# Citizen science reveals litter trends in the UK: Population density effects on coastal and inland regions

Imogen E Napper, Bede F R Davies, Aquila Erskine, Richard C Thompson, Rachel Yates, Heather Koldewey

► To cite this version:

Imogen E Napper, Bede F R Davies, Aquila Erskine, Richard C Thompson, Rachel Yates, et al. Citizen science reveals litter trends in the UK: Population density effects on coastal and inland regions. Marine Pollution Bulletin, 2025, 214, pp.117634. 10.1016/j.marpolbul.2025.117634. hal-05233287

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# Citizen science reveals litter trends in the UK: Population density effects on coastal and inland regions

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Imogen E. Napper<sup>a,b,*</sup>, Bede F.R. Davies<sup>c</sup>, Aquila Erskine<sup>d,e</sup>, Richard C. Thompson<sup>a,b</sup>, Rachel Yates<sup>e</sup>, Heather Koldewey<sup>f,g</sup>

## ARTICLE INFO

### Keywords:

Litter

Pollution

Waste management

Plastic

Citizen science

## ABSTRACT

There is limited understanding of how litter abundance, particularly plastic items, varies between coastal and inland regions with different population densities. The absence of standardised data collection methods further complicates comparisons. Moreover, the lack of data for inland areas hampers efforts to identify potential litter sources, pathways, and interventions. In this study, we address these gaps by quantifying and characterising litter across diverse settings in the United Kingdom (UK), encompassing coastal and inland regions, as well as urban and rural areas. Data were collected in collaboration with a major UK charity specialising in coastal litter removal, with 97 volunteers conducting monthly surveys along 200-m transects using a custom mobile application. Over five months, a total of 27,855 litter items were collected. Fragments (33 %), packaging (33 %), and cigarette-related debris (23 %) were the most prevalent litter types, each displaying varying trends in abundance across different locations. Litter density was higher in coastal areas (0.053 items/m²) compared to inland regions (0.030 items/m²), and urban areas consistently exhibited more litter than rural areas (urban 0.046 items/m² vs. rural 0.038 items/m²). Over time, coastal areas experienced a significantly higher influx of new litter (p < 0.0001) compared to inland regions, where litter levels were stable or decreasing. Notably, while coastal areas showed no significant difference in litter accumulation between urban and rural communities, inland urban areas had significantly more litter than their rural counterparts (p < 0.0001). These findings underscore the importance of considering both geographic region and community type when developing waste management strategies. They also highlight the need for enhanced legislation targeting common litter sources.

## 1. Introduction

Pollution by litter, particularly items made of plastic, is of increasing concern, with profound environmental impacts and socio-economic repercussions (Diggle and Walker, 2022; Kühn et al., 2015). It encompasses a wide range of persistent, manufactured, or processed solid materials that have been discarded, abandoned, or improperly disposed of, with primarily anthropogenic origins (UNEP, 2009). Diverse and pervasive litter now contaminates both aquatic and terrestrial environments on a global scale. It poses a particular challenge to nearby environments, including water bodies, as it can be transported by the wind

or washed into the nearest waterways through surface runoff (Rossi et al., 2023). Consequently, litter pollution has garnered substantial attention from various stakeholders, such as the public, the scientific community, industry and governmental bodies (Stanton et al., 2022).

The term "litter" (also referred to as debris) was chosen in this paper to align with terminology used in other scientific, governmental, and news publications (DEFRA, 2019; Kershaw, 2015; Napper et al., 2021; Stanton et al., 2022; UK Parliament, 2015; Wyles et al., 2017). However, it should be noted that some organisations, such as Surfers Against Sewage, prefer not to use this term, as they believe it oversimplifies the issue by focusing on individual behaviours rather than addressing

<footnote><sup>a</sup> International Marine Litter Research Unit, University of Plymouth, Plymouth, UK</footnote>

<footnote><sup>b</sup> School of Biological and Marine Sciences, University of Plymouth, Plymouth, UK</footnote>

<footnote><sup>c</sup> Nantes Université, Institut des Substances et Organismes de la Mer, ISOMer, UR2160, Nantes F-44000, France</footnote>

<footnote><sup>d</sup> Plymouth Marine Laboratory, Plymouth, UK</footnote>

<footnote><sup>e</sup> Surfers Against Sewage, St Agnes, Cornwall, UK</footnote>

<footnote><sup>f</sup> Centre of Ecology and Conservation, University of Exeter, Penryn Campus, UK</footnote>

<footnote><sup>g</sup> Zoological Society of London, London, UK</footnote>

<footnote>* Corresponding author at: International Marine Litter Research Unit, University of Plymouth, Plymouth, UK.
E-mail address: imogen.napper@plymouth.ac.uk (I.E. Napper).</footnote>
systemic causes.

