• 1 For a critical overview of these cases, see D'Haenens [2025].

2This article seeks to break the silence surrounding extinction in Brussels by reconstructing, as far as possible, what became of these vanished amphibians. Their histories are inseparable from broader territorial issues concerning the place of water within the city. As animals which lead a dual existence – living first as aquatic larvae and later as terrestrial adults (amphi-bios) – amphibians once inhabited the wetlands (ponds, pools, marshes and wet meadows) which were still widespread two centuries ago throughout the Senne valley and along its tributaries [Weiserbs and Jacob, 2005: 6–7]. The five stories recounted below should be understood as small episodes within the much broader history of the disappearance of surface water. This process began to reshape Brussels as early as the 15^th century, accelerated dramatically during the 19^th century with the construction of hydraulic systems [Deligne, 2003: 215–219] and the embellishment of bourgeois neighbourhoods [Leblicq, 1983: 264], and continued during the 35 years following World War II, when the city experienced “unchecked building expansion” and the “considerable development of the road network” [Leblicq, 1983: 278]. Today, questions surrounding water in Brussels have returned to the forefront of public debate through opposition to soil sealing in response to flood and heatwave risks affecting predominantly working-class neighbourhoods; through initiatives to restore open waterways and improve their ecological quality; and through campaigns led by residents’ groups to protect marshes threatened by property development or transport infrastructure projects¹. Against the backdrop of these regional struggles and transformations, stories of extinction introduce new ways to reflect on our capacity to actually make room for other living beings whose survival depends upon the urban landscape.

• 2 According to the municipal almanacs, Rue de la Grenouille (Frog Street) in Molenbeek became Rue de (...)
• 3 This tendency is evident in communications produced by the regional administration, as well as in C (...)

3An attempt to give historical depth to these animals and to the places where they disappeared reveals a second issue: the enduring silence which surrounds these extinctions. These losses are marked by both territorial and documentary blindness. In other words, the lives which have been lost are no longer perceptible, either within the physical landscape or in the available documentation. When we observe the city, we see what exists: the built environment and the living beings which inhabit its infrastructures or the empty spaces around them, rather than the traces of ecological destruction brought about by urbanisation. This is evident, for example, in the disappearance of place names which once testified to the presence of amphibians². Likewise, the memory of their disappearance is absent from almost all material intended for the general public, which celebrates nature in Brussels while overlooking the living beings which paid the price of urban development³.

• 4 This approach challenges the assumption that extinction is a distant, global phenomenon. It is rega (...)

4This concrete invisibility is compounded by the difficulty of recognising extinction itself as a catastrophe. For what is an isolated loss – a small local tragedy – within a diffuse process “shaped by an infinity of micro-decisions” which, one degradation after another, culminates in much larger waves of extinction [Semal, 2013: 11]? This article addresses the problem by drawing on the field of Extinction Studies. Rather than adopting a global perspective on extinction, scholars in this field advocate detailed case studies which illuminate the “quieter processes of loss” unfolding within particular communities and places long before the death of the last individual [Rose et al., 2017: 1; author’s translation]. Using ethnographic and microhistorical approaches, they examine how extinction brings into play ways of living and dying, as well as relationships between humans and other living beings [van Dooren, 2014: 1-18]. They invite us to tell situated histories of extinction and to explore the distinctive social, cultural and ethical questions raised by these disappearances, beyond their biological consequences [Garlick and Symons, 2020]⁴.

• 5 This research project is driven by the need to restore significance to living beings which have bee (...)

5The disappearance of amphibians first attracted my attention during my anthropological research in urban ecology with nature, conducted alongside naturalists – most of them amateurs – who are actively engaged in the conservation of threatened animals in Brussels. Regional atlases [Graitson et al., 2022; Weiserbs and Jacob, 2005] revealed the submerged part of the iceberg: the species which had vanished from the situations I am studying today. These disappearances called for a historical dimension to be incorporated into my ethnographic work, although doing so proved challenging. How can value be restored to individual lives when they disappear in large numbers? Or when sensory experience, embodied knowledge and first-hand testimony of their loss are, in most cases, unavailable [Guidée, 2021]? It became necessary to examine a sparse and fragmented body of knowledge and to reconstruct, as far as possible, a fuller account. Doing so involves scrutinising the available documentation in order to establish what can be known, while acknowledging its limitations; identifying the ways in which missing traces themselves generate indifference; and compensating for these absences by drawing on related sources to tell the story nonetheless⁵. Using regional atlases and the references they contain, together with interviews conducted between 2019 and 2025 with four biologists, I traced these disappearances beyond statistical records and as close as possible to what can still be reconstructed. This required bringing together an eclectic range of sources: biological and ethological studies of the species concerned; studies of specific sites; archives and historical maps (for the 19^th century); aerial photographs (for the 20^th century); and published field observations by local naturalists, the latter proving particularly invaluable. Each source earned its place in the investigation by contributing, however modestly, to the reconstruction. Ultimately, it became clear that much of what allows these stories to acquire substance derives from the work of two naturalists: Georges Albert Boulenger (1858-1937) and Hellin de Wavrin (1946-2016). Thanks to the publication of their field observations, we are able to come much closer to understanding what may have happened to these vanished amphibians.

