Risk of pesticides pollution (Tang et al. 2023)

Source: Tang et al. (2021), Nature Geoscience Year: 2015 Category: Physical risks · Enabling services · Water condition Coverage: Global Format: Raster grid Used in risk analysis: Yes — gates Enabling services

What it shows

This layer estimates the geography of environmental pollution risk from agricultural pesticides. Pesticides protect food production but are also pervasive pollutants that affect water quality, biodiversity and human health. The layer maps where pesticide residues in the environment are likely to exceed safe concentrations, helping to identify catchments where agricultural activity poses a heightened risk to freshwater systems and surrounding nature.

How it is built

The risk surface is derived from a global database of pesticide applications combined with a spatially explicit environmental model, covering 92 active ingredients across 168 countries. A location is treated as at risk where modelled residues exceed the concentration at which no effect is expected, and at high risk where they exceed that threshold by roughly a thousandfold. The published analysis finds that around 64% of global agricultural land is at risk from more than one active ingredient and about 31% is at high risk, with high-concern catchments identified in South Africa, China, India, Australia and Argentina. The result is a global grid of pollution-risk values.

How to read it

Higher values indicate greater estimated pesticide-pollution risk, meaning residues are more likely to exceed safe environmental concentrations and to affect water quality and biodiversity. Lower values indicate limited expected pesticide pollution. The layer is most meaningful over agricultural land, where pesticide application is concentrated.

Class thresholds

The underlying quantity is a dimensionless pesticide-pollution risk score — the base-10 logarithm of the ratio between modelled environmental pesticide residues and the no-effect concentration (the exposure / no-effect ratio). The layer is symbolised as a continuous gradient rather than discrete classes; the colour ramp runs over the score domain 0 to 6.1, where each unit corresponds to one order of magnitude in the residue / no-effect ratio:

A site is flagged on the Enabling services dimension (Water purification) when the layer value is above 3 — i.e. it reaches the "high risk" level where modelled residues exceed the no-effect concentration by about a thousandfold.

How these thresholds were set. The two anchor points — "at risk" where residues exceed the no-effect concentration and "high risk" where they exceed it by three orders of magnitude — follow the methodology of Tang et al. (2021, Nature Geoscience), who define risk as a ratio of predicted environmental concentrations to no-effect concentrations across 92 active ingredients. Darwin reproduces that published risk score as a continuous surface and sets the high-risk flag at the paper's three-orders-of-magnitude threshold; the intermediate breaks are not discretised in Darwin's configuration.

Reference: Tang et al. (2021), Nature Geoscience — nature.com/articles/s41561-021-00712-5.

Source

Tang et al., global assessment of environmental pesticide-pollution risk across 92 active ingredients and 168 countries, published in Nature Geoscience.

Comparison with the WWF Risk Filter Suite

This layer contributes to WWF Biodiversity Risk Filter indicator S2_2 Water Quality. WWF's water-quality indicator is a basin composite combining around nine freshwater datasets plus a marine signal, covering metrics such as biochemical oxygen demand, pathogens, nitrate, salinity and algal blooms. Darwin contributes a dedicated gridded pesticide-pollution signal to that theme; it is narrower in scope than WWF's full composite but more specific on pesticide pollution.

Risk analysis

A site is flagged on a dimension by combining a proximity trigger (this layer) with an activity trigger (the entity's ENCORE pressure/service). Proximity only → Potentially material; proximity and the matching ENCORE pressure/service is material → Very material; neither → Not material.

Legend

Symbolised field: Risk of pesticide pollution

Generated from darwin/layers/layer-risk-of-pesticides-pollution-tang-et-al-2023.toml and risk_indicator_pairs.toml (develop).