Numerous studies have examined litter at local and regional levels (Miladinova et al., 2020; Vidyasakar et al., 2020; Wessel et al., 2019). These investigations primarily focus on coastal areas (Serra-Gonçalves et al., 2019), although research along rivers and at river mouths is becoming more prevalent (Battulga et al., 2019; Cordova and Nurhati, 2019; Onink et al., 2019). However, these empirical studies are often restricted to a limited area, and litter data for inland locations remains scarce. Coupled with varying population densities, this introduces uncertainties regarding the fundamental drivers of litter (Schuyler et al., 2021). These uncertainties could include litter quantities, types, accumulation patterns, and the intricate relationships with environmental factors such as climate (Schuyler et al., 2021). Moreover, data scarcity also plays a crucial role in identifying potential sources and understanding the impacts of environmental contamination.

Understanding the characteristics of litter across various environments is essential for developing effective management strategies and proposing locally appropriate solutions (Nelms et al., 2020b); such as informing policies and legal frameworks and developing evidence-based strategies to combat the causes and behaviours associated with littering. For example, Single Use Plastics (SUPs) are a key contributor to litter. SUPs are typically used once, or for a short period of time, before being thrown away but have become a growing issue in waste accumulation due to their very short lifespan (often discarded after only minutes of use) (Nelms et al., 2020b; Stanton et al., 2022; Youngblood et al., 2022), their widespread prevalence (as the most common type of plastics produced) (Chen et al., 2021) and limited recyclability (Chen et al., 2021; Geyer et al., 2017). Consequently, the European Union (EU) identified ten priority plastic items commonly found on its beaches, supporting focused efforts to reduce their use through its SUP Directive (Chatain, 2019). This approach could lead to various solutions, such as deposit-return schemes (Andreasi Bassi et al., 2020; Rubio et al., 2019), Extended Producer Responsibility (EPR) programmes, bans or levies on specific products (Heidbreder et al., 2019; Nielsen et al., 2019; Taylor and Villas-Boas, 2016) and consumer education or information campaigns (Borg et al., 2022; Heidbreder et al., 2019; Wagner, 2017). By 2018, 27 countries had implemented some form of ban on SUPs, including plastic bags, plates, cups, straws or products made from expanded polystyrene (Schnurr et al., 2018), with further bans added.

The recent increase in citizen science-based research, defined as the participation of non-specialist individuals or members of the general public in scientific research alongside professionals (Fraisl et al., 2022; Newman et al., 2012), has revolutionised large-scale environmental science research. Subsequently, this has helped to obtain a more accurate understanding of litter distribution on a wider scale. Emerging methods like smartphone applications (apps) and a variety of other citizen science tools have expanded the accessibility and ease of participation, including platforms such as iNaturalist (https://www.inaturalist.org) for biodiversity reporting and the Marine Debris Tracker (https://debristracker.org) for litter mapping (Ammendolia et al., 2021). These tools simplify the collection of samples and observations, enabling greater volunteer involvement that has been particularly evident in monitoring anthropogenic litter (Ambrose et al., 2019; Gacutan et al., 2022; Merlino et al., 2023; Nelms et al., 2017; Stanton et al., 2022).

The growth of citizen science also responds to several societal needs, including making research more relevant to communities (Cohn, 2008), raising public awareness about environmental issues, and leveraging advancing technologies like low-cost sensor networks and smartphones (Buytaert et al., 2014). Smartphone apps, in particular, are popular for citizen science due to their ability to facilitate quick, easy, and often real-time data submission (Buytaert et al., 2014; Luna et al., 2018). Moreover, these apps improve spatial data accuracy, engage participants in organised activities, and enhance overall levels of involvement (Jambeck and Johnsen, 2015; Luna et al., 2018).

In the past, citizen science initiatives with a focus on coastal debris

have yielded reproducible methods and generated extensive datasets contributed by individuals of all ages. These citizen scientists range from high school students in The Bahamas (Ambrose et al., 2019) and Morrocco (Bouzekry et al., 2022), to snorkelers, freedivers and SCUBA divers along the Mediterranean coast (Turicchia et al., 2021). Citizen science methods have also been applied in an international project across seven countries that trained 15- to 18-year-olds from ten secondary schools ('high schools') to sample and analyse macro-, meso-, and microplastics in beach sediments (Catarino et al., 2023). Such results have showed that citizens can provide data over large geographical regions (Popa et al., 2022).

Citizen science was also utilised for specific purposes, for example, during the COVID-19 pandemic, to collect data investigating the increase in personal protective equipment litter due to COVID-19 measures (Roberts et al., 2021) and tracking the impact on wildlife using digital platforms (Ammendolia et al., 2022). However, voluntary clean-up efforts are seldom consistently repeated in a single area to document changes over time. Building on these citizen science foundations, our research aims to establish a replicable method for monitoring litter accumulation specifically within the United Kingdom (UK) but does not focus on comparing different citizen science methodologies.