• 6 Between 1822 and 1842, the Sonian Forest was substantially reduced when the Société Générale conver (...)
• 7 Heavy rainfall in 1865 and 1866 caused runoff to flow towards the hamlet of Boendael, while in 1882 (...)
• 8 Duquenne [1989: 82] together with Keilig's requests relating to these works. KEILIG, E., 1864-1883. (...)

8What were these habitats like? In 1876, when the young Boulenger collected his specimens, naturalists recorded natterjack toads across much of Belgium, inhabiting wet meadows, woodland edges, gardens and heathland [Dubois, 1873: 173]. At that time, they were not yet recognised for their affinity with landscapes shaped by industrial and extractive activities – quarries, brownfield sites and spoil heaps – even though such environments were already widespread in Belgium [Graitson and Denoël, 2007: 145-147]. Current ecological knowledge, which links natterjack toads to disturbed ground and construction sites, allows us to reinterpret the history of the population which lived in Bois de la Cambre. If, as Boulenger reported, they were common there, they must have occupied the site for several generations. Their ancestors probably arrived as early as the 1820s, following the clearance of this outlying section of the Sonian Forest, then managed by the Société Générale to supply timber for the industrial expansion of Belgium [Duquenne, 1989: 10]⁶. They subsequently followed successive episodes of tree felling and coppicing carried out by the state before the land was transferred to the city for the creation of the park [Duquenne, 1989: 9]. During periods of hibernation or aestivation, the toads were likely to have dug burrows throughout the site while earthworks were under way and during the excavation of the lake between 1862 and 1866 [Duquenne, 1989: 28-31]. Because natterjack toads are able to adjust their breeding periods in response to flooding, they probably benefited from the shallow, temporary pools of standing water – largely free from tadpole predators – which were created as the park’s new topography altered natural drainage patterns⁷. By the time Boulenger collected the pair which entered the museum’s collections, the construction of roads and leisure facilities was nearing completion, while tree felling, coppicing and the sowing of lawns were still in progress⁸.

• 9 This portrait is based on interviews conducted with two people who knew him well.
• 10 Based on a comparison of aerial photographs available through Bruciel, dating from 1961, 1977 and 1 (...)

10European tree frogs (Hyla arborea), small climbing frogs with bright apple-green skin and golden irises, spend most of their lives concealed among the foliage of shrubs [de Witte, 1948: 141; Figure 3]. Writing in the late 1980s, Hellin de Wavrin noted that they had once occurred “throughout much of the area surrounding the Sonian Forest” but now appeared to be “on the brink of regional extinction” [de Wavrin, 1988: 132]. A passionate amateur naturalist since childhood, de Wavrin’s commitment to wildlife had become second nature – a way of life which never wavered⁹. From the 1960s until his death in 2016, he tirelessly surveyed sites across Brussels, concentrating particularly on the southern part of the city, in Uccle and along the edge of the Sonian Forest, where he lived. Despite repeated evening listening surveys, he never again heard the distinctive breeding calls of the tree frog – a rapid succession of clear, staccato notes – reputed to be among the loudest produced by any amphibian in Belgium. In addition to sites around the city, de Wavrin had formerly heard tree frogs at a pond in a marshy valley in Uccle, which was infilled in 1964, and in a marsh in Anderlecht which was infilled in 1962 [de Wavrin, 1988: 133]. He also records that an acquaintance had heard them at the Étang des Pêcheries in Watermael-Boitsfort, where, according to an anonymous source, they persisted until the 1970s, and in Etterbeek, based on “an old record from a site which has since disappeared” [de Wavrin, 1988: 132]. It is difficult to say much more about the habitats these tree frogs occupied. When de Wavrin gives the year in which a wetland was infilled, he identifies the site only by municipality. Conversely, when he specifies a particular location (the Étang des Pêcheries), he provides no precise date. An examination of the ponds which disappeared from Uccle suggests that the site in question was probably the Lecomte pond at the foot of the Kauwberg, which was infilled in 1964, connected to the sewer network and buried beneath new housing. It is also likely that the large apartment blocks constructed around the Étang des Pêcheries during the 1970s and 1980s substantially altered the grassy and shrubby habitats where these tree frogs lived¹⁰.

