Narrator: The following presentation is part
of the Agronomy and Horticulture Seminar Series,
at the University of Nebraska-Lincoln.
Caleb: Rheinhardt Scholtz is a Post-Doc
in the department.
He is originally from South Africa.
Got his first degrees from there
and then now he is been here for,
I don't even know how long.
You were at Oklahoma State for a while,
where were you before then?
Rheinhardt: Yeah, before Oklahoma State,
I was sitting in South Africa.
I was working at South African National Parks
while doing PhD, yeah.
Caleb: So his first foray into the North America
was in the Great Plains, so.
And he has done work and published
in biological conservation landscape ecology
with breeding birds, with fire,
with landscape use and change,
so he's quite the landscape ecologist as well.
So, I'll go ahead and let Reinhardt start talking.
Rheinhardt: Thanks, Caleb.
Well, thanks again.
So I'd like to start off with acknowledging
some of the important components that have enabled
some of this research that I'll share with you today
such as the Holland Computing Center.
Sam Fuhlendorf and Steve Archer who have been instrumental
in some of the initial conversations
and the National Science Foundation that funds my research.
So this talk will kind of segue between these four points.
There might be here in there me sneaking off
and going on a little bit of a tangent here and there,
but I guess we were allowed to
it's a kind of a weird period of time nowadays, yeah.
But what's brought us a little bit closer nowadays
I think is this we in middle of a pandemic
we find ourselves in now.
We've been instructed to go out to nature
and go an experience, go for a walk.
And I think of that as someone that's,
well, speaking to the choir here for sure
but we all conservation minded
and we have those connections.
But more often than not when I think about keeping those,
separating people from nature,
I often think about natural landscapes
that are being turned down to become sort of monocultures.
So we had this heterogeneous landscape
that had some sort of biodiversity attached to it.
We convert it to something else that is generally ups
to what it was before.
And often, most times we don't really know
what that means for biodiversity but such is life.
But what we really wanna think about is this,
what is this?
This is what I'm thinking about
when I'm thinking about enjoying these landscapes.
Not thinking about what it means for biodiversity
when we destroy them but more how can I enjoy it?
And I know we all have these experiences
and that's really what I should be thinking about
when I think about how it's becoming difficult
to separate people from nature.
But we are approaching seven, eight billion people
on this planet, never been seen before.
Our society has grown in pretty much every aspect of life.
Enormous Ag farms of course, replacing natural areas.
Medicines better, we live longer,
we need to feed longer.
We need places to live.
Urban areas are expanding and they generally don't expand
at the cost of other areas.
They expand at the cost of natural landscapes
that are deemed unused.
We influence fire of course,
and this would be a recurring theme
that will come across.
They are a number of processes
that we're doing while we expand and grow and develop.
Our climate is of course changing.
And it's not just that it's changing,
it's changed a number of times before
in the geological timeline
but it's changing faster than it has before.
We are are able to track wild weather
a little bit better now
because of our advancements in technological society.
So there's a lot going on.
We find ourselves in this fast-paced world,
time flies and we often struggle
to just take a moment to breathe in.
But this pandemic really connected us.
Well, it certainly connected me back
to my feet on the ground,
the society take it in what I've got.
And think of it, there aren't many things that connect us
or connect the globe.
Too often together we all often live in our own world
and that's okay, that's what it is.
But these are those moments where you
just gotta take it in for the second
and see what is going on around me.
So what my talk will really focus on is open biomes
and rangelands, of course.
One of them grasslands,
they're called a number of things depending
on where you are in the world.
South America, they're called pampas.
In Asia you maybe find a lot of steppes,
there also rangelands.
And in Africa bunch of savannas as well as there
which can be considered open biomes.
But really what I wanna focus on are grasslands
and what I have displayed out here are two simple boxes,
taken from a Pausas and Bond's paper in 2020,
looking at the dynamics of open biome versus closed biome
and how they can switch between the two.
And really what it boils down to for a open biome
to switch to a closed biome.
