-: Thank you.
It's good to be with you here today.
It's been a pleasure
to get to know some of you in my stay here.
This is my third time to Nebraska, first time to Omaha.
And every time I come, I find good food, so I'll be back.
When you get to be my age,
certain things, the priorities change.
Food is one of 'em.
I have a handout in the back for this talk,
and I put 'em out late, so I apologize.
If someone wants to pass that around
or you just grab 'em before you leave.
Oh, oh.
See, I'm already breaking the rules.
I'm kinda known for that.
Okay.
Are we good?
All right.
It's kind of a synopsis of much of the presentation
I'm gonna be sharing this morning.
This was presented in a poster conference in Australia,
so our work is going intercontinental, which was kinda cool.
Let me...
All righty.
So, what I'd like to talk about this morning
is a project that we did related to
Milwaukee's experience with Dutch elm disease.
And not many people are talking about
Dutch elm disease today.
And this talk also incorporates some information
about emerald ash borer, as well.
When I came to Milwaukee 10 years ago,
I worked on the East Coast
in Norfolk, Virginia for 20 years,
and trees in that part of the country grow pretty large.
It was not uncommon for us to have
a 30 inch diameter willow oak standing on many streets.
And they would be 90 to 100 feet tall, big trees.
Large shade trees.
And when I came to Milwaukee, you bet my first thought was,
"Wow, the trees are small here."
And without giving a whole lot of thought to it,
I just figured, "Well, the climate is different,
"shorter growing season, different soil,
"different species palette."
But then the light came on.
This city still hasn't fully recovered
from Dutch elm disease yet.
So, I came up with the idea of and the interest in
studying that loss of elm population
over a long period of time
to see what I could learn from that and try and determine,
what could I learn that I could apply
to emerald ash borer or other future pests or diseases
that might impact my tree population in the city
and help me make better long term decisions?
I was trained as a forester,
and so what foresters are typically trained,
and this is traditional forestry.
When I went to school,
there wasn't anything like urban forestry at that time.
There was some people that were starting
to practice urban forestry, but no curriculum,
no college curriculum about urban forestry.
It was horticulture or it was forestry,
and so forestry was our training to think long term
in terms of a harvest cycle.
So for a lake states pine,
that may be a 60, 70 year harvest cycle.
For hardwoods, it may be well over 100 years.
So you're thinking long term.
And so I like to try and make decisions
that get beyond the crisis and think long term.
So this particular topic,
this is kind of a three legged stool body of individuals
that are presenting this around the country
and have for the past couple years.
I'm the practitioner in this stool.
Dr. Hauer from the University of Wisconsin
was the researcher,
and he did much of the economic modeling on this project.
And then Ian Hanou,
we've already heard about his company, plan-it-GEO,
was the one who did a lot of the image processing,
compiled a team to process imagery and so forth
and calculate benefit loss and so forth.
All three of us brought a different level
of expertise and interest to the project.
Just by way of background,
some of the reasons that I wanted to pursue this project
that influenced this work were that,
we're here today talking about emerald ash borer,
and we could be here five years from now
talking about Asian longhorn.
We could be talking about any pest.
Our urban forests are really being ravaged by invasives.
We live in an economy
that moves materials worldwide every day,
and so we're at great risk to introductions
of invasive and destructive forest pests and diseases.
That's not gonna change.
And another driver behind this project
was that we, Milwaukee, and many communities
are now starting to manage more on a canopy wide scale.
So while we don't particularly have
responsibility for managing private trees
beyond maybe removal of a hazard or dead tree,
we recognize now as we understand better
the benefits trees provide
that we should be thinking more broadly
and managing on a canopy wide scale
rather than individual tree scale.
Yeah, we still service trees on an individual tree basis,
but many communities are starting to manage
for maximum canopy benefits.
And then, clearly,
when a pest like emerald ash borer
comes through a community,
the cost to manage that pest and the restoration cost
are not well understood.
And virtually, when communities go through this process,
they'll get funding, they go through it,
no one is really ever looking back to see,
was that the right decision?
How much did it really cost us,
and what alternatives might we have pursued
that might have gave a better outcome than what we realized?
So when emerald ash borer and other pests hit a community,
and we've heard about it in this conference,
you'll hear about it everywhere you go,
many communities will put their head in the sand
and hope it doesn't come.
Well, it always comes, right?
And so oftentimes, if you wait
to either devise or implement a plan,
at the point when emerald ash borer
is found in your community, typically you're already
four or five years behind the eight ball
because it's been there.
And this pest is very difficult to detect
at low population levels.
And so we, as you'll see in my talk this afternoon,
our strategy around emerald ash borer management,
well, it made the assumption that it was already here,
and we moved ahead of the detection and the find in our city
and it was a good thing we did,
and you'll learn more about that this afternoon.
So cities tend to be reactive when these things happen,
which puts us at a disadvantage.
I feel strongly there's a need for fundamental change
in how the federal government, state governments,
and local municipalities manage for
destructive forest pests and diseases,
and you'll come and understand why.
So typically, state and federal focus,
they're focused on monitoring for diseases,
insect and diseases that might cause harm
to forest populations.
AFIS has a role in trying to intercept
and do inspections at our ports
to try and intercept destructive pests
before they become established in the country.
And yet, we know that
their capacity to inspect is pretty limited,
so there's a lot that's coming through
that they don't physically look at,
and that's how these beetles and diseases and so forth
come into our country.
And indeed, that's how emerald ash borer came in.
And the state's department of agriculture
have that same kind of responsibility of monitoring.