• 11 Midwife toads were already being recorded near Uccle at the beginning of the 20^th century [de Witte (...)

12He discovered the last wild population remaining within Brussels among the rockeries overlooking the pond in Parc de la Sauvagère, Uccle, where it persisted until the 1970s [de Wavrin, 1988: 162; Figure 4]. This final colony probably colonised the pond after 1910, following its creation by a wealthy industrialist. The toads may either have been deliberately introduced or have dispersed from the ponds which dotted the former hamlet of Petit Saint-Job, less than half a kilometre away¹¹. During World War II, the site was occupied by military forces before being abandoned. Towards the end of the 1960s it was purchased by the municipality of Uccle and converted into a public park [Pons-Rotbardt, 2021]. Increased public use of the park probably weakened the colony, which disappeared in the following years. Yet its vulnerability appears to have stemmed above all from its isolation.

• 12 As Brussels lies at the northern limit of the species' geographical range, midwife toads are partic (...)

13The relationship between midwife toads and their habitats differs markedly from that of other toad species. Mating takes place on land rather than in water. After fertilising the eggs, the male wraps the string of eggs around his hind legs – hence the species’ common name – and carries them for several weeks, periodically moistening them during nocturnal visits to water. As a result, midwife toads can breed in a wide variety of aquatic habitats, provided these remain close to rocky refuges where they shelter communally, such as quarries, industrial wasteland, old walls, cemeteries, sunny embankments, parks and gardens with rockeries, or piles of roof tiles [Graitson et al., 2022: 52]. These artificial habitats are especially vulnerable to redevelopment or natural reforestation when left unmanaged¹², although midwife toads remain faithful to them as long as conditions are favourable. If those conditions deteriorate, however, they may disperse in search of another suitable site up to one kilometre away [de Wavrin and Graitson, 2007: 106-107]. Their well-known capacity for such movements shifts our attention towards the connections – or the breakdown of connections – between the sites they occupy.

• 13 The importation of frog legs into Europe – including live frogs, of which approximately 70 % enter (...)
• 14 This hypothesis remains speculative. First proposed by August Thienemann in 1950 [Fonte et al., 201 (...)

16To understand this process, our attention must shift to another species of green frog: the marsh frog (Pelophylax ridibundus). Sometimes twice the size of the pool frog, the marsh frog is well known for its chuckling calls. Native to Central and Eastern Europe, it was introduced into Western Europe from the 1950s onwards for culinary purposes and laboratory use, where it was bred commercially [Perrot, 2017: 38]¹³. Whether these frogs escaped or were deliberately released remains unknown, but these remarkably agile amphibians soon became established throughout the major river catchments of France. In Wallonia, aquatic plant nurseries sold them to ornament garden ponds, after which they appeared throughout the Senne and Dyle catchments [Percsy and Percsy, 2013: 250]. Marsh frogs are therefore a feral species: their spread results from the unintended consequences of human projects and infrastructures. Through cascading, uncontrolled effects, such feral species transform ecological environments and thereby contribute to the creation of the more-than-human Anthropocene [Tsing et al., 2025]. In Brussels, a naturalist first recorded marsh frogs in 1968 near Parc de la Woluwe [Parent, 1974: 101]. They were subsequently found in the Jette marshes in 1992 and, a decade later, at 17 sites extending from the north of the city (Parc Royal de Laeken and wetlands near Bois du Laerbeek), to the west (Wilder and the Moeraske) and the south (Parc de Woluwe, Val Duchesse, Parc de la Héronnière in Watermael-Boitsfort and a private garden in Uccle) [Weiserbs and Jacob, 2005: 83]. During the surveys conducted for the most recent atlas, they had expanded further north to Neder-Over-Heembeek, south-east to Rouge-Cloître and Jardin Massart, west to Neerpede in Anderlecht, south to Forest, and even to sites in the city centre, including Parc Josaphat, the Botanical Garden and Square Marie-Louise in Schaerbeek and Saint-Josse [Graitson et al., 2022: 68]. It is difficult to imagine how they could have crossed such distances without human assistance, unless their spawn had become attached to the feathers or legs of waterbirds¹⁴. What is certain is that marsh frogs are sufficiently adaptable to thrive in a wide variety of water bodies, including habitats of poor ecological quality such as sewage treatment basins, roadside puddles and polluted streams [Graitson et al., 2022: 69].

• 15 This reconstruction is based on de Wavrin's article [1988] and a commemorative tribute published fo (...)