We go from open biome exceptional wet years,
accompanied by long fire intervals
which can become a closed biome and vice versa.
A closed biome accompanied by exceptional dry years,
followed by one to two fires can become a open biome.
And the reason why this is important is because
of a simple Whitaker model that was developed in 1975.
Where he pretty much mapped out
the entire world on two axes,
temperature and precipitation.
And rangelands or open biomes will find themselves
in an envelope that's shared with a number
of other ecosystems but each of them are unique.
Each of them are unique systems.
So this area that I kind of highlighted in red,
ranges between minus five degrees celsius
and about 25, 30 degrees celsius,
and anywhere between 500 mils to 1500 mils of rainfall,
which can sustain a number of ecosystems.
Now, that might be pretty cool, you know more better.
But the truth is that's not necessarily super cool
when you think of a grassland system
that becomes something else.
You generally lose that grassland system
and you lose the services that comes along with it.
So as Tony mentioned, we know that fire matters
in the rangelands and we know that woodland expansion
is a bit of a problem right now.
And it's a problem in the Great Plains,
it's a problem in the South and South America.
It's a problem in Asia, it's a problem in Africa.
It's a problem in Australia.
Everywhere we have these temperate zones
and sometimes the subtropical zones,
woodland expansion is a problem.
We did a simple little study here to show
how can we mitigate that?
And what we found was when we looked
at expansion over height classes,
we realized that the only time when we actually saw
an effect of expansion was when fire was combined
with a herbicide application.
And this was a little small study area down
in Stillwater, Oklahoma.
But most of the problem was that when you got to tall tees
your herbicide didn't really do anything,
and you really needed fire
and you kinda needed higher intensity fire.
And I know that Tony and Dirac knows a little bit more
about that than I do.
But as we scale this up,
this idea of how can we manage our tree cover
over the Southern Great Plains
or any encroached rangeland,
our current efforts are falling a little short.
I've split three panels out of Kansas, Oklahoma and Texas,
ranging from the year 2000 to 2018
where we looked at tree cover on the y-axis.
And this general trend where Kansas
has as an increasing trend,
whereas Oklahoma and Texas kind of starts where they are
and they don't really go too much higher
but the generally don't decrease.
And we proved this actually looking at
even though we had 10 years of brush management data
during our time period of information
on functional group cover.
You'll notice the pink bars are just looking
at the change between the year 2000 and 2017
of each functional group.
And the pink bars represent tree cover
and all of them are positive.
And that really means that all the time
and money and effort that's been spent right now
in the Southern Great Plains on brush management,
it's not really working.
So what's going on.
We find that, well A,
we need to really get better at mapping fires for example.
We did a simple study looking at this in conjunction
with the Kansas Department of Health and Environment.
Where these guys have, I think in recent years,
over the last 10 or 15 years, don't quote me on that,
but they've been really concerned about smoke.
And as fire generally occurs in the Flint Hills
mostly in the spring and most there's a certainly
a culture of burning.
So smoke has become a huge concern.
But in order to manage smoke,
we actually need to know how much fire
you have in the landscape.
And what you're seeing on the left panel
is a simple remotely-sensed map taken
from a MODIS fire sensor.
And on the right is a Kansas customized map
on that same center.
And what the customized map does is,
well, if a fire was predicted by the MODIS algorithm,
Kansas folks will send someone out
to actually go and check exactly where the fire was
and map that barometer.
But what we find is that when they did that
they actually improved almost 30%
of the parameters detected, that's big.
And what we took away from this message was,
while we're really terrible at mapping fires in open biomes,
there's a number of reasons for that.
And the most obvious one is that open biomes
such as rangelands recover quickly.
And it might not be detected
by simple reflectance techniques.
And most of these remotely-sensed sensors
that are out there today in fact,
were developed to map forests.
And what we also find out, well, we didn't it like this
but there is really no substitute for ground-truthing
or there's no substitute for field work.
You gotta go out there and see what's going on.
