the exponential RI scale was converted into an arithmetic scale, assuming a normal distribution.

In total, 43 stakeholders carried out the ES assessment. The main selection criteria for stakeholders included availability (i.e., time wise and physically), relevance (i.e., interest and involvement in the topic), expertise (i.e., work experience and local knowledge), and representation (i.e., a broad range of fields and interests). The most limiting factors for stakeholder participation were high organizational efforts and limited availability by stakeholders. In Group 1 (Tunisia), 19 local stakeholders participated from different sectors (i.e., science, government, municipalities, beach managers, waste managers) and disciplines (i.e., ecology, biology, geography, environmental engineering). Assessments of Group 2 (Morocco) were conducted by individual interviews with local representatives from governmental institutions (i.e., environmental and fisheries departments, tourism ministry), NGOs, and research institutions from different fields (i.e., agronomist engineering, microbiology, biotechnology, environmental science, tourism). Group 3 (Egypt) consisted of five local graduate students from different disciplines (i.e., environmental science, chemistry, fisheries, microbiology). They were allowed to change values after discussion. Group 4 (online), as part of an online module on “Coastal Zone Management”, consisted of international students coming from different European countries (i.e., Spain, Lithuania, Germany) and disciplines (i.e., coastal engineering, biology, marine sciences, biotechnology).

2.3.4. Scenario-Based ES Assessment by Literature (Step 3.b)

Additionally, a literature-based assessment was carried out evaluating the RI value in order to compare the results to the stakeholder-based assessment, as well as to the results of the same approach at the Baltic Sea [43]. Because of the contrasting beach characteristics of the Baltic and the Mediterranean Seas, such as beach length and width, flora and fauna, and protection status (i.e., emission control area), the comparison allows us to identify the approach´s suitability and transferability to other regions and seas. This was only performed for the RI value based on the assumption that the impact of marine litter (Scenario 1) and beach wrack (Scenario 2) is similar to the Baltic Sea results. Furthermore, unlike the Mediterranean Sea, the Baltic Sea is marked by spatial constraints (i.e., increased shipping activity) and substantial anthropogenic pressures (i.e., large urban centers).

Due to data scarcity in the Southern Mediterranean Sea, the literature-based assessment considers the entire Mediterranean Sea. An automated search of the Web of Science (WoS) database was carried out based on the assumption that the number of WoS articles found indicates the scientific relevance of given keywords and thus represents the RI of each ES. The search string was composed of three components: the regional focus (“Mediterranean”), the ecosystem (“beach” OR “coast” OR “dune”), and the ES, for example, recreation and tourism (C1) (“recreation” OR “tourism” OR “touristic” OR “beach sports” OR “hiking” OR “swimming” OR “sun bathing”) (see Table S1 in the Supplementary Material for a full list of the search strings). The mean value of the WoS articles found was assigned a score of 8, indicating “very high relevance”. The remaining values were automatically categorized using the following scale, adapted from the Marine Ecosystem Services Assessment Tool employed by Inácio et al. [42]: 8 (1 and above), 4 (1 to 1/2), 2 (1/2 to 1/4), and 1 (1/4 and less).

3. Results

3.1. State of Beach Litter Pollution

Surveys carried out identified high levels of pollution. Most litter found was plastic (83.7%). In Tunisia, an average of 1565 ± 1020 pieces of litter/100 m of beach length, corresponding to a mean of 0.69 pieces/m² ± 0.37 pieces and a median of 0.99 pieces/m², was found. In Morocco, the average pollution was 3599 ± 159 pieces of litter/100 m (mean 0.82 pieces/m² ± 0.68; median 1.02 pieces/m²), and in Egypt, 7778 ± 7709 pieces of litter/100 m (mean 2.70 pieces/m² ± 1.45; median 2.38 pieces/m²). According to the Clean Coast Index, the pollution levels of the surveyed beaches in Tunisia and Morocco are classified as dirty, while in Egypt they are classified as extremely dirty. In Tunisia, Morocco, and Egypt, the top ten litter items account for 70.4%, 75.0%, and 74.7% of the total litter, respectively. In total, 41.1% of the litter found was single-use plastics (SUPs) see Figure 4. Considering the sources of litter found, the distribution per country is similar; therefore, the average results of all three countries are shown here. The highest amount of litter originates from the shoreline, including poor waste management practices, tourism, and recreational activities (48.9%). Altogether, 32.7% could not be attributed to specific sources. Lower numbers of litter pieces originated from other sources, such as “shipping” (5.4%); “fisheries and aquaculture” (3.7%); “fly-tipping” (3.1%); “sanitary and sewage related” (3.1%); “medical related” (1.7%); and “agriculture” (1.4%).

