Ashley Fortune Isham: Good afternoon from
the U.S. Fish and Wildlife Service’s National Conservation Training Center in Shepherdstown,
West Virginia. My name is Ashley Fortune Isham. I would like
to welcome you to our webinar series held in partnership with the U.S. Geological Survey’s
National Climate Change and Wildlife Science Center.
The NCCWSC Climate Change Science and Management webinar series highlights their sponsored
science projects related to climate change impacts and adaptation. It aims to increase
awareness and inform participants like you, about potential and predicted climate change
impact on fish and wildlife. I’d like to welcome Shawn Carter to introduce
our speaker. Shawn. Shawn Carter: Thanks Ashley. Today it’s my
pleasure to have Dr. Clint Muhlfeld with us. He’s a Research Assistant Ecologist at the
USGS Northern Rocky Mountain Science Center in Glacier National Park, and Research Assistant
Professor at the University of Montana’s Flathead Lake Biological Station.
Clint’s involved with numerous interdisciplinary ecological studies focused on a variety of
regional, national, and international aquatic research issues of growing importance to both
society and biodiversity conservation. His applied research aims to assess the threat
of invasive species, habitat loss, and climate change on native aquatic species and habitats
in the Rocky Mountains of the U.S. and Canada in the Pacific Northwest.
And today he’s going to be talking about some of his work. So it’s my pleasure to introduce
Clint, and it’s over to you. Clint Muhlfeld: Thank you so much, Shawn.
It’s my pleasure to talk to you today about our climate change research in the northern
Rockies and the Pacific Northwest. I changed the title of my talk today to include other
biota besides salmonids because we’re doing a lot of high alpine research on rare bugs
below melting glaciers which I’ll also discuss. So the title of my talk today is, “Predicting
Climate Change Impacts on Aquatic Ecosystems across the Pacific Northwest.”
We know that climate change has impacted every centimeter of the Earth, and especially, in
the western United States. It’s no exception here. This landscape is undergoing tremendous
change in the thermal and hydrologic nature of stream and lake environments. And so the
goal of our research is to really provide tools and a good understanding of how climate
change may or may not impact different species, how these impacts may be realized at different
scales, so we can predict and then manage for these potential outcomes into the future
to build resiliency and adaptive capacity for aquatic ecosystems. Specifically a lot
of our research has focused on how hydrologic, thermal, and habitat change has already influenced
and may influence native trout and salmon in the Pacific Northwest.
We’re going to talk today about applying new techniques that we’ve developed for combining
climate data with fine scaled vulnerability assessments using genetic data, habitat analyses,
and wrapping this up to understand more holistically these processes and how they affect species
for adaptive management and conservation. Understanding how climate change may impact
aquatic ecosystems is obviously a major priority for conservation management. Changes in species
ecology associated with climate change has been documented and predicted for a broad
range of organisms, especially salmonids. Now, salmonid fish may be at particular risk
of climate warming because they’re ectothermic. They are cold water dependent. They have a
really narrow thermal range. Their life history events are adapted to the timing and magnitude
of stream flow events. And their dispersal patterns are restricted to stream networks.
They’ve really nowhere to go. Moreover, they have enormous economic, ecological, and cultural
value. I’m going to start the story today at the
top of the continent. It’s the head waters or the water storage or water tower of the
Columbia Basin system. It’s called the “Crown of the Continent.” This is one of the most
biodiverse and ecologically intact systems in North America. It’s the convergence zone
of four bioclimatic regions converging on the narrowest point along the Rocky Mountain
chain. With waters flowing to the Hudson, Atlantic, and Pacific Oceans. It’s clearly
the water tower of the continent. We’ve been trying to understand the effects
of these warming impacts across these landscapes, starting where the glaciers originate up in
Glacier National Park and understanding how those aquatic communities are impacted immediately
below these melting and disappearing glaciers understanding these impacts all along the
continuum, down to these valley bottoms where the fish roam, where there’s a host of biodiversity,
not only within the surface water of channels but out into the flood plain zones where there’s
a host of other organisms that are…some aren’t even described.