To gain a deeper understanding of litter types across the UK, our study had several overarching objectives. First, we examined how the accumulation and types of litter compared between geographical regions (coastal vs. inland). Our second objective was to understand the differences in litter abundance and types across different community settings (urban vs. rural). Building upon the insights gained from these initial objectives, our third objective was to identify the most prevalent litter items. These findings were then considered in relation to existing litter mitigation methods, current policies, and the legal framework in the UK.

## 2. Methodology

In collaboration with a major UK based charity (Surfers Against Sewage), there was a call among their volunteers nationally to participate in a five-month citizen science investigation. Volunteers were asked to participate in a monthly outdoor litter pick near their places of residence, with each litter pick conducted at the same location and covering the same distance over a six-month period.

Volunteers were chosen for an equal spread between different combinations of geographical (coastal vs inland) and community-type (rural vs urban) areas in the UK (Fig. 1); volunteer numbers were highest in inland rural (32 volunteers) and coastal rural (32), followed by inland urban (18) and the lowest coastal urban (15). Community types were defined based on the framework established by Seto et al. (2013): urban areas were characterised as regions with >50 % built land, whereas rural areas typically had <30 % built land. Geographical classification further distinguished coastal areas, those with a direct coastline, from inland areas. Therefore, for both the coastal area types (urban coastal and rural coastal), these may have been completed within or near the beach environment and such data could result in new litter (litter that had accumulated over the course of the sampling month) being washed up with the tide. However, these data sets were included as to be representative of the new litter being found within each area.

Research has shown that citizen science projects produce reliable data when they have straightforward sampling methods, clear ways to record data, and provide additional resources for participants (Bonney et al., 2009; Pandya and Dibner, 2019). This approach was applied to our project to ensure high-quality data collection and volunteer engagement. To ensure the reliability and consistency of data, volunteers used the Marine Debris Tracker app, an open-source citizen science tool designed for mobile phone use to track debris globally which has been used for litter-based studies previously (Youngblood et al., 2022). While there are several other litter-focused apps available, Marine Debris Tracker is notable because of its global scale, ability to host
<figure><img src="image_4.png" /><figcaption>**Fig. 1.** Locations in the UK and Channel Islands where citizen science volunteers collected litter data.</figcaption></figure>

bespoke locally relevant litter lists, and functionality on and offline. In addition, it is hosted by the University of Georgia with a strong academic foundation in litter research and provides free, open access data with clear visualisation tools.

For use within the app, each volunteer was assigned a unique identification (ID) number, and only data from those with a complete data set and a unique ID number were included in the final analysis, resulting in 97 participants. Before sampling began, volunteers joined a video call hosted by Surfers Against Sewage. During this call, project coordinators introduced the research, methodology and demonstrated the data collection process. This session also provided an opportunity for volunteers to ask questions, ensuring they were well-prepared for their tasks, and to define the litter list based on their local knowledge (see section 2.1).

Over a five-month period volunteers conducted monthly litter clean-ups along a designated 200-m transect, approximately two metres wide (an adult's arm span was used an approximate measurement for volunteers to gauge). The transects focused on documenting the type and abundance of litter, prioritising a straightforward and efficient approach for volunteers. Characteristics such as size, weight, and colour were not recorded to simplify the process and minimise potential sources of error, ensuring consistency in the data collected. All recorded litter was then removed from the transect and appropriately disposed of. Volunteers were asked to conduct their monthly clean-ups within the same week each month, although no specific dates were provided. This consistency helped ensure comparable data across different months.

Data collection for the volunteers ran from May to September 2021; the start and end period was the same for all volunteers to control for seasonal variation. However, prior to testing there was an additional month (April 2021) where the same methodology was used to remove all residual litter that had accumulated previously. In order to look at patterns of litter arrival, data from this initial clean were not included in

analysis. Subsequently, each month between May to September 2021 recorded the arrival of 'new litter' into the transect.

## 2.1. Litter categories

The litter list within the Marine Debris Tracker app was developed based on the OSPAR Marine Litter Monitoring Survey Form (OSPAR Commission, 2020), enhanced by inputs and validation from volunteers (Supp. 1) through virtual discussions during the initial training session and email communications after feedback on an initial draft list. A 55-item litter list was created and further classified into nine material categories: "Plastic", "Metal", "Glass", "Rubber", "Cloth", "Paper and Lumber", "Fishing Gear", "Covid Related Litter" and "Other". The "Other" category allowed for volunteers to input into the app the description of litter found.