Figure 5 shows the amount of beach wrack in Bizerte, Tunisia. Beach wrack mainly consists of Neptune grass (Posidonia oceanica) that forms large underwater meadows in the Mediterranean Sea. At the shoreline, it forms a layer of above 1 m of height and in some areas, an estimated amount of up to 1000 m³ is accumulated per 100 m of beach length. This example indicates the quantitative role of beach wrack. It further gives an idea of the inhibiting role beach wrack accumulation can potentially play for bathing tourism and the existing pressure on municipalities to remove beach wrack.

The photos indicate another issue, the increasing amount of macro-litter on beach wrack surfaces with increasing distance to the shoreline. While recently accumulated Neptune grass hardly contains any macro-litter, the pollution level of old material, further up on the beach, is high. This indicates that hardly any sea-borne litter is accumulated with beach wrack. The pollution of beach litter occurs as it is pushed up the beach during high sea levels. This secondary pollution turns beach wrack into a waste problem and restricts its use. However, it can be assumed that beach wrack accumulation does not significantly affect the beach monitoring results or the determination of the most important litter items.

3.2. Relative Importance of Beach ESs Perceived by Local Stakeholders

The Relative Importance (RI) indicates the relevance of each ES perceived by stakeholders at their local sandy beach, independent from pollution scenarios. The stakeholder-based results on the RI of ESs (Figure 6) reveal that, on average, the services perceived as most important are among cultural services (comprising 49.4% of the sum of RI values), followed by regulating and maintenance (35.3%), and lastly, the provisioning services (15.3%). The three most important services perceived by stakeholders, rated as having a very high importance (with a median value of all RIs at 8), are recreation and tourism (C1), landscape aesthetics (C6), and natural heritage (C7).

On the national group level, the Egyptian students (EGY) in particular perceived the regulating and maintenance services as very highly important (RI: 8), specifically coastal protection (RM2) and water purification (RM5). In contrast, the Moroccan stakeholders (MAR) from both the Mediterranean and the Atlantic coast assessed the regulating and maintenance services as the lowest compared to all groups, which stated a moderate importance (RI: 2). There were several outliers, especially for coastal protection (RM2), which was assessed as not important (RI: 0). Comparing the variability between national stakeholder groups, the data on SDs, thus, the stakeholder agreement, show that the Egyptian students show highest agreement (average SD of all services: 0.8), followed by the European students (SD: 0.9) and Tunisian stakeholders (SD: 1.0). Compared to the workshop format of Tunisian stakeholders, the Moroccan stakeholders (carried out by individual interviews) showed the lowest agreement (SD: 1.2). If stakeholder compositions are similar, the results indicate that the approach is generally suitable for regional comparisons of stakeholder perceptions and for transferring the approach to other regions.

Services with the lowest agreement among all stakeholders are the extraction of minerals (P4), carbon sequestration (RM7) (both SDs: 1.4), and coastal protection (RM2) (SD: 1.3). Services with the highest agreement among all stakeholders are recreation and health (C2) (SD: 0.9), natural heritage (C7) (SD: 0.9), and recreation and tourism (C1) (SD: 0.8). Regulating and maintenance services show the lowest agreement (SD: 1.2), while cultural services show the highest agreement among all stakeholders (SD: 1.0). Combining the SD (i.e., level of agreement) with the RI (i.e., importance) of services, needs for discussion and the lack of information among stakeholders can be identified, which can be seen for coastal protection with a high SD (i.e., low agreement) and high a RI (4).