So in your state, in Wisconsin, in many states,
the Department of Agriculture will do trapping
to detect and confirm where a given pest is
in a community or in a state.
And while that's helpful
to know that and have that confirmation,
perhaps for a trigger to get funding
to combat the pest or disease,
when you're talking about a pest like emerald ash borer
that's so hard to detect, and these purple traps,
they look nice, they draw attention,
but they don't catch a lot of beetles.
And so if you're relying on those traps
to trigger when you're gonna start your program
or prepare for emerald ash borer, you're gonna be late.
I'm convinced that
many states that are investing
millions upon millions of dollars
in trapping for emerald ash borer
are really wasting their state dollars.
They're not applying them the best way they could.
Once it's in your state,
if it's around you and you're a surrounding state,
you can be sure it's coming,
and it's probably in your community already.
I'll talk a little bit about a project we did
to map ash trees in our community.
And that came at a cost,
but had the state invested in that kind of technology
and gave communities a route deliverable,
an ash classification map for their community
that would point and identify
where all the ash trees were in their city,
that's something they could use and be very proactive with
rather than just to know
what's in your state or in your city
and then they rub their hands and hand off to you
and, "Here you go.
"Now it's yours to manage."
Well, thank you very much.
So, when population densities get high,
sometimes there's enough beetles flying
that they slam into these traps and get stuck,
but they really don't draw many.
But nonetheless, you still see 'em up.
When you get this story in the news,
emerald ash borer was found in your community,
you want to have a plan, right?
You can't probably see this,
but this is the city of Ash Grove, Pennsylvania,
city of Ash Grove, Pennsylvania.
When EAB hit their community,
you'd better believe they wanted a plan, right?
Their name is based on ash.
And that plan should be based on risk assessment,
not only risk of in terms of
your population of ash trees that are at risk.
You should know how many are at risk, where they are,
what kind of canopy loss you're gonna incur
as a result of that loss, of that pest.
Obviously, we need to do some budget forecasting
and be prepared for funding of whatever response plan
your community comes up with.
And then devising a management strategy
that may be based on treatment,
may be based on removal and replacement,
or some hybrid of that.
But invariably, all those options require money.
And so we've heard about that from some folks
here today, or this conference, that have gone to budget,
gone to the budget director or their mayor or council
and they requested funding in advance of EAB
because they knew what was coming.
That as background led me to this conclusion.
Are we asking the right question
when it comes to how we manage urban forest pests
and the roles of federal, state, and local government?
So the slide on the left here, it says,
"What is that purple thing hanging in the tree?"
So this is an effort by an agency
to answer the question from the public.
They see the tree, and they say,
"Oh, well, people are asking about what this purple trap is.
"This is an opportunity for us to educate the public
"on emerald ash borer."
Good idea, right?
So they put out this card.
What is this purple thing?
And if you think about what that message is
and what that purple trap is doing,
that trap is out there to answer the question,
"Where is emerald ash borer?"
For our community in Milwaukee,
we have responsibility for abating
dead and hazard trees on private property.
So we had a vested interest in knowing
where those ash trees were on private property.
We didn't have any...
Well, we had an inventory of our street trees
and we knew where our ash street trees were.
We had no information on private trees.
And we did a i-Tree Eco,
it was called UFORE at that time,
a canopy assessment project in 2008,
and one reason we did it then was because we wanted to know
how many ash trees there were in our community.
And we had no idea, but that survey
of about 210 randomly distributed plots throughout the city
indicated we had about 587,000 ash trees in our community.
That helped me understand how big of a problem
emerald ash borer would be.
Huge problem for our community.
We knew that if we could find out
where those ash trees were before the beetle would,
the beetle would perform 100 percent inventory
on the ash trees on private property very efficiently.
The only trouble is,
by the time they find them and we found them
and they've identified where the ash trees are,
they're dead.
That doesn't allow you to do anything proactive, right?
So we hooked up with, I was at a conference with Ian Hanou
back in, this must have been 2007 or 8.
And I asked him the question,
"Is there any technology that can be used
"to remotely sense and map trees to a species level?"
And he said, "Yeah.
"You can use hyperspectral imaging."
And I said, "What?"
I asked him three times.
I'd never heard of the term.
And finally I got it, hyperspectral imaging.
And this is a remote sense technology,
and I'll share little slides of this,
showing this project that allows you to map
to a target species level
from an aircraft flying over your city.
So the question I wanted to answer is not,
"Where is emerald ash borer?"
I assumed what is in our city
'cause it was in our surrounding states.
The question I wanted to know was,
where are our ash trees that were at risk?
Since we had a responsibility to manage
the safety risk associated with those
dead and dying ash trees on private property,
I wanted to know where they were
so we could do something proactive
in getting prepared for those trees,
and also messaging private property owners that had ash
so they could get prepared as well
just the same way the city could.
So in 2008, we contracted with a company
to fly the city with an aircraft.
And they put a...
Let me see.
Let me find the pointer.
Is this it?
Ah!
What did I do?
(man speaking off mic)
All right.
I'm showing you high technology
and I'm technology challenged.
I can't even work a remote.
I got a solution for that.
I brought my own laser pointer.
This thing is so bright it'll reach to Lincoln.
So you look on the back wall,
it's pretty bright back there.
This is for looking up at trees,
but it works good on presentations, as well.
It is a laser, so if you start to nod off
and you feel a warm sensation on your head,
it's probably my laser pointing you out.
You don't want that to happen.
Neither do I.
I gotta be careful when I take this on planes
'cause I'm worried they're gonna confiscate it.
Okay.
So in the plane, aircraft, there's a spectrometer.
