Hello everyone, and welcome to another episode of Eyes on Earth,
a podcast produced at the USGS EROS Center.
Our podcast focuses on our ever changing planet
and on the people here at EROS and across the globe who use remote
sensing to monitor and study the health of Earth.
My name is Tom Adamson.
EAGs, or exotic annual grasses,
have degraded thousands of square miles of sagebrush rangelands in western states.
EROS, using Landsat and other satellite data, tracks every bit of it.
In sagebrush habitats, cheatgrass is one of the big ones.
It outcompete native grasses.
It has different seasonal timing, or phenology, than native grasses.
What's worse is that it is very flammable.
It's also expanding into higher elevations.
Dr. Kelly Hopping, an associate professor at Boise State
University, is studying whether sheep can be used for targeted
grazing in these areas to help reduce the amount of cheatgrass.
The idea is to steer the sheep
to the right place at the right time to do the most good.
She has been setting up plots to test this,
and she uses EAG maps and phenology maps from EROS to do this.
We're going to talk about those maps and about the benefits of this study,
to the landowners and to the sheep producers,
but one of the biggest economic benefits of this strategy is managing fire risk.
Another thing that will come up in this discussion is NDVI,
the Normalized Difference Vegetation Index,
which is really just a measure of the greenness of plants.
The team at EROS develops NDVI measurements
from Harmonized Landsat and Sentinel satellite data.
They are now in the middle of releasing weekly EAG maps.
They do this for a 10-week time period during the season when EAGs green up.
Kelly, introduce yourself real quick. Hi,
I'm an associate professor at Boise State University in human environment systems.
I have a project
where I use your guys's product--I mentioned it to someone at the Society
of Range Management meeting recently, and I think that's why I'm here.
And thank you for doing this.
Matthew, tell us about your role real quick.
Matthew Rigge, I'm an ecologist here at EROS.
I lead the RCMAP fractional component effort.
Also lead the EAG stuff.
Trenton, will you introduce yourself real quick?
I'm Trenton Benedict.
I work on the EAG phenology portion of the project,
and I've been working on this for a few years,
since we started with the phenology. Dev, go ahead and introduce yourself too.
All right. Thank you, Tom.
My full name is Devendra Dahal. Everybody calls me Dev.
And I'm one of the person working on
the EAG mapping project we have here, over the last,
almost a decade, more than a decade now, actually, I think it starts in 2014.
Kelly, can you introduce us to the study and what's the problem
that you're trying to solve?
So we're trying to solve the problem of cheatgrass invasion.
Cheatgrass is an exotic annual grass that was introduced to the United States
in the 1800s and has spread throughout the West,
and now, spreading quite rapidly in sagebrush ecosystems in particular.
And there's been some work showing that it's also moving up
in elevation into places where it wasn't previously.
So we have a project looking at whether we can try to help manage cheatgrass
and eventually restore these higher elevation sagebrush ecosystems,
and trying to use grazing as a way to potentially do that.
Give us the brief rundown on what cheatgrass is.
What's it like? Why is it bad?
Well, it's an annual grass, and it has a little bit different
phenology, or seasonal timing, than a lot of our native plants here.
And so when it comes into an area,
it competes really well with some of the native vegetation
once it's established. It can start to turn an ecosystem from being one
with more diverse native plant community to being more dominated by cheatgrass.
And then the sort of bigger problem on top of this
is that because it tends to grow earlier in the season, it dries up
earlier in the season and creates this really good, dry fuel.
It's very flammable that can carry a fire.
So if there is some sort of ignition, it's more likely to take off
when it's got all this tinder essentially in the ecosystem.
And then after a fire, cheatgrass comes back quite readily.
And that's where a lot of that competition with the native plants can occur.
And so it can be sort of a slippery slope where the more invaded an ecosystem
is, the harder it is to get it back out of that state toward a healthier one.
And so there's some thought that if we can try to prevent it
from getting all the way to totally cheatgrass dominated,
we might have more chance of restoration success.
