Plastic pollution: archaeological perspective on an Anthropocene climate emergency

ABSTRACT

Plastic pollution is a global phenomenon offering a vivid illustration of the scale of anthropic impacts on the environment, a key characteristic in defining the Anthropocene. Plastic pollution not only contributes to the current climate crisis but is also accentuated by extreme events caused by climate change. The scale and omnipresence of the issue of plastic pollution makes it a relevant object of study for archaeologists, as well as an object of concern for heritage and archaeological sites marked by plastic pollution. In this paper, I advocate for an archaeological consideration of plastic pollution, by exploring plastics as artefacts (through visual analysis and archaeological science), as chronological markers in the stratigraphy and eventually as components of waste landscapes. While the issue of plastic pollution can be studied archaeologically, I argue that it must be considered by archaeologists, especially as natural and cultural heritage sites are threatened by the presence of plastic pollution.

KEYWORDS:

• Anthropocene
• plastic pollution
• archaeology of plastic
• plastic
• climate change

Introduction

Despite having traditionally focused on the past, archaeology is also now anchored in problems of the present and future, notably the climate crisis. The discipline is facing the consequences of climate change (e.g. Hollesen 2022). The climate crisis affects archaeological sites and contexts through erosion (e.g. Reimann et al. 2018), change in groundwater levels (e.g. Woodward and Cooke 2022, 75 for the case study of Chan Chan, Peru), floods (Daly et al. 2022 for the case study in Ayutthaya, Thailand), increased temperatures (Matthiesen et al. 2022 for potential impacts on wetland archaeology), ocean acidification (notably for underwater heritage see Gregory et al. 2022), and an increase in extreme weather events (Rivera-Collazo 2020). While archaeological contexts are increasingly exposed to climate events, archaeology can also act as a window into societies’ resilience, by studying how past civilizations have coped with climate crises (e.g. Sandweiss and Maasch 2022). But the current climate crisis is different: it is driven by human actions that have been prevalent since the Industrial Revolution. And what is more anthropic than synthetic objects? Developed in the twentieth century, synthetic plastics illustrate an increasing interest in human experimentation with flexible and moldable materials. New habits of post-war societies rushing into consumerism stimulated plastic mass manufacturing since the 1950s (Strasser 2000) turning it into an indispensable material for most households and overwhelming material spreading across natural environments.

While plastics are praised because they are clean, cheap, available, and disposable, they actively contribute to climate change (Ford et al. 2022). Their production, mostly from fossil fuels (around 90% as of 2021, Plastics Europe 2022), and (mis)management as waste contribute to the climate crisis by releasing Greenhouse Gases (GHG) (Ford et al. 2022; Lavers, Bond, and Rolsky 2022). The scale and omnipresence of plastic waste resulted in a global issue affecting most if not all, environments: plastic pollution. Despite those evident impacts, plastic (pollution) is not often considered as an aspect of climate emergency in discussions about heritage and climate change (except e.g. Pétursdóttir 2017). This paper approaches plastic pollution as a global issue of the Anthropocene and then describes how plastic pollution represents both an object of study for archaeologists and a threat to heritage sites. While this paper addresses the global scale of the issue and plastic’s degradation, the main focus is on macroplastics (more than 1 cm, after Hartmann et al. 2019) that represent a visible and tangible aspect, both contributor and consequence, of the current climate crisis. I recognise the limitations of focusing on macroplastics only, as meso-, micro-, and nano-plastics enter the archaeological record and would benefit from more archaeological studies. Due to the scope of this paper and the scarce quantity of archaeological studies of microplastic pollution (except e.g. Rotchell et al. 2024), this paper will determine how plastic pollution can be studied archaeologically, focusing on evidence from macroplastic artefacts.

Plastic pollution: a global issue of the Anthropocene

Plastic pollution is a global and visible challenge of the Anthropocene with severe impacts on the environment. Impacts encompass threats posed by the materiality of plastics, such as ingestion and entanglement (e.g. Gall and Thompson 2015), and others created by their chemical properties (Takada and Karapanagioti 2018), such as biological tissues absorbing chemicals from ingested plastics (Takada et al. 2021). The marine environment can be severely affected by plastic pollution, as plastics can be vectors for biotic colonisation (Carlton et al. 2017), transport non-native species (Rech, Borrell, and García-Vazquez 2016), and modify natural environments such as coral reefs (Lamb et al. 2018). Additionally to ecological impacts (Rochman et al. 2016) and the risk for human health and wellbeing (Beaumont et al. 2019), marine plastic pollution can have socioeconomic impacts, notably on tourism (Krelling, Williams, and Turra 2017). In addition to marine environments, agricultural areas are also exposed to microplastics (Nizzetto, Futter, and Langaas 2016) permeating through fertiliser, plastic films, atmospheric deposition, and wastewater irrigation (Zhu et al. 2019). While plastic’s potential impacts on soil are documented in rural areas (Steinmetz et al. 2016), urban plastic pollution also constitutes an environmental and socio-economical issue, from tap water containing microplastics (Pratesi et al. 2021) to plastic litter polluting cities (Seco Pon and Becherucci 2012). When plastics eventually break down, they start permeating our homes (Jenner et al. 2022) and eventually our bodies (Leslie et al. 2022).