This area provides really complex cold and clean areas for growth, survival and persistence
of a variety of species. It’s relatively intact and the water quality is impeccable. It’s
very cold, nutrient poor, and again, this is the water that originates at the apex of
the continent and flows downstream providing oxygen and really cold water for fish to spawn
in, grow, and survive in. Today, I’m going to be talking to you about
the impacts of climate change on trout populations in the headwaters of the basin, and then I’m
going to move downstream and talk about some of our vulnerability work on salmon and steelhead
populations as well. Here, in the top of the continent, in the top of the Pacific Northwest,
it’s considered a range wide and regional stronghold for a variety of species that have
survived cataclysmic changes to the environment, such as wildfire, floods, glaciation, et cetera,
for at least 12,000 years. We have the westslope cutthroat trout, these
rare stoneflies existing below these melting glaciers in the high country and threatened
bull trout, which are listed under the ESA. The bull trout is a charismatic megafauna
of the aquatic realm. It’s an apex predator. It requires large connections of impact habitats
to complete its life history. It migrates. It’s essentially an inland salmon. It migrates
250 kilometers right back to the stream they are born in. The juveniles rear one to four
years before emigrating out to the main stream where they grow to maturity to complete their
life’s history. These guys are great indicators of aquatic health, because not only do they
require intact and connections of habitats, but they also have the coldest water requirement
of any salmonid species in the Pacific Northwest. Similarly, westslope cutthroat trout are an
excellent indicator species in the face of warming climate. Unlike bull trout that spawn
in the fall, they’re spring spawners, so they’re using high flows to ascend the stream network
back to their native streams. They’re spawning in a little bit higher gradient higher up
in the watershed system than bull trout. The embryos incubate in the stream gravels into
the summer months before they emerge. Just like the bull trout they exhibit migratory
life histories as well as resident life histories where they remain in their stream their entire
lives. These salmonids have adapted to a changing climate for at least 12,000 years.
When the glaciers were receding, these species have invaded and colonized these areas for
many, many different times throughout our geologic history. At the end of the last glacial
period, the Wisconsin, we’ve seen bull trout and cutthroat occupying a variety of habitats.
During the colder periods it’s likely that these populations resided more in the valley
bottoms. These were the sources for connectivity and dispersal, and the headwaters were more
like sinks. When we had periods of extreme warming, for example, seven to nine thousand
years ago, it’s likely that those valley bottoms were the sinks and the sources were the headwaters,
because these trout had to retreat to these colder stream networks located in the headwater
areas. My point here is that these species have adapted
to persist under a changing climate for thousands and thousands of years before humans were
on the landscape. However, over the past century and a half salmonid populations and a lot
of other aquatic biota have declined dramatically, largely due to habitat loss, degradation,
fragmentation, invasive species resulting in competition predation, invasive hybridization,
disease, and parasites. It’s the combination of these existing stressors
and the exacerbating impacts of climate warming, which we’re all concerned about, to build
resiliency in our native trout and salmon populations throughout the Pacific Northwest.
Understanding the past and how as a prelude to the future is really key to understanding
the impacts of climate warming on aquatic species.
Just looking at real data over the last 100 years, we looked at air temperature trends
in Western Montana, and we found that over that record a loss of about a month of extremely
cold days and a three fold increase in the number of hot days. The kicker here was the
Northern Rockies. You think of this area as a refugium from climate because it’s high
and cold and there’s a lot of snow and glacial masses, but these air temperature trends were
tracking the global trend of increasing air temperatures. The main point here is that
we’re warming at two to three times the rate of the global average.
