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In the absence of crystal balls and time machines, scientists use natural records like ice cores to understand what happened on the planet before we arrived, and math and computers to predict whether humans can survive the changes ahead. Although it isn’t perfect, it’s the best approach available to science fiction films and fairy tales.
In Arizona, the science ecosystem change has a lot to do with trees.
Donald FalkAssociate professor at the University of Arizona’s Laboratory of Tree-Ring Research. He uses trees and forests as a lens to study how southwestern ecosystems respond — in the past, present and future — to challenges such as the rising average temperatures, worsening drought and more intense wildfires linked to climate change.
Falk and co-workers published a publication in March. Review paper“Mechanisms that forest resilience” is a paper published in Forest Ecology and Management. It is a comprehensive academic look at the ecological processes behind what, in the Southwest, is plain to see: The forests are dry, brittle and burning at unprecedented rates. Sometimes they don’t come back as forests.
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2020: More than 32 million people Arizona, even as the pandemic put a sizable dent in tourism. As any nature-loving Arizonan already knows, many of the state’s most popular destinations are forested: the north rim of the Grand Canyon, Sedona, Flagstaff, the Sky Islands and the White Mountains.
The Arizona Republic spoke to Falk about whether Arizona will still have Douglas firs and Ponderosa pines to visit in 2122, how resilient the state’s forests might be to increasing threats and what people can do to protect these beloved landscapes. To make his best predictions, he used his Rip Van Winkle crystal to create a tree ringing time machine and a Rip Van Winkle prediction.
Dr. Falk, you study the history of wildfire in the Southwest to better understand its future. Can you explain how this works?
Since the late 1990s, I have been studying wildfire in all its forms in the Southwest. My Ph.D. was about fire history in New Mexico. You can think of what I do in a past, present, future framework. Tree rings are a major tool for studying the past. We study the recovery of forests after wildfires and how resilient ecosystems are. And then, on the future side, I’m part of a group that does simulation modeling. We try to turn the clock back and ask “What will the Southwest look like in 100 Years?”
The past can teach us a lot about resilience of ecosystems. We have records that go back many centuries across the Southwest. They show that wildfires were something the forest was well-adapted to. We have individual trees that have 35 fire scars on them, meaning that fire passed by that tree at least 35 times and left an imprint in the growth of the tree but clearly didn’t kill it. That tells us something very important about fires that were happening in the past – they were frequent, but generally not the kind of burn-down-the-forest conflagration that we’re seeing today.
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What has wildfire done to Arizona landscapes?
It’s like a switch has been flipped after the year 2000. Wildfires are ten times more common. We are seeing ecosystems change, and I would say that the pace of change has really picked up. We are seeing a lot more death of trees due to wildfires and because it is becoming too hot and dry to sustain the kind of forests we used to have.
Nature hates a vacuum. Therefore, another thing will replace it.
We see oaks replacing pines, we see shrubs replacing trees, sometimes we see grasses replacing everything. Many of these grasses are invasive, brought in by humans, and are what we call pyrophilic, or fire-loving. You’re not going to burn them out, and it’s tough to push back that tide. The landscape is changing to other types of vegetation. It’s difficult to reverse the changes once they are in place.
What are the main drivers of these changes
I think it’s reasonable to think of the combination of climate, wildfire and insect pests as being the immediate drivers. But clearly, the most important thing that happened was the onset of the multi-decadal drought and associated high temperatures, and that’s not showing much sign of letting up.
Droughts do occur periodically in North America and all over the world, driven by background climate variability. It is extraordinary because of the severity and length of the drought. It’s one of the worst droughts in the last 2,000 years.
Now we could step back from that, of course, and ask, “Well, what’s driving those drivers?” The signs are that human alteration of global climate is driving the climate part of the equation. This causes longer, deeper and hotter droughts. Our attempts, for more than a century, to keep fire out of ecosystems that need fire has also contributed to the severity of wildfires. Insects are also responding to both of these because dense forests with weakened trees provide the ideal habitat for many insects.
Unfortunately, we are all to blame for some of the destructions that climate and wildfire have caused on our forests in Southwest.