This is an instrument that maps
objects on the Earth's surface
in the infrared part of the light spectrum.
While this plane was flying over our city,
it took about three days to fly the city
and capture the imagery,
we also had people up in bucket trucks
holding handheld spectrometers.
And what they were measuring
was the light reflectance from the surface of the leaf
of ash trees and other trees that were common in our canopy.
Let me go on a little bit to talk about what this is.
So, how many have heard of multi-spectral imaging?
Okay, a few of you.
Multi-spectral imaging maps
also in the infrared part of the light spectrum.
Obviously, we see in the visible part of the light spectrum.
And so everything that we see
and see as color, black and white,
is the result of light being reflected off that object
and our eyes intercept and receive and can recognize
the color or the shape and so forth.
And you can measure, actually,
the energy that's coming off of an object,
and it reflects along this electromagnetic spectrum
and along the scale of what's called nanometers.
So don't worry about the units.
Just know that for each object that reflects color,
it reflects at a different point along this scale.
And so multi-spectral and hyperspectral imaging
maps in the infrared part of the electromagnetic spectrum.
We don't see this with the eye,
but the sensors can pick this up.
So multi-spectral,
it treats this entire infrared band as one band.
So sometimes multi-spectral imaging
is referred to as four band mapping,
where you'd have the red, blue, green part
of the visible light being three bands
and then the multi-spectral being the fourth band.
What multi-spectral allows you to do
is to distinguish vegetation from non-vegetation.
So in the infrared, and you'll see a picture,
plants that have chlorophyll
reflect red in the infrared part of the light spectrum.
And so you can easily distinguish canopy
from hard surfaces like streets and buildings and so forth,
dirt roads and so forth, with multi-spectral.
So multi-spectral imagery
is really good for mapping the canopy,
the cover in your city,
and it's often used for that type of purpose.
Hyperspectral is a much more sensitive sensor.
So it can detect changes
in how light is being reflected off an object or a surface
in very narrow band width.
And you can adjust this to map any interval of band width.
And so our project had a band width of 10 nanometers,
meaning that for every object in the leaf surface,
the sensor was picking up what the energy was coming off
in terms of nanometers off the surface of these trees.
And where ash reflected, when we measured
with a handheld spectrometer on the ash leaves
at the top of the canopy, that gave a spectral reading,
what's called a spectral signature, of that ash leaf.
And that fell somewhere along this entire spectrum here.
And so what hyperspectral will do,
it'll pick up along this area every place that ash reflects.
So if you can identify where it reflects specifically
along this multi-spectral range here,
then you can train your,
you can parse that out of your image set.
So it'll pull out only the ash trees and map those,
so that's a general discussion
of how hyperspectral is different from multi-spectral.
And so this just simply shows
different species that we collected spectral signatures on,
and all I want you to take home from this
is that they're different,
so the spectral sensor could distinguish
an ash from an elm from a maple from an oak.
They reflected differently.
Even green ash and white ash reflected differently,
so you could distinguish that if you wanted to.
We didn't care about that.
This emerald ash borer tends to like both of 'em.
So this is the product that we took,
and you can see that the red canopy,
and it's hard for me to see up close here,
but you can see red trees.
So the green pixels are
what the spectral sensor picked up as ash,
and the blue dots along here, along these streets here,
are our ash street trees from our inventory
that we gave the vendor for verification.
So you can see the sensor with the green pixels
picked up the ash very accurately,
and these are confirmed ash street trees.
And so what this project did,
it gave us information about private ash trees
that we had no information on before.
So suddenly, we had information on where ash trees were.
We overlaid that on a parcel map
so we had ownership information so that we could reach out
to the property owners that had these trees
and let them know they have an ash tree.
And we did that with an intern workforce for two summers.
They initially went to about 45,000 properties
because ash canopy extended
over the property boundaries of many properties,
but we wanted to know
where that stem stood on that property.
So we went around and looked at 45,000 properties
and identified those that had ash and the ownership of that,
and we let the property owners know, "You have an ash tree.
"Emerald ash borer is coming.
"You need to be concerned about this,
"and these are your options."
And at that point, and even now,
the only options are treatment or removal and replacement.
What we found through that exercise,
we identified over 15,000 properties in our city
that have one or more ash trees,
and the vast majority, 90 percent plus
of the people we made contact with
had no idea they had an ash tree.
They didn't know what kind of tree they had.
So they weren't paying attention
to emerald ash borer messaging.
That's a challenge, and they weren't getting ready.
Okay.
I wanna move on to the...
So that was a little intro and discussion
of what we're doing in mapping ash trees
to help us get ready.
Now I wanna spend the rest of the time talking about
this project where we looked at
the loss of elm trees over a 60 year period,
the benefit loss associated with that loss of canopy.
And we did some analysis of different outcomes
based on different management strategies.
So in 1956, Dutch elm disease hit our city.
And I was fortunate that we had a full image set of the city
in aerial photography of the city that was done in leaf.
So in 1956, you can see the continuous thread of trees,
street trees in our city here,
and the vast majority of these are elm trees.
And this is the same area in 2013.
And what I take away from this is that,
yeah, we've recovered a lot of canopy here,
but we don't have the continuous threads.
Obviously, we have different types of species now,
and we're getting
more of a continuous thread along this street,
but the rest of 'em are much more sporadic.
So on the surface, it looks like here, 60 years later,
we still haven't recovered from Dutch elm disease.
That's a long time.
So, some of the questions
we wanted to answer in the study was,
how long did it take for us to recover
from the loss of 100,000 elm trees?
That's a question you might wanna ask related to ash.
Oop.
Okay.
Why is it going that way?
