Hawaiʻi’s ecosystems and agriculture face growing threats from invasive species, with about 20 new insects and 100 new plants arriving each year, undermining the islands’ ecological, cultural and economic foundations. However, a new report from the University of Hawaiʻi Economic Research Organization (UHERO) shows that efforts to use biological control—the introduction of natural enemies to suppress invasive pests—on invasive species are delivering exceptional returns on investment while offering a sustainable, long-term solution for invasive species management.
The UHERO report examined three pests: coffee berry borer (CBB), erythrina gall wasp (EGW) and fireweed. Each threatens a key sector or resource: Hawaiʻi’s premium coffee industry, dryland forests and cultural heritage, and the cattle industry.
Coffee berry borer
Hawaiʻi-grown coffee faces major losses from CBB, with current management—frequent fungal sprays—costing farmers up to 12% of profits. Modeling shows that introducing the biocontrol agent Phymastichus coffea could generate $32–142 million in net benefits over 50 years, with breakeven in 1–2 years, even under conservative scenarios. The long-term economic gains far outweigh the upfront investment, offering a sustainable solution for the state’s coffee industry.
Erythrina gall wasp
The invasive erythrina gall wasp, arriving in 2005, devastated Hawaiʻi’s wiliwili trees, threatening both ecosystems and cultural practices. The release of Eurytoma erythrinae in 2008 restored 90% of sampled trees by 2011, with a second agent, Aprostocetus nitens, planned to bolster suppression. Over 50 years, the program is projected to generate $27.2 million in benefits with a benefit-cost ratio of 24.0 (meaning every $1 spent is estimated to return $24 in value).
Fireweed
Fireweed (Senecio madagascariensis) spread rapidly across Hawaiʻi rangelands, reducing forage and forcing costly management choices for ranchers. The fireweed moth (Secusio extensa), introduced in 2012, has provided partial suppression, with long-term benefits estimated at $5–24 million over 50 years and benefit-cost ratios of 2.0–9.2.
“Across all three case studies, we find that biocontrol delivers net positive economic returns, even when accounting for the research, testing and release costs,” UHERO wrote. “Perhaps more importantly, benefits accumulate over time.”
UHERO is housed in UH Mānoa’s College of Social Sciences.