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Your recent review paper defines resilience as consisting three parts: persistence; recovery; and reorganization. Can you please explain the process and why it is important?
Resilience is something everyone is thinking about. It’s a way to ask ourselves: “How are we going to get through this stressful time? Are these things important to us still going be there?” So we wanted to make sure we understood what we actually mean by resilience.
We looked through hundreds upon hundreds of studies and discovered an interesting pattern. The first thing that a forest seems like to do is to try to. Continue to persistYou can either resist or mitigate change. Healthy trees can tolerate some stress. A big, old Douglas fir or Ponderosa pine, we might see in the pattern of the growth rings that some years were probably dry and hot and not optimal for growing. But the tree didn’t die. It simply grew less each year.
The second line is called RecoveryThis is not at the tree level, but the whole forest. Let’s say a fire comes through and kills an entire acre of trees that had been weakened by insect pests. These open areas are where seeds from nearby trees can be found and established. The forest then recovers over many decades.
Most people think of resilience as persistence and recovery. We also saw another pattern, which we call reorganization,This is where ecosystems differ from human beings. If we go through an illness, we’re not going to turn into a different kind of organism, right? But ecosystems do it all the time.
Ecosystems will change the species that make up their communities when they are under stress from climate and disturbance (as with fire). This isn’t a new phenomenon. Reorganization is a natural part of the ecosystem.
The climate we have created through our stupidity is totally unnatural. So what we’re seeing is the extinction of species, the loss of forest, the reduction in available water, the die-out of major groups. Humans should not be proud that this is happening.
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What does all this mean for the future of Arizona’s forests and the people who live and recreate there, in terms of both short-term and long-term impacts?
We’ve been seeing short-term impacts for the last 20 years with these gigantic wildfires, including the largest fire ever in New Mexico that is burning right now. They’re affecting our economy, the quality of our air, the availability of water and the integrity of our soil. People are losing their homes, their jobs, and their livelihoods. Their health has been affected. These events are not good for people, no matter how you look at it them.
In the longer run, we have pretty good reason to believe that species are going to rearrange where they’re living in the Southwest. Some will migrate to higher elevations or farther north. There are lots of species in Mexico, grasses and trees, that are well adapted to the climate we’re creating in the future, that will come in and take their place.
So, if you were to be Rip Van Winkle, go to sleep for 100 years, what would you see when you woke up in 2122? You would see a lot more areas that were once forest now looking like grassy savannas. This is because it will be much hotter and the rainfall will be more unpredictable.
Are there any Arizonans who can resist the loss of our forests or their conversion?
First, we can support those who manage our public land. They’re trying their best to keep our forests and grasslands resilient. How they do that is by forest thinning, prescribed burning and a variety of treatments for grasslands to keep them in healthy condition.
We can also ensure that we don’t have negative impacts on the ecosystems. This means that we might not drive off-road, causing huge scars that could take many decades to heal. We can’t accept the damage to ecosystems that is happening as it stands.
Obviously, being very careful with fire is as critical as it ever was. Also, be careful with how you use water. Water waste creates additional stress for many ecosystems. Our ecosystems are losing water at an alarming pace. And a lot of it, honestly, is used more for human vanity than for any essential purpose. It is not acceptable to consume water in the desert.
But beyond that, if you love forests, if you love streams and you love wildlife, then do everything in your power to reduce your carbon footprint. Don’t contribute to the problem. This means making hard choices such as not flying to another country for a weekend, or living in a smaller home, or not driving a large gas-guzzler for just a quarter mile to get a quart milk. There are many changes that we can make to our lives individually.
Then, of course, we need to make sure that we have people in Congress who understand the importance of climate change and the extreme urgency of addressing it. We can support ecosystems by supporting the movement to try not to make climate change worse. Every little thing we can do to reduce emissions makes us more conscious citizens on the planet.
Joan Meiners is the Climate News and Storytelling Reporter at The Arizona Republic and azcentral. She earned her Ph.D. in Ecology before becoming a journalist. Follow Joan on Twitter at @beecycles or email her at [email protected].
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