Life at the Top: Range Shifts of Four High Elevation Plants

This article was originally published in The Midden – Great Basin National Park: Vol. 22, No. 2, Winter 2022.

Focal species in clockwise order from top left: Nachlinger catchfly, Holmgren’s buckwheat, Pennel beardtongue, and Nevada primrose.

Wade Plafcan

By Wade Plafcan and Thomas Albright, Researchers, University of Nevada, Reno

Starting in fall of 2021, Great Basin National Park, the University of Nevada, Reno, and botanist Jan Nachlinger began a project to track changes in recent and future distributions of four rare alpine plant species.

Nachlinger catchfly (Silene nachlingerae), Holmgren’s buckwheat (Eriogonum holmgrenii), Nevada primrose (Primula cusickiana var. nevadensis), and Pennell beardtongue (Penstemon leiophyllus var. francisci-pennellii) (Figure 1) are all rare, herbaceous plant species of conservation concern. They occur in high elevation habitats and are endemics, meaning they are limited to Great Basin National Park or a few other ranges in eastern Nevada. Being limited to the highest elevations means that there is no room for them to move higher to escape increasing temperatures and having a limited endemic distribution means they don’t have ‘backup’ locations. This combination makes these species especially vulnerable to anthropogenic driven climate change.

To investigate these changes we mapped the recent, current, and predicted future distributions of these plants using two surveys separated by 15 years. Our primary objective was to detect changes in plant distribution and elevation a) between two surveys conducted in 2004-2006 and 2021, and b) between current and projected mid-21^st century climates. Additionally, we wanted to determine which environmental factors are most associated with plant habitat and identify locations important for conservation.

The veg crew works up in the alpine.

Wade Plafcan

With GPS units, sturdy boots, and lots of water, our team surveyed thousands of acres for plant locations in the summers of 2021 and 2022. On top of this, we were lucky that some forward-looking naturalists had conducted extensive surveys in 2004-2006. This gave us the opportunity to look for changes: places where the plants may be dying off and locations where new populations may be establishing. Overall, surveyors found about half of the plants occupying the same locations from the previous survey. This is an impressive survey effort, as finding a single plant sometimes takes 3-4 people on their hands and knees for several minutes! A comparative analysis between the two surveys revealed a potentially alarming trend. For all species, individuals found lower in the species’ elevational range were more likely to be absent, while the new and persistent populations occurred higher in elevation. This suggests an upward elevational range shift.

Research indicates many alpine species are moving up in elevation to track more suitable (often cooler) habitat conditions. Unfortunately, for species already occurring on the tops of mountains, they may ‘run out of real estate.’ For example, the new populations of Holmgren’s buckwheat occurred at a mean elevation of 11,150 ft compared to 10,500 ft mean elevation of the individuals lost since the previous survey. A vertical difference as tall as the Space Needle!

Example Species Distribution Model map for Nachlinger catchfly: range size change map showing year changes into 2050/2070 with four different climate projections. Colors indicate habitat changes with red indicating loss, yellow being stable, and green areas of gain. Black line is NPS boundary.

NPS

But what about conserving these species into the future? The best way to ensure the preservation of species vulnerable to human-driven climate change is to reduce the emissions of greenhouse gasses globally. Beyond those measures, an effective conservation plan for rare species needs to identify locations of suitable habitat to prioritize and target conservation efforts. Species distribution models (SDMs) give insight into these locations and allow for prediction of current and future habitat. SDMs relate a species’ geographic location with environmental variables to produce predictive distribution maps. Plant locations were matched with climate, topography, and soil variables. Through this process we were able to quantify which environmental variables were important for each species. Current habitat maps are useful for finding new populations and as an estimate of total current habitat.

To understand what might happen in the future, SDMs were projected into years 2050 and 2070. Multiple climate projections were used to hedge our bets on the uncertainty of future conditions. These projections included combinations of different amounts of greenhouse gas emissions, warming and both increasing and decreasing precipitation.

Results varied by species and by climate projection. Nachlinger catchfly is of most conservation concern, showing a potential loss of almost all favorable habitat by 2050. Pennell beardtongue may also lose a moderate amount of habitat and has the largest predicted increase in mean elevation, which could lead to habitat fragmentation over time. Holmgren’s buckwheat and Nevada primrose are predicted to be relatively stable and may even expand their habitat under some climate projections. However, contrary to the future models, the survey comparison results show these species may be experiencing upward range shifts already. Only time will reveal which method and analysis is more accurate.

Continued monitoring of these species will be important to track changes and verify model predictions. Monitoring climate change-altered precipitation levels will be of paramount importance, as the driest climate projection predicts substantial habitat loss for all species. Snow, precipitation, and temperature are very important variables for the biology and phenology of these species. Fortunately, the SNOTEL (Snowpack Telemetry) weather station, established in 2011 near Wheeler Peak, will provide great data on changes associated with these climate variables.

Our finding that range shifts from a warming climate may already be occurring is a bit jarring but not unexpected. Our hope for the future is that we can avoid the worst of climate change by reducing emissions globally, and that conservation biologists can help to ensure that species and habitats are protected in the right places to be able to weather the climate changes that do come our way.