Invasive plant species can suppress local biodiversity, affect soil properties and modify the landscape. However, an additional concern of plant invasions that has been more disregarded is their impact on environmental human health. Here, we discuss the case of Cortaderia selloana (Schult. & Schult.f.) Asch. & Graebn, as an example of a worldwide invasive species with a strong environmental impact. We summarise the main facts regarding the C. selloana invasion, the recent clinical evidence of its impact on human health and the great potential expansion of the species in the context of climate change. C. selloana constitutes a clear example to boost demands from policy makers for urgent and efficient measures to control or eradicate invasive species, also in ruderal areas. This aggressive invader is still out of relevant binding international invasive species catalogues, including the European List of Invasive Alien Species of Union concern (Union list), and is still subjected to extensive trading in some European countries. Therefore, including C. selloana in the Union list becomes mandatory to impose full restrictions on keeping, importing, selling, breeding and cultivating the species.

Alien plant, biological invasions, climate change, environmental health, pampas grass, respiratory allergy, Union list

Biological invasions pose a substantial threat to ecosystems worldwide and constitute a critical driver of global change (Vilà et al. 2011). Invasive species are a global concern due to their negative ecological impacts, which include the loss of biodiversity at local and regional scales (Manchester and Bullock 2000; McGeoch et al. 2010; Vilà et al. 2011) or changes in community structure (Domènech et al. 2006; Hejda et al. 2009). In addition, invasions are associated with important economic and human-welfare impacts (Pimentel et al. 2000; Mazza et al. 2014; Hoffmann and Broadhurst 2016). For instance, the economic costs of invasive alien species in Europe have been estimated to total €116.61 billion between 1960 and 2020 (Haubrock et al. 2021). However, beyond the damage to ecosystems and the economy, we need to address the impacts of plant invasions on human health. Unlike invasive animals, the impacts of invasive plants on human health in Europe have been scarcely studied so far and only for a very small number of species, such as Ambrosia artemisiifolia or Heracleum mantegazzianum (Schindler et al. 2015; Bayliss et al. 2017). In this context, the grass Cortaderia selloana, commonly known as pampas grass, rapidly emerges as a species with a great ecological impact (Domènech et al. 2006) and with a clear potential impact on human health as a consequence of: (i) its striking current worldwide spread and (ii) the recently unveiled allergenic properties of the pollen (Rodríguez et al. 2021).

C. selloana and the morphologically close C. jubata have been traditionally regulated as distinct taxa. However, in a new synoptic taxonomy of the genus (Testoni and Linder 2017) the authors describe C. selloana and C. jubata as two subspecies within C. selloana. Although this could be of some relevance in terms of the potential inclusion of C. selloana in binding international invasive catalogues, we will here consider these taxa as distinct species following the previous nomenclature by Ascherson and Graebner (1900): Cortaderia selloana (Schult. & Schult.f.) Asch. & Graebn. [Syn. Mitteleur. Fl. [Ascherson & Graebner]. 2(1): 325].

C. selloana is native to South America and has naturalised in many regions across the globe, mainly Australia, New Zealand, South Africa, North America and Western Europe. In the latter, C. selloana has strongly colonised several countries such as Italy and the Atlantic coast including the UK, the Netherlands, Belgium, France, Spain and Portugal (Fig. 1) (Lambrinos 2001; Tarabon et al. 2018). In Europe, C. selloana is widely traded and used as ornamental species. This ornamental use includes fencing and protecting the garden or property due to its sharp leaves and decorating purposes with dried plumes. The expansion of C. selloana is strongly associated with human activity, as it colonises preferentially anthropogenic ruderal habitats of low environmental value, such as quarries, road margins, slopes, wastelands or industrial areas (Domènech and Vilà 2007; Pardo-Primoy and Fagúndez 2019). However, the species is also invading natural and semi-natural habitats of high environmental value, such as grasslands, wetlands, marshes and coastal dunes (Campos et al. 2004; Saura-Mas and Lloret 2005; Herrera et al. 2017) (Fig. 2).

