Risk mitigation measures for diffuse pesticide entry into aquatic ecosystems: Proposal of a guide to identify appropriate measures on a catchment scale

Abstract

Measures to mitigate the risk of pesticide entry into aquatic ecosystems are becoming increasingly more important in the management of hot spots of pesticide transfer; such management, for example, is required by the European Union's directive for the sustainable use of pesticides (2009/128/EC). Measures beyond those currently stipulated for pesticide product authorization may be needed. A concise compilation of the appropriate measures for users (that are primarily farmers but also, e.g., regulators and farm extension services) and a guide for practically identifying these measures at the catchment scale is currently not available. Therefore, a proposal was developed for a guide focusing on the most important diffuse entry pathways (spray drift and runoff). Based on a survey of exposure-relevant landscape parameters (i.e., the riparian buffer strip width, riparian vegetation type, density of ground vegetation cover, coverage of the water body with aquatic macrophytes, field slope, and existence of concentrated flow paths), a set of risk mitigation measures focusing on the specific situation of pollution of a water body catchment can be identified. The user can then choose risk mitigation measures to implement, assisted by evaluations of their efficiency in reducing pesticide entry, feasibility, and expected acceptability to farmers. Currently, 12 landscape-related measures and 6 application-related measures are included. The present guide presents a step toward the practical implementation of risk mitigation measures for reducing pesticide entry in aquatic ecosystems.

Erosion rills offset the efficacy of vegetated buffer strips to mitigate pesticide exposure in surface waters

“…For example, vegetated treatment systems (i.e., vegetated ditches or constructed wetlands) can effectively reduce pesticide exposure of downstream surface water stretches and thus overcome the limited risk mitigation potential of vegetated buffer strips in the field (Schulz, 2004;Stehle et al, 2011). It is however important to note that spray drift-related pesticide exposure of surface waters can effectively be reduced by wide buffer strips regardless of their specific characteristics such as presence of erosion rills or vegetation density (Bereswill et al, 2014). In addition, vegetated buffer strips generally denote valuable components of the agricultural landscape, which, for example, increase the local biodiversity of agroecosystems.…”

“…Moreover, we found that nearly half (i.e., 49.1%) of the total tributary flow lengths were bordered by parallel field paths or farm roads (i.e., paved or heavily compacted soil). These pathways or roads often concentrate the runoff from the orchards, which subsequently enters the tributaries via erosion rills (Altmayer et al, 2003;Bereswill et al, 2014) leading to high pesticide exposure in the receiving water bodies. However, including the presence of field paths and erosion rills in addition to buffer strip width and vegetation density into the overall evaluation of the theoretical retention performance achievable by the buffer strips (i.e., by assuming a high (N75%) pesticide retention for buffer strips (i) with a width N 10 m; (ii) a vegetation density category of ≥3; (iii) without parallel field paths or roads; and (iv) without erosion rills), only about 8% of the total buffer strip length is expected to provide effective pesticide runoff mitigation potential in the investigation area.…”

Insecticide concentrations in stream sediments of soy production regions of South America

“…Although regulation of pesticide mitigation measures often focuses on application practices, landscape level mitigation measures, such as requiring riparian buffer zones, may be easier to implement and enforce. Bereswill et al (2014) reviewed the efficacy and practicality of risk mitigation measures for diffuse pesticide entry into aquatic ecosystems, and ranked riparian buffer strips as highly effective for mitigating both spray drift and runoff, with high acceptability and feasibility. However, the implementation and enforcement of new riparian buffer requirements in Brazil has been difficult and controversial, especially in regions with small-scale production where a significant amount of a landowner's productive farmland could be lost with compliance (Alvez et al 2012).…”

Do Riparian Buffers Protect Stream Invertebrate Communities in South American Atlantic Forest Agricultural Areas?

“…Although regulation of pesticide mitigation measures often focuses on application practices, landscape level mitigation measures, such as requiring riparian buffer zones, may be easier to implement and enforce. Bereswill et al (2014) reviewed global data on the efficacy and practicality of risk mitigation measures for diffuse pesticide entry into aquatic ecosystems, and ranked riparian buffer strips as highly effective for mitigating both spray drift and runoff, with high acceptability and feasibility. However, the implementation and enforcement of new riparian buffer requirements in Brazil has been difficult and controversial, especially in regions with small-scale production where a significant amount of a landowner's productive farmland could be lost with compliance (Alvez et al 2012).…”