- So without further ado, this is Mike Hallworth.
He's a data scientist with Vermont Center for Ecostudies,
and this is his talk, Living on the Edge in a Warming World,
Distributions and Thermal Refugia
of Forest Insects Across the Northeastern United states.
So we'll turn it over to you, Mike.
- Great, good afternoon everybody.
Thank you for having me here.
I'm excited to talk about some preliminary results
with you today on how climate change
may impact insights across the broader New England region.
All right, so insects are the world's most species-rich
and abundant group of macroscopic organisms on the planet,
and community science data
across the broader New England region confirm that.
So this pie chart that you're looking at
on the left-hand side here just shows
that insects are by far and away the most speciose group
that we've identified as community scientists,
over 1,600 insects species.
The problem is that they're experiencing
precipitous declines.
A recent study a couple of years ago showed
that insect biomass has been declining
in protected areas in Germany.
And so here is flying insect biomass from malaise traps
through time on the X-axis.
And the rate of global declines is still uncertain,
and there's some dispute about that,
but scientists agree that insects are in decline globally.
And we're seeing this decline in the Northeast, as well.
We're seeing beetle declines.
One example came recently from a Wellesley undergrad
who published a pretty high-impact paper
where they replicated some window trap surveys
for beetles at Hubbard Brook Experimental Forest
in New Hampshire where they did some window trap surveys
in the '70s, and then they replicated the surveys
in 2015 to 2017, which are looking at on the Y-axis here
is the mean captures per two-day period,
and time on the X-axis.
And the gray bars show the results from the '70s,
and the black bars show the more recent results,
and there's a drastic decline in the number of beetles
that were captured in a two-day period.
They found that the number of beetles that they caught
during that time period was strongly correlated
with the median snow depth during the preceding winter.
So there's some climate component there potentially
of the decline in beetle captures.
But it wasn't just beetle captures that was reduced.
It turns out that the species richness was also reduced.
So the actual species that they captured in those surveys,
so this is the original species accumulation curve
from the '70s, where you have species taxa
on the Y-axis and the number of samples on the X-axis,
and there's a drastic reduction
in the number of species that they captured
when comparing the two survey periods.
So that leaves the question, like,
what factors are contributing
to some of these observed declines?
And David Wagner and colleagues
published a paper recently this year
in Proceedings of the National Academy of Scientists,
and they suggested that insect declines
are caused by the death of a thousand cuts.
And many of these cuts are related to climate change,
whether it's species disruption,
so changing species interactions,
more intense and larger wildfires,
storm intensity that cause increased flooding,
warmer temperatures,
which could alternate their life stages, and droughts.
And all of those types of stressors
are compounding what's happening below,
so like deforestation, insecticides,
introduced species, urbanization and so on.
And so climate change is a real issue.
And so how might climate change
impact insect populations?
Well, it could reduce habitat suitability for some species,
change habitat suitability for others.
It could alter range limits and change range limits.
So we see that some species are moving northward
and some are moving potentially southward.
It could alter the timing of lifecycle events.
So, think of when caterpillars form cocoons
or when dragonflies eclose.
And why does this all matter?
Well, insects are hugely important,
and especially for forested ecosystems.
They perform many, many ecosystem services.
For example, they're culturally important
and they provide great aesthetics,
like this black swallowtail caterpillar.
They provide critical ecosystem function,
like pollination and seed dispersal,
but they're also bioindicators of ecosystem health
and for water quality.
They perform pest control and they help aerate soil,
and there are so many more.
They're also a hugely important component of food webs,
especially for vertebrates.
So just one example,
the chickadees that presumably are breeding
in your backyard, to successfully raise a brood,
they have to forage and bring caterpillars,
a lot of them, every day,
between 350 and 570 caterpillars per day
to successfully raise a brood.
So they're hugely important to our food webs.
And since they occur ubiquitously in our food webs
and they serve as bioindicators,
it's imperative that we understand how their populations
and species richness responds to climate change.
And so today we set out, I'm gonna tell you a little bit
about what we are working on,
and we set out to develop species distribution models
to better understand where species are within the landscape
and how their distributions may be changing
given climate projections.