Anyone who recreates at the wrong time of year is familiar with getting the pokey
seed heads stuck in their socks or their dog's ears, and so it's something
that we ideally would like to keep from getting to new places.
But, it'd be great if we could also learn to live with it
and manage it in places where it already is as well.
It's not possible to eliminate cheatgrass, is it?
Or is it just more about managing it?
I think
the general consensus at this point is it's probably more about managing it.
We can try to protect core areas of sagebrush habitat that aren't already
invaded, and try to keep them safe from it, essentially.
But there are other areas
where we're going to have to figure out how to live with it.
You had mentioned earlier about how it is expanding into higher elevations.
Can you talk more about that?
Like here in Idaho, we have the Snake River Plain,
which is in the Great Basin. It's lower elevation.
And if you ever look at a map of cheatgrass, it's just this red swath across
Idaho, southern Idaho.
And so that's what comes to mind for a lot of people.
It's just these kind of lower elevation, like carpets of cheatgrass.
But, where I'm working in the Sawtooth National Forest, it's a bit higher.
And it's not maybe where people classically think of it being.
And yet even there, there's hillsides that are just covered with it.
And I suspect, and what people say was a big turning point,
was that there was a really large wildfire there in 2013.
And so a lot of places then where there might have been
a bit of cheatgrass there before,
that was a turning point for the ecosystem to become much more dominated by it.
Why not use cattle?
Why use sheep for this grazing?
Yeah, that's a great question.
And there's been a lot more work done with cattle grazing cheatgrass because
they tend to have grasses as a larger portion of their diet, whereas
sheep are also eating forbs or wildflowers and shrubs,
and so they're not maybe the obvious choice.
But as cheatgrass moves
into these higher elevations, the terrain tends to be a bit more rugged.
And so when we're on public lands
like this, the area where I'm working, it's only permitted for sheep grazing.
It's not considered suitable for cattle.
And so we had the idea that sheep are already there.
They're permitted to be there.
So administratively it's an easier lift to be able to work with them.
But then another thing
that I think is so cool about sheep is that they have herders with them.
And so without having to add any extra infrastructure
or fencing or virtual fencing or any of these other
kind of technologies, there's just a person and dogs
who can guide them where we want to target on the landscape,
and we can work with the herders to try to achieve the management objectives.
And so that's why we thought
it'd be worth it to try and see if we could do it with sheep.
Sheep don't need fences? No.
They just move with a person or a couple people and dogs.
All right.
Do sheep like cheatgrass?
I can't help but imagine them being brought to this area
and they look at each other like, wait a minute.
This isn't what we normally eat.
Are they okay with it?
Yeah, it's a great question.
We spent a lot of time staring at them, saying, did they take a bite,
did they take a bite?
Then the herders have said that the sheep don't
particularly love cheatgrass, but they'll eat it
if other stuff that they prefer more isn't available.
Something that I've been really impressed by in the course of the study
so far is that we're seeing the sheep starting to learn
where to go for the plots, and so recognizing that the animals
themselves can adapt and be part of the team,
really.
So not only are the ewes who are coming back year
after year learning where to go, learning that they're supposed to, to some extent,
stay in the areas where the herders have been holding them for the plot.
So it becomes more a question of, how do we time it?
Because for sheep and cattle, they don't want to eat it
once it's too far along in the season. It starts drying out.
The seed heads become really spiky
and unpleasant, so nothing wants to eat it at that point.
But in addition to timing it just where it's green and palatable,
it's also a matter of what else is available to them.
And trying to hit windows
where the cheatgrass is a relatively better thing for them to eat.
And so in these higher elevation systems,
there are a lot more other diverse plants. And so they do have choices.
We're not putting them into a place where there's absolutely nothing to eat
except cheatgrass.
And so the challenge is, can we get them to have enough
of a treatment effect on what we want to target without
going overboard and having unintended consequences for the native plants.
And so that's a lot of the balancing act that we're trying to do.
And I also suspect, and this is something I think we can keep working on,
but I think there's quite a trampling effect occurring as well.
