Headlines often mention climate change causing coral bleaching and sea level rise, but what happens to Hawai‘i stream life?
Changes in weather patterns affect the quantity and quality of the water, which has profound effects on our native stream animals. In the Hawaiian Islands, the total amount of rain is expected to decrease as the impacts of climate change manifest. However, the frequency and severity of storms are expected to increase. Rigorous studies have prompted us to anticipate that there will be more rain in the summer months (the “dry” season) and less rain during the winter months (the “rainy” season). This will cause significant variation in stream discharge, the amount of water flowing from the stream. This predicament also threatens the native stream fish, shrimp, and snails that rely on a connection to the ocean in order to complete their life cycles.
All of Hawai‘i’s native stream animals are amphidromous, which means larvae hatch in the stream then wash out to the ocean where they develop for up to a few months. The juveniles then return to the stream and mature into adults. Decreases in rainfall lead to more frequent drought conditions, which could interrupt this crucial stream-ocean connection. This occurrence limits both the larvae from washing out to the ocean as well as limiting juveniles from recruiting back up into streams. In addition, many stream animals become relegated to pools in times of low flow.