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Will fire change Arizona's desert ecosystem forever? Researcher studies regrowth after Bighorn Fire

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Posted at 6:00 PM, Jul 05, 2021
and last updated 2021-09-27 19:28:54-04

A University of Arizona researcher is studying how fire affects the Sonoran Desert to help our rural/urban interface communities from increasing fire dangers in the future.

Dr. Ben Wilder is the director of the Desert Laboratory on Tumamoc Hill. From his office, Wilder had a panoramic view of last summer's devastating Bighorn Fire in the Santa Catalina Mountains.

Bighorn Fire

The Tucson native is particularly concerned about how non-native grasses, such as buffelgrass, burn.

"Previously, until this onslaught of invasive species that is really driving this increase in fires, you'd only get fire in the desert ecosystems like this after really wet winter rains, or El Nino driven rains," Wilder said.

Wilder explained when desert plants are so spread out, wildfires tend to be smaller and short-lived.

Some recent desert fires have been massive and threatened homes, major highways, and other structures. They include 2005's Cave Creek Complex Fire, 2020's Bush Fire in the Tonto National Forest, and the Bighorn Fire in the Tucson area.

"This is part of the larger climate change issue of there's going to be a lot of climate-prone spaces that are very risky to live in and we need to adapt accordingly," Wilder said.

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Dr. Wilder and his team started at Catalina State Park and climbed an elevation of about 4,000 feet. In October they set up 10 research plots, which were nearly 50-by-50-foot squares. Half are in Bighorn burn areas. The other half are in non-burned, control areas.

They will study the plant recovery in these research plots for years to come.

"We're going to be doing repeat photography - matching the same images over time," Wilder said. "An image tells 1,000 words."

The biggest question the UA team hopes to answer is whether fires, especially repeated fires, will change the ecosystem. Native Sonoran Desert plants, such as saguaro cacti and palo verde trees may have a difficult time recovering from a wildfire. However, buffelgrass is fire-tolerant and may take over the landscape.

Wilder wonders if the combination would create savanna-like conditions. If a wildfire was sparked, grassfires could burn hot and fast. That could more quickly endanger homes and lives in the desert-urban interface.

In the first months after the Bighorn Fire, Wilder did see some promising developments in the plots.

"Some [native species], such as kind of the limberbush right there and some palo verde have already had very high percentages of resprouting, which really surprised us," Wilder said.

Dr. Wilder will take his next set of pictures after this summer's monsoon.

The results of this study could guide public-land managers and leaders of Arizonans communities to make better decisions about building on the edge of the desert, invasive grass species, and fire protection.