The ‘extinction of experience’ describes the idea that humans are becoming progressively less likely to encounter nature in their daily lives (Pyle, 1993; Soga & Gaston, 2016). Our results partially support this idea: Google search interest for 210 invasive plant species over a 10-year period was positively and indirectly influenced by species’ state and national level abundance patterns (Figs. 1, 2). However, public search interest was most strongly and directly determined by species with greater human health risk and enhanced media coverage (through the number and tone of published articles). Together, these results suggest that public interest in invasive species in motivated primarily by direct consequences for health and well-being, and piqued not through natural encounters, but via exposure in the public media. Thus, increasing the media coverage of invasive plant species, and particularly articles that detail their negative impacts, could generate increased public awareness and ultimately affect invasive plant policy.
The quantity of media coverage is a demonstrably strong driver of public interest and behavior in other environmental issues. For example, heavy media coverage of droughts in San Francisco, California from 2005 to 2015 were linked to a subsequent decrease in urban water consumption (Quesnel & Ajami, 2017). In Japan, a dramatic increase in media coverage of global warming led to increases in public concern over anthropogenic warming (Sampei & Aoyagi-Usui, 2009). Similarly, invasive species that are reported on more frequently in local newspapers in Japan also have increased search interest in those same areas (Fukano & Soga, 2019). Increased media coverage is important because it can directly influence policy action. For example, invasive wild pigs are an increasing problem in the US, and the amount of congressional activity on policy to control them is directly linked to increased negative media coverage (Miller et al., 2018). In our study, 60 of 210 (29%) of the most common invasive plant species in the US generated no Google search interest over a 10-year period and had only 191 articles written about them over the same time-period (out of 70,963 articles, or only 0.27% of total media articles). The lack of media articles and subsequent lack of search interest is indicative of a substantial communications shortcoming in addressing the invasive plant problem in the US.
Most of our analyses show that negatively toned news articles about invasive plants garnered greater search interest, highlighting the role of negative advertising in environmental awareness campaigns. However, the use of negative media coverage to influence environmental issues is controversial. For example, in socially contentious environmental topics like climate change, some communication researchers believe that negative, fear-based messaging can effectively alter public behavior and policy action (Reser & Bradley, 2017). In contrast, negative media coverage of large predators can hinder their conservation and protection (Jacobson et al., 2012; Ostrovski et al., 2021; Sadath et al., 2013). In our study, purple loosestrife, garlic mustard, and kudzu (Pueraria montana) were some of the most negatively described species, with words like “aggressive,” “difficult,” and “dense” being among the most frequently used negative words. These species, however, were also some of the oldest and most abundant invaders (Fig. 1), and residence time has been shown to influence the range size and spread rate of invaders, highlighting the interactive role of multiple drivers in generating media coverage (Pyšek & Jarošík, 2005).
Some of the negative coverage and public interest in these invasive plant species can be traced to species with human health risks. For example, search interest in giant hogweed was relatively high and occurred largely throughout the US despite its relatively limited distribution (Figs. 1D, 3A). Giant hogweed produces a photoactive sap that can burn human skin when exposed to sunlight (Chan et al., 2011), resulting in widespread media coverage after a particularly notable incident widely reported on in July 2018 (Fig. 3B; 62–64). Indeed, “sap,” “poisonous,” “toxic,” “burns,” and “dangerous” were among the ten most frequently used words in the sentiment analysis on articles mentioning giant hogweed. A few grass species with high search interest in our study, like timothy grass (Phleum pratense) and bermudagrass (Cynodon dactylon), pose a health risk through their production of allergens (Fuchs et al., 1997; Liao et al., 2020). Similarly, common ragweed (A. artemisiifolia), a noxious invader in Europe, also produces allergens that have been linked as an important factor causing hay fever in North America, where it is native (Bassett & Crompton, 1975; Smith et al., 2013). Another common invader with high search interest was multiflora rose (Rosa multiflora), a species that by harboring infected ticks (Ixodes spp.), can amplify opportunities for transmission of Lyme disease pathogens (Adalsteinsson et al., 2018). Cheatgrass (Bromus tectorum), another invader with high search interest, increases the risk of wildfires in the western US (Bradley et al., 2018), posing a health risk to local residents (Black et al., 2017). Recent research suggests that articles detailing the higher health risks of invasive plants can motivate individual landowners to better manage invasive plants on their properties (Clarke et al., 2021), suggesting that a lack of public support for invasive species management can be traced to a lack of knowledge of these negative human health risks (Novoa et al., 2017).
Unexpectedly, national occurrences and other ecological plant traits influenced Google search interest not directly, but only through media coverage, again supporting the idea that interest arises from reporting and not from actual encounters in nature. Similarly, while we initially hypothesized that plants’ ability to form monocultures would make them more noticeable to the public, monoculture formation did not significantly predict the quantity of media coverage nor search interest. Search interest, however, did fluctuate seasonally (Fig. 3B), peaking in the summer when plants are productive and therefore most noticeable, suggesting that local observations could still be a key driver of search interest through time. Nevertheless, the number of media articles published over time also fluctuated seasonally (Fig. 3B), suggesting that media coverage could still be the main driver of search interest as suggested by the SEM. Importantly, however, analyses such as ours cannot reveal the potential for bi-directional or feedbacks within the proposed causal network. Thus, although public search interest is highest for invasive plant species written about more in the media, suggesting that media coverage drives search interest, it is also possible that increasing search interest simultaneously drives science writers to write more articles on species already garnering interest in a feedback loop. Other studies that analyzed search interest in and media coverage of invasive species also concluded that the relationship could be circular (Fukano & Soga, 2019), which is an avenue ripe for future investigation.