- Hi, I'm Tom McNamara, host of "Arizona Illustrated."

Last year, as the pandemic was tightening its grip worldwide, Tucsonans looked up at the Santa Catalina Mountains and watched as a wisp of smoke on Pusch Ridge quickly developed into a raging inferno that engulfed most of the range.

It's an image that encapsulated the fear and anxiety of the year, and it's seared into the memories of Southern Arizonans who witnessed it.

Well, the following fall, Arizona Public Media producers, editors, and photographers put together a 30-minute special exploring the causes and impacts of wildfire here.

On this episode of "Arizona Illustrated," we give you an encore presentation of that program.

And stay tuned for information about a live event you can participate in featuring fire and forest experts who'll discuss ongoing research in the Catalinas and their thoughts on the upcoming fire season.

Here now is "Understanding the Bighorn Fire."

(ominous music) On the evening of June 5th, lightning struck Bighorn Mountain in the Santa Catalina Mountains north of Tucson.

The Bighorn Fire had begun to burn.

Over the next 48 days, the fire raged through the entire mountain range, burning down into Pima, Finger Rock, Esperero, and Upper Sabino Canyons, at times threatening homes and forcing people to evacuate around Oro Valley and the Catalina Foothills.

It continued to grow and spread, burning just below and then around Mount Lemmon, then into the grasslands and the foothills north and east of the range.

Through the efforts of nearly 1,000 personnel, thousands of gallons of fire retardant, water, and a little rainfall, the fire was declared 100% contained on July 23rd, 2020, having burned nearly 120,000 acres.

(soft Western music) This week, an "Arizona Illustrated" special, "Understanding the Bighorn Fire."

Welcome to "Arizona Illustrated."

I'm Tom McNamara.

The AZPM crew and I are here in the Loma Linda area of Mount Lemmon, high atop the Catalina Mountains and surrounded by the aftermath of this summer's Bighorn Fire.

If you were in Southern Arizona back in June and July, you saw it: smoke towering above the Catalinas by day and an eerie glow and hot orange flames from afar at night.

For a month-and-a-half, the Bighorn Fire captivated all of Tucson.

In just a moment, we'll explore the interaction between wildfire and wildlife, accompany scientists into the post-burn area to better understand the fire's impact, and we'll journey to the Chiricahua Mountains to see how vegetation there has changed since a massive wildfire in 2011 and what that might mean for the Santa Catalinas.

But now, here's an update on the coronavirus in Arizona.

Arizona's week-to-week numbers remained relatively stable over the past week, with coronavirus-related new cases, deaths, and testing positivity showing slight declines, this as the city of Tucson will receive more than $135 million in federal pandemic relief to fund continued COVID-19 mitigation efforts.

And as of May 13th, parents and guardians with children ages 12 to 15 will be able to access the Pfizer COVID-19 vaccine for them at the state-run sites.

For more on that and other coronavirus news, visit azpm.org/coronavirus.

As we watched the Bighorn Fire burn through the Catalina Mountains, it's only natural that our first concerns would be for the firefighters' safety and for the life and property of those who live near the blaze.

But what about the creatures who inhabit the mountains themselves?

Here is "Wildlife and the Bighorn."

- Fire is an incredibly important part of the web of life in Southern Arizona, natural biological cycles, and it definitely has a role, and we need to let it get back to playing that role.

But when fires happen these days, they happen in a context of forests that have already been seriously damaged by human impacts over the years and a lotta different types of impacts, but probably the biggest one is fire suppression.

So, for decades, for actually a century now, we have not let fires play their normal role on the mountain.

And therefore, when they happen today, they happen differently.

- Rarely is wildlife overrun by wildfire.

They're fleet of foot enough to get outta the way or, in cases of smaller creatures, burrow underground.

And these animals, for generations, are adapted to these fires.

Yes, maybe they're not where we would expect them to be.

