Announcer: The following presentation is part
of the Agronomy and Horticulture Seminar Series
at the University of Nebraska-Lincoln.
Caleb: Thanks everybody for coming.
My name's Caleb Roberts.
I have the pleasure today
of introducing Victoria, or Tori, Donovan.
She is a native of Canada.
She got her bachelor's at Queens University in Ontario,
and, Laurentian University in Sudbury, Ontario,
and then she moved down here to be in Nebraska,
and got her PhD in the Agronomy Department, UNL.
She studies landscape ecology,
and has a lot of her research, obviously, with fire.
One of her papers, "Surging Wildfire in the Great Plains",
published in 2017,
she had some interviews with the Washington Post,
got some national news on that, some really awesome stuff,
been cited many times.
More recently, I mean,
she's already knocked out three papers for 2021,
and we're only two months in, so pretty great work
that she's published in the "Ecology and Society",
"Biological Conservation", "EARTH Futures",
and multiple papers in rangeland, ecology, and management.
So today she's gonna be talking to us
about coexisting with fire in rangelands, so.
Victoria: Awesome, thanks so much, Caleb!
So as what's said, my name's Victoria Donovan.
I'm a postdoctoral research associate here
in the Department of Agronomy and Horticulture.
I'm really excited to be invited to talk today.
And today I'm gonna be talking to you
about coexisting with fire in rangelands.
So I'm sure many of you are used to seeing images like this
in the news at this point.
This is a picture of some California wildfires
from back in October 2020.
And we're seeing news stories like this increasingly,
you know, a lot of increasing wildfire activity,
particularly documented out West,
a lot of damage to property,
and this is causing wildfire to be a big issue
and a big discussion topic here in the US.
Now we know that large wildfire risk out West
has been quite high, or has been deemed quite high.
You can see this map that I've altered
from the National Cohesive
Wildland Fire Management Strategy.
All the dark red areas are areas that they've designated
as high risk for large, long duration wildfire.
So you can see the West has a lot of high risk areas,
whereas if you look at the Great Plains,
which I've outlined in black,
you can see that this region has largely been designated
as an area that's low risk for fire,
and this has been pretty consistent over the last century.
But as Caleb mentioned, with my publication back in 2017,
we actually identified that this is changing.
And so we actually found across the Great Plains,
we're seeing surges in wildfire activity.
We had a 400% increase in the total hectares burned
by large wildfires, and a 350% increase in wildfire number
between 1985 and 2014.
Now, we're seeing that there is a lot of spatial patterning
associated with these increases.
So in these maps of the Great Plains I've got here,
I've isolated different eco regions in the Great Plains,
which are basically a way
that we can subset the landscape to look at areas
with similar biophysical and geophysical properties.
I've color coded each one of these ecoregions
based on the rates of increase in wildfire number
and total hectares burned,
where the darker red areas are areas
where we saw greater increase in those two variables.
So you can see in terms of wildfire number,
we saw some of our greatest increases occurring
in the western and southern regions of the Great Plains,
whereas for total hectares burned,
we're seeing a lot of our increases
occurring along this western border of the Great Plains.
Now, of course, when we find this results,
one of the first questions that we ask is why.
Why are we seeing this change in wildfire activity
when we've had almost no large wildfires
occurring in the Great Plains of the last century?
And we can really investigate fire by breaking it down
into these three different components
that we know fire needs to exist.
So we need an ignition for fire to start.
We also need weather and climate that is conducive to fire,
and of course we need fuels for fire to burn as well.
And so we can break it down
and look at each of these components
to try to understand fire activity and changes.
So we talk about ignitions to begin with.
We know that human ignitions have been extremely important
here in the Great Plains historically.
Before Euro-American settlement,
indigenous stewardship of the land utilized frequent fire
to help to maintain the grassland systems
that we come to know today.
And you can see in this map here
that I've altered from Guyette et al. 2012,
outlined the Great Plains here in dark gray.