This landscape is undergoing dramatic change. The warmer air temperatures are decreasing
our snowpack and our glacial masses are receding. We’re seeing increasing disturbance events
such as wild fires throughout the West. These changes are altering the hydrologic regimes
of our stream and lake networks. Overall, we’re seeing a decline in stream flows across
the Pacific Northwest and the Northern Rockies. Several recent studies, shown here, have shown
that the annual discharges had declined over the past several decades.
These flow regimes are shifting and changing. Here’s an example of the Flathead river where
positive values indicate increasing flows, negative values indicate decreasing flows.
As you can see here, since 1958 on the shoulder months of the winter period, we’re seeing
the snow turn to rain. We’re seeing increase in fall and winter fawning mostly on the shoulder
months of the winter. We’re seeing an earlier spring freshet, in general, about two to three
weeks earlier. That’s leading to reduction in stream flows during the summer months.
Here is a depiction of the hydrograph. We see high flows in the spring. We’re seeing
a shift to the left. A decrease in terms of the magnitude. Here is a spike in the fall.
It shows a fall flooding event that nearly matched the preceding high flow associated
with the runoff. Summer discharges are declining as I mentioned before, throughout several
USGS gage stations in the Western United States namely in the Pacific Northwest. That’s a
general statement. There are different changes elsewhere but, in general, stream flows have
declined. Associated with that, temperatures are also
increasing. So we’ve seen a steady increase in water temperatures across these stream
networks for the past several decades. Perhaps, most iconic about the combining fact that
changes in flow and temperature and melting snow masses is the melting glaciers in Glacier
National Park. It’s kind of the poster child of climate change. At the last little ice
age in 1850, there was approximately a 150 glaciers on the landscape. Glacier’s losing
its glaciers. Now, there’s only 25 named glaciers in Glacier National Park.
The most conservative climate change estimates show that all these glaciers will be gone
by 2030. Glacier Park will no longer have its glaciers by 2030 based on the best available
science. We’re trying to understand these impacts across these landscapes at different
scales. We’re setting up a lot of different monitoring networks for stream temperatures
such as the NorWeST Program in the Western United States. We’re trying to understand
how stream temperature is responding and how these ectothermic organisms are responding
to a changing temperature and flow regime. This example here shows our stream networks
and the head waters of the basin where we have nearly 950 sites. We’re developing both
seasonal and daily temperature models to understand impacts on species over different scales.
These include covariates such as land cover, ground water influences, elevation, and glacier
and lake effects. Scale matters when understanding temperature responses over large and small
areas throughout the landscape. Landscape models are really important to understanding
patterns and processes over large time and space scales. They’re really important for
integrating these changes into ecological and management issues for scenario planning
and adaptive management, so scale definitely matters. But time does as well. That’s commonly
overlooked. We substitute space for time in a lot of instances. Whether that’s right or
wrong, we’re trying to understand more about the temporal dimensions of climate change
and the impact in aquatic systems. We can understand over core scales and develop
these monthly and seasonal models to understand average conditions, how these systems are
changing, and link them with climate simulations to predict where across broad landscapes this
change will occur. But there’s also a need for these fine scale assessments of using
daily models to then link with daily models of climate change to understand how species
key components of the life’s history are responding, such as life history traits in terms of shifting
in the timing of spawning, fry emergence, growing days and incubation days. I believe
that these different scales, these temporal scales are complementary in understanding
the impact of climate warming on the thermal dynamics and response of the species.
Here you can see our stream temperature projections for August compared from the baseline to an
RCP 4.5, which is kind of a conservative, middle of the road climate change forecast.
As you can see here, we can understand and predict down to 30 meters, actually, potential
stream temperature changes across the networks. We can then understand how critical thresholds
may be exceeded under different climate warming scenarios.