You never know 'cause it's wildlife and they do what they wanna do, sometimes reentering burning areas when it's still smoldering.

A Gould's turkey we observed doing that very thing.

And it's a 155,000-acre mountain range; there's still plenty of territory out there for them and they're gonna use it.

- The Catalinas are a typical Sky Island mountain range.

They rise up very steeply from the desert floor and the arid grasslands that are around the base.

And up at the top, you go all the way to spruce fir conifer forest, and that means that every step of the way you have a different set of plants and animals that call it home.

The biodiversity of our Sky Island mountain ranges in Southern Arizona is globally recognized and they have been recommended as a huge priority for protection from a global biodiversity perspective.

- The initial burning took place in the Bighorn Sheep Management Area, and most of that Bighorn Sheep Management Area burned.

(soft orchestral music) But we're cautiously optimistic the bighorns will make better use of that area and perhaps expand their territory.

It will be cleared of dense vegetation, there will be new growth coming up, and it will be perfect for them.

Sprouting prickly pear, for example, is a favorite.

It's like a bighorn sheep salad bar after a fire.

The way they defend themselves is through their keen eyesight, which, if a predator is concealed by a brush, they can't really use and then their ability to climb rapidly over rough terrain.

For sure, it's going to help them deal with mountain lions, and other ungulates, I should add.

Whitetail deer at higher elevations and mule deer at lower elevations will also reap the benefit of that cleared-up habitat and that new growth.

- The Sonoran Desert is renowned for its diversity of bees and other insects, and we also have many mammals, coati and ringtail and foxes and coyotes and black bears and bobcats and other predators.

And we also have a lot of reptiles, lizards and snakes and Gila monsters and some species that aren't found anywhere else, and I think we should be proud of that.

It's something that we should care for and protect.

When you look at the interaction of fire with endangered species, you really have to look through a different lens, and Mexican spotted owl is one of 'em.

And so, we have what are called protected activity centers where those owls are known to do their business, either nest or hunt.

So, they rely on a certain combination of vegetation, plant species, and water availability, and a certain topography or forest structure.

We need to be nimble to respond to these threats and give these species the best chance that we can to survive.

- We also take a look at desert tortoise habitat.

We don't worry about desert tortoises being overrun by fire.

They burrow underground.

But what are they gonna eat when they come outta that burrow?

Everything around them is gonna be burned and they're gonna have to travel a long way to get there.

We had a case a few years ago with the Monument Fire for Chiricahua leopard frogs, which are a threatened species.

They were in a pond and we could look above them and see a major burned area.

We got in there, we pulled all the frogs out, sent 'em up to Glendale Community College for a while.

The very next day, a slide came in and silted in the entire pond that they had been inhabiting.

Woulda killed 'em all.

That's why we took almost 900 endangered Gila chub outta the west branch of Sabino Creek and farmed them out to the UofA, International Wildlife Museum, and the Desert Museum for safekeeping.

When the monsoon passes, when all that silting action is over, we'll put them back in.

(soft orchestral music) - We hardly had any monsoon at all, so there wasn't really a big problem with a lot of erosion and a lot of soil being lost as a result.

Now, that could still happen at any time, you know?

I mean, it only takes one really big storm to have that kinda impact.

So, in one way, maybe that was a good thing.

But in another way, it just makes it that much more difficult for the habitat to recover, for those seeds to germinate, and for the vegetation to come back.

Water is more scarce, food is more scarce for the time being, and that is a challenge to many species.

Now, that said, the Bighorn Fire in particular burned pretty well for the most part.

There were a couple of really bad days with high winds.

But for the most part, it burned in a mosaic.

It did not burn really severely, and I think you'll see the mountain bouncing back pretty well.

- It's not gonna look like it used to look tomorrow, but a year or two it's gonna be good.

In most cases, wildfire is a natural process that improves the overall health of the mountain range over time.

Lightning started this fire, as it did long before man inhabited Tucson.