3.3. Scenario 1: Impact of Beach Litter Perceived by Local Stakeholders

The scenario-based stakeholder assessment results of Scenario 1 (Figure 7) evaluate the stakeholders’ perception and awareness level regarding how marine litter affects the ES provided by beaches. The results indicate that the most impacted ES category by marine litter pollution, as perceived by stakeholders, is cultural services (comprising 48.6% of the sum of absolute impact values), followed by provisioning services (27.1%) and regulating and maintenance services (24.3%). The overall impact trend is negative. Services with the strongest negative impact (median: −3) are recreation and tourism (C1), recreation and health (C2), landscape aesthetics (C6), and natural heritage (C7). Services with no perceived impact (0) are driftwood (P5), coastal protection (RM2), and groundwater regulation (RM7). These findings indicate that stakeholders are well aware of the adverse effects of marine litter on ESs, particularly on cultural services.

Comparing the groups on a national level, the SD results reveal that Tunisian stakeholders (TN) show the strongest distribution of impact values (average SD of all services: 1.7). It can be assumed that this low agreement among stakeholders is based on significant misunderstandings of the participants (9, 11, and 18 of the TN group), presumably due to language barriers, as well as on the highest heterogeneity of stakeholders among the groups (see Table 1). This is supported by the high share of 21% of all impact values, indicating a beneficial effect of marine litter on ESs, such as on nutrient regulation. Additionally, during the discussion with Tunisian stakeholders, misinterpretations could be identified, as some participants evaluated based on their own additional interpretations. For example, they assumed an increase in all cultural services within the marine litter scenarios, as they identified increased tourism as the main cause of marine litter pollution. The highest agreement among stakeholders is shown for European students (SD: 1.1), followed by Moroccan stakeholders (SD: 1.3) and national Egyptian students (SD: 1.6). On the service level among all groups, the highest value distribution was found for cultural services, in particular for recreation and tourism (C1) (SD: 2.3) and recreation and health (C2) (SD: 2.1). However, international students show the lowest value distribution for recreation and tourism (C1) (SD: 0) and landscape and aesthetics (C6) (SD: 0). The findings indicate that the approach is applicable across diverse regions, contingent upon factors, such as stakeholder diversity, representation, and cultural adaptations, including addressing language barriers.

3.4. Scenario 2: Impact of Beach Wrack Perceived by Local Stakeholders

The scenario-based stakeholder assessment results of Scenario 2 (Figure 8) evaluate the stakeholders´ perception and awareness level regarding the impact of beach wrack on ESs provided by beaches. The findings reveal that stakeholders perceived the regulating and maintenance services to be most impacted by beach wrack accumulation (share of the sum of absolute impact values: 47.6%), provisioning services (28.6%), and cultural services (14.3%). The overall impact trend is mainly positive. While provisioning services and regulating and maintenance services were assessed as mainly positive, apart from some outliers on the group level (i.e., extraction of minerals, sediment storage, pest and disease control, groundwater regulation), the results for cultural services do not show a clear positive or negative trend. However, stakeholders clearly perceived beach wrack as having a negative impact on recreation and tourism (C1) (median: −1). Apart from Tunisian stakeholders, other groups also perceived beach wrack as slightly negative for landscape aesthetics (C6) (median: −1). Services with the strongest positive impact are biomass as an energy source (P3) (median: +3) and biodiversity and habitat (RM3) (median: +2). These findings reveal that stakeholders have diverse perceptions regarding beach wrack, with some viewing it rather negatively, particularly concerning cultural services, while others perceive it positively. This is reflected on both the national group level and within stakeholder groups.

