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Satellite imagery reveals ‘unprecedented’ die-off of junipers in Northern Arizona

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The Tunnel Fire burned through Sunset Crater Volcano National Monument and headed north toward the edge of Wupatki National Monument, through a woodland of pinyon-juniper trees. That region experienced a dramatic die-off of junipers in the last few years. Before the fire, National Park Service staff partnered with NASA to map the dead trees using satellite images. KNAU’s Melissa Sevigny spoke with ecologist Nicole Ramberg-Pihl, a member of the NASA team, about their findings.

Tell me about the geographical area where you studied the dying junipers?

Sure. In 2021, the National Park Service noticed a dramatic juniper tree mortality event throughout the greater Flagstaff, Arizona area, mostly around Wupatki National Monument, which is managed by the National Park Service…. So the NASA DEVELOP team at Goddard Spaceflight Center studied a 1.5 million acre study area. That included portions of Coconino National Forest and went all the way to the southern rim of the Grand Canyon.

What did you find out in terms of the extent of the die off?

The first important result honestly was that the team was able to successfully map pinyon juniper woodlands and mortality within the area, using remotely sensed products. Second, the team found very few areas where mortality did not occur throughout the study region. In fact, mortality was actually so widespread that some stands in the region showed 80 to 100 percent mortality according to our classification. That’s concerning. Overall 43 percent of the pixels that were classified as living pinyon juniper in 2015 showed mortality in 2021. Within Wupatki National Monument specifically, 47% of the pixels that were previously classified as pinyon juniper in 2015, showed mortality in 2021.

So we know this really widespread die off is happening, or did happen. Do you have any ideas of what might be causing it?

This is an area experiencing drought conditions for over 25 years. In recent years, the area has experienced even more intense drought conditions. This is a concern, even though pinyon juniper trees are known to be relatively drought tolerant…. Between 2015 and 2021, we found significant decreases in monthly precipitation and soil moisture. However, more work really needs to happen in order to determine causality between environmental factors and tree mortality. So this is the beginning, but we do have plans moving forward to address some of these issues.

Okay, so it’s still not pinpointed in terms of the cause, but we know it’s got to be connected to the drought?

That’s what we suspect.

What does this mean for the future of the pinyon juniper woodlands in this area?

Pinyon juniper woodlands are an important component of the landscape, ecologically and culturally. Pinyon juniper woodlands support a variety of wildlife species, especially mammal and bird species…. Loss of pinyon juniper woodlands threatens the ecosystem and could leave to potential loss of habitat and nutrients and breeding grounds for local wildlife. Mortality in pinyon juniper woodlands also leaves trees vulnerable to things like bark beetles, and dead stands are at increased risk of wildfires.

Right, and as we speak there’s a wildfire burning through the area we’re talking about, Sunset Crater and Wupatki. I don’t know if you’re planning on going back in and doing some future research on that, but I assume there’s a connection between all those dead trees and the wildfire that’s burning right now.

And Sunset Crater is actually part of the original study area that we looked at.

Do you have a sense that junipers is fairly resilient; like the weather will get better and the junipers will come back? I’m curious because in a lot of areas we actually cut down junipers as part of restoration projects to bring back grasslands. So it’s an interesting situation that we have junipers here that are dying off and we’re worried about it.

Absolutely. We do know that they’re resilient in terms of the typical drought conditions; and that those are conditions they often do exist in. So this is really an unprecedented die off that we have seen, I think honestly we just need more research at this point.

Nicole, thank you so much for speaking with me.

Thank you so much, Melissa.

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Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.