My bad. Sorry.
Okay.
I also wanted to know, when was the low point?
How long did it take
for Milwaukee's elm canopy to be largely gone,
and what was that low point in terms of canopy cover?
What was the loss?
What was that change in canopy over time?
Here you can see on a neighborhood scale,
1956 fully lined streets with elms,
on a neighborhood scale in 1979.
Well, we don't get hurricanes in Milwaukee.
This was our hurricane.
It literally wiped out entire neighborhoods and changed
the composition and character of those neighborhoods
in a huge way.
We also wanted to know
what the cumulative loss over time was
with removing that elm population.
Elm is a large stature tree, large leaves,
and they're very efficient and produce a high,
I guess per leaf surface area, amount of benefits.
As an example, Minneapolis.
You heard a little bit about Minneapolis
yesterday from Philip.
When they did their canopy assessment project in 2004,
they looked at the various species
and the benefits those trees provide.
And at that time, they had about
10 percent of their street tree population was still elm
and these big elms that were still remaining
from the early '50s and '60s.
Those 10 percent elms were providing
40 percent of their canopy benefit.
So these were very valuable trees
in terms of the benefits they provided
and a significant loss when you lose one.
So we wanted to calculate
what that cumulative benefit loss was over time
because I'm convinced that when you're facing a decision,
"Should I remove or replace a tree,
"or should I treat that tree
"to preserve those canopy benefits over the long haul?"
I think it's important for us to understand,
what's that risk?
Part of the risk assessment is not only to know
it's an ash tree that's at risk
or an elm tree that's at risk
or to know that the public is at risk
from a safety perspective of dead and dying trees
that could damage property or injure people,
but what are these benefits that these trees provide,
the storm water benefits, the energy saving benefits,
the air quality benefits?
Those are also at risk when that tree population goes away,
and so it's important to understand
that part of the equation to make, I think,
long term decisions that are right for your community.
And as part of this project, we also wanted to understand,
what was the influence
of various management intensities on outcomes?
Would a high management intensity yield a higher outcome,
a higher net present value, a greater benefit
than a strategy where when you see disease
and when you see insect infestation,
you take the tree out and replace it
on those two different extremes?
Where is the sweet spot, I guess,
is what we were trying to find.
How aggressive should we be in managing these pests?
And then we wanted to see, okay,
at understanding what our experience was
with Dutch elm disease,
how could we apply what we learned with Dutch elm disease
to emerald ash borer to help us make better decisions
for emerald ash borer and other forest pests moving forward?
Back in 1956 when Dutch elm disease hit our city,
while we were performing...
Milwaukee has had
a professional urban forestry program since the 1920s.
In 1924, we had 50 arborists on staff
that were pruning trees.
We had a nursery that was established in the '20s.
So we were very much actively managing
the tree population at that time,
but in 1956, we had no inventory.
The city was doing cycle pruning in the '50s,
so I'm sure they had some records, paper records,
of trees and when they were last pruned.
But there was no concept
of a spatial GIS inventory at that time.
So we didn't have a lot of information
about the starting population of our elms in 1956.
What the city did have is very good removal records,
so we knew on a year by year basis
how many elm street trees came out of our city
over a 60 period.
And we had a lot of information about private elm removal.
So with that, we were able to establish
a starting population of elms for this project.
But we didn't know and didn't have any information
about diameter, about the height, about the canopy spread.
These are all inputs that you need to put into i-Tree Eco.
i-Tree Eco is a software.
It was mentioned yesterday.
The i-Tree Suite, so it's a free tool
developed jointly by Davey, a tree expert company,
and the US Forest Service,
and i-Tree Eco is a free software you can download
and calculate benefits of a tree population.
But it requires inputs.
You have to put in inputs of,
what's the height of the tree?
What's the crown diameter?
What's the stem diameter?
We didn't have that information.
So we had to model that from other studies.
So our project had three phases.
Phase one, we wanted to look at
how the canopy changed over time.
And I'll talk a little bit about how we did that.
So we did point sampling.
And the red area that you see in the image on the left
was the developed section of the city in 1956
that had established tree canopy.
And so we randomly distributed points,
enough points to give us the standard error
or the measure back to see what we were looking for
in that area of interest, that red area,
and you can see the points in the other two images.
And then over time,
as we looked at imagery from 1956, '63, '69,
'79, '93, and 2013,
so six image sets,
we looked at the change of canopy over time.
So when you do point sampling,
this point here in 1956 might have had a tree,
and as we looked at progressive imagery,
at some point, that tree was gone,
and then we removed that dot as a canopy.
So that's how we measured the change in canopy over time.
Here's just a mosaic
of the different image sets that we used,
all leaf on imagery that we were able to buy.
This is the change on a block level.
In 1956, we had this nice, continuous thread
on many of our streets.
And look at the canopy here.
These houses set back from the street probably 30 feet,
and so this canopy from these elm trees
extended from the house to the house.
It was a cathedral of elms along the streets.
But by 1979, they're all gone.
And by 2013 in this block,
we still haven't recovered on this block.
I will say that Milwaukee didn't have
the advantage that even Minneapolis had
in managing Dutch elm disease because the technology,
the understanding of how to manage it, wasn't known,
and certainly what was known wasn't transferred
in terms of the technology transfer in the '50s very well.
So we were caught much like Detroit was
with emerald ash borer in 2002,
and we had no option but to remove dead and dying trees
to protect public safety.
So we couldn't have influenced our outcome.
Minneapolis did, but certainly communities today
that are faced with major pest decisions
can chart a different path.