SD results for Scenario 2 are slightly higher than in Scenario 1. Only Moroccan stakeholders (MAR) show a relatively low value distribution (SD: 1.4) compared to the other stakeholder groups (TN, EGY, EU) with SDs of 1.8 or 1.7. Among service categories, cultural services show the highest value distribution (on average SD: 2.1), with the highest for recreation and health (C2) (SD: 2.3) and landscape aesthetics (C6) (SD: 2.2). The lowest value distributions are found for provisioning services (on average SD: 1.6), with lowest for wild plants for materials (SD: 1.3). These findings indicate a notable deficiency in stakeholders´ awareness regarding the socio-ecological significance and impacts of beach wrack on ESs across various regions.

When comparing the impact of the results of Scenario 1 (marine litter) and Scenario 2 (beach wrack), a greater consensus was observed regarding the adverse effects of marine litter on ESs, while perceptions on the effect of beach wrack are more contentious, with greater disparities among stakeholders.

3.5. Stakeholder Involvement Approaches—Lessons Learned

With the aim to engage a variety of local stakeholders, the ES assessment was carried out in three different approaches, including a workshop (Tunisia), interviews (Morocco), and teaching (Egyptian and European groups). During the stakeholder workshop, local stakeholders in Tunisia emphasized the trade-offs between environmental preservation (incl. coastal protection) and tourism demands, highlighting marine litter pollution and beach wrack removal as major concerns for coastal managers. Regarding beach wrack, they acknowledged its potential uses as a natural resource (i.e., as biofuel or in cosmetics) but stated a lack of initiatives for its utilization. They assumed that construction activities, like building ports, would contribute to an increase in beach wrack accumulation, altering coastal dynamics and enhancing the need for management (i.e., beach wrack removal). Despite some inconsistencies in assessment values (presumably due to language barriers and misunderstandings), the ES assessment approach was successfully applied and served as a helpful base for group discussions. Stakeholders experienced an awareness-raising and learning effect during group discussions through the exchange of opinions and experiences from different stakeholder perspectives (detailed documentation in Table S2 of the Supplementary Materials).

In the interviews, local stakeholders in Morocco recognized the potential of beach wrack for various uses, like material for further use, human nutrition, and bioenergy, but stated that it remains largely unexploited. Stakeholders highlighted the economic importance of mineral extraction, particularly salt and sand, but noted that extraction occurs partly illegally (mainly sand). Indicating the interconnectedness of environmental issues, stakeholders evaluated marine litter pollution to negatively affect salt extraction as further used for human consumption. Stakeholders expressed significant concerns about coastal erosion and the increasing need for coastal protection, especially for Mediterranean coastal cities, emphasizing the vulnerability of these areas. There is a lack of awareness and knowledge regarding pest and disease control (RM4), carbon storage (RM7), and groundwater regulation (RM6). Despite stakeholders highlighting the very high importance of water purification (RM5) due to the high water pollution, improvements are limited due to lack of financial resources. Compared to the workshop format (in Tunisia), a lesson learned was that by carrying out the assessment as individual interviews, misunderstandings could be avoided directly, individual results could be more robust, and stakeholders could give more valuable and detailed input, personal experience, and expertise.

Using the ES assessment in teaching, both student groups recognized the potential of beach wrack for product development and similarly noted a lack of initiatives, which indicated an opportunity for innovation and entrepreneurship. Egyptian students showed a different understanding of mineral extraction, particularly sand mining, highlighting the importance of clarifying concepts during teaching. Egyptian students stated that their perception of beach ecosystems was evolving during the assessment. For example, some students only then recognized the ecological importance of beaches beyond recreational purposes, emphasizing the need for education on the whole range of beach ESs. The overall understanding of the approach and the services was higher in the European group than in the local group (Egypt), resulting in shorter discussions of the results. Another lesson learned was that the ES assessment can serve as an effective tool for learning and increasing interest in environmental topics among students, in particular of lower level of awareness and education, with some students indicating changes in their perspectives and motivations for further study. This underpins the value of incorporating such assessments into university teaching methods.