We can also use these data to understand the relative change across these landscapes, so
it’s not just about the threshold, because of what areas are going to change the most
over a given amount of time. As you can see here, the lower valley bottom, the major forks
of the Flathead are predicted to change the most over the next several decades. Then we
can move to a daily time step, as shown here with Leslie Jones’ work, where she’s developed
these seasonal based models. Now we’re going to a daily time step, the real data. The empirical
data are shown here and the black circles show our predictions. As you can see, they
match pretty well. Then we can link these daily time step climate simulation modeling
data with key components of life history and development of trout and other aquatic organisms
in the system. One way we’ve done that is to apply to critical
habitat for bull trout in this example. We’ve looked at both critical foraging, migrating,
and overwintering habitat in the main rivers. Then these key spawning and rearing areas,
where they go right back to spawn and the juveniles rear in. This paper came out this
year, and what we found is we use our stream temperature models to predict stream temperatures
across these different types of habitat. What we’ve found is that bull trout really occupy
the very coldest places of the landscape. We can then use these different temperature
thresholds to then understand and predict better how these habitats are going to change
into the future, so we can inform management. In this case, if you increase, under this
model scenario, if you increase the stream temperatures one degree, we can expect more
loss of habitat in these critical river corridors that they use, especially during the summer
months, to ascend and spawn in their native trips. Then we can take that out over different
time steps. We can then scale up to the scale of the crown. We’ve done that by looking at
critical thresholds, such as 11 degrees, and then understand how that’s going to potentially
impact bull trout in the upper Kootenai system, in the Flathead system, and then over in the
Hudson as well, the south Saskatchewan. And then look at the relative change across the
landscape to then be able to prepare managers where we’re going to see this change the most
over the coming decades. Obviously, with these analyses, high elevations,
northern latitudes, and groundwater in glacial influence reaches are going to be really important.
We’re seeing a lot of warming in the lower elevations, in the lower latitudes. These
areas in the northern regions, in the high elevations, are going to provide more thermal
refugia. But, at the local level there’s still spatial heterogeneity going on. We’ve been
tracking bull trout to their known spawning areas and what we’ve found, over time, is
these unconfined alluvial valley reaches are really important for bull trout spawning.
At the reach scale, they’re going back to these alluvial valley bottoms where there’s
a lot of groundwater and surface water interaction. There’s, essentially, huge upwelling zones
providing really cold temperatures in the summer and nutrients and well oxygenated water
for the embryos to survive in. We’ve set up temperature sensors throughout
the flood plain and into the main channel. As you can see here, there’s a great degree
of diurnal temperature fluctuations in these bull trout spawning areas elsewhere. But you
can see here, there’s groundwater influence. On an average, these areas are almost two
degrees colder during the summer months. These are likely areas that are going to be thermal
refugia in a warming climate. However, these areas, because they’re unconsolidated substrates,
because they’re multi channel habitats, the incidence of winter flooding may scour these
reds. That’s another concern, into the future, that we need to learn more about.
It’s not only about the temperature. It’s about the flow too. If they’re building these
nests in areas that are susceptible to scouring effects associated with fall and winter flooding,
like I showed you before, they could be vulnerable to those impacts other than temperature alone.
We’ve been trying to understand not only how contemporary patterns are influenced by climate,
and other human impacts, but how can we use the past as a prelude to the future. Can we
use real data to then understand the relative influence of climatic variation on fish populations,
in terms of abundance, distribution, genetic diversity, and phenology, and then build that
into our climate projections so we can more accurately forecast climate effects into the
future? We just wrote a paper, a few years ago, focused
on Rocky Mountain trout, using real data. Managers have been collecting fish population
data for decades. Can we go into the archives and learn about the relative influence of
climate and other human induced stressors on fish populations? One example of that is
our recent paper entitled, “Invasive hybridization in a threatened species is accelerated by
climate change.” This is the westslope cutthroat trout here. Like all other 12 extinct cutthroat
trout species, hybridization is clearly the leading factor contributing to the decline
of genetically pure populations. We need to figure out how climate might trigger expansion
of hybridization in nature. Hybridization, unlike a mule, where they’re
sterile. Hybrids produce hybrids. Hybridization spreads and eventually you might lose the
genomic integrity of the species. That’s really critical for conservation in the face of climate
change because those locally adapted genes and gene complexes are a link to these locally
adapted traits which have enabled these fish to adapt and persist in a changing climate.