So we took this one step further
and using some of Dan Uden's work from spatial imaging
and we wanted to know,
well, we've got the most frequently burnt tall grass prairie
in the world.
There is none other like the Flint Hills, it burns.
And we wanted to know, well, just how much fire
is required to sort of maintain this undesired transition
which is woodland expansion.
How do we keep it at bay?
And what we did was...
So on the right you're seeing a little animation
that's just ticking through from the year,
I think it's 2000 to 2017 or 2018.
And everywhere you see these orange and red areas pop up
it just shows the severity of the undesired transition
which is the grassland becoming a woodland.
And what we've actually quantified is that
if we experience a fire between every...
Any pixel that experiences a fire
between two to three years,
we can actually move away from that time decision.
We can curb it, we can stop it.
So if it is in the middle, for example,
you kind of see it stayed green.
And those are those acres that tend burn every year.
There is no opportunity for woodies to come in.
But on the edges, on the South is generally wetter
and the East is the generally wetter.
And of course the riparian zones,
there's opportunities for woody plants to go in
and its opportunities where fire generally
doesn't carry as often because
of the underground herbaceous layer.
So it's really cool that now we have this information
coming from the rangeland analysis platform
to actually quantify exactly what's the
desired fire return interval.
And that brings me to my next slide
that really talks about fire return interval.
and it's perhaps, I guess.
Maybe Tony would know better but fire return interval
tends to be the most commonly talked about component
of the fire regime.
And early in 2020 Dirac and a bunch of us as well.
We worked on this idea where,
the fire regime actually is made up of
a number of components and the return interval
is just the one.
And what we have on the left pie charts
ranging from colors of orange to red
are what we consider sort of eras of society operating
on the world and on the landscape using fire.
We kind of this is all theoretical
and we call this the orange fire for example,
the coexistence era where we have natives
all over the world generally utilizing landscapes however,
in terms of fire burning throughout the year, for example.
So that would be the seasonality pie.
So you could think of the seasonality pie broken up
into 12 months and you could highlight exactly
how many months do we detect fire.
And we suspect that during the coexistence era
people would burn as needed and that didn't change.
It didn't really matter what time of the year,
it was just perhaps more based on the conditions.
We'll never know for sure but that's what we suspect.
But if we take their seasonality pie
and move it through each year,
we can actually see how it's changed
based on how society has behaved.
So suppression era, we pretty much eliminated fire
off that landscape.
The shadow which we currently see green,
we've reduced seasonality.
So for example, as I mentioned,
most fires in the Flint Hills occurred in the spring,
sort of March, April.
And now we're kind of approaching this wildfire
that Tony mentioned that perhaps we are now getting back
to the coexistence era in some of these components
where we can find wildfires any time throughout the year
and et cetera, for example.
So what we now wanted to see was,
well, how could we really studied
this components of fire in rangelands?
And the truth is it looks a lot like the shadow era,
'cause we haven't really studied fire in rangelands.
Because they are just many other concerns
that we have to deal with.
Tony brought this up.
Safety, for example.
So why this all matters is because
we know fire as a global herbivore.
And William Bond and John Keely did this cool study
back in 2005 where they plotted tree biomass on the y-axis,
plant moisture on the x-axis and the solid line
sort of increasing linearly with plant moisture
that pretty much showed the more water you have,
the more rainfall you have the higher the kind of potential
you can have for tree biomass or woody cover,
or you can change it to something whichever you feel like.
Number of plants, et cetera.
It doesn't really matter at this point.
But what they realized was we actually don't see that
when we go out in the field.
Most times we don't see that.
What you actually get is something much less
than the climate potential just because of our landscapes.
We think of biomes, biomes are some sort of association
of climate vegetation and fire.
Fire is an integral component in developing these biomes.
So consumer control really matters,
and we can include fire in that
but we can also include humans in there.
We can include anything that influences the landscape
to manipulate fire regime, that's what the consumer is.
Some recent work has actually shown
that over the last I don't know what is that 12 years or so,
we've generally just seen a decline of fire activity
at a global scale.