The scale and consequences of anthropic impacts on the environment (of which plastic pollution is representative) led Crutzen and Stoermer (2000) to propose the term Anthropocene to differentiate this epoch from the Holocene (the last 11,000 years). At the time of writing, the Anthropocene has still not been accepted as an official geological epoch by the International Union of Geological Sciences (IUGS) despite the repeated events and discussions of the Anthropocene Working Group (AWG) exploring how the term could overcome the nature-culture divide shaping society (Rosol et al. 2023). To recognise the Anthropocene as an epoch, the geological signal needs to be evident and present in most parts of the world. In 2023, researchers proposed several potential sites presenting sections that could illustrate the presence of the Anthropocene chrono-stratigraphically (see the Special issue on Global boundary Stratotype Section and Point – GSSP- for the Anthropocene series edited by Waters et al. 2023). Far from being only a geological question, the concept caught the attention of archaeologists who debated the discipline’s role in defining and studying the Anthropocene (see The forum Archaeology of the Anthropocene in 2014). The relevance of the concept for archaeology was defended on the basis that geologists use the archaeological record through stratigraphy to define this new period (Edgeworth 2014). The role of archaeology is also evident in the proposal of the anthropogenic urban sediments of Karlsplatz, Vienna, as a reference section for the Anthropocene (Wagreich et al. 2023). While archaeology plays a key role in defining and illustrating the Anthropocene, the term, and its consideration as an epoch, also has limitations.

While some consider archaeological and geological strata as complementary systems characterising the Anthropocene (Harris 2014), others see the problem the term poses both as a period only relevant for the western world and as an over-simplistic category erasing local differences (Graves-Brown 2014). I here consider the Anthropocene as a political term that considers the impacts humans are having on their environment evident in the scale of the climate crisis. While the term has been considered too deterministic (Clarke 2014), I advocate that the Anthropocene serves as a platform for all disciplines to emphasise the severity of climate change, facilitated by extractivism and mass production, while stressing the urgent changes needed. I also recognize that the term is western-centred but globalisation has led to an ultra-connected world where this speed and scale of production have consequences, although unequal, on all humans. While the term ‘human’ takes away responsibility from the white western male at the core of the destruction (González-Ruibal 2018) characterising the ongoing climate crisis, the contribution of patriarchy, along with capitalism, was not fully recognised in debates on the Anthropocene. My use of ‘Anthropocene’ here draws inspiration from eco-feminist scholars (e.g. d’Eaubonne 1974; Mies and Shiva 2014) to consider the submission mechanisms at the core of nature’s destruction and women’s oppression (see Burgart Goutal 2020).

The consideration of plastic production, use, and pollution through a gender lens (see for a review see Lynn, Rech, and Samwel-Mantingh 2017) offers insights into how this material has shaped new dynamics (Hawkins, Potter, and Race 2015). While the invention of disposable alternatives (e.g. diapers, plastic bags) facilitated the domestic lives of western women from the mid-twentieth century and liberated time for them to focus on other things, it contributed to the unprecedented production of plastic waste representing a threat to human and environmental health. Women of the Global South are particularly exposed to the consequences of its presence and (mis)management as waste. Yet, they sometimes rely on their reuse for their economies, particularly for waste pickers (Wittmer 2021). This contributes to the reality of plastic waste reproducing colonial dynamics, particularly affecting marginalized groups, through waste export practices (Barnes 2019). From that perspective, an archaeological lens can prove useful by highlighting patterns of use of plastic artefacts and distribution of plastics in the landscape, and how these can be considered through a gender and intersectional lens. Gender dynamics influence plastic use and exposure to its impacts but also act as a determining factor linked to environmental responsibility (e.g. Hanson 2017) and higher levels of pro-environmental behaviours adopted by women consumers (e.g. Muralidharan and Sheehan 2018). Gender archaeology as a discipline (see Conkey and Spector 1984; Sørensen 2000) can therefore contribute to the study of plastics as modern and contemporary material culture and reveal the gender dynamics they were entangled in, for example during their use.