Summarizing, through stakeholder workshops, interviews, and teaching, valuable insights were gained regarding the perceptions, challenges, and opportunities related to marine litter pollution and beach wrack within coastal management. These lessons learned shed light on the effectiveness of different engagement methods and highlighted the potential of the ES assessment approach in fostering awareness, knowledge exchange, and stakeholder participation in environmental decision-making processes.

3.6. Comparison of the Literature- and Stakeholder-Based Assessment Results: Mediterranean Sea and Baltic Sea

The aim of comparing the results of the literature-based and stakeholder-based ES assessments of both the Mediterranean Sea and the Baltic Sea was to identify differences in perceptions and scientific relevance in order to assess the applicability and transferability of the assessment approaches worldwide. The results of the literature-based assessment of the Mediterranean Sea (Northern and Southern parts) are shown in Figure 9. The three most important services with an RI score of 8 (very high importance) based on the literature results (i.e., WoS indicator) are biodiversity and habitat (RM3), recreation and health (C2), and knowledge systems (C3). A total of 68% of services show only low importance (RI: 1) due to the low number of scientific articles found, while the service regional identity (C5) was not reflected by the literature at all (RI: 0). Compared to the societal view (i.e., stakeholder results), the literature-based results reflecting the scientific relevance of services show clear differences for 86% of the services. Wild plants for material (P1) and driftwood (P5) were assessed similarly by both approaches, while the main discrepancy (three classes of change) was found for regional identity (C5), landscape aesthetics (C6), and natural heritage (C7), which were assessed much higher by stakeholders than reflected in the literature. Differences in RI values of the stakeholder-based and the literature-based results are much higher in the Mediterranean Sea (68% of services) than in the Baltic Sea (33% of services). In contrast to the Baltic Sea results, the discrepancy between societal perception (i.e., stakeholders) and the scientific view (i.e., the literature) reveals that the literature-based assessment approach for evaluating the RI of ESs provided by sandy beaches in the Mediterranean Sea was tested and found to be unsuitable due insufficient scientific literature.

In the Southern Mediterranean Sea, stakeholders perceived provisioning services as more important on average (RI: 2) than the Baltic stakeholders, as reflected in the literature results (RI: 1). Regulating and maintenance services were perceived as slightly more positive on average by Southern Mediterranean stakeholders, with the exemptions of sediment storage (RM1), coastal protection (RM2), and biodiversity (RM3). Regarding marine litter (Scenario 1), data reveal a much stronger negative impact of marine litter on the ES as perceived by stakeholders in the Southern Mediterranean (median: −2) compared to the Baltic Sea (median: 0). In contrast to the Baltic results on provisioning services (median: 0) and regulating and maintenance services (median: 0), Southern Mediterranean stakeholders considered marine litter as having a stronger negative impact on both service categories (median: −2). Regarding beach wrack (Scenario 2), the results show a similar positive impact trend for both seas (median: +1). Contrary to the Baltic results, Southern Mediterranean stakeholders perceived beach wrack as not having any impact on the provisioning service extraction of minerals (P4), driftwood (P5), and natural ornaments (P6). Additionally, Southern Mediterranean stakeholders perceived beach wrack accumulation as having a lower negative impact (−1) than indicated for the Baltic results (−2). These findings reveal that, overall, Southern Mediterranean stakeholders perceive marine litter to have a stronger negative impact on ESs than perceived by Baltic stakeholders, while beach wrack is perceived as more beneficial by stakeholders from the Southern Mediterranean Sea.

3.7. Mitigation Measures

Participatory ES assessments can raise awareness about, provide a deeper understanding of, and enable a broader view on a problem, but they remain an enabling approach that alone cannot solve a problem. As a consequence, they have to be linked to concrete measures, in this respect, measures that help to manage beach wrack and/or reduce the pollution of beaches with litter. Since freshly accumulated beach wrack along the Southern Mediterranean coast hardly contains any litter, it can be regarded as a resource and potentially enables multiple uses. Only after some time at the beach does it become polluted with litter and turn into waste. Therefore, the problem is the litter pollution at beaches, and measures for reducing litter pollution have the highest priority.

