The troubling use of plastic habitat structures in freshwater ecosystems – or when restoration is just littering.
The utilization of using plastics for ecosystem restoration – plastic panels and pipes – is gaining popularity, but scientists note that this “evidence base supporting the use of plastic structures in freshwater systems is limited in terms of ecological benefit and assurances that the use of plastics does not contribute to pollution via plastic degradation or leaching.”
The report, The Ecological and Pollution Risks of Plastic Structures in Freshwater Habitat Restoration: A Call for a Science-Driven Approach, reveals the increasing usage of plastic structures for freshwater ecosystem restoration, a trend that scientists warn may inadvertently contribute to pollution and biodiversity decline. The study underscores the need for science-based solutions to ensure that restoration activities do not lead to unintended environmental harm.
Freshwater ecosystems are under significant pressure due to habitat alteration and loss, contributing to a severe reduction in biodiversity. As the report noted, the losses have been so extreme that protection and restoration of freshwater systems are included in the “emergency recovery plan” for freshwater biodiversity.
Scientists highlight that while the use of structural aspects of freshwater habitats such as woody materials has demonstrated some ecological benefits, there is a lack of robust evidence supporting the ecological value of artificial plastic structures. This lack of evidence presents a serious concern as the full life cycle of these plastic structures and their potential environmental impact are not being considered fully.
“Ensuring that such efforts benefit freshwater and in no way harm aquatic life should be paramount to those engaging in such restoration and habitat enhancement efforts,” the authors argue. However, they point out that the addition of plastic structures, without a decommissioning plan in place, could be seen as littering the ecosystems.
There is a historical context to these concerns. About four decades ago, there was a surge of interest in using anthropogenic materials, including tires and warships, for artificial reefs in marine ecosystems. But over time, studies showed that such materials could release contaminants, leading to more caution about what is placed in the ocean.
Unfortunately, the use of plastic materials in freshwater habitats appears to be gaining momentum. Yet, scientists warn of similar concerns to those raised about marine artificial reefs, particularly about the pollution risks and the true ecological value of these plastic structures.
What does plastic restoration mean for fish?
Fish are frequently the intended beneficiaries of artificial habitats, with these plastic structures being designed to offer them shelter and breeding grounds. However, there’s an inherent complexity in truly determining whether these structures are beneficial or harmful to fish populations. Some studies suggest a potential short-term benefit as fish are attracted to the novelty of these habitats, but the long-term effects are less understood.
Studies have shown that survival and growth rates of fish in artificial habitats do not differ significantly from those in natural habitats. However, this data is typically taken from fisheries enhancement efforts where plastic structures are used, and it is not applicable in a broader context where the goal is ecosystem restoration. Also, these studies often lack appropriate controls and fail to differentiate between attraction and production, and do not typically investigate impacts on other organisms or ecosystem processes.
Artificial habitats may also be leading to overfishing. The local concentration of fish around artificial structures makes them an easy target for anglers, which could lead to overexploitation of these populations.
A Call for Better Policy
The use of plastic materials in aquatic restoration projects remains largely unregulated. With a mounting body of evidence suggesting these practices are neither beneficial to the ecosystem nor to the fish populations they’re meant to serve, a call to policy makers is warranted. The need for better regulation and oversight in this area is clear. As we aim for true restoration and conservation, our policies should align with our ecological goals. Artificial structures made of plastic should not be labeled as conservation or restoration projects. Indeed, funding bodies that support conservation and restoration should be more vigilant about not supporting projects that involve the use of plastics in aquatic environments. Policymakers should ensure that any restoration or conservation activity is grounded in sound ecological principles and that any potential negative impacts, such as the introduction of invasive species or pollution, are thoroughly considered and addressed.
The researchers advocate for a science-based approach in freshwater restoration efforts, stressing the need to “embrace natural materials.” They underline the importance of including relevant actors in decisions about materials used for restoration and maintaining a focus on minimizing potential long-term harm. The authors unequivocally state, “Restoration of freshwater ecosystems is critically important, but those efforts need to be guided by science and not result in potential long-term harm.”