Categorising litter items beyond the material has successfully informed environmental policy (Stanton et al., 2022), so for analysis each item was then further allocated into seven main litter classifications; 'Fragments' (plastic material only), 'Packaging and Utensils' (known hereinafter as 'Packaging'), 'Marine Related Debris', 'Clothing', 'COVID-19', 'Cigarettes' and 'Other'. As well as the new litter arrival every month for each litter category, the total quantity of litter collected over the five-month period was also reported to identify the most abundant litter categories and then subsequently the top three items within each category.

## 2.2. Statistical analysis

To assess any differences in litter recorded over time and location, Generalised Linear Mixed Effects Models were used. Models were fitted using the R packages 'lme4' and 'glmmTMB' (Brooks et al., 2022; Douglas et al., 2022). Response metrics were assessed as a function of Month (continuous: 4:9), geographical location (categorical: coastal and inland) and community-type (categorical: rural and urban), with volunteer as a random factor. The response variables tested were the quantity of litter per 200 m transect of: Total Litter, and then the three most abundant litter types based on the total quantity of individual items collected across the five months (Table 1). A Poisson distribution was used for all response variables as they are count variables, with a zero-inflated component modelled on month for all response variables apart from Total Litter. Sample vs fitted residuals, quantile-quantile and autocorrelation of temporally sequential samples were assessed visually, to fit assumptions of the models used.

# 3. Results

In total 27,855 pieces of litter were collected over the five-month survey period by 97 volunteers, across 45 counties of the UK and Channel Islands (Fig. 1). Counties within the UK were not compared as new litter arrival quantities were likely to be skewed by volunteer numbers; for example, the highest volunteer count in a county was Cornwall (15 volunteers), whereas all other areas had ≤5 volunteers.

## 3.1. *Variations in litter abundance between geographical contexts - coastal and inland*

Our first objective was to gain understanding of variations in litter abundance within different geographical contexts ('coastal vs. inland'). Regardless of community type, coastal (0.053 ± 0.004 items/m²) areas had nearly double the amount of litter when compared to inland areas (0.030 ± 0.002 items/m²). Arrival of new litter in these coastal areas increased over time, while inland areas were significantly lower and stayed consistent or decreased over time (Fig. 2, Supp Mat 2 Table 1: *p* < 0.0001).
<caption>**Table 1**</caption>

Total amount of litter items removed over the five-month period. Including, mean count per metre (m⁻²) ± standard error and top three litter items by Litter Category Type. Values are the quantity collected across the five-months.

<table><thead><tr><th>Litter Category</th><th>Total Quantity Recorded</th><th>Mean item count (m²)</th><th>Standard Error</th><th>Top Three Items within Litter Category</th></tr></thead><tbody><tr><td>Fragments</td><td>9222</td><td>0.095</td><td>0.011</td><td>Hard Plastic Fragments (49.2 %)</td></tr><tr><td>Packaging and Utensils</td><td>9148</td><td>0.094</td><td>0.008</td><td>Film Fragments (22.9 %)<br>Foam Fragments (12.3 %)</td></tr><tr><td>Cigarettes Related Debris</td><td>6327</td><td>0.065</td><td>0.009</td><td>Food Wrappers (29.2 %)<br>Bottle or Container Caps (11.6 %)<br>Paper and cardboard (11.1 %)</td></tr><tr><td>Maritime Related Debris</td><td>1744</td><td>0.018</td><td>0.005</td><td>Cigarette (89.0 %)<br>Cigar Tips (10.1 %)<br>Disposable cigarette lighters (0.90 %)<br>Plastic Rope/Small Net Pieces (58.3 %)<br>Fishing Lures and Lines (26.7 %)<br>Rope or Net Pieces (non-nylon) (14.3 %)</td></tr><tr><td>Other</td><td>815</td><td>0.008</td><td>0.001</td><td>Other (30.1 %)<br>Dog Poo bag (17.7 %)<br>Tape (14.5 %)</td></tr><tr><td>Textile Related Debris</td><td>396</td><td>0.004</td><td>0.001</td><td>Fabric Pieces (60.1 %)<br>Clothing and Shoes (19.4 %)<br>Towels or rags (15.9 %)</td></tr><tr><td>COVID-19 Related Debris</td><td>203</td><td>0.002</td><td>0.001</td><td>Single-Use Facemask (53.2 %)<br>Fabric Facemask (22.7 %)<br>Other (COVID) (12.8 %)</td></tr></tbody></table>

## 3.2. Influence of community types on litter accumulation - urban and rural

Our second objective focused on different community types ('urban vs. rural') to understand if population density played a significant role in litter accumulation. Generally, our findings showed a similar amount of litter in both urban (0.046 ± 0.004 items/m²) and rural (0.038 ± 0.002 items/m²) areas summarised across all months.