And you can see that we had a mean fire return interval
of about 2 to 12 years, so very frequent fire.
This made the Great Plains
one of the most frequently burned regions
in the continental US, but also globally, the Great Plains
is one of the most frequently burned biomes.
Following Euro-American settlement, as I've said,
we saw this complete shift in how firewood is utilized
and viewed on the landscape,
and so we went from this application of fire
by indigenous peoples to a complete halt in,
or an almost complete halt in fire management
across the Great Plains.
And instead we switched to active fire suppression.
So if we saw fires ignited through lightning
or other types of ignitions,
we generally move to suppress those as fast as possible,
trying to eradicate as much wildfire
as possible off of the landscape.
And so one place that a lot of researchers have been looking
is a change in ignition sources
to see if that could be driving
some of the changing wildfire activity.
This is particularly of importance out West.
We see in California, particularly,
human ignitions are playing a large role
in some of the increasing fires that we're seeing there.
And so this is a map
that I've stolen from Balch et al. 2017,
and basically each one of these points in this map
represent the number of fires and the percentage of fires
that are human ignitions.
So as the point size increases,
we have a greater number of fires,
and then as our color shifts from blue to red,
we have an increasing percentage of those fires
as human ignitions over their study period.
And so you can see our Great Plains,
I outlined here in the center of the continental US,
you can see that the majority of fires
that are composed of human ignitions are really occurring
along this Eastern portion of the Great Plains.
And if you recall, most of our large wildfires
where we're seeing the greatest increases,
is along this western and southern portions
of the Great Plains.
So while we know that human ignitions
are playing a role here in the Great Plains,
it doesn't seem like that might be a major driving factor
for some of the increases
that we've documented most recently.
Another thing that's really important
for us to think about is weather and climate.
We know that this is playing a huge role out West
in terms of fires,
and there's a lot of research documenting that.
While we have a lot of information in the Great Plains
at smaller scales, looking at the interactions
between things like drought and fire,
we have a lot less information and research
looking at these large scale shifts in wildfire patterns
and regime characteristics relative to drought.
So I'm just gonna show you some preliminary analysis
that I've conducted on this.
You can see here in our map,
this is a large portion, at least, of the Great Plains,
where I've taken out wildfires from 2000 to 2012.
And we've color-coded those based on the drought conditions
under which they occurred.
So if you have a perimeter here
that's colored in dark green, for instance,
that's a wildfire that burned under very moist conditions.
Whereas if you have a perimeter that's orange or red,
those are more severe or extreme drought conditions.
So you can see, again, this kinda spatial patterning
on this eastern portion of the Great Plains.
We're seeing a lot more fires occurring
under near-normal and moist conditions.
When we shift over
to this western portion of the Great Plains
where we're seeing more increases in large wildfire,
we see that those fires are more likely to be occurring
under severe, moderate, and extreme drought conditions.
And we can look at this another way
if we break this down by fire frequency relative to PDSI,
the Palmer Drought Severity Index,
which is our drought indicator.
You can see I've got these color codes
down here on the bottom,
and you can see that we definitely have
a lot more frequent fires under drier conditions,
particularly under moderate and severe drought conditions.
So clearly weather and climate are gonna be playing
a huge role in our fire distribution in the Great Plains,
and it's something that we need to look into further.
But a lot of my research has focused specifically on fuels.
One reason is because for individual landowners,
it's a lot easier for them
to manage for fuels on their property
rather than trying to manage for global climate.
But the other thing is that we've seen massive changes
in fuels here in the Great Plains over the last century,
in addition to fragmentation and agriculture development.
We've also seen this large shift
from grassland to woody vegetation in a number of areas.
And this has really been associated
with the removal of fire from the Great Plains
that's leading to all of this woody encroachment
into grassland areas.