There were fires in the Catalinas and these other mountain ranges.

And these animals, for generations, they've survived.

- The general consensus is by the end of this century, half the species on this planet could be gone.

And to me, that's very alarming, even from a perspective of self-interest.

I am a species on this planet, homo sapiens.

I still rely on that mountain for clean water and clean air, just like all the animals do.

We gotta get serious about protecting these places and the web of life that supports all of us, including homo sapiens.

- Immediately after the Bighorn Fire was contained, many Southern Arizonans were anxious to get back up into the mountains, maybe none more so than UofA scientists Don Falk and Laura Marshall, who were eager to survey the damage after the burn.

(pensive music) - [Reporter] The Bighorn Fire is still burning in the Catalina Mountains.

- [Reporter] 11,500 acres have been burned so far.

- When I was sitting down here in Tucson watching the evening news and watching the progression of the fire on the web, it began to get closer and closer to places I know and love really well, such as the high-elevation forest.

And I began thinking, "Oh my gosh, "I hope it's not gonna get in there.

"Please don't burn there.

"Please don't burn that forest down."

There's a really interesting dynamic being a person who loves the forest and a scientist who studies it.

One part of you wants to say, "I love this forest, "I never want it to change."

And the other part of you looks at a forest that's changing and say, "Wow, that's interesting.

"I wonder why that happened that way."

And when a big fire happens, you're really kinda poised on the head of a pin about which of those is gonna be dominant because it's so interesting and yet can also be so devastating.

Okay; are you going in that forest?

- [Man] Yeah, I'm going all the way to the UofA, to the service- - After a wildfire, that's our time to get out and do research, and we try to prepare for that moment by having study plots out in the mountains before fires happen.

And so, we have the unique opportunity to be able to return to those and look at how things have changed, not only in the short term, the first few months, but to track over many, many years how the forest recovers following a big fire.

- I'd say, at the first look driving up the road, doesn't look too bad until you get up to the Loma Linda area and can look down the north slopes of the mountain.

That burnt very hot.

It's a little devastating to just come around the mountain and see just burnt sticks as far as you can see.

We're seeing bigger, larger fires many places in the Southwest.

This could be a bellwether for what's gonna be happening in the next couple decades in other areas.

- So, we live in what's called Sky Island Bioregion.

The Sky Islands are a network of more than 60 mountain ranges from northern Mexico up to the Colorado Plateau.

And people often refer to them as islands because they're islands of forest surrounded by lower desert or grassland.

And what that means is that each island could be a unique biological location, much like islands in the ocean.

This is part of what makes the Sky Islands such a unique resource.

- [Laura] You can go from the low desert all the way to basically a spruce forest that feels like you're in Canada in just a matter of an hour.

I just love being out there and just having a great view all the way down through the different ecosystems out to the desert.

- Our fieldwork often begins with a geographic positioning system, a GPS, because we're trying to get back to a particular location on the ground, and so we'll navigate to that point.

In here under the live tree canopy?

In there?

- Yeah, yeah, on the edge.

- This could definitely work.

- Looks pretty good.

- What we do is study the plants and animals on the ground, the soil.

It's a lot of hands-and-knees work, very, very detailed, trying to look at every plant, looking at whether trees are regenerating, whether there are seedlings, whether the overstory trees were damaged or not, whether they are gonna bounce back.

We'll use tapes to measure the diameter of trees.

We'll sometimes use increment corers to extract a core from the tree to look at their growth.

- Yeah, that looks good.

So, tree rings can tell you all kinds of things about a forest, the past climate.

You can match up the ring patterns to figure out exactly what ring goes with what year.

And using that, you can match patterns back and back in time, basically for as long as you can find remnant wood still present on the mountains.

The changes that are happening now are happening very quickly compared to change in the past.

So, now we're seeing major changes, burning entire mountain ranges, large severe fires in a matter of years to decades.