And we need these detailed maps
to understand both the current risks and the future risks
that these species may encounter,
and these distribution maps help fill critical data gaps
as identified in a lot of the state wildlife action plans
across the Northeast,
and this data will help allow stakeholders
to make really informed decisions
about where to place management or take management action
in the future, given climate change.
So I'm gonna talk briefly about the methods.
We used community science observations
submitted to GBIF
or the Global Biodiversity Information Facility
through iNaturalist and eButterfly and other sources.
So we took the presence data for species,
and all the insects with more than five
independent research grade observations,
so that means that someone else said,
oh, yes, that is a black swallowtail,
so more than one person, it was confirmed by many people.
And we know that there's sampling bias
in where people submit their observations,
that, like, they tend to submit where they live
and near roads.
So we accounted for that sampling bias in the location data,
and then we associated those occurrence records
with bioclimactic data,
so things like mean annual temperature,
precipitation, for example.
And we used that relationship between the current data,
the occurrence data, and the climate data,
to make predictions about how occurrence will change
given climate change,
and that allowed us to make both current distribution maps,
like shown here on the top,
at one by one kilometer resolution.
And then we also are able to feed, okay,
well, how will the climate change
given some ensemble models,
and what is the projected relationship
or the distribution of these species moving forward?
So given the climate projection,
the current relationship between climate,
we can get a distribution map,
and if those relationships stay similar,
then this is the projected distribution
for that species in the future.
So I'm gonna dive right into some results here.
Where are forest insects across the Northeast?
So what you're looking at is the estimated species richness
on the left here, this is the current range,
where they are, and on the right
is where they're projected to be
given the most likely climate emission scenario,
which is RCP 7.0 in the year where the climate
that encompasses 2071 to 2100.
You can see the range and species richness here
between the current and the future.
So this is a great first picture of where things are,
but I was kind of really interested
in where things will be changing.
And so what you're looking at in this slide
is this is the previous map
on the previous slide for reference.
This histogram here on the lower left
shows the change in species richness on the X-axis
and the frequency of cells on the Y-axis.
So there are some places where we're losing
200-ish species, and there are lots of places
where we're gaining lots of species, upwards of 800.
I should say gaining, I should say moving.
Species are moving, because I eliminated the taxa
to what is currently in New England
and not what is potentially moving into New England.
And this is where it's happening in space.
The red indicates areas where species richness
will be lower in 2100, and the warmer colors
means that more species are potentially leaving that spot.
And the cooler colors in blue indicate areas
where there's a species richness increase.
On this histogram on top shows how that change
is distributed in longitude.
So this is on the west, and this is east,
and then this on the right, this histogram on the right,
shows how it will change with latitude,
so this is south and north.
So you can see
where the projected changes may occur at latitude.
So this is all taxa,
so what I'm gonna do now is talk about some insect groups.
So how will climate impact the major insect orders?
And I just picked these major insect orders
because I thought they were interesting,
but we did 20 insect orders.
So on the maps,
you'll see more of these maps in a little while,
but the current species richness is on the left,
and the species richness for those orders
is on the right in in 2071 to 2100.
Now I was interested in how to kind of numerically
or quantitatively measure
how things will change in the future,
and so this is like a climate velocity analog
to species richness.
And so what you're looking at here is,
this is the current richness,
and then this is the projected richness in the future.
And so what this velocity is measuring
is the rate of change
between the current species richness value
and where the closest analog pixel will be in the future.
So how far does this cell need to move per year
to represent this cell in the future?
That's the rate of change.
So it's in kilometers per year.
The direction of change measures which direction
this particular cell will need to move with respect to north
to represent this cell in the future.
So there are two metrics here,
velocity, which is rate, and direction.
You'll see a few of these histograms coming forward,
so I just want to describe them a little bit.
On the X-axis is the rate of change in kilometers per year.
So this value here, there's a few values
of six kilometers per year, and a lot of values
that are close to zero,
whereas that pixel does not have to move through time.
The rose plot up on the upper right
shows the direction of change,
where north is zero, east, south, and west.
And so in this particular example,
almost all the pixels were moving northward
to match their species analog future.
So diving into these results,
how will climate impact the major insect orders?