Basically, historically, if we had frequent fires
moving through grasslands,
they would've killed woody seedlings
that were trying to establish in a grassland,
and it would prevent woody establishment and growth.
So I just want to give you an example here,
looking at Nebraska,
in terms of patterns of woody encroachment for this region.
If you look on the left here, we've got different plots
from all of our conservation landscapes here in Nebraska,
and in each of these plots, we're looking at the change
in woody cover and hectares over time.
So on our x-axis, we're looking at time from 2000 to 2017,
on our y-axis, we've got woody cover in hectares.
And you can see
in the majority of our conservation landscapes,
we're seeing an increase in woody cover.
This can be looked at another way as well.
If we look at this map that we've gotten here,
excuse me, you can see all of our rangelands here
are color-coded, all of our rangeland areas in Nebraska,
and everywhere that's red is an area where we found increase
in percent woody cover through time between 2000 and 2017.
Blue areas are where we saw a decline.
So you can see that in Nebraska here over the last 20 years,
we're seeing a major shift towards woody vegetation.
And this isn't just happening, kind of,
in remote areas or conservation landscapes,
we're also seeing it in our managed areas,
and areas where we thought might be less susceptible
to woody encroachment.
So we did an assessment looking in the Nebraska Sandhills,
and we were tracking eastern redcedar establishment
from windbreaks, and its encroachment
into our our rangeland systems and near our farmsteads.
And what we found is that about 25% of windbreaks
that we assessed actually had established eastern redcedar
spread in the Nebraska Sandhills.
So I was really interested to understand
how woody encroachment and other land use changes
might be influencing wildfire patterns.
And so in this map here,
we're looking at the five different land use types
that we assessed in the study.
We were looking at herbaceous vegetation, woody vegetation,
crops, pasture and hayfields, and developed areas.
We've got all our wildfire perimeters that we assess.
This was from 1993 to 2014, these wildfires.
And what we wanted to see is
if wildfires are burning disproportionately more
within certain land use types.
And so if we look for the Great Plains as a whole,
what you can see is that we have really low wildfire risk
in crops, pasture, hayfields, and developed areas,
whereas we have higher wildfire risk
in herbaceous and woody vegetation.
Now, the really interesting thing about this
is that we see that woody vegetation
actually holds the larger,
or the highest large wildfire risk,
while herbaceous vegetation is generally more flammable,
it's more pyrogenetic.
We are seeing that woody vegetation
is hosting the highest wildfire risk.
When we break this down and look at the relationship
between the amount of cover of herbaceous
and woody vegetation on an individual landscape,
and how that affects large wildfire risk,
what we can see is that you need about 60% of your landscape
to be covered in herbaceous vegetation
before we see this spike in large wildfire risk.
So a relatively contiguous herbaceous cover
across your landscape.
Whereas when we look at the same thing for woody vegetation,
we see you only need about 20% of your landscape
covered in woody vegetation
before we see this increase in large wildfire risk.
So only small amounts of woody encroachment
within these areas before we're seeing
an increased large wildfire risk for that area.
When we broke this down,
and looked again at those different ecoregions,
I mentioned in the Great Plains,
you can see there's clearly a lot of variability here,
but when we isolate the ecoregions
where we had the greatest increases in wildfire number
and total hectares burned,
we can see that in almost all of these ecoregions,
woody vegetation by far
held the greatest large wildfire risk.
And recall that I mentioned
that the Great Plains' fire regime is now really dominated
by our ability to suppress fire.
And so the reason why we think we're seeing more wildfires
occurring in woody vegetation,
even though we know that grassland vegetation
is generally more pyrogenic,
is because there's a pretty big difference
in our ability to suppress fires
that are occurring in grassland vegetation
compared to woody vegetation.
And you can see this pretty clearly with this image
I've stolen from Dirac Twidwell.
On the left here, you can see flame links
that are occurring in herbaceous vegetation,
and when you look on the right,
here you can see the flame links that are created
when an eastern redcedar tree is alight.