Figure 10 gives an overview of the most relevant measures for reducing litter pollution on beaches and is based on Weischedel [47]. The measures are restricted to those that can be implemented by municipalities or be implemented directly at beaches. The responsibility for the implementation of some measures lies with municipal decision makers and the administration or results from a change in behavior by locals and guests. This compilation serves as a basis for the integration with ES assessments.

4. Discussion

4.1. The ES Approach: Applicability and Transferability

The present study was designed to test the applicability and transferability of the ES assessment approach in data-scarce areas, such as North African countries bordering the Mediterranean Sea, which are hotspot areas of marine litter pollution.

Only recently have a few studies on ES research focused on North African countries using former ES concepts, such as monetary valuation methods based on Costanza et al. [23] and Abdel-Hamid et al. [48], or using the classification of the Millennium Ecosystem Assessment [49] in a literature review by Santoro et al. [50]. This study used the classification system CICES (V.5.1 in Haines-Young and Potschin-Young [44]), which is based on the Millennium Ecosystem Assessment [49] and was further developed in the last decades. Despite that the ES literature is scarce in North African countries [27], it indicates the general applicability of the ES concept, as well as the methods and classifications in the North African study areas. The scenario results, based on stakeholder perceptions, further support the notion that this approach is applicable across various regions, targeting to fill the gap of local interdisciplinary studies.

The use of scenarios for assessing ESs represents a common approach for studying socio-ecological systems. For example, scenario development enables the investigation of alternative future states and the assessment of possible impacts of management measures and decisions on ESs [51]. The simplicity of the scenarios (i.e., few parameters) allowed for the involvement of various stakeholders, supported a fast and easy understandability, and increased the willingness to participate. Scenario visualization and description play a crucial role in the ES assessment, as they enable a common understanding among stakeholders and reduce misunderstandings, thus shaping the robustness and quality of data. This study highlights the importance of stakeholder engagement in scenario assessment, as it ensures the incorporation of diverse perspectives and enhances the relevance and applicability of the scenarios to real-world decision-making processes. Although the study results demonstrate that the developed scenarios are, in general, applicable on a global scale, it can be recommended to co-develop and adapt scenarios according to local knowledge and socio-economic–ecological contexts.

Evaluating the local relevance perceived by stakeholders through the RI allows us to prioritize ESs for decision making and emphasizes the importance of certain services for management. The RI results demonstrate the suitability of the approach for weighing ESs, providing the basis to reduce the number of ESs for simplified use in local beach management. Both the RI results and stakeholder feedback during discussions demonstrated that this approach is suitable for assessing and comparing perceptions and priorities across various regions, even worldwide.

Following a comparative approach, stakeholders assessed the relative change (or impact) and relative importance by a given scoring, which also reduced existing language barriers. By this, the approach was considered to be suitable for fast and easy understanding, acceptable time requirements, and handy applicability of assessment sheets. The assessment sheet and guidelines were distributed in different languages (English and French), which reduced but not entirely prevented language barriers and misunderstandings. This necessitates an introduction and discussion moderation in appropriate languages, which was only partly given within the assessments.

Regarding the transferability of this assessment approach, the case study areas are similar to other coastal areas globally, in terms of increasing marine litter pollution and increasing tourism numbers both putting high pressures on sandy beach ecosystems. However, the socio-economic context (i.e., income level), as well as the environmental conditions (i.e., beach wrack accumulation, erosion rate), vary and demand for case study-specific adaptations, in particular, for the services, their descriptions, and scenario visualizations. For example, the list of ESs selected for assessing sandy beaches in Northern African countries was adapted from the Baltic study by Robbe et al. [43]. For the Mediterranean Sea, the provisioning service wild plants for human nutrition was added (P2) due to its assumed relevance, which was also confirmed by the stakeholder results (median RI: 2). Thus, the ES list was tested and found to be suitable, and all ESs of at least low importance (RI: <1) were assessed by local stakeholders.

