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Rare Plant Populations in Hawai'i: Addressing Climate Change-Driven Risks

Project Summary

Hawai‘i is home to many rare and endemic plant species, and is also known for its highly variable climate and topography. Climate change is causing warmer, drier conditions, particularly at high elevations. In addition, periodic El Niño (ENSO) events typically bring drought during Hawai‘i’s rainy season and can have major ecological impacts, particularly at high elevations. The interaction of climate changes and ENSO events are producing exaggerated effects. The last big ENSO event in 2010 strongly impacted some rare plant populations, particularly those found in Hawai‘i Volcanoes National Park. Current models project that changes in temperature and moisture regimes over the coming decades will cause dramatic range shifts and population reductions for many native plant species. Such changes create a perilous situation for species with small population sizes within a limited geographic range.

In 2010 the National Park Service started a project to help rare plant species in Hawai‘i Volcanoes National Park and Haleakalā National Park survive as the climate changes. This project will establish satellite populations of 36 rare and endangered species within their modeled ecological range to increase their population size and geographic range. In so doing, this multi-park project will build capacity among these species to persist in a changing climate.

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Project background and scope

In Hawai‘i, climate change projections indicate a 10-20% reduction in winter rains and a 5% increase in summer rainfall due to changes in the trade wind patterns. These changes are predicted to cause dramatic shifts that may render many currently suitable areas no longer hospitable for rare species. In addition, disturbances such as hurricanes and fire are projected to increase with climate change, and could further stress rare plant populations. In response, managers could increase populations of rare plants with limited natural dispersal capacity and expand their distributions across their ecological ranges to increase their capacity to respond to habitat changes and disturbance.

The National Park Service at Haleakalā National Park and Hawai‘i Volcanoes National Park have combined resources and know-how to give three dozen species a fighting chance to remain on the planet in the midst of climate change. Current models project that changes in temperature and moisture regimes over the next decades will cause dramatic range shifts and population reductions for many native plant species. Such changes create a perilous situation for species with small population sizes within a limited geographic range. The focus of this project is to establish satellite populations of 36 rare and endangered species within their modeled ecological ranges.

Although climate change presents new challenges, the survival of rare plant species has always been a concern. Previous projects have centered on stabilizing existing rare plant populations where they have persisted. Still, many of the selected species number less than 50 individuals and remain geographically isolated. Park resource managers have worked to locate individual plants and populations, collect plant material, and develop effective propagation techniques. Managers in both parks have conducted planting efforts to boost the numbers of 135 different plant species, and restore biodiversity. Plant establishment has focused primarily on fenced, ungulate-free areas near remnant populations or in adjacent areas containing similar habitats. These planting projects have been limited to sites near documented occurrences (current and historical) and do not necessarily reflect the actual ecological range that these plants may have occupied in the past and could occupy now.

This project builds upon earlier work by expanding rare plant populations across a wider ecological range. It uses habitat modeling to identify the most suitable ecological ranges for rare species and establish rare plant populations in favorable micro-site conditions, building greater capacity for these species to persist in the wake of climate change. This is a proactive effort to keep these species alive.

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Project Process and Implementation

The two national parks used models created by Dr. Jon Price at the University of Hawai‘i to determine suitable ecological ranges for different rare plant species. The habitat models combine information on historical plant occurrences with habitat features such as soil/substrate type, elevation, temperature, and moisture conditions to determine potential suitable habitat locations for each species.

The parks are using these model results to help select planting locations. Efforts at both parks focus on expanding rare plant populations in subalpine habitats, dry ‘ōhi‘a woodlands, and mesic/wet montane zones where climate change is most likely to cause dramatic habitat shifts. On Haleakalā, these efforts include a collaboration with the state of Hawai‘i Plant Extinction Prevention Program to establish populations on state-owned protected areas adjacent to the park. The species selected for expanding populations were those for which successful propagation and planting techniques have already been developed and plant survivorship has been found to be strong.

Project Outcomes

The project is ongoing, and the ultimate goal is to plant 14,200 seedlings. Seeds or cuttings have already been collected for all of the 36 target species, and thousands of seedlings are being propagated in park greenhouses. To date, both parks have made significant progress by planting nearly 6,500 seedlings of 32 species at multiple sites, and the project is on track to accomplish its goals by the winter of 2016.

Project challenges and lessons learned

The project is ongoing; increased monitoring of outplanting successes and failures will provide critical information about the microclimates in which these species do best.

https://www.fs.usda.gov/ccrc/adaptation/adaptation-examples/rare-plant-populations-hawaii-addressing-climate-change-driven-risks