The Importance of In-Field Habitats and Biodiversity in Agroecosystems
Agricultural fields cover nearly one-third of the European landscape, serving not only as production areas but also as crucial habitats for a diverse array of species. This includes segetal flora (plants thriving exclusively among crops), facultative arable plants, soil fauna, insects, and farmland birds – all of which are adapted to the conditions provided by traditionally managed agricultural areas. These farmland species have significant functional roles in maintaining agroecosystem health, such as supporting soil fertility, pollination, and natural pest control.
However, over the past 70 years, there has been a substantial decline in biodiversity across taxa and ecological guilds in agricultural landscapes. One of the primary drivers of this decline is the widespread use of pesticides, which can have both direct and indirect effects on non-target species. Direct effects occur when non-target species are directly exposed to pesticide overspray, residues, or off-field drift, impacting their population abundance. Indirect effects may arise through altered food web interactions or changes in competition and facilitation processes.
Shortcomings in the Current Regulatory Framework
The European Union’s pesticide regulation, Regulation (EC) No. 1107/2009, requires that pesticide products placed on the market do not have unacceptable impacts on the environment, including non-target species and biodiversity. However, the current risk assessment framework has several critical shortcomings in addressing the impacts of pesticides on in-field habitats and associated flora and fauna.
The main issues are:
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Insufficient Consideration of In-Field Risks: The current risk assessment does not adequately address the direct effects of pesticides on non-target terrestrial plants (NTTP) and non-target arthropods (NTA) within the in-field (cropped) area. For NTTP, the risk assessment only considers off-field exposure via spray drift, omitting the in-field habitat. For NTA, the in-field risk assessment allows for up to 50% initial effects on reproduction or mortality, and a “potential for recolonisation or recovery within one year” – which may be insufficient to protect species that are heavily dependent on insect availability within a critical time window, such as farmland bird chicks.
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Lack of Consideration for Indirect Effects: The current risk assessment framework largely ignores the potential indirect effects of pesticides on higher trophic levels via alterations to the food web. Declines in NTTP and NTA populations, both in-field and off-field, can have cascading effects on consumer species, including farmland birds and mammals.
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Inadequate Representation of Realistic Field Conditions: The risk assessment is based on standard laboratory studies and does not adequately consider factors such as the cumulative impact of multiple pesticide applications, the lack of refugia in homogenized landscapes, and the non-representativeness of the test species for assessing risks to the overall protection goal.
Proposed Approach to Assess In-Field Risks
To address the shortcomings in the current risk assessment framework, a workshop was organized in July 2023 by the German Environment Agency (UBA), the UK Game and Wildlife Conservation Trust (GWCT), and experts from the German Academy of Sciences Leopoldina. The workshop aimed to develop a feasible method to assess the direct and indirect effects of in-field pesticide exposure within the existing regulatory context.
The proposed approach involves a two-step assessment:
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Checking for Toxic Effects on NTTP or NTA: If the available toxicity data for the pesticide product indicates toxic effects of more than 50% on in-field NTTP or NTA species at the intended field rate, a potential for unintentional adverse effects on species at higher trophic levels and overall biodiversity is expected.
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Evaluating Broad-Spectrum Activity: If the pesticide product has a broad-spectrum activity, i.e., the effects on NTTP or NTA communities are non-selective (affecting more than one family or order, respectively), a high likelihood for a significant impairment of the ‘food web support’ function is concluded.
When both conditions are met, the proposed method indicates that the in-field exposure of the pesticide use under assessment could lead to unacceptable direct effects on non-target species in-field and subsequent indirect effects on the food web.
This approach utilizes the currently available ecotoxicological data and does not require additional animal testing, making it a feasible option within the existing regulatory framework. It also provides a transparent and scientifically sound basis for risk managers to identify the necessary risk mitigation measures.
Implementing the Proposed Approach and the Need for Further Improvements
The proposed assessment method addresses a significant gap in the current risk assessment framework by focusing on the direct and indirect effects of in-field pesticide exposure. However, it is essential to note that this approach is not a comprehensive solution to the challenges faced in the regulatory assessment of pesticides.
There are several other critical issues that need to be addressed, including:
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Limitations in Assessing Exposure Routes and Effects: The current risk assessment considers only certain effects and exposure routes, neglecting aspects such as oral exposure by ingestion of contaminated food, direct overspray, and growth effects for NTA, as well as run-off exposure and reproductive endpoints for NTTP.
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Representativeness of Test Species: The use of a limited number of standard test species, such as a mite and a parasitic wasp for invertebrates, raises concerns about their ecological representativeness for the entire non-target community.
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Accounting for Additional Stressors: The risk assessment is primarily based on single-species tests performed under ideal laboratory conditions, failing to consider the increased sensitivity of species in natural habitats due to interactions, predators, and other stressors.
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Addressing Cumulative and Mixture Effects: The current risk assessment focuses on the effects of individual pesticide products, neglecting the impacts of spray series, tank mixtures, and specific landscape contexts.
Addressing these limitations would require more fundamental changes to the regulatory framework, going beyond the introduction of the proposed assessment method. Nonetheless, the successful implementation of the proposed approach within the existing system is an important step in reducing the in-field impact of pesticide products on biodiversity and ecosystems.
Towards a More Sustainable Agricultural Paradigm
While improving the regulatory assessment of pesticides is crucial, it is not sufficient to drive a transformation towards a more sustainable agricultural system. Additional profound changes are necessary, including measures to reduce pesticide use and risk at the national and farm levels.
Strategies such as expanding organic farming, implementing agroecological methods, and promoting sustainable regenerative farming practices have the potential to minimize pesticide impacts and support the recovery of insect populations and other biodiversity. However, the adoption of these approaches is still limited, and further efforts are needed to establish and refine guidelines, directives, and incentives to facilitate their wider implementation.
Adopting a more holistic and systems-based approach for ecological risk assessment, including better collaboration among various stakeholders, is vital to develop a more sustainable agricultural paradigm. Ongoing EU research and innovation projects, such as the Partnership for the Assessment of Risks from Chemicals (PARC), are working towards a new generation of risk assessment that better protects biodiversity within and beyond the current legal framework.
By addressing the gaps in the current risk assessment, implementing effective risk mitigation measures, and promoting the transition to more sustainable farming practices, the EU can take significant steps towards safeguarding the biodiversity and ecological integrity of its agricultural landscapes.