<b>Dataset: Weather Surveillance Radar measured nocturnal insect emergence rate in the UK, 2014-2021</b>

We process dual-polarisation data from nine radars into spatially explicit time series of nocturnal insect emergence rate over 19,242 km² of England from 2014–2021, comprising 310,452 emergence events. Weather surveillance radar provides a new, low-cost, standardised measure of landscape-scale ‘source strength’ — the degree to which a landscape provides habitat from which insects can reproduce and disperse into the wider landscape.</p><p dir="ltr">3.

Emergence rate was strongly related to land cover. Doubling the proportion of seminatural relative to farmed land beneath a sampling column was associated with a 38.8% increase in emergence rate (95% confidence interval: +28.2% to +50.3%), consistently across radars and robust to sensitivity analysis. Built-up cover was weakly negatively associated with emergence rate, except in North London, which appears to be a stronger insect source than the surrounding green belt.</p><p dir="ltr">4.

Associations between agri-environment scheme expenditure and emergence rate were inconsistent across model specifications and radars. Evaluating the landscape-scale causal effect of agri-environment schemes across 56 before-after control-impact natural experiments involving paired intervention and control sites, we find no evidence of a positive causal effect of agri-environment scheme investment at 300, 500, 700 or 900 m above ground level.</p><p dir="ltr">5. <i>Policy implications.</i> Agri-environment schemes appear not to be increasing nocturnal insect source strength at landscape scale, whereas seminatural habitat is associated with substantially higher insect production — evidence favouring land sparing over sharing in the design of agricultural subsidies.

We present an approach pairing weather surveillance radar entomology with econometric impact assessment methods, applicable to large-scale conservation interventions generally. Around 1,500 weather radars operate worldwide. We show this infrastructure can be repurposed for conservation impact assessment.</p>