Plastics are central in the argument that human impacts on the environment are leaving long-lasting and undesirable traces representing a different epoch, one shaped by the climate crisis as a result of anthropic activities. They illustrate how synthetic materials became entangled with the natural environment in the shape of plastiglomerates (a multi-composite material made of plastic and rock first identified by Corcoran, Moore, and Jazvac 2013) and plasticrusts (plastic waste entangled in the geology of intertidal shores, see Haram et al. 2020). In addition to their presence in geology and archaeology, plastics’ ubiquity (Barthes 1957) theorised by Davis (2022, 5) under the concept of globalised unlocality (separation from a specific location) has contributed to their emblematic nature. Plastics as artefacts created in the West for the West rapidly reached all corners of the world. The disposable nature of this material culture facilitated western post-war domestic life but has far-reaching and long-lasting impacts on the environment once plastic waste enters global networks and dissociates from the local scale of its production and use. Plastic pollution is then a global issue, facilitated by the spread of plastic mismanaged waste, notably from rivers to the marine environment (Lebreton et al. 2017; Meijer et al. 2021). Plastic abundance and specific flexibility were used to define the Plastic Age (Thompson et al. 2009) or Plasticene (see Haram et al. 2020 for the development of the term) referring to a period starting in the 1950s and centered around plastics as material culture. This period is parallel to the Anthropocene as an epoch marked by a series of anthropic impacts and signals, including plastics, on the chrono-stratigraphic record. In that perspective, plastic makes both an artefact indicative of the Anthropocene (Davis 2022) and a techno-fossil representative of the Plastic Age due to the extractivist strategies at the core of their deadly production from trapped organic matter (de Araújo 2019), their impact on the environment (Gall and Thompson 2015), and the western lifestyles associated with their disposability (Strasser 2000).

Archaeology of plastic pollution

Current understanding of plastic pollution benefits from contributions from several disciplines including (but not limited to) marine biology, oceanography, chemistry, and environmental psychology. Plastics are already shaping an archaeologist’s work, for example through the use of hi-vis and Wellington boots to excavate during rainy days to plastic bags used for soil samples and storing artefacts. Plastic tarpaulin was also used to delimit areas already excavated when filling up excavation pits and trenches. Those uses of plastics in archaeological practices are also shaping the future of the discipline and the archaeological record, from the bags containing samples for decades to the degradation of tarpaulin if contexts are re-opened and excavated. Despite plastic permeating the living and working environment of archaeologists, the discipline has been slow in considering plastic pollution an object of study. In this paper, I advocate for the use of archaeology to study plastic pollution, from individual artefacts to components of stratigraphic layers and emblems of wider waste landscapes.

Plastics as artefacts

Despite archaeology’s interest in human experimentation at the core of artefact design (e.g. Ingold 2000), archaeology has been relatively slow to consider plastics of interest for the discipline. Since the focus on contemporary waste including plastics during the Garbage Project in the 1970s (Rathje and Murphy 2001), only a handful of studies (e.g. Mytum and Meek 2020; Schofield et al. 2021) and projects (e.g. the Plastic Archaeology project developed by A. Agbe-Davies, E. Deetz, and R. Frohardt) are considering plastics as archaeological artefacts potentially yielding relevant information for contemporary societies. If the global presence of plastic is insufficient to prove the existence of an anthropocenic strata, plastics serve as artefacts informing a site’s occupation. Plastics are mostly fossil fuel based materials (i.e. ‘matter considered in respect of its occurrence in processes of flow and transformation’, Ingold 2012, 439) that can become artefacts (i.e. ‘objects thought to be made rather than grown’, Ingold 2012, 439) at any point. While archaeologists can study plastics as materials, focusing on plastic production sites as contributors to climate change, they can also study them as artefacts, focusing on their omnipresence and degradation as waste constituting an additional aspect of the climate crisis. It may be challenging to identify ‘the limits of where a plastic artifact begins and ends’ (McMullan 2019), just as identifying a plastic’s birth and death when reconstructing its biography (see Praet et al. 2023 for an evaluation of object biographies and itineraries applied to plastics). The focus of this paper will be on studying macroplastics as artefacts, stratigraphy markers, and components of waste landscapes. While this limit is arbitrary and we recognise that microplastics entering our bodies could also be considered artefacts, macroplastics offer a tangible and visible illustration of the many aspects of the climate crisis.