So it goes beyond just what they want to eat, but also indirect,
or nonconsumptive, I should say,
impacts on cheatgrass because sheep are smaller
and they're really gregarious, or like to stick together.
You end up having many more hooves in a small area than you do with cattle.
And then another difference is the lambs, when they're there
with them in the spring, they have quite different behavior.
So the sheep owners, like they talk about them a lot.
I've heard multiple different people refer to them as like gangs of teenagers
running around together.
And you do see it, like you have the moms, the ewes, are being pretty calm.
And then the lambs are just like racing around in little packs.
And so I think that all of that adds up to differences that are--
I really do think impacting the effect they're having on cheatgrass.
After they've grazed an area,
can you tell if the native grasses are coming back?
Are you seeing benefits in the areas where they're grazing?
Yeah, the way that we set up the study was that
we have a baseline year in 2022 before we did any grazing treatments.
And then, we did fall and spring targeted grazing.
And then we're heading into our third season.
But right now we have two-year post-treatments in hand.
And the weather and the phenology was very different in those two years.
The cheatgrass production was also very different in those two years.
So it sort of depends on what year we're talking about.
But they did manage to reduce the cheatgrass with spring
grazing in both years by around like 12 or so percent, 12-14%.
But where we saw the biggest reduction so far was with the fall grazing.
So something we didn't talk about earlier,
but cheatgrass can green up again in the fall
when the native plants pretty much are on their way to dormant.
So if the rain comes at the right time that cheatgrass can green up,
and one of our years, we hit that window where it rained,
we got the sheep out there,
and they were able
to reduce the cheatgrass by around 20%, which we were pretty happy
with because the first year when it wasn't green,
they really didn't have an impact on much of anything.
And so
I think we're starting to learn a lot about how we can time
it most effectively, though
we'll keep doing it as we're doing it every year for this study.
But the hope is that we can eventually make management
recommendations that could say, okay,
when the conditions are like this, it's worth going and doing it. Okay.
If not, maybe not.
So I think that we're
not only learning a lot, but we're starting to get
some good outcomes from it. We're making a dent.
I think it's time to turn to talking about the data
a little bit more now. Dev, what data goes into these EAG maps?
The first thing is we use
Harmonized Landsat Sentinel, HLS. Okay,
both Landsat and Sentinel. Yes.
Those are harmonized, developed by NASA, weekly HLS, actually.
So we grab individual scenes and create
weekly NDVI from those individual scenes.
That's the main input for us.
We also have other soil data,
weather, climate, elevation,
DEM, and solar radiation.
So multiple dataset goes into it.
Okay,
it's not as simple as saying we use satellite data, we use just Landsat.
There is more that goes into it than that.
So that's the work that that goes on. Yeah.
And you end up producing EAG maps weekly.
But that's only a certain time of year
that they're weekly that you produce,
right? Yes.
It's only from the peak growing season,
from early April to late June.
When we started, when the project started, we had only two maps from one in the May,
first week of the May and last week-- the first week of July.
So from there we started biweekly and weekly, and from last year we are
developing 10-weekly maps from April
to July. Every week for ten weeks
during this time frame. That started last year?
Yeah, that started last year.
Are these maps showing just the presence or absence of cheatgrass?
Actually, this is the percent cover.
That means 30 by 30 pixel.
How much is this cheatgrass.
How much of cheatgrass is in a pixel.
Yeah, in a pixel.
Not only cheatgrass,
but cheatgrass covers like around 90% of the total EAG.
We cover like, other 15 different species.
Oh, other species as well. Okay.
But cheatgrass is the highest one, so we can call it cheatgrass anyway.
Okay.
In that 30 by 30 meter pixel, how much is the EAG grasses?
Okay, I get it.
Is there any use of AI, artificial intelligence,
in the production of these maps?
What we get from the satellite will have, very often, especially in this
early spring, gaps, because of the clouds and snow and everything.
So we use artificial intelligence, this model, to fill those gaps,
so it can learn from the previous years in all the different weeks
and tell us, okay,
what should be there at that time of the year or that week.
So we use that in the modeling to predict NDVI
and then that feeds to the EAG model.