4.2. The ES Approach: Benefits and Shortcomings

In regions with limited data availability, ES assessments frequently rely on qualitative approaches such as surveys, participatory methods, and expert and/or stakeholder knowledge [51]. Despite low data availability in North African countries, most ES research applies quantitative approaches, mainly focusing on land use data [48,52]. This study successfully tested a qualitative approach involving local stakeholders and gathering their perceptions and knowledge by applying three different assessment formats (i.e., workshop, interview, teaching).

First, the ES approach can be a suitable base for stakeholder discussions and consensus building, as also shown by other authors [53,54,55]. As also reported by von Thenen et al. [56], a scenario-based comparative ES approach can be a supporting tool for stakeholder involvement and decision-making processes in coastal areas, such as fisheries. The approach of this study was tested to be useful for awareness raising and supporting a better understanding of the relationship between nature (i.e., sandy beach ecosystems) and human activities (i.e., marine litter pollution and beach management). This is supported by other studies that show that the ES approach can be used as a stakeholder engagement tool to increase awareness, for example, by participatory mapping in coastal areas [57] or identifying stakeholder priorities and demands of coastal ESs to be used in policy decisions [58]. The discussion results are restricted by the availability of time, number of participants, and language barriers. It is recommended to include no more than 12 stakeholders per workshop to guarantee a fair speaking time for each person.

Second, this ES approach can be a suitable elicitation tool for stakeholder perception and knowledge. A lesson learned from the interview format was that it can be used for in-depth analysis of the perception and existing knowledge of the stakeholders involved. Additionally, the workshop format can be used for robust data collection, but it is recommended to include only a few stakeholders (up to 10) per workshop.

Third, this ES approach shows potential as a teaching and learning tool. As students and stakeholders pointed out during discussions, there was a learning effect as well as increased interest in the topic while carrying out the assessment, and during discussion, the approach was tested successfully to raise awareness among all participants. Both the approach and the result can be used to clarify misunderstandings and misconceptions among different stakeholder groups (i.e., beach managers, tourists, and locals). In accordance with the present results, previous studies have demonstrated the didactic potential of the ES concept in formal education and ocean literacy [59] and in education for sustainable development and acquiring knowledge and skills (i.e., argumentation capacity) [60]. The stakeholder-based approach serves as a tool for local stakeholders that can be easily adapted and applied to concrete local case studies.

Contrarily, the literature-based approach was tested for the relative importance of services but was considered to be not suitable for the study sites in North Africa. Due to high data scarcity, the results show high discrepancy to the stakeholder-based results and show strong bias because of the scientific relevance of each service (represented by the number of WoS articles found).

The study results indicate the potential of the ES assessment approach for stakeholder engagement, as also shown for the Baltic Sea [43]. However, case studies in Morocco and Tunisia show that stakeholder engagement often depends on the specific project, availability of resources, the political will and institutional capacity, and prioritization by the administration [61]. Nevertheless, Derak et al. [62] showed that there is wide acceptance for restoration measures (here forest) across different population sectors in North Africa and found that barriers to participation (i.e., time, labor, and financial constraints) within stakeholder involvement can be effectively reduced.

The main finding of this study is that there is a high awareness among local stakeholders of the negative consequences of marine litter pollution. The results show that stakeholders perceived an overall negative impact trend, mostly on cultural services (almost 50% of the sum of absolute impact values), in particular recreation and tourism (C1). This is also reflected in Herrera et al. [26], highlighting the high awareness of the public regarding the consequences of marine litter pollution on coastal ESs in Galicia (Spain). Despite that awareness is high, beach pollution is hardly reduced. The main reasons for this can be the lack of financial means for adequate waste management of municipalities [22] and the lack of legal frameworks and political resistance [63]. Additionally, cleaning operations are often carried out at beaches that are of high tourist relevance, where the demand is high and where beach pollution would cause severe income loss. This is supported by field experience in all study countries (Morocco, Tunisia, Egypt), where urban municipal beaches mostly used by locals showed high pollution levels compared to cleaned touristically used hotel beaches. The results emphasize the need for supporting the implementation of policies and mitigation measures against marine litter pollution.