Visual analysis

Despite the design of plastic objects as universal and untraceable (Davis 2022), using an archaeological framework yields information to reconstitute an object’s journey. In that perspective, the use of production and expiry dates on labels, and object design of litter found in Svalbard allowed for an increased sourcing (by 19%) and dating (by 22%) (Falk-Andersson et al. 2021). This set of information is commonly used by archaeologists for relative dating: the production date can be understood as a terminus post quem with the object entering the environment after this date. While these elements were often considered anecdotal in environmental studies, bottle manufacturing marks were used to infer production date and country of origin, contributing to identifying plastic pollution sources (e.g. Ryan 2020). If dates of production and/or consumption are not visible on the plastic artefacts, assigning them a date becomes a challenge. The composition of artefacts may give an insight into their chronology, for example, Bakelite preceding PVC. But as plastics remain in the environment and their chemical composition becomes more complex through time and the use of additives, assemblages of plastics in stratigraphy may be complicated to locate chronologically as the plastic signal becomes more integrated into the stratigraphic layer. The design of plastic objects can also be a source of information on the object’ chronology through the use of typologies and their chronological situation. Dating a plastic artefact through design, labels, and composition is not necessarily a straightforward task, particularly for fragmented plastics, a common finding in archaeological contexts and the broader environment.

Suppose a date cannot be assigned to the objects from visual analysis only. In that case, plastics may still hold information regarding the object’s use and/or taphonomic processes the object has gone through. The potential to use sediments as natural archives to approach taphonomy for plastics remains largely unexplored (see Bancone et al. 2020 for a review of the gap of knowledge regarding taphonomic processes for microplastics). And this is maybe where archaeology can be most helpful. The discipline can provide historic samples and include taphonomic processes within artefact analysis (whether buried or exposed) to explore the factors that contributed to plastic degradation (e.g. yellowing, breaking, loss of colour, …). Despite their mass manufacturing, plastics remain cultural objects (Ingold 2000) as they are revealing of ‘western cultural values and assumptions, economies and epistemologies’ (Davis 2022, 38). There are more cultural decisions in plastic production than meets the eye, and their design can change reflecting cultural decisions. Similarly to ceramic, some plastic objects can become diagnostic (e.g. plastic papel picado, originally made from paper) but others will appear across different cultures (e.g. a global PVC tube).

For example, the red bucket bottom in Figure 1 contains several elements of information. The HDPE stamp indicates the plastic category it belongs to, namely high-density polyethylenes. It has a partial inscription ‘ … Ecuatorianos Guayaquil Ecuador’, indicating its potential fabrication in Ecuador, and a clock with years indicating 98, potentially corresponding to the bucket production date. Found on Galapagos shores during a beach clean-up, the bucket fragment has smooth edges indicating a long time spent in water, whether at sea or partially submerged in the coastal environment. It is weathered and slightly whitened and has remains of a mollusk shell. The bucket is most likely to have been used in marine activities, potentially on fishing vessels. It may have reached the ocean after breaking, and not able to fulfill its assigned function. This exercise based on a simple plastic fragment shows the interest in asking archaeological questions to re-construct plastic itineraries (after Joyce 2015). But while visual exploration presents limitations for the study of artefacts, archaeological science can complement the study of origin (e.g. Cabadas-Báez et al. 2017), making (e.g. Ménager et al. 2021) and use (e.g. Plaza Calonge, Figueroa Larre, and Martinón-Torres 2022), and their potential for plastic is explored next.

Figure 1. Bucket bottom found in Galapagos with a stamp for plastic type 2 - high density polyethylene (HDPE). Picture by the author.

Archaeological science

Archaeological science can be used to approach plastic’s composition, use, and degradation notably to infer elements of chronology and making. The composition of plastics has changed drastically, notably through the use of additives and plasticizers diversifying the chemical signatures of synthetic plastics (Geyer 2020). The chemical composition of plastics became highly complex over time, with more than 10,000 chemical substances that can potentially be added to create plastic objects (Wiesinger, Wang, and Hellweg 2021). Here, the use of categories becomes helpful to analyse plastics as artefacts. Despite the diversity of plastics’ chemical signatures, a common categorisation is the use of seven plastic types (PET, HDPE, PVC, LDPE, PP, PS, other), used to sort and recycle materials (Jung et al. 2018) and helpful to approach marine plastic litter as PE, PP, PET, and PS are greater contributors to the issue (Andrady 2011). But this limited classification is not the only way to divide plastics into categories, as their degradation pathway (biodegradable or not), material properties (thermosets that do not remelt once hardened or thermoplastics that can remelt), and their source (either fossil or biogenic) also define plastic categories (Geyer 2020) (Figure 2).