And this is really in contrast to what we see
when we're focusing to little areas such as what Tony
was mentioning in the Great Plains
where we start seeing these spikes in wildfires, et cetera.
But from a global perspective,
it's just generally decreasing that's...
And data it's all that actually pointed that out,
directly linked to agricultural expansion.
And that might be in certain areas
that once had huge fire components
whether it be burned area or number of fires
and no longer contributing that amount
to the global signals.
But also some previous work has shown
that we know that fire is so important
that it's actually the determining factor
for these open biomes.
And that's very clear in African savannas,
for example if we think of passability
between alternate states.
And there's no substitute for fighting these landscapes.
If we think of some places like tropical
and subtropical Africa and Australia for that matter,
fire is the reason why we have those landscapes,
those savannas.
Without fire, we really don't know what we're gonna get.
And this brings me to some of my next ideas
of conceptualizing this I suppose grand idea.
But it's to think about how we've studied biomes
over the past century?
So we can sort of agree that the biome
is the largest unit in our vegetation classification.
But the truth is it's not just vegetation,
it's climate and we know for a fact that it's also fire.
If we think back to Clemens days,
we know that climate was the idea,
the sort of the one exogenous
sort of factor driving vegetation.
What we saw on the landscape was because of climate.
And for several years, several decades,
that was how this holy grail and that's just the way it is.
And strangely enough, nobody will ever disagree with that.
That climate really will determine vegetation
but we now know that as we start diving into deeper details,
there's other things that really matter.
So we move from this climatic climate concept,
all the way to the ecosystem landscape concept
to national fire regimes.
Where we see soil and water and elevation start
to really influence the vegetation patterns we see.
But as we move to this fire idea,
we realize, well, actually if we have vegetation
as a result of rainfall or climate,
we can actually burn that
and it can look like something else.
But in today's time,
we realize that who's really controlling fire.
Why do we see declines of fire over the world,
what's happening?
We think that, well, we know that most of the fire today
is ignited by humans by some way or another.
Yes, there are exceptions.
Lightning fires certainly happen,
but the incidences of those are not as high
as the ones that are ignited by humans.
I don't remember exactly what caused the fires in Australia,
but I know that most of the indigenous groups down there
were not very happy with the kind of practices
of prescribed fire.
There was a huge suppression treaty happening
over recent years and then accompanied
by a number of years of drought
which actually led to the Australia fires.
But if we dive deep into this idea
of biomes changing over time,
we can jump into areas that used to burn a lot.
So we know if we look at temperate grassland savannas
and shrub lands all over the world,
we know these areas used to burn a lot.
That's what maintained,
open biomes stayed that way because of fire,
thinking of the people that live there.
So when we compare that now.
If we consider the amount of contribution
of each continent on earth,
contributing to temperate glass and fire signal,
it's pretty low, it's very low.
In fact, there's like a tiny slither
of red showing out there and that might be the Flint Hills
but it's not that high.
If we switch over to the tropical and subtropical grasslands
what we actually see is only Africa and Australia
is really contributing to an annual fire signal
for this entire biome.
You could even think of it as it's getting the biome signal.
So this again, there's this mismatch between
what we know set these biomes up in the way they are,
but now people are controlling it.
We don't really know what that means for the future.
So if we can focus a little bit further
into this temperate grasslands for example,
we wanted to dive a little deeper and see what's going on.
Why do we see these varying signals?
So one little thing that has popped up for us
is that we notice a difference in fire season
throughout the temperate biome.
So in North America as we know,
most burns happen in the spring.
But when we switch over to Asia,
most burns are happening later in the year.
There's no right or wrong
but that influences the fire regime,
that actually influences the fire intensity for that matter
when you decide to burn.
And fire intensity is a large component or the fire regime
and we don't know what that means for changing
at least at the biome scale.
And when we take the step further,
we developed some theoretical ideas.
We like to do that if you haven't noticed by now
but what we have is each biome listed from top to bottom.