Once hybridization occurs, it breaks down those key linkages between the genes and their
adaptive traits, or phenologies, on the landscape. With that, we might see their ability to adapt
and persist greatly diminished in the face of climate change.
Building in the time component was really key, in this study, to understand how hybridization
might spread in the face of climate change. What we did is we used temporal genetics data.
Managers collected genetic data, back in the late 60s, early 70s, and into the early 80s.
We used that to then resample areas in the 2000s to see if there’s a change in hybridization.
We found hybridization dramatically spread over just a few decades.
Despite, up until 1969, preceding these data right here, there was over 20 million rainbows
stocked into the system. These are non native introduced rainbow trout. There was 20 million
stocked in the system. The only spot in the system, that we know of, that had high proportions
of rainbow trout hybridization occurred in the lower valley bottom. This population here
was essentially a time bomb waiting to go off under the right environmental conditions.
What we did is we resampled those areas. We found hybridization spread in nine of the
18 previously non hybridized populations. Then we took a snapshot to look at the genetic
integrity across the entire spatial extent of the stream network. We found this genotypic
gradient with a lot of hybridization occurring in the valley bottom and a reduction in hybridization
as you move away from the source. We found, in some of these peripheral populations
that we looked at…we actually used genetic techniques and paternity analysis to see if
hybridization effects fitness in nature. What we found is as you increase the amount of
non native rainbow trout genes in female trout, in this example, in cutthroat trout, you see
a dramatic reduction in fitness. With up to 20 percent non native genetic admixture, or
hybridization, with rainbow trout, we found nearly 50 percent reduction in fitness.
In the face of climate change, if there’s a signal here, we can expect the resiliency
and the adaptive capacity of cutthroat trout to be greatly reduced in a warming world.
We linked this with our high resolution stream temperature models, and then data from NASA,
to reconstruct the invasion processes and the spread of hybridization over this time
period. What we found is hybridization basically spreading into areas with reduced spring precipitation.
In general, the rainbows are spawning as flows increase in the spring and cutthroat are spawning
on the descending limb or when flows are declining in the spring. What we think happened here
is these high flows that we saw for decades kind of precluded rainbows from pioneering
out into the river system. They kind of kept them abated because they’re spawning as flows
increase so those scour effects might wash away their nests, they might wash away their
fry. They kind of prevented hybridization from spreading.
Again, 20 million rainbows were planted in the valley until 1969, until this happened.
What we saw was a period of extreme drought, in the early 2000s, and a reduction in spring
flows. This was likely a window of opportunity through which hybridization spread massively
in the system, irreversibly corrupting the native genomes that have evolved over millennia
in the system. To a lesser degree, stream temperature played a role as well. Rainbows
typically have a little bit higher tolerance for maximum temperatures. We did find a correlation
between increasing stream temperatures and the presence and the amount of hybridization.
These effects were realized in both our spatial models and our temporal models. I want to
underscore here that the sources combined with the climatic variables were really driving
the spread of hybridization here. As you moved away from the source vein, incidents of hybridization
decreased. But it’s the sources persisting on the landscape which then radiate out and
hybridize and irreversibly corrupt these native genomes. We’ve showed this in a recent paper
that’s actually coming out tomorrow. It showed, in a very cold stream, we’ve got mean summer
temperatures well less than 10 degrees in Langford Creek and a very hot stream…we
saw hybridization increase over time. What we did is we looked at the population
dynamics using real data over several years. We found that despite the very strong selection
against admixture, in both environments, hybridization increased over time due to the continued dispersal
of rainbow trout from downstream source populations. If these sources persist, climate alone won’t
impede or prevent hybridization from occurring. It’s just a matter of time where you get these
dramatic changes in the environment, like those periods of extreme drought, that are
conduits through which hybridization will spread in nature. It’s a combination of these
sources with the climate that might lead to the eventual loss of native cutthroat trout.
