Research Roundup: Burning Questions

Dr. Scott Franklin shares insight into causes and concerns surrounding Colorado’s wildfires.

Research Roundup is a series that features Q&As with UNC faculty to share insights about their research in an approachable, bite-sized format. Each installment highlights the questions driving their work, why it matters and how it connects to broader issues in our community and beyond.

Colorado is no stranger to fire. Year after year, burn after burn, wildfires spread across the state, damaging forest ecosystems and destroying homes.

Of the 20 largest wildfires in Colorado history, all of them have occurred in the past two decades, and four of the five biggest happened within the last five years.

For a state so beset by blazes, researching and understanding the causes and impacts of these fires is of paramount importance. And that’s precisely what Scott Franklin, professor of Ecology and department chair of the School of Biological Sciences, strives to do.

“I study how vegetation communities and the surrounding respond to fires and other disturbances, as well as how we can potentially use that knowledge for mitigation and management.”

– Scott Frankling, Ph.D.

The Research Brief sat down with Franklin to discuss his research, his approach to understanding wildfires and even how those fires might be beneficial for Colorado’s wildlife – if managed correctly.

I study vegetation, primarily at the community level. That means looking at plants and their interactions together in their environments. I tend to take an applied approach, so I like to study things that potentially would be put into management. Often, that deals with “disturbances” as well – things like looking at how fire can be used for vegetation management or how wildfires can be managed overall. I do the same kind of thing for flooding and the same kind of thing for fracking.

There are a variety of ways. Disturbances can potentially change the entire dominance of species that are found in an area. If you have disturbances that are happening quite often, they could potentially shift an area from being one vegetation type like a forest to primarily being another vegetation type like a grassland. Disturbances, as well as how frequently they occur and how large they are, will have major impacts then on the vegetation for those areas.

Generally, it has to do with the fuels that are available in the area – things like how much wood there is, how many needles or leaves there are on the ground and any other debris that’s in the area. Those fuels, the things that can actually burn, are the starting point.

The second stage is how many small trees are in the area – if there are enough of what we call “ladder fuels” to allow the fire to move from the ground up to smaller trees and then up to the canopy of larger trees. If we have those ladder fuels, that tends to increase how quickly fires move through the landscape and how dense those fires become.

Other factors; how dry are those fuels? How hot is it outside? How much are the winds blowing? All of that can feed a fire and make it move or behave in a very different way. They can take it from a slow burning blaze to something moving very fast with less capability to be controlled.

It depends on the vegetation in question. There are actually several species that are adapted to fires. The lodgepole pine, for example, has what we call a serotinous cone, which has this waxy covering. It requires fire to basically melt that wax off, and when it does, the cones open up and drop their seeds on the ground. When a canopy fire comes through and kills the adult trees, it leaves all this lovely fertilizer in the soil from the burning, and there’s plenty of light because the parents are gone. So, lodgepole pine reproduces quite well in that fire situation.

Ponderosa pine has kind of the opposite idea. It likes to maintain a more open woodland structure instead of a closed canopy – more space between trees and a lot of grasses in the undergrowth. So, if a ground fire comes through, ponderosa pine has this really thick bark so that ground fire doesn’t actually hurt the tree. If ground fires are occurring regularly enough so that it keeps the number of trees down and it keeps that open woodland structure, then those ground fires are actually a very positive thing for the ponderosa pine.

The one thing that’s really clear about most disturbances is that they decrease competition. After that disturbance gets rid of some of the vegetation in the area, it’s kind of a free-for-all. The species that spread seeds quickly and grow the fastest following that disturbance end up dominating, at least for a while.

Yes, absolutely. What’s happening to the lodgepole pine right now is an excellent example. In 2020, we had two of the largest fires on record in addition to a bark beetle come through that devastated the lodgepole pine.

In cases like this where you get these very large landscape burns, the trees need to have seeds on site in order to recover. Typically, lodgepole pine would have the seeds in the canopy, and those seeds would drop and everybody would be happy and they’d be back to normal.

But because of the double disturbance where we had the bark beetle come through, the seeds were no longer in the canopy. Then, when these big fires came through, the trees were left with no real seed sources to recover. In this case, where we have this double disturbance going on, it truly was detrimental to the system being able to recharge itself.

One of the things that I look into trying to do is controlling fires so that they aren’t out of hand. That’s especially true in what we call the “wildland urban interface” – the spaces where people live as they move up into the mountains. I look into how we can maintain a landscape that is less likely to burn these homes down when a fire does occur. Generally, that’s done through something called fuel reduction. One way or another, going out there and thinning the forest or doing prescribed burns to make the area generally cooler and more moist so that the fires don’t get out of hand.

We have some pretty good anecdotal evidence that in areas where fuels have been reduced – where trees have been thinned, essentially – the fires coming through are cooler, much less detrimental and much more controllable.

In addition to wildfires being an important and necessary part of how nature organically maintains vegetative communities, part of the problem comes from the classic “Smokey the Bear” policy in the early 1900s. Back then, we wanted to put out all fires and we did so until around the 1970s or 1980s.

That’s when we started to see that all those fuels – things like dry wood, leaves and smaller trees – that were built up over those 60 or 70 years of fire suppression contribute to much greater fires. They spread further, they were more intensive and they were less controllable. That’s when we changed our approach to more of a “let burn” policy or a fuel reduction policy.

Disturbances have been happening on these landscapes for a very long time. To take them completely out actually harms some plants and animals – they’re less likely to be able to maintain their populations without those disturbances.

So we want to maintain those disturbances to the landscape in a way that is friendly to the species there. They have the ability to respond within certain types of frequencies and certain magnitudes of those disturbances, so we try to ensure that what disturbances do occur don’t overwhelm the vegetation communities in the area.

Planting native species is a very good way of doing that, because those natives are adapted to the fires that are coming through these systems. Additionally, homeowners near the forest should cut back the vegetation surrounding their houses – don’t have shrubs right next to your house and make sure that there’s plenty of space between your house and any organic fuels that can be found in the area. It’s not perfect, but it certainly will help if the fire is partly controlled in that area and not too hot.

Fire and flooding are absolutely related. Some of our worst floods come after our largest fires. The idea is that, naturally, vegetation soaks up a lot of water. The way the roots are structured in the soil helps that soil absorb water. So when that vegetation is lost through something like a fire, less water is able to be absorbed into the soil. When that happens, you end up with a lot more of what we call “overland flow” – water going over the surface rather than through the soil itself.

In addition to that, as you lose some of that root structure, it’s more likely the soil itself will move and erode, causing landslides, rockslides and debris flows.

I think for us to believe we can take disturbance out of the system is a really bad idea. I don’t think we’re ever going to be able to do that. The more we understand about the impacts of disturbance and how we can potentially mitigate or manage them in a way that is more safe for humans and a way that also increases the diversity and the populations of our native organisms – I think it’s a win-win.

If we can actually accept disturbances on the landscape and utilize them to the best of our ability, we absolutely should. Societies like many Native American tribes did that very well and it’s something that we have the ability to do as well.