Hawaiian honeycreepers, a group of birds native to Hawaiʻi, include a range of threatened and endangered species that have experienced extinctions, population declines, and limited elevational distribution due to avian malaria. Honeycreepers, including the iconic ʻIʻiwi, are particularly susceptible to malaria, which is transmitted by the Southern House Mosquito. Rates of infection are generally lower in cooler temperatures, which has driven Hawaiian honeycreepers to higher elevation forests where transmission is limited. However, future changes in temperature and rainfall are predicted to expand the range of mosquitos, and the malaria they carry, to high-elevation forests and intensify malaria infection at lower elevations. This could result in future extinctions and a decrease in avian biodiversity in Hawaiʻi, which could have far-reaching ecological impacts. 

To address this threat, scientists funded in part by the Pacific Islands CASC are exploring whether gene editing, a form of facilitated adaptation, may offer a solution. In facilitated adaptation, genetic engineering is used to endow animals with adaptive traits that make them more resilient to climate change. Gene editing has benefited humans by improving crops, treating disease, and providing targeted medical therapies. If malaria-resistant honeycreepers can be developed, facilitated adaptation may be a feasible option for the reestablishment of abundant avian populations in Hawaiian forest ecosystems. While this approach has significant technical challenges and upfront costs, it may offer a more permanent solution to the rising threat of malaria compared to landscape-level mosquito control strategies, which require costly long-term efforts. 

In a recent study, researchers employed an epidemiological model to evaluate the release of malaria-resistant honeycreepers in the eastern flank of Mauna Loa volcano in the southeast corner of Hawaiʻi under projected future climate change scenarios. Three native species – the Hawaiʻi ʻamakihi, ʻApapane, and ʻIʻiwi –were studied in a 96-year simulation to predict the changes in bird and mosquito dynamics throughout the 21st Century. Results show that, depending on multiple factors, malaria-resistant honeycreeper populations may not be practical in high-elevation forests, but population recovery in mid-elevation forests could be feasible. More gene-edited birds would need to be released in high-elevation areas compared to mid-elevation areas, in order to make populations malaria-resistant. However, because forest birds move seasonally between high- and mid-elevation areas, a resistant population at mid-elevation could help establish resistant populations at high elevations in the southeast corner of Hawaiʻi and may help ʻIʻiwi populations across the Hawaiian Islands.  

Conservation strategies that use facilitated adaptation to rescue Hawaiʻi’s honeycreeper populations will need to face rigorous scientific, logistical, and social analysis before being implemented. However, this study shows that the release of malaria-resistant honeycreepers is a potentially viable solution for natural resource managers to consider as part of their efforts to preserve Hawaiʻi’s unique biodiversity. 

This research is a product of the Pacific Islands CASC project Vulnerability of Hawaiian Forest Birds to Climate Change and was funded in part by USGS Ecosystems Mission Area. 

This news announcement was written by Gina Fiorile, National CASC Science Communication Specialist.