Study by Hawaii researchers suggests expansion of taro farming could help save endangered Hawaiian stilts

While the number of endangered Hawaiian stilts, or aeo, has been on the rise in recent decades, the long-term outlook for the species is much more uncertain as sea level rise threatens to wipe out much of its best coastal habitat.

But a new study by a team of Hawaii researchers offers hope for the future of the long-legged, black-and-white waterbirds while suggesting greater food security in the islands with the expansion of traditional taro farming.

The research, to be published in the June edition of the science journal Anthropocene, indicates that restoring loi, or wetland taro fields, in certain areas across Hawaii could increase aeo habitat by 171% — even after accounting for losses due to sea level rise.

“Loi is amazing waterbird habitat,” said study co-author Melissa Price, a University of Hawaii at Manoa professor who runs the Wildlife Ecology Lab in the College of Tropical Agriculture and Human Resources.

Price said her lab has been studying the Hawaiian stilts for years, and the question kept coming up about how climate change would affect the species, along with Hawaii’s other endangered waterbirds, the Hawaiian coot (alae keokeo) and Hawaiian gallinule (alae ula).

“People kept bringing up the effect of sea level rise on habitat loss, but no one had quantified it,” she said.

With doctoral student Kristen Harmon leading the way, the study did just that, describing the loss of nearly 30% of prime nesting habitat by the year 2100 and what would suggest a corresponding decline of waterbird populations.

Ironically, the study’s findings come as the U.S. Fish and Wildlife Service is looking at a proposal to downlist the aeo — from endangered to threatened status — because of the recent trend of positive population estimates.

As the new research indicates, however, the species may actually be facing the eventual possibility of extinction without the helping hand of expanding nesting habitat.

The paper offers up a solution: loi farming.

It’s a bit of a controversial idea because not every wildlife scientist thinks a functional wetland taro field is acceptable waterbird habitat due to the presence of humans. But the truth is, according to Price, a healthy, well-maintained taro patch is the equivalent of prime wetland managed for wildlife conservation.

As many folks in the islands know, she said, stilts thrive in the vicinity of humans and are not easily startled by people they recognize.

“There’s an indigenous relationship with the waterbirds,” Price said.

While sea level rise is expected to swamp key nesting areas, it will also expand freshwater wetlands as the water table is pushed to the surface, creating opportunities to revive the practice of wetland farming, which once thrived across Hawaii in historic times.

The study indicates that nearly 29,000 acres of land will be suitable for loi cultivation under climate change. That’s a level comparable with historic levels of taro farming, according to biologist Natalie Kurashima, a paper co-author.

Recent estimates indicate only 610 acres are currently under taro cultivation in the islands.

Kurashima, integrated resources manager with Kamehameha Schools, is the author of a 2019 study that found that indigenous agriculture has the potential to play a major role in feeding Hawaii in the years to come. Her research found that traditional agriculture is resilient and capable of remaining viable even under the most severe future climate scenarios.

“Sustainable and resilient agricultural systems and practices like those found in indigenous agriculture will become more important as climate change worsens,” Kurashima said.

Climate change, she said, is expected to affect the shipping and energy infrastructure of Hawaii’s current import-dependent food system.

The state imports roughly 87% of its food, while the majority of agricultural products grown locally, such as coffee and macadamia nuts, are exported, according to the study, making the islands vulnerable to natural disasters or global events that disrupt shipments of food supplies.

Flooding and sedimentation are expected to increase as the climate warms, along with periods of intense drought, storm frequency and wildfires.

“Loi and wetlands have been shown to aid in slowing surface water flow, retaining sediment, increasing groundwater recharge, thus combating some of the impacts we’re already experiencing from climate change here in the islands,” Kurashima said.

Another co-author of the paper is climate scientist Chip Fletcher, associate dean and professor in UH Manoa’s School of Ocean and Earth Science and Technology.

“There is no scenario in which sea level does not keep rising for centuries. Nature is our best ally in meeting this challenge,” Fletcher said in a statement.

Others listed as study authors are Kawika Winter, an ecologist at the Hawaii Institute of Marine Biology, and Haunani Kane, a National Science Foundation postdoctoral fellow at UH Hilo.