Figure 2. Categories of plastic according to carbon source, biodegradability and material properties (after the categorization from Geyer 2020).

Determining the composition of fragmented plastic waste is a challenge if no information is available on the object. Yet, several methods, based on microscopy, spectroscopy, and thermal approaches (Lakshmi Kavya, Sundarrajan, and Ramakrishna 2020), exist to identify plastics and determine the polymer types, notably attenuated total-reflectance Fourier transform infrared spectroscopy (ATR FT-IR) (e.g. Jung et al. 2018), portable x-ray fluorescence spectrometers (pXRF) (e.g. Turner and Solman 2016), pyrolysis gas-chromatography mass-spectrometry (Py-GC/MS) (e.g. Hermabessiere et al. 2018). Some of these methods are also used in archaeological contexts, for example, pXRF as a non-intrusive method (Forster et al. 2011) shedding light on a material’s composition (e.g. Plaza Calonge, Figueroa Larre, and Martinón-Torres 2022). The method of pXRF applied to plastics can identify their elemental composition (Turner 2017), and the presence of pollutants including heavy metals (Turner and Solman 2016). Using methods to determine plastic types then becomes a way to identify the presence of additives and pollutants in plastic waste, which can eventually contribute to understanding the object chronology and use.

Plastic poses the challenge of an ever-resisting material that slowly degrades and infinitely breaks down to the despair of material engineers and policymakers, becoming harder to retrieve and manage the smaller it gets. Archaeologists are exposed to the degradation of material culture, and accustomed to recovering fragmented artefacts through excavation. But plastics’ degradation is difficult to grasp and even more difficult to avoid, particularly for museum curators, conservators, and restorers caring for collections including culturally important plastic artefacts (Kean 2021). Archaeology can build on this knowledge of plastic conservation when encountering culturally important plastics. While plastics conservation is not necessarily a priority for archaeologists, the discipline can provide more data through the excavation of modern material culture, and shed light on plastic degradation processes. This helps in understanding how degradation occurs and what factors contribute to it. Once the presence of plastic types is determined in the archaeological record thanks to the methods outlined above, the focus can shift to identifying degradation processes of plastics (Zhang et al. 2021) facilitated by their exposure to a series of biotic (e.g. bacteria, funghi, insects) and abiotic (e.g. light, air, temperature) factors. To study artefact degradation, archaeologists use a wide range of microscopic and spectroscopic methods such as scanning-electron microscopy (SEM) and FT-IR (e.g. Łucejko et al. 2015). For plastics, degradation can be identified by a loss of molecular weight and mechanical strength, colour, texture and spectral signature changes (Turner, Arnold, and Williams 2020). On the one hand, degradation is physically visible through modification of the polymer’s surface (Chamas et al. 2020). Changes in morphology and porosity can be evidenced by SEM and atomic force microscopy (AFM) (e.g. de Araujo 2019). While the use of SEM for plastics is rare (Corcoran, Biesinger, and Grifi 2009), it has been used extensively by archaeologists to understand processes of manufacturing (e.g. Ménager et al. 2021), use-wear (Cuenca-Solana et al. 2013), and composition (Sáenz-Samper and Martinón-Torres 2017). On the other hand, plastic’s degradation can also be understood chemically by comparing ATR FT-IR spectra of virgin with degraded polymers found in the marine environment (e.g. Ioakeimidis et al. 2016). A few studies combined insights into physical and chemical degradation such as Turner et al. (2020) who used ATR FT-IR and SEM to better understand the weathering of Lego blocks. But often studies focusing on degraded plastic waste use weathering and degradation interchangeably. Weathering, at least in the archaeological sense, refers most often to subaerial weathering, the exposure of the material to open air conditions (e.g. Madgwick and Mulville 2012). Considering subaerial weathering as a specific degradation pathway would be particularly relevant for plastics, notably as exposure of plastic waste to solar UV, the main driver of plastic fragmentation (Bancone et al. 2020), and their oxidation produce secondary microplastics (Andrady 2022).