So what we found is that
our street tree canopy of elm in 1956 was 19.2 percent,
and while we had Dutch elm disease identified in that year,
the canopy of those elm trees were growing.
By 1963, that canopy had grown to 23, almost 24 percent.
But then as the disease took a foothold in our city,
we started losing elm trees by the thousands.
There were years in the late '60s, early '70s,
where we were taking out 16,000 elm street trees a year.
Huge loss.
So it dropped down to 12 1/2 percent,
so we lost literally 50 percent of our street tree canopy
over that period of time.
And then it wasn't until 2008, 2013 that we recovered
on a canopy wide scale, citywide scale,
but a lot of the canopy that was replaced
that was adding canopy to our city
was private trees that had been planted after the World War
and had grown and were contributing to our canopy.
But as you can see, many of our blocks,
the street trees and the blocks in the city
still haven't recovered to this date.
The second phase of this project, we wanted to model
some of the attributes of that elm population,
the diameter, the height, the crown spread and so forth
so we'd have input data to put into i-Tree Eco
to be able to calculate the benefits that
that tree population provided.
We did that through two methods, through i-Tree Eco,
and then we also used
the Council of Tree and Landscape Appraisers' methodology,
which has built into its formulae the benefits of trees.
So it's just two different models
as a kind of a check and balance.
And then we wanted to look at,
what influence would different management strategies have,
and intensities of management have,
on the outcome of that population of trees over time,
both in terms of how many trees you could retain
and what that present value of that asset,
that asset of trees, might be over time
following different management strategies?
And also, what influence would that have,
management strategies have,
on canopy benefits related to those trees?
We knew that we had good, detailed removal records
from 1956 to '96.
We documented the loss
of almost 104,000 elm street trees during that time.
We did have a partial street tree inventory
that was done by the University of Wisconsin in 1979,
and that inventory suggested that
the mean or the average diameter
of elms in our city at that time was 19.6 inches.
The University of Wisconsin has also done
a long term street tree mortality study
in Milwaukee and in Minneapolis over a 27 year period,
and from that data,
we were able to establish that in our region,
elm grows about a third of an inch a year.
So we were starting to get some of the pieces that we needed
to be able to do the canopy benefit assessment in Eco.
So, just like we could forecast that,
if we knew a tree was gonna grow
a third inch in diameter a year,
we can forecast the size of that tree 10 years out
and say with confidence that tree is gonna grow
three inches in diameter in 10 years.
Since you can forecast, you can also back cast.
So we wanted to find out what that mean diameter,
or the average diameter, of that elm population was in 1956.
So we took that known diameter in 1979 of 19.8 inches,
I think it was, seven inches, and we worked backwards,
a third of an inch each year back to 1956
to come up with a mean or average diameter
of about 12 inches average diameter in 1956
of the elm population.
We also needed to know what the average height was,
the average crown spread, and the average live crown ratio.
How much crown area versus the total height did we have?
And so we used regression,
and I'll just show you a couple slides.
We're not gonna talk about detail about that.
But for mean live crown ratio,
we estimated that, yeah, arboricultural standards say that
two thirds of the tree should be crown,
no more than one third stem.
So we just used that as an average on our elm population.
And we also assumed that the condition of the trees,
since they were being professionally managed,
was at least 70 percent or good
and that we had less than three percent canopy die back
in any of the trees at any given time.
So this just simply shows
how we calculated height based on diameter.
So this is just a regression curve,
and all this simply says is that
if you know the diameter of an elm tree, you can predict
with a high confidence level of about 90 percent,
or 90 percent of the variability
can be accounted for by this curve.
So for instance, if we knew we had a 30 inch diameter tree,
we could follow up here, intersect over here,
and get the height of that tree.
So it's just a curvilinear relationship there
based on a lot of data at a high level of accuracy.
So we could establish
based on known information about growth data on elm
what the height of a given diameter tree would've been.
The same thing for crown width.
There's good metric data out there for elm
on crown width by diameter.
So just by knowing diameter,
we could establish what the height is.
Okay.
These are our image years here.
This is how the canopy changed over time,
the percentage canopy.
And here the diameter, remember, we had a known diameter
of 19.6 inches in 1979 of the elm population.
We back cast that to 1956, came up with 11.78.
And we projected that forward to 2013,
and you can see how the diameter changes.
And then the associated difference in
how the height of the tree would change over time
and how the crown width would change over time, as well.
Okay.
So there was some work done by Cannon and Worley in 1976
that modeled the mortality of elm trees
based on how aggressively that disease was managed.
Here on this left axis, it shows
the number of trees left per thousand of original trees,
and this is over time.
So this is years since outbreak,
so this projects out to 16 years.
And so under a no control scenario, their data showed
from these different cities that lost trees
that under no control,
you would have a rapid loss of tree canopy and elms
over the first eight years,
and then eventually it would level off,
but you'd have a rapid loss of canopy.
If you followed
a fair, a good, or a best management strategy,
you'd have a much better outcome.
You'd retain a lot more of your elm population
by actively managing that disease.
And so what's the difference between fair, good, and best?
Well, fair would be, let me go back to no control.
So no control, with Dutch elm disease,
when the tree starts to show symptoms of Dutch elm disease,
you get wilting.
You get a limb that's starting to wilt or turn color.
That's indication that
the xylem in the tree is getting plugged
and that the water is not flowing so it's starting to wilt.
So under no control scenario,
when you observe that, you take the tree out,
and you wait 'till you see the next tree
and you take it out.
That would be no control.
Under fair, fair control by their study indicates
that you would perform one inspection a year
of that elm population.
If you'd observed Dutch elm disease,
you would take the tree out within 20 days.