So, basically, things are moving too fast for the forest to keep up in a lotta places.

2020, we're seeing fires all over the West.

And basically, I think, in the future, a dendrochronologist will definitely know, "Oh, that's a 2020 ring.

"You can tell; there's a fire scar."

(laughing) - The really big important question in post-fire research right now are what are called post-fire trajectories; that is, what direction is this site gonna go?

Is it gonna go back to being a forest with the same species and similar processes from what it was?

Or is it gonna go off in a different direction?

There's no question that the contemporary fires we're seeing appear to be very, very different in kind from the historical fires.

And the big concern here is not that this was a big fire per se, but that it was a big fire with a lot of areas of very, very high severity effects, and that, we believe, is the legacy of a century of keeping fire outta the forests.

So, the fuels have accumulated and, laid on top of that, the unmistakable signature of climate change.

- So, what tree are you working on over there?

- 210.

- 210, great.

- So, an important question now in everybody's mind is, "Is that a permanent transition?

"Has that gone past a tipping point "so it's now gonna be a different kind of ecosystem, "not a forest?

"Or is it just a slow bending of the curve "back to becoming forest?"

And this is why we need this historical background to understand the Bighorn Fire that happened in the Catalinas.

(soft piano music) I have to say that the research we do really increases my appreciation for the complexity and resilience of these forests.

We'll go up and study a plot and we'll find trees that have survived.

They somehow managed to make it through and they're green on top and they're growing.

And we'll often think, "How did this happen," because this is supposed to be in the middle of a high-severity patch, and yet here's life.

The poet Gary Snyder once said, "Science walks in beauty."

And in a sense, we can't see wildfires as always a catastrophe or a tragedy or something terrible.

In fact, there's a big part of wildfire that is about renewal and it's about resilience and it's about adaptability.

And that's actually a really positive lesson because it means that many things that we're seeing that look like they've gotten stuck or damaged or lost irretrievably perhaps aren't that way at all.

Maybe somebody will come along 50 or a hundred years from now and look at our notes and understand that this was just the process or recovery at its very beginning.

These were just the first few steps at eventually the process of nature healing itself.

- This is not the first major wildfire in Southern Arizona's Sky Islands and it won't be the last.

So, what can past fires tell us about the Bighorn and the lasting impact of fires in the future?

Perhaps there are lessons to learn from the Chiricahuas.

(light wind chime music) - The Chiricahuas has a fire history pretty similar to most of Southern Arizona; that is, with a period of repression of fires in the early-1900s all the way up until at least the '80s.

We had a period of dryness and drought, and that drought resulted in the Horseshoe Tooth Fire in 2011, which burned almost the entire mountain range, about 200,000 acres.

There's not been a similar fire since.

In some parts of this mountain range, nine years would be a reasonable time for it to come back and burn again.

I'm Jim Malusa, I'm a research scientist with the School of Natural Resources and the Environment in the University of Arizona, and I'm here with my wife, geologist Sonya Norman of the Desert Museum.

And together, we're gonna look at the recovery from the Horseshoe Tooth Fire.

Okay, now we're very close, and now comes the fun part, where we take a look at the picture.

'Cause look, there's that tree.

And this one...

I consider myself a plant ecologist, and vegetation mapping is one of my specialties, and that is why things live here and not over there.

And as part of that work, I also do repeat photography to see how vegetation changes through time.

- [Sonya] I can see that ridge.

This one...

This is the closer one.

- Repeat photography's a great way to keep your finger on the pulse of ecosystem changes, mainly because it's so understandable and easy to see.

With pictures, everyone can just look at it and say, "Oh, the pines are all being replaced by oaks."

And so, it's a visual and informative way of seeing what's going on in our world.

It's more than just taking a picture.

We're gonna try to get an idea of the relative ground cover of the different species out here.

Here's last years.

You can see Sonya with the, I have here, struggling QUEM.

That's Quercus emoryi.

And it looks like that one has died as well.