Plastics as an archaeological layer

The widespread presence of plastics in the environment means that they enter, as micro- or macro-plastics, archaeological contexts, and stratigraphies. The focus of this paper is on macroplastics entering archaeological layers illustrative of the Anthropocene. This paper argues for considering the presence of plastics in stratigraphy as a source of information. In that perspective, macroplastics can become chronological markers for the strata, often offering more precise dating than pre-industrial materials, especially if found with labels. Several studies have aimed at considering plastics as a source of information on the site use and chronology, notably in landfills (Rathje and Murphy 2001), on heritage sites (Mytum and Meek 2020), in underwater excavations (Praet and Delaere In press) and urban sedimentary record (Wagreich et al. 2023). More systematic archaeological studies of macroplastics in stratigraphies, with plastics sampled, quantified, and classified, could contribute to understand plastic pollution through time. Here again, macroplastics found in stratigraphy are visible and often colourful items that make the presence of modern humans and their impact on the environment undeniable. In addition to providing good archaeological indicators of the Anthropocene, plastic artefacts can also act as a way to engage on the topic of plastic pollution and anthropic impacts on the environment.

It is the presence of microplastics in sea sediments, and the fossilisation of plastic in landfills that led Zalasiewicz et al. (2016) to advocate for the use of plastic as a stratigraphic indicator of the Anthropocene while cautioning more studies to understand this new stratigraphy. Microplastics also hold the potential to serve as stratigraphy markers notably of the Anthropocene, facilitated by their exclusive anthropogenic nature and the comparison of their widespread presence at a global level (Bancone et al. 2020). While microplastics are not the focus of this paper, their presence in archaeological contexts holds the potential to provide diachronic perspectives of microplastic presence in soils. While not explicitly adopting an archaeological lens, several environmental studies have become interested in identifying temporal trends of microplastic pollution, mostly focusing on coastal sediments (e.g. Brandon, Jones, and Ohman 2019; Long et al. 2022; Matsuguma et al. 2017). But more research is needed to understand microplastics’ distribution, and the taphonomic processes they undergo (Bancone et al. 2020). Despite the potential of archaeology to consider the stratigraphy of archaeological sites as an archive of plastic pollution through time, there is a striking lack of archaeological studies considering macro- and micro-plastics in the stratigraphy. This paper highlights this gap of knowledge of plastics in stratigraphical contexts from archaeological sites. Contributing to this literature would help understand and measure how anthropic impacts on soils and sediments have changed through time, and what that means for future soil use.

In addition to plastic becoming a topic of interest for archaeologists through stratigraphy, areas receiving plastic pollution can benefit from an archaeological perspective. Environmental and marine biology studies of plastic pollution on beaches and shorelines are often limited to sampling of surface-level sediment. Yet, studies have highlighted that microplastic pollution is more abundant below the surface (e.g. Tavares et al. 2020). Despite their importance for contemporary archaeology (see Harrison and Schofield 2010 for an introduction to contemporary archaeology), surface assemblages (e.g. Harrison 2011) and surface sampling can only give us a partial understanding of plastic pollution, especially given the breaking down of plastics into microplastics. Adopting a stratigraphical perspective, for example, through augering polluted beaches, can reveal buried plastics and contribute to developing an understanding of these supermodern landscapes.

Plastics as part of waste landscapes

As plastics enter marine and terrestrial environments, they can be studied not only as artefacts and components of archaeological layers but also as a material that permeates a multitude of landscapes. The global ubiquity (after Davis 2022) of plastics questions the scale at which archaeologists are usually working. For plastics, the scale may be planetary, contrasting with traditional archaeological approaches working at the household, town, or one river valley level (Agbe-Davies in McMullan 2019). This scale disruption is characteristic of contemporary archaeology (see Edgeworth 2010, 2013). It is also the scale of plastics’ presence and impacts that transforms some environments into waste landscapes. Ubiquitous and diverse, waste landscapes share a characteristic omnipresence of waste materials that have lost socio-economic and symbolic value (compared to their value as products) and are no longer entangled in terms of ownership (see Reno 2013 for losses of ownership and value as central to the definition of waste). The concept of waste landscape is here used to approach landscapes marked by plastic pollution (see Praet et al. 2023 for a consideration of plastics as components of waste landscape). As the scale of plastic pollution, its visibility and impacts on landscapes may greatly vary. As a result, a diversity of waste landscapes shaped by plastic pollution emerge, from the ones marked by invisible micro- and nano-plastic leaking resulting from agriculture processes to the melting and incorporation of plastics into the geological record (see Rangel-Buitrago, Neal, and Williams 2022) and the highly visible accumulation of mega- and macro-plastic in Garbage patches (see Tamoria and Schofield In press). Those newly formed landscapes both contribute to climate change, for example through the presence of synthetic objects of all sizes having a series of impacts on their environment, and are impacted by climate change’s consequences, when severe weather further spreads plastic pollution.