There's no real order.
I think it's in fact alphabetical.
And we have the mean burned area over a 17 year period.
The gray, the darker gray bars are actual MODIS fire
that we calculated for the percent mean burn area
for a particular biome.
And the gray bars are what we think
is a sort of a pre-settlement signal.
We don't really have data for this.
We would probably never really get data
but they are global scale papers written
by David Bowman et centra, Stephen Pyne
who talk about these patterns.
So for example, we could see something
like the temperate grasslands had a generally
a fire signal similar to the tropical grasslands.
But where do we see the biggest changes nowadays,
it's out there.
So we know that temperate grasslands do not burn as much
as they used to.
But all of a sudden we seen tropical forests burn
a lot more than they used to.
We don't really know what that means for the longterm.
And we actually wanted to find out exactly
why temperate grasslands are doing what they're doing.
And we looked at this from a land cover perspective.
So the top spatial map is just showing you the amount of...
We looked at grassland fire activity over time.
So what we got from each pixel was a slope.
So we know, well, unfortunately what we see
is decreasing slope for every pixel in this biome
and each pixel refers to a particular land cover type.
And the one that shows the biggest decrease over time
is the grassland pixel.
And almost all of the other pixels align somewhere negative
which generally just shows a decrease
in fire activity over time.
But the most pixel that's representative in this biome
is in fact grassland pixel.
So it's carrying the signal essentially
of showing a general decrease over time.
That's a concern 'cause we don't know
what that means for our systems.
We don't know what that means at a biome scale.
So and I'm approaching the end of my talk,
but I wanted to just bring this slide back up
about why it's important to think about our open systems
in a more holistic view that they are able
to become something else.
And it's really essential that we keep processes
that are in the yellow box,
keep them the way they are if we want to maintain them.
And we are building a case
about why we should maintain them the way they are.
So we've isolated most of the grasslands in the world.
We actually refining this but these are,
if you just focus on the temperate regions
which are on the top section and mostly on the bottom.
We wanted to see how many of these eco regions
in parts of the world meet this criteria.
And all we did was we took little grassland pixels
and we wanted to just quantify how many of them meet
this queens case criteria?
How many of these pixels are surrounded
by eight other grassland pixels essentially?
And we find some really cool results.
Well, cool for North America,
because they are two in that region.
The Wyoming Basins Steppe and Nebraska Sandhills
in fact have a very intact grassland system.
But they are many others that don't.
We think that when we wanna consider
what it means to be intact,
we know that it's more than just how many pixels
are next to one another and that's for sure.
But if we can identify regions such as these,
we might be able to prioritize where we wanna go.
So I know I'm preaching to the choir here on this talk
but I think it's really important why we need
to be predicting these major last grasslands.
And other than these open systems
there are several world heritage sites out there.
They are home to many endangered species.
And the cultural hidden teach that actually exists
on these landscapes are, it's invaluable.
We really can't replace that.
And what's very cool about them is that
no matter where they are in the world,
they are all linked by this lifestyle dependent livelihood.
And that's something really cool that we don't wanna lose.
However, we cannot talk about why
they are these last grasslands
without thinking about the threats.
And in 2017, we published a paper looking at
number of land use changes using crop scape data
which is high-res, I think it's 3 meter resolution data.
Just we wanted to know how many
of those grassland pixels became something else
over a 10 year period.
Initially, we thought it was a small period of time.
But when we looked at the results,
we realized there were enough of them
that turned about eight times over the time period.
So between Oklahoma and North Dakota,
we found that places like the Sandhills and the Flint Hills
actually remained relatively stable.
And some of our latest papers are actually
confirming some of that result.
But we do realize that where they did change,
most of the grasslands became either croplands
or became encroached by woodlands.
And the one other threat I wanna add to that
is energy development.
And perhaps in North America,
most of the energy development is,
well, at least from a development perspective
it could be mostly wind.
But if you move to Asia,
most of the threats in the Asian grasslands are mining,
and it's oil mining and mineral mining.