Figure 1.

Current distribution of Cortaderia selloana (red squares) in Europe and nearby Mediterranean countries. Data retrieved from the Nature Database of Spain (available at: https://www.miteco.gob.es/es/biodiversidad/servicios/banco-datos-naturaleza/) and GBIF-Global Biodiversity Information Facility [GBIF.org (21 September 2022) GBIF Occurrence Download https://doi.org/10.15468/dl.fze4z8].

Figure 2.

Cortaderia selloana can invade natural and anthropogenic habitats A Saltmarsh community in the Butrón estuary near Plentzia (Basque Country, Spain) B Saja-Besaya Natural Park in the municipality of Cieza (Cantabria, Spain) C urban area in Castro Urdiales (Cantabria, Spain) D abandoned quarry in Cuchía (Cantabria, Spain).

Until recently, skin cuts due to the sharp leaves of C. selloana were the only impact associated to this species reported on human health (Mazza et al. 2014). However, grasses are a main source of human allergy (García-Mozo 2017). The potential allergenicity of the pollen of C. selloana had been suggested (Street et al. 1979; Başnou 2009; Pyšek and Richardson 2010; Kumar Rai and Singh 2020), but only recently has this allergenic potential been empirically confirmed in a human pilot study conducted in northern Spain (Cantabria; Rodríguez et al. 2021). This study concluded that the grass allergy season in Western Europe might be extended by several months. This first clinical study of the impact of C. selloana on human health emphasises that authorities of the international community should run larger clinical allergy tests, especially where it is highly invasive. While the allergenic capacity of C. selloana has only recently been demonstrated, a small bunch of other invasive plant species were already known to affect humans. These include giant hogweed (Heracleum mantegazzianum) and common ragweed (Ambrosia artemisiifolia) (Pyšek et al. 2007; Hemmer et al. 2011; Mazza et al. 2014; Montagnani et al. 2017). However, the potential impacts on human health of many other invasive plant species widely distributed in Europe are far less known. The estimations of the socioeconomic impact of the C. selloana invasion and other species should also be re-evaluated considering their impact on human health.

Under a scenario of increasing temperatures in the context of climate change, it is expected that plant species will experience spatial shifts in their distribution ranges (Parmesan and Yohe 2003; Rasmussen et al. 2017), reaching regions that currently are climatically unsuitable (Thuiller et al. 2005; Storkey et al. 2014; Rasmussen et al. 2017). This has been tested for some highly allergenic invasive alien plants present in Europe, such as common ragweed, which is predicted to expand its distribution range northwards and eastwards in the forthcoming decades as global temperatures continue to rise (Storkey et al. 2014; Lake et al. 2017; Rasmussen et al. 2017). A similar trend is to be expected with C. selloana. Tarabon et al. (2018) reported that while this species already occupies large areas along the western and Mediterranean French coasts, their models predicted an expansion northward and inland to the east under future climates. They define C. selloana as a ‘climate warming winner.’ This suggests that the species may colonise in the future other European regions that currently are climatically unsuitable as temperatures continue to rise, with a potential increase in human health impacts caused by its allergenic pollen.

In this sense, the European Union has recently made a good projection of current and future suitability for C. selloana establishment in the EU under current climate and under two scenarios of climate change with similar results (Fig. 3) (Brundu et al. 2021). When comparing the current presence of the species (Fig. 1) with the projected current suitability (Fig. 3), we can see that the southern Atlantic coast has a similar suitability to that of the Mediterranean Basin. Yet, while the presence of C. selloana is currently overwhelming on the Atlantic regions it is less abundant on the central-eastern Mediterranean regions (Fig. 1). This is likely due to an initial colonisation of the plant in Europe through Atlantic countries. This means that current conditions might be even better for C. selloana in the Mediterranean coasts, especially in humid soils, which predicts a strong invasion in these countries. Regarding the projected maps of suitability in the 2070s based on estimated future climate conditions under the Representative Concentration Pathways (RCP) 2.6 and 4.5, which represent low and medium emissions scenarios, respectively (Brundu et al. 2021), the whole of Europe and the Mediterranean region are expected to be highly suitable for the establishment of C. selloana under both scenarios (Fig. 3, RCP 4.5 scenario).

