# Mind the gap—national pesticide monitoring data needs for invertebrate effects assessments in English rivers

## TL;DR

The study highlights gaps in UK pesticide monitoring data and its impact on freshwater invertebrates in English rivers.

## Contribution

The paper identifies specific pesticides exceeding toxicity thresholds in rivers and highlights regional monitoring biases.

## Key findings

- Seven of nine high-risk pesticides exceeded effect concentrations in English rivers between 2000 and 2023.
- Anglian and Midland regions showed the most pesticide exceedances, possibly due to higher use and sampling bias.
- More sampling is needed in southern and northwest England to assess pesticide impacts on invertebrates.

## Abstract

Pesticides are an integral part of agriculture in arable and pastoral farming and in animal and pet care, but they have been shown to have detrimental impacts on biodiversity, including of freshwater systems. The United Kingdom (UK) has the 7th highest pesticide usage per area of arable land across 30 European and African countries assessed between the years 2000 and 2012 and thus an associated higher likelihood for impacts on riverine biodiversity. In our analysis of the UK’s 24-year national chemical monitoring program (WIMS database; years 2000 to 2023), we show that of the nine pesticides that pose the greatest likely threat to UK freshwater invertebrates based on concentrations measured in British rivers exceeding the lowest effect concentrations (ECs) in laboratory-based toxicity tests, seven pesticides have exceeded the ECs across England between the years 2000 and 2023. The Anglian and Midland regions of England that have the highest regional arable pesticide use recorded the greatest number of pesticides exceeding the ECs for aquatic invertebrates. However, this finding may also be influenced by the more limited sampling/monitoring bias across England, and greater sampling of southern and northwest rivers is needed to better establish the potential impact of pesticides on riverine invertebrate communities in those regions.