NAU researchers awarded DoD grant to investigate invasive species impacting threatened, endangered plants  

The Department of Defense Strategic Environmental Research and Development Program (SERDP) has awarded Northern Arizona University a grant upwards of $1 million to support a five-year research project aimed at understanding the impact of invasive species on threatened and endangered (T&E) plants. Principal investigator Clare Aslan, director and associate professor for the School of Earth and Sustainability (SES), will work with Sara Souther, assistant professor in SES, and Karen Haubensak, associate research professor in the Department of Biological Sciences. By evaluating the effects of invasive foundational plant species on T&E plants, the researchers hope to develop effective control measures required of T&E species in future climate change scenarios. 

“Foundational invaders can alter the full function of an ecosystem, from the soils to the interactions,” Aslan said. “Such wholesale effects can diminish biodiversity and impact ecosystem function”. 

The research project aims to address the impact of invasive species on ecosystem structure and function. These “foundational invaders” can disrupt focal species interactions and alter the ecosystem dynamics, posing a significant threat to T&E species, particularly on oceanic islands. As a result, the project focuses on the largest DoD installation in Hawaii, the Pöhakuloa Training Area (PTA), which is home to a high number of T&E species. DoD lands have been found to support the highest occurrence of threatened and endangered species of all federal jurisdictions.  

“This is in part because installations are protected from development and other anthropogenic disturbances,” Aslan said. “The PTA contains populations of 20 endangered plant species, including some that occur only on that installation.” 

Aslan, a conservation biologist with expertise in critical species interactions, is building on her previous research in endangered plant species’ responses to invasive predators at PTA, which laid the groundwork for this comprehensive study. The project emphasizes the urgency of understanding how climate change, biological invasions and habitat loss impact biodiversity and natural systems. By identifying the critical factors impacting each focal species, the research team aims to assist managers in prioritizing and implementing effective conservation strategies. 

The team will employ various methods to collect demographic data on invasive and T&E plant species at the PTA sites. They will assess plant growth, survival and reproduction within populations of T&E plant species. Using quantitative models, they will project population growth rates for each species under different scenarios including the presence of invasive species, control efforts and climate-driven fire risk. These projections will be essential in understanding the complex dynamics between invasive species, T&E species and fire regimes.  

“We aim to provide information about the drivers of population declines among a suite of endangered species,” Aslan said. “We expect that different factors are at work for each species, but the commonalities we observe will help us better understand how environmental change is affecting species’ persistence in highly threatened environments.” 

The findings of this research project will provide valuable insights into the factors affecting the population dynamics of T&E species, which will help resource managers in their conservation efforts. One of Aslan’s goals for the project is to inform managers’ decisions regarding invasive species control, fire risk management and climate change adaptation.  

“A recent fire at the installation has impacted a significant portion of many species’ populations, further highlighting the urgency of understanding the needs of these endangered plants,” Aslan said. 

Developing a comprehensive invasive control plan that accounts for competition with T&E species, non-target effects of weed controls and fire risk are other key objectives of the project. By working closely with PTA managers, the research team aims to provide guidance and recommendations on the most efficient methods for monitoring T&E species populations. Collaboration with land and resource management agencies will ensure the practical application of research findings and enhances the effectiveness of conservation efforts. The research team’s expectations revolve around shedding light on the drivers of population declines among endangered species. By identifying commonalities and differences in the impacts of environmental change on various species, they hope to contribute to the field of community ecology and conservation ecology in general. The insights gained from this study will help guide conservation efforts and enhance our understanding of species persistence in highly threatened environments. 

The research team maintains an active collaboration with DoD managers, and the selection of focal species addresses the concerns and priorities of the Department of Defense, ensuring that the findings directly benefit land and resource management agencies. Continuous communication and knowledge exchange will facilitate the practical application of the research findings and strengthen the ongoing conservation efforts.  

“This work will require measuring, mapping and tracking the performance of hundreds of individual plants,” Aslan said. 

This NAU research project funded by the Department of Defense SERDP program represents a significant step forward in understanding the complex interactions between invasive species and Threatened and Endangered plants. By bridging the gap between scientific research and practical conservation, this study aims to safeguard the unique biodiversity of Hawaii’s fragile ecosystems while supporting the military mission of DoD installations on the islands.