Let me ask Trenton if you have anything to add to that part of it,
or is there anything you can add about the maps themselves,
the work that you do on that?
Yeah,
so we developed another machine learning model
that tries to estimate the phenology of our 16 group of exotic grasses.
These maps produce our phenology, which is
basically the sustained growth of these exotic annual grasses, which show
when it starts to bring up, how long it stays green for,
when it greens down, and then everything in between those greenness.
And it's about eight different products, the timing,
and then we have NDVI products
for when that timing occurs, what the NDVI looked like.
So, NDVI basically shows when it starts
to green up, those profiles, and then their maximum greenness
and the NDVI, and that's also with the HLS 30-meter pixels.
The phenology part of it, is that in just the weekly product
for this 10-week time frame?
So that gets produced annually.
That's annual.
Yeah.
So we try to produce it at the end of the growing season
for the year prior, but I think we might start looking into a more of a near
real time predicting it, or estimating it, like the year of maybe.
But we're still in the works of looking into that.
But it's usually the year, that just that prior year
that we're going to produce, just so we have the full NDVI
yearly profile and then produce
based on those NDVI profiles, basically.
Kelly, how were the EAG maps used in your study?
So when we started this project, we had selected
two grazing allotments, which are pretty big areas.
And one in particular is a very, very big area where the sheep
are spending anywhere from like a month to several months.
We had a lot of criteria on our plate of what we had to consider
when we were choosing where to do it.
So we had to think about just what's good experimental design.
But then the Forest Service had a lot of requirements around
where we could put the site, and two of the big ones were,
we couldn't put them on slopes that were considered too steep
to be suitable for sheep grazing, because we didn't want to have,
like creating erosion problems and that kind of thing.
We also needed to be a certain distance from trails.
The sheep have guardian dogs with them.
And so there's a lot of recreation in this area.
And just in general, wanting to not put the sheep and the dogs
and all of that right on top of a trail is another priority.
So just separate the interactions with recreation, the extent that we can.
But then the sheep themselves have needs of the-- a big
one in their case is needing to be able to access water daily.
Also from the science perspective, like, we have a research team
that needs to be able to actually get to these places.
And so we're looking at these huge allotments
and trying to think of how to prioritize all these different things.
And so I loaded up a bunch of geospatial layers of
where are the trails, where is the water and the distance to them.
What's the slope, like sort of clip out everything that's above a slope
that's considered too steep, and then had a number of
these fractional vegetation cover products that try to know
where is the cheatgrass
that actually falls in meeting all these different criteria that we have.
And this EAG product for our area
was really, I think, the best, the most accurate. But that EAG product
worked really super well for being able to go to a place
where it showed a high cover of cheatgrass and then sure enough, there was.
And so we did just a tremendous amount
of hiking that first spring before setting it up.
And it made all the difference in the world
to be able to know where to go and have a pretty good chance
of finding something that would fit our criteria.
It was just tremendously helpful for that.
It made a big difference for why the whole study is designed the way it is.
What are the economic benefits?
There are a lot of different avoided costs that could come into play here.
And so if you do it this way, where we're just using sheep
that are already
there and herders that are already there, then that's essentially cheaper
than spraying herbicide or doing some other sort of treatment,
which would take a lot of human labor, might not even be feasible at all.
And then because we're changing the timing of when they're out there, in our case,
they're coming earlier in the spring or staying later in the fall,
so they're getting access to areas that are outside of their normal permit dates.
So that's a huge benefit for them, like at a time of year when they might
in some cases, depending on the set up, like feeding them hay
back at a ranch, they're now able to stay out on the land
longer because there's this different
phenological window that's now available to them to do the grazing.
And so that lowers cost.
And then the biggest one is that, if this could be successful in reducing
wildfire risk, then we've avoided the tremendous cost
of potentially managing those fires and restoration
and the indirect toll that it's
taking on society to have large areas burn in catastrophic fires.
And so we are looking at whether these treatments are reducing wildfire risk.
