Biologists Capture 40 Years of Climate Change on Endangered Montana Prairie

Bison resting in prairie grass at the National Bison Range in Montana. (Courthouse News photo / David Reese)

(CN) — In a research effort four decades in the making, experts have constructed a comprehensive picture on the health of the bunchgrass prairie, one of the most endangered ecosystems in North America.

Despite once being one of the most eminent ecosystems in the North American continent, particularly in the Rockies, intermountain bunchgrass prairies have found themselves on a steep decline in recent decades. Widely regarded as one of the most threatened ecosystems, bunchgrass prairies cover less than 1% of the land they once did and have gradually become drier, hotter areas in recent years.

Despite their diminished domain, bunchgrass prairies have often been neglected in studies looking to better understand how grasslands are responding to the ecological problems of today, leaving many to wonder what the future may hold for these fragile environments.

In an effort to help shed some light on how these endangered ecosystems have responded to these challenges, particularly amid the ongoing threat of climate change, researchers from the University of Notre Dame spent the last 40 years studying the National Bison Range in Montana — one of the largest bunchgrass prairies left in North America.

In studying this unique range — which has never been farmed and has been protected by the United States since 1908 — for so long, researchers made several crucial observations on the state of bunchgrass prairies in the modern era.

They revealed their findings in a study published Wednesday in the open-access journal PLOS ONE.

Perhaps one of the most startling findings researchers made during their 40-year look at the National Bison Range is the relationship between climate change and plant production. While researchers observed that increases in annual temperatures and decreases in rain made the prairie dryer and more vulnerable to fire, the annual amount of plant material produced on the land increased by around 110% — spurred by the more favorable conditions during the plant-growing months of May and June.

These findings suggest bunchgrass prairies may be more prone to following seasonal trends than annual ones. Researchers observed, for instance, that summer temperatures at the National Bison Range were higher than the annual trends would otherwise suggest, resulting in increased summer senescence — the yearly browning process plants experience in the warmer months — for the bunchgrass prairie.

Study authors Gary Belovsky and Jennifer Slade of the University of Notre Dame said these results may serve as a reminder that when it comes to understanding how climate change influences plant health, employing a more seasonal perspective may be the most accurate.

“Forecasting climate change effects on plant production based on expected average annual increased temperature and decreased precipitation may not be appropriate, because seasonal climate changes may be more important and may not follow average annual expectations,” Belovsky said with the release of the story.

A susceptibility to seasonal patterns were not the only changes researchers observed during their exhaustive study of the National Bison Range, however. Researchers also found the plants on the bunchgrass prairie saw a 108% increase in invasive species, with drought-tolerant species emerging as the most favored variety.

Researchers also found that dicotyledon non-grass plants, a type of flowering plant commonly known as dicots, saw their health gradually deteriorate over the study period with a decrease in population size by around 65%. 

Taken together, the researchers say the changes point to an uncertain future for bunchgrass prairies. Wednesday’s study suggests that as the endangered ecosystem responds to changing ecological factors, bunchgrass prairies could be transforming into an entirely new grassland ecosystem experts have never seen before.

While researchers can’t definitively say what the future holds for bunchgrass prairies, they stress that comprehensive local research efforts like theirs can help give experts the data they need to forecast how these threatened ecosystems will respond to climate change and other threats moving forward.

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