Ecological Drought in the Hawaiian Islands: Unique Tropical Systems Are Vulnerable to Drought
Hawaiʻi is a state of dramatic landscapes, seascapes, and ecosystems. The extreme topographic gradients and highly seasonal weather patterns that characterize the island chain have resulted in a landscape that is richly diverse and supports an abundance of unique species. In fact, 90% of Hawaiʻi’s plants and animals are found nowhere else on Earth. Native Hawaiian cultural practices are closely tied to the natural world, as is the quality of life for all of the islands’ communities.
Though one of the wettest places in the nation, Hawaiʻi has dramatic gradients in water availability, and drought poses a central threat to many of the state’s ecosystems and communities. Long-term records show a drying trend over the past 500 years, with an accelerated rate of drying over the past 160 years.
In order to effectively manage Hawaiʻi’s ecosystems, agricultural systems, and human communities, managers require information on how droughts have changed over past centuries, how drought impacts ecosystems, and how drought interacts with other threats – such as invasive species and wildfires.
The Department of the Interior Pacific Islands Climate Science Center (CSC) is working to address these information gaps in Hawaiʻi and across the U.S.-Affiliated Pacific Islands. As part of this effort, a group of climate and ecological experts from Hawaiʻi, as well as resource managers, met in March 2017 to discuss the issue of drought in the state. During this workshop, the group identified several core challenges posed by drought:
Drying trends are accelerating Hawaiʻi receives nearly one foot less rainfall today than it did 100 years ago. These declines vary both spatially and geographically – declines are larger in the dry season than the wet season, and on the leeward side of islands (which normally experience drier conditions).
Drought reduces streamflow and increases the likelihood of wildfires Along with rainfall, streamflow has also declined over the past century, with implications for groundwater storage – which supplies 99% of Hawaii’s drinking water. Meanwhile, the area burned by wildfires has increased. Drought increases the likelihood of wildfire, which in turn kills native plants and supports the spread of fire-adapted (and often fire-promoting) invasive species.
Iconic imperiled species are on the brink Together, drought, wildfire, and invasive species threaten many of Hawaii’s iconic plants and animals. When coupled with land use change and the spread of diseases facilitated by warming temperatures, maintaining native species and their habitat is a key challenge facing the state’s natural resource managers.
Despite these challenges, the group agreed that effective management can limit the impacts of drought, reduce wildfire risk, protect native species, and sustain the delivery of the critical goods and services that support Hawaiʻi’s ecosystems and communities. Learn more about ecological drought in Hawaiʻi here
Additional Information This workshop was hosted in partnership by the Pacific Islands CSC, the University of Maryland Center for Environmental Science Integration & Application Network, and the USGS National Climate Change and Wildlife Science Center. The workshop was the sixth in a series of eight workshops held across the U.S., each in a different region. Each workshop results in an informational newsletter that synthesizes the current understanding of ecological drought in the region. Learn more about ecological drought in other regions of the U.S. here >>
Photo: North Kohala District, Hawaii - Credit: Alan Cressler