## 3.3. Influence of combined geographical context and community type on litter accumulation

When assessing location and community types together, there were different temporal trends. Over the five-months, inland areas had significantly greater new litter quantities in inland urban (0.035 ± 0.004 m²) areas compared to inland rural (0.027 ± 0.003 m²) (Fig. 2, Supp Mat 2: p < 0.0001). However, there was no significant difference for new litter accumulation in coastal areas; coastal urban (0.060 ± 0.009 m²) and coastal rural (0.050 ± 0.005 m²) areas. Additionally, the arrival of new litter within coastal urban and coastal rural areas exhibited significantly higher accumulation compared to their inland counterparts (Fig. 2, Supp Mat 2: p < 0.0001). It is important to note that

coastal urban areas consistently maintained the highest mean litter quantity per square metre (m²). However, when examining the total litter quantity across all locations, regardless of the number of transects conducted, coastal rural areas exhibited a higher overall total (Fig. 3).

## 3.4. Examining the top three most prevalent litter items

Fragments, Packaging, and Cigarettes emerged as the three most common litter items (total quantity of individual items collected: Table 1). Within the individual litter categories, each classification was predominantly composed of a single common item which had more than double the amount of the next most common item, such as the prevalence of single-use facemasks in COVID-19 related debris (Table 1). Despite these variations, the relative proportions of the different litter classifications remained relatively stable over the five-month period, with debris related to Fragments comprising 33.15 %, Packaging at 32.80 %, Cigarettes at 22.71 %, Maritime-related at 6.26 %, Clothing at 1.42 %, COVID-19 at 0.73 %, and Other related litter at 2.93 % (Fig. 3).

Examining various community population densities within both coastal and inland locations revealed patterns in the influx of different types of litter over time. In urban settings, there was a significant and progressive increase in the quantity of new Fragments and Packaging items (Fig. 3, Supp Mat Table 1 p < 0.0001 & p = 0.048). This trend was also observed in rural settings for Packaging items (Fig. 3, Supp Mat Table 1: p = 0.048). However, when focusing specifically on Fragments, rural communities exhibited differences between locations. A significant increase in new fragments was observed only in rural coastal areas (Fig. 3, Supp Mat Table 1: p < 0.0001), while a consistent quantity of Fragments arrived in rural inland areas. In the case of Cigarette litter, a comparable consistent monthly accumulation was observed in coastal urban and coastal rural communities. However, for Cigarette litter in inland rural communities, there was a significant increase, contrasting with a decreasing trend in inland urban areas (Fig. 3, Supp Mat Table 1: p < 0.0001).

# 4. Discussion

## 4.1. Litter trends by location

This study investigated litter trends throughout the UK with 97 volunteer citizen scientists for five months. With each volunteer doing the same monthly transect, we were able to identify the quantity and proportions of litter types within different geographical areas and community-types. Our data suggest that litter is influenced by geographic location (coastal or inland) and community-type (urban or rural) across the UK. To the best of the authors' knowledge, this is the first UK-based peer-reviewed research that investigates litter based on population density. Specifically, litter quantities in coastal (0.053 items/m²) areas exhibited a significantly higher amount of new litter over time compared to those in inland (0.030 items/m²) regions (p < 0.0001). Although pinpointing the exact origins of this litter is challenging, the higher quantities of litter in coastal regions may stem from additional sources and transport mechanisms such as marine debris (e.g., fishing gear) (Richardson et al., 2019; Wright et al., 2021), riverine litter (Lebreton et al., 2017; Nelms et al., 2020a; Onink et al., 2019; Schmidt et al., 2017; Seo and Park, 2020), storm overflow events (Gill et al., 2021; Liu et al., 2019; Werbowski et al., 2021), increased tourism (Jiale and Quoquab, 2023) and transboundary transport (Macias et al., 2022; Napper et al., 2021a, 2021b).

Additionally, the data were collected over a five-month period (May to September), which coincides with the UK's school summer holidays. During this time, there is typically a higher number of people visiting the coast, leading to an increased likelihood of litter being left behind. As a result, the abundance of litter observed in the data could be influenced by the seasonal rise in coastal visitors during the summer months. Understanding such nuances around litter distribution is crucial for
<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Temporal change in litter quantity recorded each month (Total Litter, Fragments, Packaging and Cigarettes) per 200 m transect from urban and rural locations in coastal and inland areas. Lines show model estimates with shading showing standard error. Specific interactions highlighted in Supp. Table 2.</figcaption></figure>

designing effective waste management strategies that address the specific circumstances of each environment. Such research can help us understand how litter on land, at the coast and in the ocean are connected, leading to better strategies to reduce litter in all environments.