Archaeologists became interested in those landscapes and adapted archaeological techniques, notably surveys and excavations, to study them (see Pétursdóttir 2017 for a study of drift matter). While these studies do not solely focus on plastics, they represent a considerable part of the landscape. Recognising the geographical amplitude of plastic pollution allows for its consideration as a global issue. These newly configured landscapes offer another argument for an archaeological study of plastic pollution. Building on the potential of archaeology to approach and reconstitute past landscapes, a series of techniques can contribute to understanding these recent waste landscapes. Coupled with artificial intelligence (e.g. Politikos et al. 2023) or Citizen Science (Merlino et al. 2021), drone surveys can identify the proportion of plastic types in a defined area (e.g. Andriolo et al. 2021) providing an aerial perspective on the issue when the landscape is visibly marked by plastic pollution. An archaeological approach to the issue could combine this aerial perspective with surface sampling in transects, and stratigraphical views of plastic pollution through augering. The presence of plastic at depth was shown to sometimes reach higher levels than those of surface sampling (e.g. Tavares et al. 2020). While plastic distribution depends on the landscape dynamics, archaeology brings a stratigraphic approach to the landscape. Archaeology contributes to the study of these landscapes by questioning the formation of these landscapes and adopting a multi-level approach, combining aerial, surface, and in-depth inquiries into plastic presence within one landscape. Studying how these spatial and temporal levels relate to each other would offer an archaeological perspective on this specific landscape. It may confirm if areas that appear as most polluted on drone images are also characterised by specific plastic types in surface sampling alongside increasing microplastic pollution below the surface. This could contribute to improving monitoring practices and offer policy recommendations for cleanups.

Archaeology covered in plastic pollution

Plastic pollution is a visible issue, one that can hardly be hidden. Despite being linked to climate change (Ford et al. 2022; Lavers, Bond, and Rolsky 2022), plastic pollution has not often been recognised as an issue in the heritage literature discussing climate change impacts. Pollution is recognised as a threat to the Outstanding Universal Value of World Heritage Sites (UNESCO), for example, but is most discussed for natural heritage sites (see Woodward and Cooke 2022). With the global interconnectedness of marine currents, waste dropping, marine activities, and rivers as sources of plastic, plastic pollution characterises most landscapes including important natural and cultural sites. Plastic pollution can occur as a result of increasing tourism but also due to the site’s geography being exposed to marine and/or land sources of plastic pollution.

The impacts of tourism on archaeological sites have long been documented for world renowned sites (e.g. Green and Vaschetto 2022). While tourism can have a multitude of impacts (see Wilson 2008), this paper has focused on environmental impacts notably resulting in plastic pollution and how this directly relates to the climate crisis. Construction and operation of tourism facilities can negatively impact the environment by respectively provoking vegetation, soil, and habitat loss, and producing byproducts such as solid waste (Leung 2001). From that perspective, an increased number of visitors puts pressure on the site and nearby facilities including waste management. Tourists’ behaviour (e.g. littering) can also become a threat to heritage sites (Leung 2001) and contribute to plastics entering the site and its surroundings, with known consequences for wildlife (Ayala et al. 2023) and soils (Zhu et al. 2019). The potential impacts of plastics, entering the stratigraphy of archaeological and heritage sites, are unknown and would benefit from more research. These could include impacts on the soil properties and eventually on the preservation of other materials. Before they degrade and enter the stratigraphy, the visible accumulation of plastics in and near the sites poses a threat to local livelihoods, and potentially transforms the tourist experience negatively (as in Umm-Qais in Jordan, see AlMasri and Abadneh 2021), as plastics affect negatively landscape aesthetics (e.g. Gascón 2022). WHS such as Angkor Wat and Machu Picchu saw the unprecedented development of cities next to the sites, respectively Siem Reap and Aguas Calientes, to accommodate tourists but lacked adequate waste management systems. While the issue of plastic pollution is acknowledged in the literature, more research is needed to identify strategies adopted by archaeological and heritage sites to limit and address plastic pollution.

The entry of this recent material culture in heritage sites was documented at Castell Henllys, Wales. Excavations of two reconstructed Iron Age roundhouses shed light on tourist behaviour (Mytum and Meek 2020). A careful analysis enabled the differentiation of material culture between the Cookhouse, usually quickly inspected by the visitors, and the Earthwatch where benches invited people to sit and pupils to eat their packed lunches. Even though both spaces were regularly cleaned to provide the illusion of authentic Iron Age houses, plastic items have made their way into the soil facilitated by rodent and human factors. While the authors’ analysis is limited to the interpretation of the spaces and reflections on the ‘Plastic Age’, those same findings could be used to make recommendations for policymakers and heritage site managers to limit the entry of plastic pollution. This shows the potential contribution of (contemporary) archaeology to policymaking and its relevance nowadays (e.g. Holtorf 2009; Kaufman, Kelly, and Vachula 2018; Sabloff 2009; Vince et al. 2022), hopefully contributing to the design of solutions to address plastic pollution along with other disciplines.