We’re even studying effects of climate not only in the valley bottoms, where there’s
neighbor trout, but we’re also studying them in the headwater areas below these melting
glaciers. There’s a couple different aquatic invertebrates, that are endemic to Glacier
National Park, that have been petitioned for listing under the Endangered Species Act because
of climate change induced threats. Unlike the polar bear that was listed, no other stream
invertebrates have been petitioned except a couple in Glacier National Park.
We’re trying to understand how the recession of the glaciers, the changes in these streams
from perennial sources to more intermittent, and the stream warming, is effecting these
bugs. It’s squeeze play at the top of the continent. There’s nowhere to go. These guys
have been retreating upstream, tracking these cold waters, as the glaciers recede. They’re
confined to these 500 meter reaches, immediately below these melting glaciers, that are highly
susceptible to change as these glaciers continue to recede. Like I said earlier, all the glaciers
are predicted to be gone by 2030. This is Lednia tumana. Joe Giersch is an aquatic
etymologist studying these stream systems. This is the first footage of this ESA candidate
species for listing because of climate warming. We did a broad scale habitat analysis using
MaxEnt. We found that the highest probability of occurrence occurs in over 23 square kilometers
of habitat across Glacier Park. If you take away the glaciers and the permanent snow masses,
we’ll see an 81 percent potential reduction in distribution. This species is strongly
linked to glaciers. If the glaciers go, they’re going to be highly threatened with extinction.
There’s another species too, the Zapada glacier. We’ve found, using time series data collected
back in the 1960s, where this species was confined to the Many Glacier area of Glacier
National Park. This is in dew specimens. We were able to kind of reconstruct where people
sampled this species back in the 1960s. Then we resample these areas over the past several
years. We found a massive range contraction of this rare endemic invertebrate. You can
see here, these two glacial basins within the Many Glacier system, you can see large
tracks of glacial masses with massive recession over the past several decades. During the
study period, these glaciers receded about 35 percent from 1960 to 2012.
Here’s the historic distribution of the Zapada glacier as we knew it. We re sampled these
areas using morphology to identify the species, using DNA barcoding to find these cryptic
species at the nymph stage. Joe did this over several years and found only one population
remaining in their native range in the Many Glacier system, way up at the tippy top of
the continent. The summer temperatures increased over the study period; glaciers decreased
by 35 percent. There’s a strong correlation here between the loss of glaciers and a range
contraction of this rare bug retreating in colder water. Here’s where we know they occur.
They’re at the top of the continent. There’s really nowhere to go. These might be some
of the first species to go under climate change. We’re not only studying how species respond
distributionally and over time and space, but we want to gain an understanding, too,
of how their demography and genetic diversity plays into it. We worked with a variety of
folks here, and we recently developed a framework that combines demographic and genetic factors
to assess population vulnerability in strained species. My point here is that it’s not all
about distribution. There’s important components of persistence we’ve got to think about.
We’ve got to think about abundance. We’ve got to think about life history in diversity.
We’ve got to think about genetic diversity which is the basis for evolution and adaptation
in the face of climate change. We need to think about all these things when we’re thinking
about vulnerability. This is a framework that combines demography
and genetics to come up with different “demogenetic,” we call it, indexes of population vulnerability.