Figure 3.

Maps of projected current and future suitability for Cortaderia selloana establishment in Europe and other countries of the Mediterranean region. Left: Projected current suitability. Right: Projected future suitability in the 2070s under Representative Concentration Pathways (RCP) 4.5, equivalent to a medium emissions scenario. Source: Brundu et al. (2021).

In this context, some goverments have begun to take measures against the invasion by C. selloana. In some countries, such as the UK or Spain, where the grass is extensively established, it has been officially classified as an invasive species, with prohibition to import, plant, maintain or commercialise (Bayón and Vilà 2019). The species is also in the European and Mediterranean Plant Protection Organization (EPPO) list of invasive alien plants (https://www.eppo.int/ACTIVITIES/invasive_alien_plants/iap_lists). However, the European Union (EU) has not yet included C. selloana in the List of Invasive Alien Species of Union concern (the Union list; Regulation (EU) 1143/2014 and subsequent updates), despite having approved in recent years a €3.5 million LIFE project to tackle the invasion in the Western Atlantic coast from 2018 (LIFE Stop Cortaderia, http://stopcortaderia.org/), which has been recently granted another aid of €6.5 million starting in 2023 (LIFE22-GOV-ES-Coop Cortaderia). Other EU projects tackled restoration of natural areas, where C. selloana was one of the main invaders (Basic Search on LIFE Public Databases). Consequently, we encourage the European authorities to implement an EU level plan to tackle the invasion by C. selloana. Although some local plans are being implemented, a common EU plan would be instrumental. To serve this purpose, a first step should be its inclusion in the Union list, which involves restrictions on keeping, importing, selling, breeding and growing of those species included in the list. This is especially important given that numerous suppliers are listed throughout EU Member states and that both seeds and dried plumes can be easily purchased via online suppliers (Brundu et al. 2021).

The C. selloana invasion is not yet as prominent in the Central or Northern EU countries and this might pose some conflict of interest within the Union. However, in the latest risk study report, the European Commission has identified this species with high risk and pointed out that a ban on sale could act to prevent further spread of the species (Brundu et al. 2021). According to the same report, C. selloana might be worth more than €200 million every year in Europe as a result of 20–25 million plants being cultivated at European nurseries. Our request to include C. selloana in international binding lists is also in line with the conclusions of the IUCN World Conservation Congress held in 2021 in Marseille, France, which included a call on governments in the EU to propose the inclusion of this species in the Union list (https://www.iucncongress2020.org/motion/005). Finally, it can only be paradoxical that Cortaderia jubata, a morphologically close species of the same genus not widely present in the EU, was included in the Union list in the second update entered into force on 15 August 2019. If the ecological facts were not sufficiently convincing, the recent findings proving the allergenic capacity of the plant reinforce the urge to implement an EU common plan against the C. selloana invasion. Our further conclusive message is that invasive plant species must be fought not only because of their ecological impact, but also because of their impact on human health. This adds another level of concern that will require the involvement of health governmental authorities, agencies, and policy makers.

We thank Fernando Rodríguez and the members of the Stop Cortaderia Project (especially Santiago García, Blanca Serrano and Hélia Marchante) for discussions, as well as Marta Uranga for the photograph of C. selloana in the Saja-Besaya Natural Park of Cantabria. We are also grateful to Giuseppe Brundu for his helpful suggestions.

DL and JAC were funded by the Basque Government (IT1487-22). The authors have declared that no competing interests exist.