And I think that's something
that we'll see build more slowly over time
because we're not trying to do it as a fuels treatment,
we're trying to have this slower
built toward a restored ecosystem that would be less likely to burn
or to have a fire go through it quite as quickly.
And so if we can keep chipping away at it and avoid those large, more
frequent fires and the economic benefit of that would be huge.
Is there a benefit to the sheep themselves? We are really concerned with,
we didn't want to put them at a nutritional deficit,
and this is a particular concern
when the lambs are out there,
because raising a lamb to a certain weight is the goal of those sheep owners.
And so we don't want there to be a negative impact for them
at the end of the season
if their lambs end up lighter as a result of participating in the study.
And herders are really concerned about that.
They're really thinking about their animals' health
and wanting to prioritize that.
We're not just holding them on a patch of land in a plot for a really long time.
Instead, they're kind of making multiple passes
through the area, so they're spending a lot of the day
grazing the way they normally would, choosing what they normally want to eat.
But then they're making sure to come through the plot in sort
of a more concentrated than usual type of way.
But still not just holding them there for really long periods.
It's more a matter of trying to just make sure that they stay healthy
and really keeping a close eye on them, which has been working so far.
It's fun to just think of them out there, just having fun
helping us out with this study.
Yeah, I heard someone who's doing this like as a private operation
where it's like people can hire her sheep to do targeted grazing in California.
And I heard a podcast with her and she talked about the sheep
as part of the team.
And I really liked that because it's how it feels, like,
yeah, we have a team of, you know, thousands working on this
and it just happens to include a lot of sheep.
Are the sheep herders on board with this, too,
are they cooperating with this study?
Yeah.
The sheep herders and the sheep owners,
they're called producers,
like basically the ranchers, they've all been really, really great to work with.
I think for the sheep owners, they have a big incentive
to do this, to try to help restore these areas
and hopefully lower the wildfire risk because that can be devastating.
And so to be part of the solution, I think, is highly motivating for them.
And just to be able to use their animals for something that's useful
to the world as well, I think, is attractive.
And then the herders,
they've just been great to work with and we've done interviews with them.
There's even some plots where the combination of spring and fall
grazing that we do, like some of those plots are on some areas
where they're reducing the cheatgrass and there's not as much
native plants left. We're getting--
starting to have a lot more
exposed soil, which isn't necessarily a bad thing
if other plants can come back in.
But the herders are telling us, like we're concerned that,
are you going to make us do that again?
Like we're not sure that this is the right move for the environment,
like we really care about the impact we're having with the sheep.
And so they're totally cooperative and willing to do
what we need to do for the science,
but they're keeping an eye out for like, oh, maybe we should back off on
these plots. Like, I think we're having too much impact.
And so anyway, they've been really amazing to work with as well.
It's been a really nice collaboration.
And there's also many other scientists and Forest Service partners,
and it's a really large team that's working together to make this happen.
We did our best to set up this study from a scientific perspective
and a Forest Service perspective,
and incorporated the ranchers' perspectives to an extent.
But if I had it to do over again, or if this is going to be something
that others could use as a management tool, I think working
even more closely with the sheep producers and talking with the herders
about what will actually work, where will the sheep go,
what can you realistically accomplish with your herding?
I think then it could just get even better.
Kelly, your study seems to be getting a lot of attention.
Why do you think that is?
I think that, at least around here, and probably in other places where
cheatgrass is a big issue,
the public is aware of it and cares about it and is concerned about it.
So I think having a positive
story in the sense that it's a pretty diverse group of people
who's working together on this, trying to come up with a solution.
I think that's maybe interesting to people.
I think people are kind of interested in sheep.
And so to have all the sheep out there
with their lambs, it's, I think, also intriguing to people.
And it's just a really beautiful area where a lot of people go to recreate.
They care about it.
People who live in that valley are right up against the areas
that burned in the past, like people are concerned about that happening again.
What's next for the EAG data?
Are there any refinements that you're working on?
You're in the midst of this 10-week, you know, weekly release right now.
After that's done,
are there improvements, refinements and things like that that you will make?
Absolutely.
It's always an ongoing process actually.