So the giant elephant in the room,
we control most of the world's fire.
It's really up to us to maintain these biomes.
And especially if we don't wanna lose
our temperate grasslands.
So some concluding remarks is that
the world is changing of course,
but it's really changing at a faster rate than we think.
And I have to remind myself every day
that the small-scale changes that we make
can really make a big global ecological impact.
And something that really stood out for me
when I was looking into these regions of the world,
these temperate grasslands
when I compared North America to Australia,
both regions have a shared vision.
But in Asia, a shared region meant protected area
that was federally mandated.
In North America didn't necessarily mean a protected area.
In fact, most of the landscape is privately owned
and I know you know that.
The point is it doesn't matter.
It doesn't have to be protected area.
As long as there is a shared vision, that's all.
As long as it's shared vision,
we all have the same common goal.
We don't really know what reorganization
of biomes will look like.
We don't know what it would lead to,
and we might have to rethink what we think we know.
And that might be something for the future
or for future generations or it might creep up on us
a lot faster than we are prepared for I suppose.
And another thing that it's really important
as we've come into this age of information
where a platform such as the Rangeland Analysis Platform
are becoming really available and easy to use
for real-time monitoring.
And they've used remotely-sensed information combined
with some epic long-term ground-truthed data points
to develop those products.
I really think that that combination
between field data and the remotely-sensed products
is really where we headed for some global scale
so it's where are we gonna keep our toes on it.
And with that, I say thank you very much.
Caleb: Thanks Rheinhardt.
We actually have a question lined up right now
from Andrew Hopkins.
I'll unmute you Andrew and let you ask it.
Andrew: Just curious how much of the woody encroachment,
what's that doing to aquifers
and water supplies and so forth?
Is it having a pretty negative effect?
Rheinhardt: A very interesting question.
So I don't know exactly what the woody encroachment
is doing at least from a global perspective.
But I know that during my time in Oklahoma state,
there were a number of eco hydrological sort of problems
that they found when as Juniper increase
the amount of water that was available
to the herbaceous layer most certainly dropped drastically,
even more so than just being out completely.
But I know for a fact, so the Sandhills
and I think it sits under the Ogallala aquifer sits there
and it touches about eight States.
We don't really know what that means
if we start expanding more woods start to come in.
We don't know what that means in terms
of how much water they will actually take,
which would really affect that ecosystem service.
So quantifiably, we don't know what that means
at bigger scales but we know that generally woody plants
tend to out-compete herbaceous layers for water.
Caleb: All right Rheinhardt,
so what do you think as far as the doom and gloom
versus bright side of this?
How can you speculate a little bit
and see what we would have to do
or what the future is looking like here
for grasslands and steppes.
Rheinhardt: Good question, Caleb.
Well, I thought of it before and I thought of it as,
I think it might be a two-step process.
One, we need to increase awareness of our grasslands
that are in peril.
We know publications but publications can only get us so far
and most times it only reaches the scientific community.
What we really need is we need to have politicians involved.
And I think of the Paris Agreement,
I don't know at what point did climate emissions
or did carbon emissions become a talking point
for the politicians?
I don't really know exactly
but there has to be that sort of breakthrough
where we need a list of what is happening to our world
and we are changing it,
and what does that mean for the longterm?
So I tend to equate it to a Paris Agreement type thing
from a globe perspective.
But at a smaller scale, if it's from the NRCS
that are sort of focused on the Great Plains
that are looking at ways to increase funding,
to increase research, more stakeholder engagement.
And that's sort of way we got ahead on
perhaps the small scale stuff
which would eventually tend to move
towards the global scale ideas.
And if I think of something like Asia
where Mongolia sort of mandated,
they wanted each about 50 or 35%
of the entire country protected by 2030.
That's really cool to have that sort of mandated
but they've got all the,
they're controlling all that land
and that's just the way they're doing it
and that's fine.
So I think there might be a number of ways
of which we can get to it but I just hope we do get to it.
Caleb: Thanks everybody for coming.