And so obviously it's gonna be a lot more difficult for us
to control and suppress fires in this woody vegetation
compared to the herbaceous vegetation
under the same conditions.
So basically what we're learning from this
is that removing fire from the Great Plains
has really helped to promote woody encroachment,
and woody encroachment
seems to be helping fuel more wildfires.
So we kinda have this cyclical pattern here,
and it makes me think of this quote,
"Can't live with it. Can't live without it."
Over the last century, we really thought,
we can't live with fire,
let's try to remove it as much as we can from the landscape,
and it's turning out that we really can't live without fire.
If we remove prescribed fire
and the application of more controlled burns
on the landscape, we're seeing this shift
towards more of a wildfire dominated regime.
And so I wanna just put a question mark
beside the "Can't live with it".
And that's because we've seen that people can live
and co-exist and thrive with fire here in the Great Plains.
Just again, as a reminder, indigenous land stewardship
utilized fire frequently across the Great Plains
to maintain grassland systems
for thousands and thousands of years.
And we're starting to see an uptick
in people embracing burn culture in the Great Plains
to help mitigate against woody encroachment
and large wildfire risks.
So, as an example, in the Loess Canyons of Nebraska,
a location that's seen a large amount of woody encroachment
into their rangeland systems,
we're seeing landowners band together
and start applying prescribed burns
across a lot of their landscape.
So in the map in this corner here,
you can see the outline of the Loess Canyons,
and all of these orange polygons in the map
represent prescribed burn perimeters
that were applied by landowners in the Loess Canyons
over the last, around 20 years.
So why are we not seeing more prescribed fire
on the landscape?
Well, there's a lot of concerns
around prescribed fire that people have.
So I'm just gonna talk about a few of these,
and try to kinda cancel out some of the fears of fire
that some of us might hold.
The first one that a common concern is for people is that
prescribed fire, and fire in general, is quite risky.
And so I'm gonna steal an example
from Dirac Twidwell's paper that he published back in 2015,
where he was looking at the rate of fatal injuries
associated with different surrogates for range management.
And I want to focus particularly on two here,
looking at firefighters over here on the far left,
and logging workers over here on the far right.
And firefighters, he uses, really,
as a surrogate for fire management,
obviously a little bit more extreme,
'cause firefighters are generally dealing with fires
that are out of our control, whereas fire management
is dealing with prescribed planned fires.
And then logging workers can be compared
to this idea of mechanical tree removal.
So a lot of us
are currently applying mechanical tree removal
to try to get rid of eastern redcedar trees
and woody encroachers,
it's a lot more costly method,
but a lot of people perceive this as a more safe method
than using prescribed fire.
And so you can see
when we compare the rates of fatal injuries,
clearly this perception is a little bit off.
We see a lot lower rate of fatal injuries for firefighters
compared to logging workers.
We also know that the number of fatal injuries associated
with wildfire is much higher than prescribed fire.
So if we choose to use prescribed fire proactively
to help prevent wildfires,
we should have a much safer outcome
than waiting for wildfires on our landscape.
Another common concern people have with fires
is that fire can drive losses in grasses.
And a number of people have concerns associated
specifically with desertification driven by fire.
So this is when we shift from grasslands
into a bare ground state.
So if we have a very hot fire under drought conditions,
there's concern that the grasses
are not going to be able to reestablish.
And we see a lot of people applying seeding to the landscape
after fire to try to help grasses regenerate.
And so we wanted to see how grasses are regenerating
across the Great Plains, relative to fire,
and we wanted to use extreme examples.
So we, again, went back to our wildfire perimeter data,
and we wanted to track how vegetation was responding
to these wildfires across the Great Plains.
And so what we did here, you can see in these plots,
we're looking at the relationship
between mean cover and time since fire.
I've got two different cover types here.
We've got perennial forbs and grasses,
and then we're also gonna look at bare ground as well.