What this allows managers to do is you can put different resistant surfaces across a
stream network, and you can forecast out to see how these changes in demography and genetic
diversity will be realized under different climate change scenarios, or any kind of habitat
use or invasive species scenarios as well. You can see here in Generation 0 we can show
the genetic and demographic integrity of these populations, and then give managers a glimpse
at their future in terms of demography and genetic health. These are the kinds of things
we need to build in our climate change predictions to better understand species’ responses. We’ve
learned a lot at the top of the continent, and we’ve been working on a grant with the
Northwest Climate Science Center that has funded a lot of that work, as well as expanded
it out to the Pacific Northwest. We’re also working with a group lead by Gordon
Luikart from NASA, where we’re scaling up to the Pacific Northwest to predict climate
change vulnerabilities in salmon and in trout across this landscape. It’s a huge landscape
where these species have a freshwater phase of growth and they’re migrating to the ocean
to grow to maturity just like the bull trout in the inland Rocky Mountain region.
We wanted to not only look at patterns of distribution, but look at patterns of genetic
diversity and how those relate to vulnerability. Vulnerability is defined as the degree to
which a system is susceptible to adverse effects of climate as a function of exposure, looking
at climate change, namely temperature and flow in this case, sensitivity, looking at
habitat buffering potentials like the groundwater influence areas that I showed you with bull
trout, and their adaptive capacity such as genetic diversity and their ability to cope
with change. We launched this study, first to focus on
bull trout to understand how climatic variation influences both ecological and evolutionary
processes. Very few studies have done this, have looked at how climatic variation influences
genetic diversity across landscapes and over different time scales. We sampled 130 populations
of bull trout throughout the Pacific Northwest to test whether patterns of genetic diversity
were related to climatic variation. We then determined whether bull trout genetic diversity
was related to climate vulnerability at the watershed scale which we projected into the
2040 and using existing habitat complexity data as well.
Here’s an example of how we can look at the relative rankings of climate and habitat and
genetic variables for watersheds occupied by bull trout. Here you can see that summer
temperature, winter flood frequency, valley bottom habitats, those alluvial valleys I
told you about, and allelic richness, genetic diversity here. You can see there’s a strong
gradient in genetic diversity as you progress up the system. Areas in the lower basin, they’re
warmer, on the fringe of the distribution, have less genetic diversity or allelic richness
in this case. As you move up into the Columbia headwaters, there’s a strong pattern of increased
genetic diversity. Was this related to these patterns of landscape change in terms of both
climate and habitat? You can see here after accounting for the
spatial pattern of this genetic diversity from down in the lower Columbia to the Headwaters
with linear mix models, we found that allelic richness in bull trout populations was positively
related to habitat patch size and complexity and negatively related to maximum temperatures
and the frequency of winter flooding. There’s a very strong correlation with genetic diversity
and these climatic and habitat variables across the scale of the Pacific Northwest in terms
of bull trout. When we look at vulnerability in terms of
exposure to temperature and flow plus the habitat buffering effects of these alluvial
valley bottoms, we found that the average allelic richness was strongly correlated with
those variables. We can anticipate in a future climate scenario that as things warm, these
flows change, we might see their genetic diversity change still.
What was most of concern here is that we found in areas that are most vulnerable to change
currently, are the areas with the least amount of genetic diversity. We can expect that as
climate continues we’ll see inbreeding effects, potentially, and the loss of adaptive capacity,
potentially. We’re also expanding this work to look at
salmon and steelhead as well. I just wanted to give you an understanding here of the scale
we’re dealing with both winter run and summer populations of steelhead. Alisa Wade and Brian
Hand are working hard on this analysis now. We’re also adding bull trout to the mix for
this vulnerability assessment across the Pacific Northwest.
Looking at patterns of genetic diversity and how those correlate with climatic features.
In the case of steelhead, we looked at these major evolutionary significant groups to see
if there was a correlation with climatic variation and genetic diversity. We did find one. We
found that winter precipitation, in this example, was strongly related to patterns of genetic
differentiation. So there’s a strong relationship between climatic variation and these patterns
of genetic diversity in steelhead populations as well.
