“We've all seen phragmites, that giant tall grass. It's widespread across the entire US,” said Pete Goodwin, a wetland ecologist with the Utah Geological Survey (UGS).
He is working to map and model the distribution of phragmites, an invasive grass, in Utah’s wetlands.
“It's not great habitat for a lot of wildlife. … It excludes a lot of light, so nothing else can grow and establish, and it's super aggressive," said Goodwin.
Claire Spangenberg Kellner, a hydrogeologist with the UGS who is also working on the mapping efforts, said that this invasive species of phragmites was introduced from Europe.
“It's found kind of all over North America now, but it really took off at the Great Salt Lake in the 80s, after we had some years of really high water,” Spangenberg Kellner said.
To better understand the extent of phragmites infestation, the UGS is working with the Utah Division of Forestry, Fire & State Lands, and the U.S. Fish and Wildlife Service.
A 2014 survey used manual photo interpretation to map phragmites in the Bear River Migratory Bird Refuge.
“Basically, me or Claire or some other skilled ecologist looks at some images, identifies what's phragmites, and draws a polygon around it,” Goodwin said.
Recently, Goodwin and his colleague, Rebecca Molinari, tested this method against an automated approach that uses computer models to classify satellite imagery.
Both methods identified phragmites with a high degree of accuracy, revealing dense phragmites stands covering 2,000 to 2,300 acres, or 7% to 8% of the 30-thousand-acre project area.
Because the automated approach is more efficient, it can be used to update large-scale mapping efforts regularly.
“As we were proposing our current project, that's one of the things that came up in conversation," Goodwin said. "Folks managing state lands don't have a good way to show how effective they've been at treating Phragmites over 10 plus years."
Goodwin and Spangenberg Kellner are working on a follow-up project applying similar methods to map phragmites at the Farmington Bay Wildlife Management Area.
Learn more about phragmites mapping efforts by the UGS here.