However, our understanding of litter proportions within inland settings tends to be more limited than within the marine and coastal environment (Chen et al., 2020; Chen, 2021; Nelms et al., 2017). For example, Hartley et al. (2018) analysed public perceptions of marine litter and contributing factors using data from 1133 respondents across 16 European countries. The participants within their study reported high levels of concern about marine litter, and the vast majority (95 %) reported seeing litter when visiting the coast. However, participants also thought most litter reached the marine environment via direct releases at sea, which contradicts research stating that the majority of marine litter originates from human activities on land (Jambeck et al., 2015). As a small proportion of the UK population live by the coast (e.g. approximately 28 % of the UKs population live within 10 km of the coast (Barton et al., 2022), improving public awareness and targeting litter within inland areas will have a greater impact for litter reduction overall and may influence coastal litter patterns (Jambeck et al., 2015).

## 4.2. Community type and litter accumulation

Focussing on community-type (rural vs urban) areas, there is an expectation that high-population density regions might naturally accumulate more litter due to increased human activity or the generation of

more waste (Borrelle et al., 2020), which this research found to be statistically relevant for inland areas (inland urban vs inland rural). The majority of the UK population resides in urban areas (82 %) due to factors like employment opportunities and infrastructure (DEFRA, 2021). Despite urban areas covering only 8 % of land in the UK, rapid urban population growth challenges waste management and can result in litter issues (Environment Agency, 2021; Office for National Statistics, 2015). Litter accumulation in these areas may occur through direct littering, overflowing waste bins and infrequent waste collection.

Additionally, in Europe (the Netherlands), research conducted by Ballatore et al. (2022) analysed crowdsourced data (digitally mediated collaborative work that empowers citizens to collect and share geographic knowledge for a variety of purposes (Quattrone et al., 2014)) on urban litter to understand its characteristics and potential biases. This study combined methods from industrial ecology and geographic data science to examine data biases at the province and municipality levels. With this method they investigated a local case study in Purmerend, the Netherlands, and their research found that most hotspots for litter occurred in agglomerates of urban points of interest within the city (such as the train stations and shopping malls) suggesting a strong relationship between urban flows and litter (Ballatore et al., 2022).

However, coastal areas showed no statistical difference in the rate of new litter arrivals between urban and rural communities (coastal urban vs coastal rural). On a per capita basis, rural areas also face distinct challenges. With smaller populations spread over larger areas, waste and litter distribution becomes more dispersed, leading to logistical
<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Spatial, temporal and community type patterns in percentage of new litter items arriving monthly per 200 m transect from community-type (urban and rural) and geographical (inland and coastal) areas over a five-month study. The total quantity for litter type is stated at the top of each bar.</figcaption></figure>

complexities. Typically, rural regions often have less frequent waste collection and less developed waste management recycling infrastructure than urban centres (Vinti and Vaccari, 2022). For example, research conducted by Youngblood et al. (2022) demonstrated that rural areas adjacent to the Ganges River in Bangladesh and India had higher levels of litter. They report that sites with higher populations (>10,000 people) had a lower average per capita litter density (0.19 items/m² per 1000 people) when compared with lower populated areas (<2000 people; 6.43 items/m² per 1000 people). These disparities are attributed to the scarcity of waste management infrastructure in rural regions, highlighting the advantages of urban centres with more robust waste management systems.

However, other studies have stated that that mismanaged waste may be influenced by other factors additional to population density (Borrelle et al., 2020; Lau et al., 2020). Research by Schuyler et al. (2021) assessed

plastic leakage into the environment using empirical data collected in seven different countries/territories (China, Kenya, South Africa, South Korea, Sri Lanka, Taiwan and Vietnam) and found that those factors such as land use, infrastructure, socio-economics, as well as local site-level variables (e.g. vegetation height and site type) were more strongly correlated with plastic in the environment than population density (Schuyler et al., 2021).

### 4.3. Waste management policies, enforcement, and mitigation strategies

Littering is legally an offence, backed by regulations designed to deter such behaviour, leading to potential prosecution in magistrates' courts and fines of up to £2500 (DEFRA, 2022a). However, the effectiveness of these laws can vary based on regional specifics and enforcement practices at the local level. Diverse waste policies operate
across the four nations of the UK (England, Northern Ireland, Scotland, and Wales) with varying implementation timeframes and specifics. Local councils bear the primary responsibility for litter removal, with substantial variations in the implementation and efficiency of litter collection processes across different localities. The involvement of various organisations in litter collection, often integrated into broader activities like street cleaning, complicates the precise determination of costs. Nonetheless, councils across the UK collectively spend around £1 billion per year dealing with littering and fly-tipping (Local Government Association, 2016).

At the national and local level, our research suggests that there needs to be more focused geographic-specific litter mitigation strategies alongside different community types. This should take into account the multifaceted aspects influencing litter dynamics; such as waste collection routines, industrial environmental incentives, and public education campaigns targeting litter prevention and proper disposal habits. Furthermore, while this study collected data and removed litter within a limited timeframe, it is evident that the process of waste cleaning, collection, and management alone falls short in fully addressing the litter problem, especially as growing population densities place strain on waste management efforts (Hartley et al., 2018); emphasising the importance of proactive interventions over in-situ clean-up. This is particularly important as the production of waste becomes more abundant, due to the demand for consumer goods such as packaging and disposable items, which is a key driver of litter accumulation across diverse environments. Based on this rise of consumer goods (especially plastic), it is estimated that the annual rate of macro-and microplastic entering aquatic systems from land will increase by 2.6 times by 2040. However, it has also been stated that 78 % of plastic pollution could be solved by then using current knowledge and technologies (Lau et al., 2020).

