Abstract
The invasive apple snail (Pomacea maculata) appeared in 2010 in the Ebro Delta Natural Park, an important area for rice production and waterbird conservation in the eastern Mediterranean. To control crop damage, farmers stopped flooding their rice fields in winter, an agri-environmental scheme (AES) applied for more than 20 years in some European and American regions to favor flora and fauna from wetlands, including wintering waterbirds. Thus, apple snail control is controversial because of its potential side effects on international waterbird conservation efforts. Despite the fact that 10 years have passed since the first flooding limitations, and the alarms raised by the managers of the Natural Park, the side effects of apple snail management on waterbird conservation have not been evaluated. Here we fill this gap by analyzing a 35-year time series to assess whether abundance trends of 27 waterbird species, from five functional groups, decreased in the Ebro Delta after stopping winter flooding. We considered the effects of confounding local factors by also assessing trend changes in l’Albufera, a similar nearby not invaded wetland where flooding has not been interrupted. In addition, as a control of the positive effect of winter flooding, we also assessed whether abundance trends increased in both wetlands after applying this AES winter flooding. Our results showed complex and decoupled trend changes across species and geographical areas, without statistical evidences, in general or for any particular functional group, on the positive effect of winter flooding in both wetlands neither on the negative effect of its cessation in Ebro Delta. These results suggest the safety of this apple snail control in terms of waterbird abundance at a landscape scale. In addition, these results question, at least in two important wintering areas in Europe, the attractor role associated with the flooding agri-environmental scheme applied for decades.
Highlights
It is widely recognized that invasive species cause negative impacts on the environment, the economy and human health (Mack et al, 2000; Pimentel et al, 2000, 2005; Doherty et al, 2016; Diagne et al, 2021), and that, due to globalization, biological invasions are growing at a dizzying rate (Seebens et al, 2017, 2021)
To ensure that our inferences are robust and avoid spurious relationships due to local trend variations unrelated to winter flooding, we studied the changes in abundance trends of the same 27 species in l’Albufera Natural Park, another nearby Spanish wetland included in Natura 2000 network, and a key site for waterbird conservation
During the no agri-environmental scheme (AES) flooding period, 2010–2020, i.e., after the invasion of the apple snail and the cessation of winter flooding in the Ebro Delta, only in four out of 27 species the abundance trends decreased in the Ebro Delta, while they did not change in l’Albufera
Summary
It is widely recognized that invasive species cause negative impacts on the environment, the economy and human health (Mack et al, 2000; Pimentel et al, 2000, 2005; Doherty et al, 2016; Diagne et al, 2021), and that, due to globalization, biological invasions are growing at a dizzying rate (Seebens et al, 2017, 2021). Pesticides have been the most widely used practice to control and eradicate invasive and nondesirable native species, albeit with detrimental effects on the environment and biodiversity and on human health (Pimentel, 1971; Geiger et al, 2010; Beketov et al, 2013). These impacts prompted the regulation and eventual restriction of their use [e.g., European Union, 1991; European Union, 1992; OTA (US Congress Office of Technology Assessment), 1995]. It is essential to enhance our knowledge of the side effects of any management against invasive species, especially in fragile areas such as wetlands
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