- 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 I'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 and how climate change may impact insects
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 insect 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,
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.
What you're 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.
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?
Ad David Wagner and colleagues
published a paper recently this year
in "Proceedings of the National Academy of Sciences".
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 caused 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.
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 life cycle events.
So like think of
when caterpillars form cocoons
or when dragonflies enclose.
And why does this all matter?
Well, insects are hugely important,
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 bird.
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 the 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.
That means that someone else said,
oh, yes, that is a black swallowtail.
So more than one person,
there's confirmed by many people.
And we know that there's sampling bias
in where people submit their observations,
that like, you know, 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 bioclimatic 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 the 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 the 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 in species richness here
between the current and the future.
So this is 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 said.
I should say moving; species are moving.
Because I limited 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 and blue indicate areas
where there's 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 with 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 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 a rate, and direction.
You'll see a few of these histograms coming forward.
So I just wanna 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 in the 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 north.
And the mean velocity 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 and 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 in the future.
So one thing to take home from this part of the talk
is that all the cell, 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 leps,
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 hat all forests at the top here,
and deciduous forest seems to be moving,
has the fastest climate velocity.
And that pattern holds
for most of all the five orders.
So I wanna 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.
The high colors or the warm colors
shown 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 an 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, phenology, 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 the climate velocity and the protected areas
overlapped 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 wanna, 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 coauthors on this that have been helping this process.
So I apologize for going over.
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 a 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 my understanding that correct?
And that's why you said, got to look at species next.
Is that what's going on?
- Yeah, so looking at like 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, you know,
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.
- [Moderator] 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 Research 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 type of components will give us
great things to do in the future,
and it would likely be very interesting as well.