Prior research has highlighted that human behaviour can play an important role in the quantity of plastic and litter in the immediate environment (Axelsson and van Sebille, 2017). Modifying certain aspects of an environment can impact pro-environmental behaviours by increasing convenience; for example, research by Robinson (2023) altered the availability and location of rubbish bins along multiple beach sites in Orange Beach, Alabama (USA). Litter and bin waste weight were recorded everyday over 21 days, and significantly more bin waste was collected when ten trash cans (rubbish bins) were positioned in the middle compared to back of beaches.

Additionally, the necessity of specialised measures and initiatives that target specific products are required (Xiong et al., 2022). The UK has taken recent legislative actions targeting specific products as an example. The introduction of a charge for plastic carrier bags, previously free, in England in 2015 at a rate of £0.05 per bag (increased to £0.10 in 2021) discouraged the use of plastic bags across the UK. The result is a considerable reduction in the average person's use of single-use carrier bags, dropping from approximately 140 in 2014 to around three per person annually (DEFRA, 2022b). This legislation has also been associated with a decline in bags found in some environments, such as a decrease in seafloor litter in the coastal seas of Northwest Europe over twenty-five years (Maes et al., 2018).

The UK is now set to implement further legislation with the potential to reduce the amount of anthropogenic litter in the environment and overall waste. For example, the Scottish Government has enforced a ban from 1 June 2022 on the following single-use items: plastic cutlery (forks, knives, spoons, chopsticks), plates, straws, beverage stirrers and balloon sticks; food containers made of expanded polystyrene; and cups and other beverage containers made of expanded polystyrene, including their covers and lids (Scottish Government, 2022). Additionally, England and Wales introduced an almost identical ban in October 2023 (DEFRA, 2023; Welsh Government, 2023). Further, by 2026 the Welsh Government has stated Wales will ban plastic single-use carrier bags and oxo-degradable plastic products (Welsh Assembly Government, 2010; Welsh Government, 2023). Northern Ireland has modelled different

policies based on SUP beverage cups and food containers: these include a ban on their use; a levy of 25p on each cup and 50p on each food container; and a voluntary scheme or schemes implemented by businesses that make use of SUP cups or food containers, which may comprise a range of charges, discounts and communication efforts (Northern Ireland Executive, 2021).

Such bans aim to reduce the amount of plastic waste generated by these products and encourage the use of more sustainable alternatives. Due to the starting date of this research, it cannot assess the effectiveness of these legislative measures as it lacks data from before their implementation. However, it underscores that current and future regulations do not specifically address the most prevalent types of litter found throughout the UK. For example, Packaging and Utensils debris (specifically including food wrappers) and Cigarette-related debris remains a substantial concern. A study by Stanton et al. (2022) also used citizen science to survey anthropogenic litter across environments in the UK and similarly reported that the majority of anthropogenic litter was beverage containers and non-beverage packaging. Therefore, the methods within this research could provide useful tools for monitoring the impacts of such bans by local government, Non-Governmental Organisations (NGOs) or interested citizen groups.

### 4.4. Future directions for litter reduction

Focussing on key litter types in different areas can help identify trends and different mitigation strategies; for example, within this study there was a significantly higher occurrence of Packaging in rural coastal areas compared to rural inland areas. This finding emphasises the importance of tailoring strategies and interventions to address packaging-related litter, particularly in coastal regions where it appears to be more prominent. Additionally, although some measures already target specific items (such as Packaging which was found to be 33 % of total litter in this study), it is important to recognise other prominent litter items. Our study also highlights cigarette-related debris (23 %). Despite various campaigns, such as government taxes and revised labelling designed to reduce cigarette use, the primary focus remains on health concerns rather than environmental impact. Over the past two decades, the prevalence of tobacco smoking among people aged 15 and over has steadily declined worldwide owing to growing awareness of the many health risks. Now nations worldwide are aiming to introduce some of the tightest restrictions ever on smoking and vaping, especially among young people (Wong, 2024). However, we now need similar ambitious restrictions and awareness for common litter items.