For this year, we are on week five right now.
That's processing--started this morning, so.
Yeah? Okay.
And once we are done with this expedited release,
we will spend another few months making it better in every aspect.
Accuracy and everything.
Trenton, does that sound good?
Is there anything else that you have to add in that area?
I'm hoping to try to get out the phenology products a little sooner in the years.
I think we might try to expand our study area, too,
maybe utilize the RCMAP study area, and that will increase more of a range
and our elevation as well.
Just always trying to refine that phenology
work, trying to make sure everything looks how it should.
But Kelly, if you ever see anything lining up correctly,
incorrectly, reaching out really helps.
And yeah, just making sure everything looks green when it's green.
This is a little silly to say because like, I work with remote sensors,
like I know your normal people, but it's a little bit like celebrities.
Like you're the ones who made this product that is so useful.
And to know that you actually invite, you know, ecologists out on the ground
to interact with you about it is really helpful to hear, because
it didn't even occur to me until I met you and talked with you about it.
So thanks for saying that.
Well, thanks for calling us celebrities, but I do not feel like a celebrity.
We appreciate it.
We certainly welcome,
if you've got sort of Landsat equivalent vegetation data,
that sort of thing can be integrated into the model.
Like you said, Kelly, it's hard to get every pixel just right.
There's a lot of pixels to get right.
And these models are trained over a large region.
There's trade offs made that way as well.
I mean, if you trained a model for cheatgrass over just the Sawtooth
National Forest, it might perform somewhat better than a regional model would.
But then you've got regional discrepancies between models,
and that creates a mess for for that sort of scale analysis.
And remote sensing is always a game of of trade offs.
I was curious if you would ever consider doing something
similar for the fall to catch if it is greening up again?
I think from what we're seeing it could be
really helpful from a management perspective to be able
to have that data to complement what's going on in the spring
because it's such an important window in the lifecycle of this particular grass.
Yeah, we tested, but we don't know how good we did.
But we tested that last fall.
In some ways the fall map might be easier than the spring map
because there's less other grasses green at that time.
Does that track with your observations, Kelly?
Yeah, it does.
It would be really neat to to have that as a product if it's possible.
Yeah.
I mean that's something that we can certainly look into.
It sounds like, Dev, you've done some research on that that I wasn't even aware of.
So that's good to know.
One year
we had the pass that the sheep needed to walk over to get to the study area
didn't melt out as early as we needed it to.
So the sheep got there kind of late by calendar days.
But that also meant the phenology of the area was later that year.
And so being able to look at the phenology product, the EAG phenology product,
is then really illuminating to show what we think we're seeing on the ground.
But to show that it's not really about calendar date
and trying to pick a certain date and stick to it
every year that's going to be the most effective,
it's really timing the grazing treatment to when is the right time for the plants,
when is it going to be where they can graze there,
or trample the cheatgrass, most effectively and then hopefully minimize
the less desirable impacts to other native species.
With these kind of products, we can get closer to making those recommendations
for other types of livestock like sheep, or other areas,
and try to really hone in and understand when is it
worth doing, when is there a year where maybe we shouldn't even try,
because, you know, you miss the window or the window wasn't here this year
and so it's not worth
putting all the resources into getting all the animals out there
in a year where it's not going to work.
Conversely, how do we target it in a year that is potentially going to be
having a high impact, like how to get them out there
at the right time to accomplish the desired effect,
then make more useful recommendations for others wanting to apply it.
It's just so helpful to have this product ready to go.
I think if we can use studies like ours to identify the right window,
if when the treatment can be effective,
then managers could really use these products to make decisions
like seeing where they-- what the cheatgrass is doing from year to year, and then know
the right time to send out the livestock to have the most beneficial impact.
So I think it's really exciting to have this kind of work available.
Thank you to Kelly, Matthew,
Dev, and Trenton for joining us for this episode of Eyes on Earth.
Data from EROS are directly being put to use
to see how effectively sheep can graze away invasive grasses
like cheatgrass in sagebrush ecosystems in the West.
And thank you, listeners, check out our social media accounts
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