So in these plots, this red bar here
represents the time of the fire,
so when the fire occurred,
and then this gray bar is representing
our pre-fire range of variation.
So we looked 10 years before each fire,
and we wanted to see how much variability
in perennial forbs and grass cover,
or bare ground cover, there was,
before the fire occurred to kinda get a pre-fire,
like I said, a range of variation
that occurred before the fire.
We wanted to track and see if our vegetation
returned to this pre-fire range of variation,
which would indicate recovery.
And so you can see pretty clearly here
with perennial forbs and grasses immediately following fire.
We see this drop outside of our pre-fire range of variation,
but within a year, we're already back
into our pre-fire range of variation
for perennial forb and grass cover
when we look at all fires averaged across the Great Plains.
Similarly with bare ground,
we see this corresponding spike in bare ground cover
the year of the fire, and we see that rapidly return
to our pre-fire range of variation.
So basically this response was so consistent
across fires in the Great Plains
that we could detect it at this biome level.
We also broke this down and looked at smaller scales,
so again, we're looking at our individual ecoregions here,
and you can see again, rapid recovery of perennial forbs
and grasses following fire,
and actually in a lot of cases,
we don't even see that fire drives a decline in cover
below that pre-fire range of variation.
We also went down even further
to individual wildfires and individual pixels as well,
so a 30 by 30 meter area, to assess vegetation recovery,
and we saw rapid returns to pre-fire range of variation.
So I'll give you an example here,
from the Region 24 Complex fire that burned
in the Nebraska Sandhills back in 2012,
and the Nebraska Sandhills is perceived as an area
that's quite sensitive to fire,
particularly under extreme drought conditions.
And this fire burned
under extreme drought conditions back in 2012.
And we can see this rapid recovery
of perennial forbs and grasses.
In contrast, we see that trees are quite sensitive to fire.
So we can look at an example here,
the Northwestern Great Plains ecoregion.
At the ecoregion scale, we detected a persistent decline
in tree cover following wildfires.
We see this pattern again, when we go to smaller scales,
if we look at the wildfire scale or a local scale as well.
We can also see the ability of fire to remove trees
from a landscape if we look at this.
That paper I was mentioning before,
that was led by Dylan Fogarty,
where we tracked changes in woody vegetation cover
through time between 2000 to 2017.
In these maps here, everywhere that's blue
is where we've lost woody vegetation cover.
And we've outlined here, wildfire perimeters in dark red.
And so you can see the association
between wildfire perimeters and the loss of woody cover.
But it's not just wildfires that are driving declines
in woody vegetation.
We can also see that as well
when we look at the prescribed fires,
if we go back to the Loess Canyons again.
So here, all of these black outlines
are perimeters of our prescribed fires,
and you can see the effectiveness of these fires
at either preventing further woody encroachment
into the prescribed fire perimeter,
or we see that it's driving losses
in woody vegetation cover.
And we tracked tree cover through time in the Loess Canyons,
we actually saw this plateau
in the increasing amount of tree cover in that region,
and we associate this with an increased amount
of prescribed fire on that landscape.
So to sum up with this,
what we know is that prescribed fire can help us
to fight increasing wildfire
by reducing fuel buildup in grasslands.
It also can prevent woody encroachment in grasslands,
and it can help to remove woody vegetation
in invaded grasslands.
So this is a really great method for us
to try to reduce large wildfire risks,
which we're seeing increasing across the Great Plains.
We know that prescribed fire can be used more safely
than other more costly options,
like mechanical field treatments,
and we also know that using prescribed fire is a lot safer
than waiting for wildfires to burn on our landscape.
And so I think it's time,
as we see this increasing amount of wildfire
in the Great Plains,
that we start to embrace more of a fire culture.
In order to coexist with fire,
the best path forward for us is to embrace prescribed fire,
and embrace the fact that fire belongs
on our Great Plains landscapes.