Good and best escalate the number of inspections you do.
So under a best control scenario,
you'd be doing four inspections a year.
So you're spending resources, you're spending money
to send people out to look at your trees
to assess their health.
So that's a higher level of management.
But under a best management strategy,
you'd be inspecting four times
and removing within 20 days of detection
of any symptoms of Dutch elm disease.
By following that over a 16 year period,
you'd be expected to retain well in excess
of 75% of your trees.
So it does help you to retain trees
and is an effective strategy.
So we applied Milwaukee's actual elm data, starting data,
of 106,000 elms that we knew we had at that time
to these various management strategies.
So this is Milwaukee's actual population decline.
So you can see we started out at 106,000 in 1956.
By 1996, we only had 3300 left.
Had we followed a best control strategy
where we were doing four inspections a year,
we'd expect that to only yield
one percent annual loss and mortality by 1996.
We would've retained about 53,000 of those elms,
and they would've been big elms.
So clearly, based on Cannon and Worley's work,
the more intensively you manage the population,
and this would apply for not only Dutch elm disease,
but for emerald ash borer and any other pest,
the more actively you manage that pest, the better outcome,
the larger population of trees
you're gonna preserve over time.
This is just what it looks like on a graph.
This data line is Milwaukee's
actual population curve of elm,
and we lost a lot of 'em over a short period of time.
Had we followed a best management control strategy,
we would've been able to retain, like I said,
about 53,000 elms by 1996.
And just to show you that this model is accurate,
this actually is Minneapolis data.
This red line is what their population curve
would've looked like under a very minimum sanitation effort,
tree shows symptoms, you take it out and so forth.
Had they been able to practice
a more aggressive management strategy,
this is what the population curve suggests
from Cannon and Worley
what they would've been able to retain
in terms of elm population.
These green bars are what Minneapolis actually retained.
So they did preserve.
They got Dutch elm disease
about six or eight years after Milwaukee.
By that time, the US Forest Service had understood better
what Dutch elm disease was, how to manage for it,
and how the benefits of active sanitation,
getting that disease out of your population
so the beetles in that tree don't breed
and transmit that disease,
they understood how that could help
to manage Dutch elm disease.
And so Minneapolis had
a very different outcome than Milwaukee
because they had the technology,
the knowledge, the technology, and the practices,
but we didn't.
Okay.
I mentioned we wanted to measure
the lost canopy benefits over time.
So we used i-Tree Eco to do that.
And the way we did that,
since we just had average diameter of our population,
we calculated the ecological service benefits
of a single tree for each of these image years.
And obviously, as a tree goes over time,
it gets larger and larger and produces larger benefits.
We all understand that.
Then we plugged in the actual numbers of trees
under the different management strategies
that we would expect to retain over time.
So this is Milwaukee's actual curve.
I know you can't see these numbers.
Along these different management strategies,
we plugged in the actual number of trees
that we would expect to retain over time
and calculated that the ecological services benefits
for this population of elm trees
following different management strategies over time.
And as you might expect,
the more we had, the larger they were,
the more benefits those trees were churning out.
When we compared what Milwaukee's
actual benefits were over time,
and this is looking at storm water savings
over about a 60 year period,
this is our actual curve dropping way down,
had we followed a best management strategy,
we would've retained and actually increased
the storm water benefit of that tree population over time,
even though we would've had fewer trees.
Remember, we started with 106,000 12 inch diameter trees.
But by 1996, had we followed a best management strategy,
we would've had 53,000 much larger elm trees
that were producing an equivalent benefit amount
as that larger population of elms were in 1956.
So we would've been able to hold that benefit steady
or actually increase it.
We see that same type of scenario play out
for air pollution removal over time.
And it was important to note that
each of the years is a foregone benefit.
So each yeah, this is the gap that the city
no longer realized in terms of benefits
because those trees were gone.
They weren't there to produce benefits anymore.
The same type of curve for energy savings
and carbon sequestration savings.
When you look at it cumulatively over time as well,
the total ecological value over time
when you combine all the values together,
you get the same type of relationship.
Good management provides
a much higher, three million dollar annual benefit retention
versus our actual, which is well under
half a million dollars of benefit retention
over that same period of time.
And the take home message here is that
if you can't do a best management strategy,
you can't inspect four times a year,
inspecting three times a year still gives you
a much better outcome than not inspecting.
So we calculated that
the total cumulative benefit loss over time,
and that was about 120 million dollars of lost benefits
related to the removal of those 100,000 elm trees over time.
And then the third phase of this,
we wanted to understand the influence of management
on what the value of that population of trees
we would have over time
following different management strategies
and what the return on investment would be,
or the benefit ratio, to understand,
is it worth, realizing that it costs more money,
to manage at a higher level of intensity?
Is it worth it?
Do you get a higher return on your investment
of resources and time when you manage at a higher level?
Is it cost effective to do that?
So we looked at the net present value,
the benefit cost for Dutch elm disease,
and also for emerald ash borer
looking prospectively out 20 years.
A lot of numbers in a slide.
I don't want you to focus on any of the numbers,
but I want you to look at this relationship.
So this just shows this is just tracking
the management cost over a 40 year period
for Dutch elm disease following
these different management strategies.
So it's not surprising that a best management strategy,
where you're inspecting four times a year
and you're removing trees that show symptoms within 20 days,
that's gonna be your highest cost.
But notice the distribution.
Here, the green, that's your management cost
for inspecting and removing trees, or the inspection cost.
And then the removal cost is a fairly small bar
'cause you're not removing many.
You can still do a lot of pruning at that time
'cause you're preserving that canopy.