What you're looking at here is Lepidoptera.
And so this is the histogram on the left
of climate or the velocity, kilometers per year,
and the rose plot, so which direction do they have to go
to meet that analog?
Most of the species are moving northward.
Pixels, sorry.
Some pixels are moving towards the east
and some are moving towards the west,
but the majority are moving northward.
And the main velocity, it was about 1.5 kilometers per year
between the current distribution
and the distribution in 2100, let's say.
So for Coleoptera, for beetles,
the mean is 1.48 kilometers per year,
so about the same as Lepidoptera,
but almost all of those pixels are moving due north.
For Diptera, we see a similar pattern.
The mean is about 1.6 kilometers per year,
so Diptera are the flies.
And most of those pixels need to move north
to reach that species richness analog in the future.
Hymenoptera, bees, ants, et cetera,
their mean is about 1.5 kilometers per year.
That's how far the pixel would need to move
to reach a species analog in the future,
and almost all of those pixels need to move north.
Hemiptera, so the true bugs, things like cicadas,
aphids, plant hoppers and the like,
their mean is about 1.45,
and almost all the cells would need to move
in a northward direction to meet
their species richness analog future.
So one thing to take home from this part of the talk
is that most of the cells and all the orders
would need to move northward.
Almost all of them, so four of these five groups,
are moving almost exclusively north,
with the caveat of Lepidoptera,
and that's likely because there are many, many more species
in the Lepidoptera.
There are thousands of species in Lep,
so they could be responding slightly differently
than some of the other insect orders here.
So how does velocity differ by forest type?
So I'm gonna skip through here.
The take-home here is that that all forest
at the top here, deciduous forest,
has the fastest climate velocity,
and that pattern holds for most of all the five orders.
So I want to get to this slide,
where insect velocity is really high across New England,
so where is that happening?
The cool colors represent slower velocity areas,
and the warm colors shown in here in red,
and I should note that the insect velocity is way higher
than a lot of the other taxa in Western hemisphere.
Birds are about 0.6,
and here are the 20 insect orders that we looked at.
They're in order of magnitude higher than birds,
amphibians, and mammals.
And why might that be?
It's likely because the insects are closely tied to climate,
so they're following the climate velocity faster.
So their development, phonology, their migrations,
and because their life histories are faster,
they may be able to respond faster
to how climate is changing.
How can we use these data?
Well, this is a, the climate velocity
and the protected areas overlap on that map,
and you can see, there are lots of areas
with slower velocity,
so these cooler colors that are not protected.
And I should note that that's the species-richness.
It doesn't necessarily mean that the community
under those cells will be the same,
and so that's the next step.
So where in the landscape will we see
novel communities in the future that we don't see now?
That's the next step that we're gonna take.
And I just want to, I'd be remiss
if I didn't thank everyone that's submitting observations
to iNaturalist or eButterfly.
This work is only possible because that data are there
and to play with, so thank you for being curious,
and I just want to say thank you to all the funders
and my collaborators and co-authors on this
that have been helping this process.
So I apologize for going over, but thank you very much.
- [Tim] Tim Howard here.
This is just a quick question.
Can you hear me?
- Yes.
- [Tim] Yeah, so that's fascinating stuff
and very interesting.
So the velocity was richness to richness.
So if the cell stayed from a richness of three
to a richness of three, but changed the species,
that would be a velocity of zero,
am I understanding that correct?
- Exactly. - And that is,
and that's why you said gotta look at species next,
is that what's going on?
- Yeah, so looking at novel communities in the future
is the next step.
So will we see new communities popping up elsewhere
that we don't see today?
And that will have to involve modeling species
that could be coming into New England
that aren't currently in New England.
So yes, this is a species richness velocity.
- [Tim] Thank you.
- [Woman] We had one quick question in the chat,
which is, what was behind the decision
to focus on temperature refugia
versus hydrologic or other gradient refugia?
- That's a great question,
and the simple answer is that in my former life,
I was at the Climate Science Center
and we focused a lot on climate,
and so hydrology changes would be a great thing to look at,
but, you know, I'm very familiar
with how temperature will change.
But adding those types of components
will give us a great things to do in the future
and will likely be very interesting, as well.