The effectiveness of legislation on specific items and its actual implementation in curtailing litter issues involves examining factors such as enforcement, public awareness, and the resources allocated to litter prevention and clean-up. Furthermore, community members also play a crucial role in driving initiatives aimed at reducing or eliminating specific items/products within their local area. Therefore, it is important to actively involve citizens and businesses, especially in co-designing interventions, to ensure that solutions are targeted and evidence-based, thereby leading to impactful results (Winton et al., 2023). For example, 'Plastic Free Communities', a programme managed by Surfers Against Sewage (the charity collaborator in this research), empowers communities to achieve the 'Plastic Free Communities Award' by meeting specific criteria. These include collaborating with local councils and forming steering groups to spearhead local change initiatives (Surfers Against Sewage, 2023).

It should be noted that due to the length of the study (five months; May to September 2021), there could be further differences for litter accumulation and type due to seasonal variation across a whole year. For example, a study by Orthodoxou et al. (2022) investigated anthropogenic litter along the coastline of Cyprus. Their research found higher average marine litter densities at tourist sites compared to non-tourist sites. They suggest that increased clean-up efforts are necessary in the more popular tourist locations, especially during the peak tourism
season, to minimise littering and more effectively clean the coast. Therefore, as our research was conducted in peak tourism season, our results may reflect higher litter quantities than other periods in the year. Additionally, research by Garces-Ordóñez et al. (2023) investigated plastic litter during high and low rainfall seasons in mangrove waters and sediments of the Saija and Timbiqui river estuaries in the Colombian Pacific. They found that plastic littering follows a rainfall-driven seasonal pattern with the total abundance of plastics increasing during the high rainfall season. Therefore, to further identify seasonal trends, additional research should investigate litter within different geographic regions and community types over a whole year.

Efforts to tackle plastic pollution often centre on improving waste management and encouraging behavioural change. While these actions are valuable, they overlook the root cause: the continued production of plastic (MacLeod et al., 2021). Unless industries take responsibility by cutting plastic output and rethinking product design, the strain on our environment will persist. Interestingly, consumer expectations reveal a disconnect. For example, recent research by Nuojua et al. (2024) examined consumer perceptions around plastic alternatives and substitutes of packaging by employing a life cycle approach. They report that consumers tend to value recyclability or composability as the most desirable end-of-life attributes for packaging, and they overwhelmingly reject the idea of plastic packaging being released into the natural environment. However, concerningly, this preference does not extend to biodegradable plastics or glass, where consumer assumptions about their environmental benefits may inadvertently lead to increased mismanagement of waste. Addressing this gap demands collaboration across the entire system, from producers to policymakers to consumers.

## 5. Conclusion

In conclusion, our data reports that there is variability in litter accumulation and type across different geographic regions and communities. Overall, across all months, this research revealed a comparable prevalence of litter in both urban (0.046 ± 0.004 items/m²) and rural (0.038 ± 0.002 items/m²) communities. However, differences were observed when looking at community type within geographical areas, so both need to be considered when designing appropriate waste management strategies. This study also emphasises the challenges posed by increasing urbanisation and the limitations of waste management in effectively addressing the litter problem. As urbanisation continues, it is crucial to address this issue not only along the coasts but also in inland areas. A holistic approach involving comprehensive legislation targeting common litter sources within specific areas, combined with robust community engagement and educational initiatives, is required to shape local and national policies, and effectively address this multifaceted issue. The effectiveness of measures on specific items like the plastic bag charge and single-use item bans emphasises their potential role in reducing litter abundance. Notably, it underscores the importance of proactive interventions (especially within inland areas) over in-situ clean-up. Without a reduction in plastic output and a rethink of product design, environmental strain from pollution will persist. Additionally, this research highlights the valuable contribution of citizen science in collecting large datasets to identify national trends.

Supplementary data to this article can be found online at https://doi.org/10.1016/j.marpolbul.2025.117634.

### CRediT authorship contribution statement

**Imogen E. Napper:** Writing – review & editing, Writing – original draft, Visualization, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.
**Bede F.R. Davies:** Visualization, Validation, Methodology, Formal analysis.
**Aquila Erskine:** Writing – review & editing, Writing – original draft, Methodology.
**Richard C. Thompson:** Writing – review & editing, Writing – original draft, Supervision.
**Rachel Yates:** Writing – review &

editing, Writing – original draft, Project administration, Investigation.
**Heather Koldewey:** Writing – review & editing, Writing – original draft, Supervision, Project administration, Methodology, Investigation, Funding acquisition, Formal analysis, Data curation, Conceptualization.

### Declaration of competing interest

The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Imogen Napper reports financial support was provided by National Geographic Society. Two co-authors work for a marine conservation charity (Surfers Against Sewage). This had no influence on results of the paper. All research and final edits were approved by lead author Imogen Napper. The other authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

### Acknowledgements

Thank you to all the volunteers who participated in this research. It could not have been completed without your dedication, passion and curiosity. This work was funded by the National Geographic Society (NGS-83447R-20). H.K. is funded by the Bertarelli Foundation.

### Data availability

Data will be made available on request.

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