Connecting ecosystems from mountains to the sea in a changing climate

Angled aerial view of wetlands near a sandy coastline
Climate-induced changes to precipitation and streamflow affect freshwater dynamics from the mountains to the ocean, influencing rivers, estuaries, and coastal habitats. (Photo: Dan Polhemus)

Freshwater is a critical driver for island ecosystems. In Hawaiʻi, though rainfall intensity has increased, total rainfall has been on the decline for the last two decades and, as a result, streamflow has also been reduced.  The changes in dynamic patterns of streamflow could result in impacts to river, estuarine, and coastal habitats. In turn, these changes also affect the nine native Hawaiian aquatic species found in these habitats at different stages of their amphidromous life cycle (in which they migrate from fresh to salt water or vice versa).

To examine how changes in streamflow regime have impacted habitat quality for native migratory aquatic species, an ongoing project has been examining statewide long-term stream records and found a general drying across islands with a significant decline in baseflows in recent decades (1987-2016). This project is building hydrological models and connecting the stream dynamics with biological data to understand the climate impacts on stream habitats, and any connections to downstream estuaries and coastal ecosystems. Results will develop and improve tools to prioritize conservation efforts for Hawaiian aquatic ecosystems from ridge to reef (mauka to makai).

Broadening the reach of this concept, the research team of this project will connect with like-minded researchers in Alaska to explore and develop a parallel study addressing changes in aquatic ecosystems from mountain to sea in Alaska and exploring how those changes compare to ones in the ridge-to-reef ecosystems in Hawaiʻi. This research project has arisen explicitly from discussions with local stakeholder groups (e.g., Commission on Water Resource Management, Hawaiʻi Fish Habitat Partnership, National Fish Habitat Partnership) about science needs for aquatic ecosystems to manage water resources better in current conditions and prepare for projected changes. Preliminary results will be presented to stakeholders to determine the most useful format for final dissemination to user groups.





Yinphan Tsang
Associate Professor of Natural Resources and Environmental Management, UH Mānoa


Tim Grabowski
Cooperative Fishery Research Unit, USGS


Yu-Fen Huang
Department of Natural Resources and Environmental Management, UH Mānoa
Leigh Engel
Department of Natural Resources and Environmental Management, UH Mānoa


Abigail J Lynch
Climate Adaptation Science Centers
Gordon Smith
U.S. Fish and Wildlife Service
Ayron M Strauch
State of Hawaiʻi Department of Land and Natural Resources
Glenn R Higashi
State of Hawaiʻi  Department of Land and Natural Resources