Revisiting biosecurity actions with hindsight: estimating the realised economic value of a historic medfly eradication

Biosecurity decision-making typically weighs up predicted future outcomes and impacts, but only rarely do we look back to assess and learn from historical decisions. Here, we quantified the contemporary benefits realised from a successful biosecurity action informed by over 100 years of subsequent economic data. New Zealand’s 1907-08 eradication of invading Mediterranean fruit fly (medfly) incursions facilitated ongoing access to premium fresh fruit markets. Our results estimate cumulative losses to 2020 for apple and kiwifruit exports, had medfly not been eradicated, at 7.6 to 10.2 billion NZD 2022 equivalent. The greatest economic harm would have been loss of market access for kiwifruit exports, which did not even begin until seventy years after the 1907-08 eradications. This example demonstrates massive time-lagged benefits from a biosecurity action and informs the long-term considerations that biosecurity managers regularly face in deciding how to respond to incursions of exotic organisms.