Quantcast
Environmental News for a Healthier Planet and Life

Warming Climate Pushes Plants Up the Mountain

Climate
Warming Climate Pushes Plants Up the Mountain

The University of Arizona

By Daniel Stolte

In a rare opportunity to directly compare today's plant communities with a survey taken in the same area 50 years ago, a University of Arizona (UA)-led research team has provided the first on-the-ground evidence that Southwestern plants are being pushed to higher elevations by an increasingly warmer and drier climate. 

The researchers assessed plants growing at different elevations in the same areas surveyed by botanists 50 years ago. Photo credit: Jeffrey Eble.

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.

Today, living alligator juniper first begin to make an appearance on upland slopes of the Catalina Mountains at around 5000 feet elevation. Photo credit: Rick Brusca.

In a rare opportunity to obtian a "before-after" look, researchers studied current plant communities along the same transect already surveyed in 1963: the Catalina Highway, a road that winds all the way from low-lying desert to the top of Mount Lemmon, the tallest peak in the Santa Catalina Mountains northeast of Tucson. 

"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, a research scientist in the UA's department of ecology and evolutionary biology who led the study together with Wendy Moore, an assistant professor in the UA's department of entomology. "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."

The study, published in the journal Ecology and Evolution, 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 Moore 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. 

Below 5,000 feet, hundreds of dead juniper attest to a former range much lower down on the mountain, reflecting cooler and wetter years of the past. Photo credit: Wendy Moore.

Specifically, Moore and her team 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. As far as the plants' upper elevation limits were concerned, the researchers observed a mixed trend: They found it to be higher for four species, lower for eight species and unchanged for 15.

For example, in 1963 Whittaker and Niering recorded alligator juniper as a component of upland desert and grassland communities in the Catalina Mountains, beginning at an elevation of just 3,500 feet. Today, one has to drive to the 5,000-foot elevation marker on the Catalina Highway to see the first live alligator juniper trees in upland habitats. 

According to the authors, 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. Rather, individual species shift their ranges independently, leading to a reshuffling of plant communities.

The scientists in this multidisciplinary group gathered the data during fieldwork in 2011, and included UA postdoctoral fellows and professors from several programs, including the UA departments of entomology and ecology and evolutionary biology, the Center for Insect Science and the Institute for the Environment, as well as botanists from the Arizona-Sonora Desert Museum

Mixed conifer forests like this one high up in the Catalina Mountains and the animals dependent on them could disappear in the near future due to a steadily warming and drying climate in the Southwest. Photo credit: Rick Brusca.

Based on studies done by other scientists, including UA researchers, the researchers believe that a "thirstier" atmosphere might be a major driver behind the shifts in plant distribution, possibly even more so than lack of precipitation. As the atmosphere becomes warmer and drier, plants loose more water through their leave openings and become water-stressed. 

According to the authors, the results are consistent with a trend scientists have established for the end of the Pleistocene, a period of repeated glaciations that ended about 12,000 years ago. By studying the distribution of plant seeds and parts preserved in ancient packrat middens, for example, paleo-ecologists have documented that as the climate warmed up, plant communities changed profoundly.

"In southern Arizona, some species moved north to the Colorado Plateau, others moved up mountain slopes, and others didn’t move at all," said Moore, who has been collecting data on ground-dwelling arthropods, plants, leaf litter, weather, soil and other ecological factors in the Santa Catalina Mountains for the Arizona Sky Island Arthropod Project based in her lab.

The Sky Islands encompass an "archipelago" of 65 isolated mountain ranges rising from the surrounding low-elevation desert and desert grassland in an area that constitutes the only major gap in the 4,500-mile long North American Cordillera, which runs from northern Alaska to southern Mexico. The Sky Islands, often referred to as the "Madrean Sky Islands," span this gap in southeastern Arizona, southwestern New Mexico and northeastern Sonora, Mexico. They include the Santa Catalina Mountains, the Pinal Mountains and the Chiricahua Mountains.

Visit EcoWatch’s CLIMATE CHANGE and BIODIVERSITY pages for more related news on this topic.

——–

Recycling and general waste plastic wheelie bins awaiting collection for disposal in Newport, Rhode Island. Tim Graham / Getty Images

Reduce. Reuse. Recycle. According to The National Museum of American History, this popular slogan, with its iconic three arrows forming a triangle, embodied a national call to action to save the environment in the 1970s. In that same decade, the first Earth Day happened, the EPA was formed and Congress passed the Resource Conservation and Recovery Act, encouraging recycling and conservation of resources, Enviro Inc. reported.

Read More Show Less
EcoWatch Daily Newsletter
The coal-fired Huaneng Power Plant in Huai 'an City, Jiangsu Province, China on Sept. 13, 2020. Costfoto / Barcroft Media via Getty Images

One of the silver linings of the coronavirus pandemic was the record drop in greenhouse gas emissions following national lockdowns. But that drop is set to all but reverse as economies begin to recover, the International Energy Agency (IEA) warned Tuesday.

Read More Show Less
Trending
A grizzly bear killed an outdoor guide in a rare attack near Yellowstone Park. William Campbell / Corbis / Getty Images

A backcountry guide has died after being mauled by a grizzly bear near Yellowstone National Park.

Read More Show Less
Representative Alexandria Ocasio-Cortez (D-NY) re-introduces the Green New Deal in Washington, D.C. on April 20, 2021. Mandel Ngan / AFP / Getty Images

By Brett Wilkins

In the latest of a flurry of proposed Green New Deal legislation, Reps. Cori Bush and Alexandria Ocasio-Cortez on Monday introduced the Green New Deal for Cities Act of 2021, a $1 trillion plan to "tackle the environmental injustices that are making us and our children sick, costing us our homes, and destroying our planet."

Read More Show Less
Offshore oil and gas drillers have left more than 18,000 miles of pipelines at the bottom of the Gulf of Mexico. Drew Angerer / Getty Images

Offshore oil and gas drillers have discarded and abandoned more than 18,000 miles of pipelines on the floor of the Gulf of Mexico since the 1960s, a report from the Government Accountability Office says.

Read More Show Less