And your planting costs are also low.
Under no control, no control is your cheapest option.
If you're a city manager or you're a budget director
that says, "I don't care what you do.
"Just spend as little money as possible."
Well then, for Dutch elm disease,
that option would be do nothing.
When the tree starts to die, you take it out.
That would be the cheapest option,
but if your goal is to manage trees
and the benefits that they provide,
then it's gonna be more costly to do that.
That wasn't a surprise.
What was a surprise was, I guess,
or at least that was a revelation to me, was that
the time frame that you expend those dollars
to manage that pest or disease varies widely
based on your management strategy.
So this red line would be...
So here, you have cost in millions,
and this is over time over a 40 year period.
So if you didn't do any control with Dutch elm disease,
when you find the disease you take the tree out,
you'd lose your population rapidly.
Your cost would spike considerably
over the first eight years or so,
and then it would start to decline
as you lost your population.
This hash line was Milwaukee's cost over time,
and we lost a lot of our trees
over a short period of time as well, so our cost tripled.
So you've heard from other speakers
that they've added a million dollars to the budget
to manage emerald ash borer.
I can tell you as a manager of a population of trees
that has to present and request for funding
that your mayors, your city administrators,
your budget directors, they hate to see a spike like this.
They'd much rather see a flat line budget
where you might see a little bit of increase.
So for instance, under a best management strategy,
yeah, you'll get a slight increase
'cause you're spending more money inspecting,
but you're not losing many trees.
So your cost to manage Dutch elm disease,
and as we'll see, emerald ash borer,
flat lines your budget.
So you'll get a slight increase, but it remains steady.
That is a lot easier for a city to manage
than these types of spikes.
That's very difficult.
And when these spikes occur, what happens?
There are things in your city that doesn't get done.
So in Milwaukee, over that,
about a 17 year period when we were just hammering,
taking out a bunch of elm trees for public safety
and replanting those, we weren't doing any pruning.
So for about a 17 year period,
all these trees that were being planted,
they weren't being structurally pruned.
And even today, I live with the results of that.
So we have a higher than desirable number or percentage
of (mumbles) maples in our population.
A lot of those trees have really crappy structure.
They branch low.
They have multiple branches coming together.
They're splitting apart in storms.
And so the attention that we had to give to removing
dead and hazardous elm trees over this period of time
forced us off pruning.
It'll force every community off of something else
that's a priority that you've been doing
that's gonna have an impact well beyond
your management of that disease or insect.
This particular slide looks at the net present value,
so realizing that, like any asset,
the more you have, the bigger it is,
the more valuable it's gonna be.
With Dutch elm disease over a 40 year period,
if you did nothing but took those trees out as they died
over a 40 year period, you would have
a cumulative asset value of about 50 million dollars
over that 40 year period.
Under a best control scenario,
that yields a much larger asset value of about 175 million
'cause many of the trees that you're protecting
and managing over that time are still in your population.
You still have that asset.
The best scenario is no Dutch elm disease,
which isn't relevant here because we did have Dutch elm.
The red dots indicate the benefit cost ratio.
So in other words, for a best control strategy,
every dollar invested to manage at a higher level,
remember we said that it cost more to manage
at that high level, we understood that,
but when you do that, you manage at a higher level,
you retain a higher asset value.
For every dollar you invest,
you get a dollar 22 back in asset value.
That asset value considers
the ecological service benefits
that those trees are providing that you're retaining.
And here's Milwaukee's actual experience.
Had a asset value of around 80 million
after 40 years of that elm population
realizing that not every tree died on day one.
It took a period of 20 to 40 years
for all the trees to be gone.
So during that time, there was asset that was retained.
But for every dollar invested,
we lost, in essence, 21 cents on the dollar
following the strategy we followed.
Nobody would invest in a strategy
that loses money like that, right?
So the take home here is that you retain
a much larger asset value if you actively managed
for insect and disease,
and your benefit cost return is also positive.
When we project using this same modeling
with emerald ash borer forecasting out 20 years,
we see this same type of scenario.
This is actually Milwaukee's data,
and this is the management cost over time.
So we're spending about, over a 20 year period,
we're expecting to spend about 19 million dollars
to treat about 28,000 ash street trees.
We've got a very aggressive treatment program.
And so you can see
most of our cost over that time are treatment.
Our cost for planting is two million and three million
projected for removal over time.
So trees that die, break apart in storms or whatever,
for other reasons, would still be removed over this time.
If your interest is minimizing your cost,
then preemptive removal without replacement
is your lowest cost.
That will cost you 14 million dollars over a 20 year period
with the population size of ash trees that Milwaukee has,
about 33,000 ash street trees.
But what I want you to see here is,
a lot of communities are pursuing
preemptive removal and replacement strategies,
and that is the most expensive strategy.
And you'll see in a minute,
it also yields the lowest net present value.
So if over a 20 year period
this is the asset value, the net present value,
based on different management strategies
for emerald ash borer,
a no control strategy will yield a higher,
which is interesting, a higher asset value over time
'cause trees die more slowly over time.
If you're pursuing a preemptive removal strategy,
that will yield your lowest asset value
'cause you're taking 'em out much more quickly.
But look at the asset value, the net present value
that you retain by treating those trees over 20 years
'cause you retain most of the population.
Your net present value, or I'm sorry, your benefit cost
following a treatment strategy for emerald ash borer
is about 300 percent.
So for every dollar you invest in that tree
to treat it and keep it for 20 years,
you're getting a 300 percent return back on that tree
in terms of the value of services
that tree provides for your community.