This study was able to demonstrate the lack of awareness among local stakeholders of the ecological value of beach wrack at sandy beaches. The results show that the impact of beach wrack perceived by stakeholders has an overall positive trend on regulating and maintenance services (almost 50% of the sum of absolute impact values) but a negative impact on cultural services, such as recreational and tourism (C1). Similarly, Hofmann et al. [64] point out that in the Baltic Sea Region, beach wrack is rather experienced as a nuisance to the beach experience of most people, but small quantities of beach wrack are tolerated, which also highly differs among countries and amounts of beach wrack. Other authors support these findings, indicating that people commonly view beach wrack accumulation as annoying [16] and even consider the negative effects of the presence of seagrass banquettes [18]. Regarding beach wrack in combination with litter, Sanchez-Vidal et al. [65] even highlight the importance of seagrass accumulation as a novel ES by serving as a trap for marine plastics. Other authors also point out the function of dune plants and beach wrack being important plastic traps and sinks, thus preserving the biodiversity and health of beaches [66,67]. To capture this ecosystem service by the assessment of this study, another ecosystem service could be added in the future, e.g., mediation of wastes by other chemical or physical means (e.g., via filtration, sequestration, storage, or accumulation). It can be recommended to apply ES-based approaches for stakeholder involvement in order to increase awareness.

4.3. Towards a New Approach—Integrating ES Assessments in Litter Management Measures

The combination of participatory ES assessments with litter reduction measures can be regarded as a pathway towards solving the serious beach litter problem in North African countries and beyond. Especially, litter reduction measures that are the responsibility of decision makers on the municipal level could be well addressed with this approach because the number of relevant stakeholders that need to be involved is limited. This allows an ES assessment in the form of an event with subsequent discussions and agreements (Figure 11). The precondition is that a moderator compiles a list of ESs, develops scenarios visualizing the present and the desired state of the beach as the basis for the assessment, organizes the assessment event, moderates the process, and guides the discussion towards a joint agreement as to whether measures should be taken or not. It is important to compile suitable measures/sets of measures that are cost-effective and tailor-made for an implementation by the municipality. In case there is an agreement for improving beach quality, concrete measures are enabled and can be discussed, and pathways towards implementation can be sketched. In principle, this approach can be applied to beach wrack management, as well.

Measures that are the responsibility of locals and/or guests (Figure 10) require improved environmental awareness, acceptance of their own role in the litter pollution problem, and a change in their own littering behavior. To achieve this and possibly an improved acceptance of litter reduction measures by the municipality, a different ES assessment process is required. The challenge is the large number of people that potentially need to be involved. In this case, an internet-based approach might make sense, as sketched in Figure 11.

5. Conclusions

This study underscores the severe impact of marine litter on sandy beaches along the North African Mediterranean coast, particularly in Tunisia, Morocco, and Egypt. The high levels of plastic debris, primarily originating from shoreline activities, tourism, and poor waste management, highlight the urgent need for effective mitigation strategies. For this, a holistic and interdisciplinary approach was applied to assess the ES provided by sandy North African beaches along the Mediterranean coast—perceived by stakeholders. The scenario-based ES approach, incorporating stakeholder engagement through workshops, interviews, and teaching, has proven valuable in regions with limited data availability. Stakeholders consistently reported a negative impact of marine litter on cultural services, which they also perceived as the most important, while recognizing the positive role of beach wrack in regulating and maintenance services. The main added value of the stakeholder-based approach is its function as a tool for consensus building, awareness raising, gathering local knowledge and perceptions, and teaching. The findings of this study complement those of earlier studies in the Baltic Sea Region. The results also show the applicability of the previously developed approach in regions and seas (e.g., tropics), particularly with high data scarcity.

The scenario-based approach proved to be an effective tool for raising awareness, enhancing understanding of the issues, and gathering stakeholder perceptions. However, while essential, these steps alone are insufficient to address the urgent litter problem. Therefore, this method has to be linked to concrete measures and integrated into measure planning and decision-making processes.