18Standing in darkness beneath the trees, Hellin de Wavrin walked in the pond in chest waders, lowered his net into the water and searched the pond bed by the light of his head torch alone¹⁵. In the spring of 1987, he had spent four years trying to determine whether great crested newts (Triturus cristatus) still inhabited the ponds of the Sonian Forest which he had been visiting for more than two decades (Figure 5). Only one population survived, in a pond in the Petite Flosses valley in Tervuren, less than a kilometre from Brussels. The colony had been seen there since at least the 1930s. These large newts, whose males are distinguished by their prominent dorsal crest, are difficult to detect because they spend most of their time in deeper water, with only the females returning to the shallows to lay eggs among the vegetation. By this time, however, the pond had become increasingly shaded as surrounding beech trees matured and blanketed it with fallen leaves. It had become a less suitable habitat for these particularly demanding newts. Yet de Wavrin could not understand why none had colonised another pond, barely one hundred metres away, which remained open to sunlight and was fringed with emergent marsh vegetation. “The survival of this colony,” he wrote, “is of great interest, as it represents one of the last, if not the last, surviving remnant of a population once widespread throughout the region” [1988: 121]. The reason was straightforward: the ponds inhabited by great crested newts had been infilled one after another. During the 1960s, the pond alongside Drève du Tambour in Watermael-Boitsfort disappeared, as did another in a meadow in Uccle. De Wavrin does not explain why these ponds were reclaimed. Great crested newts have never since returned to Brussels. The Ring Road and the E411 motorway, separating the Petite Flosses valley from the remaining ponds in Brussels – too small, too shaded and too heavily stocked with fish – now constitute insurmountable barriers preventing recolonisation [Weiserbs and Jacob, 2005: 72].

• 16 The first amphibian rescue operations during seasonal migrations began in the 1980s with the creati (...)

21Today, frogs, toads and newts are most visible in Brussels between February and April, when their pre-breeding migrations prompt local residents to help them cross roads which would otherwise prove fatal. This takes place along the edge of the Sonian Forest, in the Geleytsbeek valley in Uccle, the Tweebeek valley in Neder-Over-Heembeek, and around Parc de Woluwe and Parc du Vogelzang in Anderlecht¹⁶. The observation most frequently shared by residents who return to these sites year after year is unequivocal: fewer amphibians cross the roads with each passing season. Amphibians are also found in protected and actively managed wetlands, including those in Jette and Ganshoren, the Broek marsh in Uccle, the Moeraske in Evere and Hof ter Musschen in Woluwe. Here too, residents and volunteer site managers tell the same story: the spring choruses which once filled these wetlands have become little more than murmurs. Meanwhile, residents’ groups campaigning to protect threatened marshes – such as Wiels and Bempt in Forest, or Biestebroek in Anderlecht – continue to encounter amphibians there. These struggles highlight the vital role of urban wetlands in an era of climate change, both as permeable landscapes which help absorb floodwaters and as cooling refuges within densely built neighbourhoods. The vegetation of these aquatic environments is also increasingly recognised for its capacity to purify water and, over the longer term, to contribute to the remediation of polluted sites [Bastin, 2025: 8]. In the context of the current biodiversity crisis, the stories of the disappearance of the natterjack toad, European tree frog, common midwife toad, pool frog and great crested newt confer an additional significance upon the remaining wetlands in Brussels. They remind us that the amphibians observed and protected there today are not simply the species which happen to be present: they are those which remain. Without appealing to a nostalgic vision of a more authentic past, these stories reveal that the continuing decline in their numbers takes place against the backdrop of earlier disappearances. The amphibians and the habitats which still survive in Brussels therefore matter not only because of their present existence and vulnerability – and certainly not merely as components of “biodiversity”, a term which obscures their histories – but because they are the survivors of a landscape shaped by profound and cumulative losses whose underlying processes remain far from arrested.

• 17 See Hache [2024] on this way of becoming terrestrial again, and Solnit [2016] on the transformative (...)
• 18 It is worth noting that the first case study, drawing on official archival sources relating to a si (...)

22In this sense, these narratives of extinction contribute to an urban political ecology which brings forgotten histories back into view. By reconnecting us with neglected living beings and the vulnerabilities they recall, they deepen our understanding of the transformations unfolding around us and open new ways of attending to the places in which we live¹⁷. This is why it is necessary to recover little-known histories despite the lack of available evidence. Doing so runs counter to prevailing tendencies in academic research, where projects are typically defined by the availability of sufficiently extensive source material to guarantee their feasibility, thereby excluding subjects which cannot meet this expectation. Yet, in some cases, the only way to approach the lived experience of these losses and to explore their implications is to work patiently with a small body of knowledge – in this case, a handful of writings by two experienced naturalists who continued to care about these disappearances over many decades – and to enrich it with every other document capable of adding another piece to the puzzle. This requires directing attention towards the limits of what can still be known, searching there for traces, and patiently weaving together different forms of knowledge without sacrificing scholarly rigour¹⁸.