On the flip side, if your strategy
is preemptive removal and replacement,
for every dollar you invest,
you're getting just 70 cents back on the dollar.
So it's losing money
because you're removing those trees from your population,
and the benefit loss is greater
than the cost that you're investing
to remove and replace those trees.
Take homes here from our study was that
active pest management strategies
that maximize urban tree canopy retention
results in positive net benefits.
Benefits from one ecosystem service benefit alone,
like air pollution or storm water retention,
can pay for that higher level of management
for that pest population over time.
So you don't have to have all the benefits,
consider all of them.
Just one of 'em alone would pay for
that increased amount of management.
For emerald ash borer, preemptive removal and replacement
is the most expensive option
and provides the lowest benefit cost ratio.
You get the worst return on your investment
following that strategy.
Canopy restoration may take 50 to 75 years
depending on where you live in the country.
Are you prepared for that?
If that's your strategy
and your city is diversified on a block or street basis
where entire blocks of ash trees
are gonna be removed and replaced over time,
it's gonna take a generation
for you to reestablish that canopy.
That will have a profound impact on your community.
And then strategies that minimize budget peaks
will reduce the need to reallocate resources
from other core services.
So those are the summary points
that I hope you take away from this.
And I'll say that, while this is Milwaukee's strategy
and this study supports what we're doing,
much like Urban Wood, which we'll hear more about today,
the strategy that you develop for your community
is maybe very different and may be very appropriate
for your community.
I'm not saying that our strategy
is better than anyone else's.
I'm just presenting
what our experience was with Dutch elm disease
and what projecting with emerald ash borer,
what those outcomes would be under aggressive management
versus a lesser management intensity.
But still, this is a decision that each community
is gonna have to determine on their own
what their best path forward is.
And for communities that have a lot of ash trees,
right now, Milwaukee's ash population
is about 17 percent of our canopy,
17 percent of our street tree population.
So it's one in every six trees is an ash tree.
So it is a significant impact for us.
If you only have a few hundred ash trees in your community,
you probably don't wanna invest the time in doing this.
But if it's a significant part of your canopy
and you value the benefits those trees are providing,
you may wanna consider at least some treatment
to preserve those benefits over time.
Okay.
There.
(man speaking off mic)
So your asset value, because remember, one of the inputs
that we had to put in the model was condition.
So in this case, we estimated a 70 percent condition factor.
In this part of the country where ash struggles,
that may be a 40 percent condition factor, or 50.
So that would lower the asset value.
Yeah, it would have an influence.
And I think if I was managing
a population of ash trees like I'm seeing here
that I think removal and replacement
probably does make better sense.
You'd get something better in that landscape
that's gonna provide a tree
that's a better fit for the site, yeah.
Yeah.
(man speaking off mic)
Yeah.
I'm not sure how that would be done,
but I think the modeling
that resulted in the outcomes we got here
could be tweaked to provide that data.
And I will tell you that when we started,
our EAB strategy initially,
when we started treating in 2009, we anticipated removing
about five percent of our ash trees over a 20 year period.
We didn't wanna have that same experience
that Dutch elm disease gave us
where our entire blocks and neighborhoods
were wiped out of trees.
While we are more diversified than we were in the '50s,
we still, unfortunately the city, in replacing trees,
continued to plant on a street or block basis
the same species.
So people that have live on those blocks that have ash trees
are at significant risk of losing everything
and realizing the outcome
that Dutch elm disease provided for our city.
So we wanted to spread it out over years,
not only for budget reasons to smooth that out over time,
but also to minimize impact on neighborhoods.
And we were going along.
At the point where we tried to get funding
to start removing trees and replacing them,
the treatments were so much cheaper
than removal and replacement that our budget office said,
"No, we'll just give you more money to treat."
So our initial threshold
was eight inches and larger in diameter.
We felt that an eight inch tree had enough of a canopy
that it was providing enough benefits
that it was worthy to protect.
Anything below that we felt we could
remove and replace with minimal impact.
But now, well we've been treating since 2009,
so some of the trees that were below eight inches in 2009
have grown into our treatment pool now,
so they're larger than eight inches.
In addition to that, we're now having to treat smaller trees
because our budget office isn't willing to fund
additional removal and replacements
'cause it's so much more expensive.
We can treat a tree in house with our in house crews
with emamectin benzoate, Arborjet,
get two years of control for about $70.
That's a 19 inch diameter average tree.
So our per diameter inch cost is about $3.75.
So we're well below what the commercial market is
because we use an internal workforce to do that,
so we pay 'em a internal wage of 12,
now it's gone up to about 15 bucks and hour.
But still, we can do it much cheaper
than a contractor that has to earn a profit.
Following this story, Rich Hauer told me that, he said,
"At the point at which emerald ash borer
"removal and replacement is equivalent to the cost to treat
"is about $33 per diameter inch."
So if we had to pay $33 per diameter inch
to protect our ash trees,
it would be just as cheap to remove and replace those trees.
So we're at $3.75 per diameter inch.
We're gonna treating 'till the cows come home,
and preserving the benefits over time.
So I think there's other positives here.
You don't have all the drama that is created
when you start taking trees out,
healthy trees in neighborhoods when you have an alternative
that can preserve that population of trees.
And just from a political perspective,
no politician wants to be labeled as
taking down trees unnecessarily.
Because the emamectin benzoate is so effective
and it's so much cheaper than removal and replacement,
I don't expect to ever get support
to transition to other species
other than just through natural attrition.
Unless at some point the trees become so wounded
that they don't take up product anymore.
That could certainly happen.
Any other questions?
Okay.
Thank you for your attention.
(audience applauds)