That's that little one right there next to the turpentine bush.

- I see it.

- The main driver of ecosystem change is gonna be disturbance, when something happens.

It can be a drought, it could be a fire, it could be grazing, it could be many things, and that sets in motion a series of changes in the species, and that sometimes returns the ecosystem to what it was before and sometimes it doesn't.

As a young man, I was lucky enough to have parents who let me wander, and that was a big part of exploring the world was I was actually released into it.

And so, when I got my first backpack as a 16-year-old, I said, "I wanna go overnight in the mountains."

And they said, "Have a good time," (laughing) as Mom drove me up Sabino Canyon, back when you could drove up Sabino Canyon, scraped the side of the station wagon on the bridges, the skinny bridges, and just let me loose.

(soft ambient music) (soft chatter) There's some hikes that I've done since I lived here so long, there's a particular one in the Rincons I've been hiking every year since '74.

It's like 45, 46 years of making the same hike.

And I remember when changes happened early on in those trips in my life when I was in year 10 or 20, and there'd be a landslide or fire and things would fall down, and I'd be distraught actually.

I'd be going, "Oh god, I've lost my favorite place."

But I didn't lose it; it just turned into something else.

And I think every loss is an opportunity for another species.

Of course, we hate to see change that we can blame on ourselves and say that we made it hotter.

From the repeat photography that we've done in the Chiricahuas so far, it's apparent that ecosystems with a lower level of, for example, the pine oak ecosystem, they're susceptible to losing particular species that need cooler conditions, cooler conditions or wetter conditions.

And so, our primary concern with the Bighorn Fire would be losing forested areas and having them turn into scrubland just because it's now a bit warmer and drier.

And if that does occur, the things at the very tippy-top are gonna be pushed off into oblivion, and that would include the corkbark fir, which is a species that, it's in the Catalinas and the Pinalenos, and that's the only two places that it's found in Coronado, the national forest.

All right, so where we gonna go next?

(soft piano music) We're gonna go up the mountain a little bit higher, up the road toward Barfoot Park, and visit pine ecosystems.

You ready?

- Yeah.

- Okay.

Well, when I first got here, I was pretty disappointed to see that the Chihuahuan pines, who were my kind of hero of this ecosystem that had come back so strongly, now they're all brown.

And at first I thought maybe they're dead or they're almost dead.

But it ends up, after we've measured 10 of these trees, that they actually did grow.

They managed to grow 20 centimeters over the last two years.

But it's clear to anyone that gets up close to one of these trees, they're stressed out.

And so, everything's gonna rely on probably the next year of rain.

And so, if we get a late-season hurricane, that would help, October rain in here.

But one more dry summer and so that could be the end of this pine forest.

Humans like trees.

And especially in a hot place, they wanna sit under a tree and they don't wanna sit under a bush.

And so, we have a natural tendency to lament the loss of forest.

Whether or not you would call that a natural change, the forest burns and it comes back as oak scrub, depends on your definition of "natural," you know?

Humans are a part of nature and we've always changed the world around us.

And so, people need to decide what we want our world to look like and act to help that happen.

- I hope you've enjoyed this encore presentation of "Understanding the Bighorn Fire."

Now, over the past year, University of Arizona scientists and researchers have been venturing into the burn areas where and when it's safe to do so to conduct research, including repeat photography, taking core samples, and understanding the role of invasive species in the start of the fire.

Some of the experts you just heard from in this program will be on-hand to discuss their observations during a live virtual event called "Fire and the Future: "Tucson's Bighorn Fire One Year Later."

The online event is June 2nd at 6 p.m. For more information and to register for this free event, visit environment.arizona.edu/fire-on-the-mountain.

I'll be moderating that discussion and I hope to see you there.

And thank you for joining us here on "Arizona Illustrated."

I'm Tom McNamara.

We'll see ya next week.

(soft acoustic guitar music) (bright orchestral music)