In addition to the number of visitors constituting an environmental issue (Leung 2001) and leading to plastic waste entering the archaeological record, the location of certain sites makes them particularly prone to receiving plastic pollution. Coastal heritage sites, as well as islands, are exposed to the global flows and dynamics of plastic pollution coming from a variety of sources including marine activities and land pollution. The World Heritage Site of Galapagos receives pollution from oceanic currents, marine sources, and local pollution although the latter is scarce (Jones et al. 2021). Aside from coastal sites, natural heritage located close to river basins can also suffer the consequences of microplastics’ presence and toxicity (Amrutha et al. 2023), especially as rivers play an important role as sources of marine litter (Lebreton et al. 2017). With plastic pollution entering and accumulating on the seafloor (acting as a sink for marine plastic litter, see Cau et al. 2022) and riverbed (van Emmerik et al. 2022), the impact of plastic pollution on submerged heritage, for example, shipwrecks, may be extensive but remains largely unexplored. Urban sites can also receive plastic pollution in their sequence (see Wagreich et al. 2023), as illustrated in this road cut, containing deposits from 200 years ago to the present where plastic represents another layer of the urban history (Figure 3; Morgan, pers. com.). There, plastics are present in the road cut stratigraphy, as eroding from the top surface, and accumulating at the base (Morgan, pers. com.). While plastics seem to be imported from worldwide sources, their weathering and the lack of comparative typologies make the identification of their origin challenging (Morgan, pers. com.). In brief, heritage can be exposed to a series of factors, from anthropogenic actions to natural elements allowing the entry of plastic into these iconic and protected areas and sites. Those sites suffer from the socio-economic impacts of plastic pollution, notably impacting tourism and people’s wellbeing, as well as requiring a budget to remove the litter and manage the waste. Bio-ecological impacts of plastic pollution are also threatening these sites, notably as plastic poses a threat to local, and sometimes endemic, wildlife, and constitutes a danger to human health through certain additives.

Figure 3. Dr Colleen Morgan recording a road cut with plastic in the stratigraphy as part of the origins of Doha/Qatar project in 2012. Picture by Daniel Eddisford. License CC-BY.

Conclusion

In this paper, I argue that plastic pollution represents an object of study for archeologists amid a climate crisis. There are several ways in which archaeologists can decide to approach the issue. First, plastic objects can be studied as cultural artefacts, considering the amount of information they hold to reconstruct sections of their journey, from production to waste. In addition to visual examination, notably of labels, archaeological scientific techniques can contribute to a better understanding of plastic’s physical and chemical degradation. The occurrence of plastics of all sizes in stratigraphy can also be revealing of occupational trends and yield chronological information useful for relative dating. As the scale of plastic pollution is characteristic of the Anthropocene, archaeologists might want to explore how plastics affect a diversity of landscapes and create new geographies.

Archaeologists need to account for plastic pollution, especially in times of climate crisis. While plastic pollution actively contributes to climate change (Ford et al. 2022; Lavers, Bond, and Rolsky 2022), it is likely to be exacerbated by consequences of the climate crisis turning it into a threat to archaeological sites. Sites face climate change consequences such as erosion (Reimann et al. 2018), floods (Daly et al. 2022), increased temperatures (Matthiesen et al. 2022), and extreme weather events (Rivera-Collazo 2020). Those critical events, notably floods and extreme weather events, can contribute to the increased spread of plastic pollution (Ford et al. 2022), whose accumulation can become a threat to these sites and their environment. In the Anthropocene, there are infinite ways to develop an archaeology of plastic pollution, and to actively engage with archaeological and heritage sites affected by and covered in plastic pollution.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author’s research, as part of her PhD, was supported by the Arts & Humanities Research Council [grant number AH/R012733/1] through the White Rose College of the Arts & Humanities.

Notes on contributors

Estelle Praet

Estelle Praet is an archaeologist who participated in excavations in Peru, Mexico and Europe. After specialising in Latin American archaeology for her undergraduate and master at the Université Libre de Bruxelles (Belgium), Estelle undertook a Masters degree in gender studies (Université Catholique de Louvain) and then a MPhil in archaeological science (University of Cambridge). It was in Cambridge that she developed an interest in building projects at the crossroads of archaeology and environmental conservation, a topic that she is exploring in her PhD on Galapagos marine plastics at the University of York supervised by Professor John Schofield.