Conservation efforts protecting Kauaʻi’s native forests yield significant returns in groundwater recharge (process of water replenishing underground aquifers), with each dollar invested producing an average of 593 gallons of recharged water, according to a study released in March 2025 by the University of Hawaiʻi. The study analyzed existing and potential conservation fence units and their impact on groundwater over a 50-year period.
Researchers found that protecting watersheds from invasive plants and animals, such as feral pigs and deer, is crucial for maintaining the island’s freshwater resources. Increased groundwater recharge ensures a steady supply of fresh water, vital for drinking and other essential needs.
The study, conducted by the UH Economic Research Organization (UHERO), Institute for Sustainability and Resilience and Water Resources Research Center, in partnership with The Nature Conservancy, revealed that areas with natural barriers, such as Wainiha and Nāmolokama, showed even higher returns, reaching up to 2,625 gallons per dollar.
Expanding conservation efforts to include proposed fenced areas could increase cumulative groundwater recharge from 21.4 billion to 34.4 billion gallons over 50 years, although the average return per dollar would slightly decrease. Mid-elevation areas were identified as providing the highest groundwater recharge benefits per dollar, as these regions are particularly vulnerable to invasive species.
Benefits of conservation in higher-elevation areas
The study also highlighted the long-term benefits of conservation in higher-elevation areas, where invasive species are expected to spread over time. Beyond groundwater recharge, watershed conservation contributes to biodiversity, reduces erosion and enhances climate resilience.
“The findings indicate that existing conservation efforts have been strategically implemented in high-impact areas, delivering significant returns in terms of groundwater recharge,” the report said. “Expanding these efforts would further enhance water security for the island.”
The report added, “This work contributes to a broader understanding of how conservation investments can be evaluated in hydrologic and economic terms, providing a framework for future decision-making regarding watershed management on Kauaʻi and beyond.”
Read the entire report on UHERO’s website.
UHERO is housed in UH Mānoa’s College of Social Sciences.
