Increasingly warmer and drier climate is pushing plant species to higher elevations on a southern Arizona mountain, scientists say.

Comparing plant communities today with a survey taken 50 years ago, University of Arizona-led research provides the first on-the-ground evidence for Southwestern plants being pushed to higher elevations by climate change.

The findings confirm that previous hypotheses are correct in their prediction that mountain communities in the Southwest will be strongly impacted by an increasingly warmer and drier climate, and that the area is already experiencing rapid vegetation change.

“Our study provides the first on-the-ground proof of plants being forced significantly upslope due to climate warming in southern Arizona,” said Richard C Brusca, lead researcher.

“If climate continues to warm, as the climate models predict, the subalpine mixed conifer forests on the tops of the mountains — and the animals dependent upon them — could be pushed right off the top and disappear,” said Brusca.

The study was made possible by the existence of a dataset compiled 50 years ago by Robert H Whittaker, often referred to as the “father of modern plant ecology,” and his colleague, William Niering, who catalogued the plants they encountered along the Catalina Highway.

Focusing on the 27 most abundantly catalogued plant species, Brusca and colleagues discovered that three quarters of them have shifted their range significantly upslope, in some cases as much as a thousand feet, or now grow in a narrower elevation range compared to where Whittaker and Niering found them in 1963.

Wendy Moore, an assistant professor in the UA’s department of entomology found that the lowermost boundaries for 15 of the species studied have moved upslope; eight of those species now first appear more than 800 feet higher than where Whittaker and Niering first encountered them.

Sixteen of the studied species are now restricted to a narrower band of elevation, the researchers noticed.

According to researchers the main point emerging from the study is that plant communities on the mountain were different 50 years ago because plant species do not necessarily move toward higher elevations as a community.

The study was published in the journal Ecology and Evolution .

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