With that, I'd just like to thank some of the funders
that helped support this work.
Of course, thank the department for having me,
and I'd be happy to answer any questions
that you might have.
Caleb: Thanks, Tori.
That was really, really good.
So Tori, with everything you've done,
what are, like, maybe next steps for looking at fires
across the western rangelands,
what are your, maybe, next research priorities?
Victoria: Well, for me,
one thing that I do want to look into more
is the relationships between climate vegetation and fire.
I think that's something
that we really need to couple together.
There's a lot of information
that we still need on those patterns.
I'd also really like to investigate the relationships
with changing wildfire out West,
and how that's kinda moving into the Great Plains.
I'm kinda interested to see,
because we've got this western,
kind of, edge of the Great Plains
where we're seeing a lot more increasing wildfire,
and I'd like to understand if that's linked to changes
in the western US as well.
Caleb: Maybe I could just talk, maybe,
about the interactions you've had with media about fire,
and just your experience with that.
What do you think is the thing
that drives people's imaginations with fire research
and fire on the landscape the most?
Victoria: I mean, I think there's a lot of concern
about fire, rightfully so.
You know, if you look at this picture that I have here,
it's kinda scary,
but I think the big thing that we need to push for
is the understanding that, you know,
fire can be used safely, and in a controlled manner,
and it's not a negative thing.
So, you know, we have Smokey the Bear,
and all of these fire prevention,
outreach pieces, and, you know,
I think from a media point of view,
there's a lot of doom and gloom about increasing wildfire.
And I think it's important to recognize the benefits of fire
and how we can use fire, and co-exist with fire
in a safe manner in these landscapes.
Announcer: There is a question in the chat
from Erin Scheffler,
"How do you think the initial burn of the existing trees
"in these landscapes could be managed effectively?"
-: So, Erin, are you speaking about the tree skeletons
that exist after a fire or?
Erin: Yeah, the existing skeletons could be fine too.
I just didn't, it seems like there's so many trees already,
but like, it would be kind of unmanageable
to start the program, you know?
-: Right, well, it depends on the area,
I mean, the Loess Canyons is a really great example.
They use something, I think this is what they say is,
tuck and stuff, is that right,
where they'll cut other eastern redcedars down
around the perimeter and stuff those
underneath standing trees to help move the fire
from the ground into the tree.
Because it is true once cedars establish, it is quite dense.
You know, all of the herbaceous fuels underneath
aren't there to carry the fire through anymore,
and so you do sometimes need those extra management steps
to help move a fire up into the canopy
to kill the cedar trees. -: Cool, thank you.
-: Thanks -: Thanks, Erin.
We have Dan Yude. -: Yeah, thanks, Tori.
I was just, you know,
you were mentioning there at the end,
looking at maybe comparing Great Plains wildfire activity
with, you know, further west, maybe the Great Basin,
or further, the entire western US.
And I was also thinking about, you know,
it was about a year ago that Australia
was really in the midst of those massive wildfires,
and there was so much about that in the media,
but then of course COVID came on the scene,
and then all of a sudden
that kinda dominated much of that news,
but I guess I just never really followed up
on some of the Australian impacts.
I mean, I guess I'm asking
if you could speculate on globally,
moving from even a North American perspective
to a global perspective,
are there any sort of similarities there,
in perhaps regions of Australia
that would be more similar to the Great Plains
that you can make connections with?
-: I honestly don't, I am not as familiar,
or I can't recall right now, all of the drivers
about why that wildfire season was so bad in Australia,
I'm assuming it was linked to changing climate,
I think there was a drier period,
and obviously there's changes.
I think, you know, in most locations you see,
if there's more precipitation in a certain area,
you get fuel buildup,
and then you have a more extreme drought period,
and then it's easier for fuels to ignite and burn.
You have a greater fuel buildup.
Caleb: Thanks so much.