Drought research in Haleakalā National Park is featured in Discover Magazine

A CSP associate looks at the effects of El Niño–driven drought — specifically, fluctuations in the line that defines the upper limit of the Hawaiian cloud forest.

A research program led by Dr. Shelley Crausbay, a CSP associate, will be featured in the April 2016 issue of Discover Magazine, which showcases science in America’s national parks. This research is being conducted in Haleakalā National Park, located on the island of Maui in Hawaii. It focuses on the role of El Niño–driven drought in montane ecosystems and integrates information about plant community ecology, paleoecology, ecophysiology, and climatology. A major data source for the study is the Little HaleNet climate array, one of just a few tropical montane climate networks in the world that measures rainfall, air temperature, relative humidity, soil moisture, and photosynthetically active radiation.

HaleNetThis research relies on paleo and modern data to examine how changes in the frequency of El Niño–driven drought affect the forest line, which defines the upper limit of habitat for many endangered birds. Distribution models constructed using the paleorecord show the forest line fluctuating up and down slope over the past few thousand years in response to drought frequency. One critical factor in defining the upper limit of forests is atmospheric moisture; distribution models for the modern landscape show that this parameter impacts nearly half of all species. For example, ecophysiological data show that a single rainless day impacts Metrosideros polymorpha, the primary canopy tree in Haleakalā National Park, because of its sensitivity to atmospheric demand for moisture, which is higher above the forest line.

This work is especially relevant today. This winter (normally the wet season), the Hawaiian Islands have experienced a strong El Niño–driven drought, with seasonal rainfall deficiencies as high as 80 percent. By monitoring climate and ecophysiological response across the forest line ecotone during this drought, we can better predict whether the upper limit of the cloud forest will move up or down slope in our future.