What we’re doing is we’re using vulnerability analyses to then look at how changes that
are built on these empirical relationships, built on our hypotheses, built on real data
and published data. They’re all hypotheses. All these vulnerabilities assessments are
hypotheses driven. But we know some of the things that are strong drivers of change like
thermally suitable habitat, like run off patterns, these valley bottoms, land use, critical habitat,
and building in other things than just changes in occurrence or distribution, building in
local abundance such as red trouts. We’ve collected tons of this data throughout these
networks and combining them with patterns of genetic diversity, as I’ve discussed,
as well. This is our model for steelhead. We’re doing
this for each species across the Pacific Northwest. We can look at vulnerability in a lot of different
ways. There’s no really right or wrong way to do this. But in this case that Alisa provided,
we looked at exposure in terms of changes in temperature and flow, so we have a spatially
explicit temperature model that’s linked to a flow model, VIC, to then predict that the
watershed scale, the vulnerability of different habitats now and into the future.
We have habitat predictions across the network. We also are building in patterns of demography
and genetics and understanding how these are going to change into the future. What it comes
down to, and don’t get caught up in this huge mess over here, these elements that we’re
including in vulnerability assessments greatly dictate the outcome. From these simple models
that have been predicted or developed, we have exposure in habitat equals vulnerability.
Here we’re arguing that demography and genetics that are critical components of persistence,
need to be built into these vulnerability assessments as well, and genetics, especially,
where we find strong linkages. As you can see here, if you build in demography
compared to the simple approach verses genetics, you’re going to get different answers depending
on what you’re looking at. Understanding the real patterns in space and time, building
that into these vulnerability in assessments, and then doing sensitivity analyses, looking
at how climate variation might be sensitive to these changes as well as the different
components of the vulnerability scores. Finally, I wanted to let you know about a
new project funded by the USGS in the Rockies where we’re moving beyond the space for time
models, where we’re looking at that other temporal dimension that’s so critical to look
at in terms of determining the relative influence of climate variation on fish populations.
We’re looking at using these high resolution daily stream temperature models, linking them
up with real data that have been collected from the crown of the continent up in Banff
and Jasper National Parks, all the way down through Glacier Park, down to Yellowstone,
down in Wyoming, into Southern Colorado where we can quantify these relationships between
climatic variation and demography and genetic integrity. Then we can look at how this change
influences assemblages and the non-native and native species interactions over space
and time. To summarize, we’ve entered a new realm of
disequilibrium in the 21st century. Our predictions show that these habitats will become more
and more variable and shift. Some will decline or become intermittent. Many populations will
adapt and track. Others won’t. Combined with these existing stressors, many of these populations
are already depressed and already have reduced resiliency in the face of climate.
Conservation needs will be real daunting and informed management is more crucial than ever
in this changing world. But I’d argue that we have the tools necessary right now. Maybe
not all of them, but we do have some. In many cases, it’s back to the basics for informed
decision making because management decisions now will have enormous effects on the amount
of native aquatic biodiversity a century from now. We’re on the critical point of conserving
these species for future generations. As Wayne Gretzky says, we’ve all probably
seen this slide, “skates where the puck is going to be, not where it’s been”. We
need to look over broader time and space scales to understand species’ responses for adaptive
management because we’re going to miss 100 percent of the shots you don’t take. In the
face of uncertainty, managers are going to have to make difficult decisions to try to
keep some of these organisms on the landscape for future generations. We can do that through
an adaptive framework where we’re constantly identifying and prioritizing and learning
about our different management impacts to get to our goal of species conservation.
A lot of this is already occurring on the landscape, so I would argue it’s back to the
basics with a lot of things that we can deal with existing stressors that humans have induced
on the landscape over the last century. We’re restoring flows and temperatures at the major
hydroelectric dams. We’re restoring connectivity like fish passage ladders or removing dams
entirely, dealing with invasives when they get in stream networks.
In this study we showed that if you get on it early enough in the stages of invasion,
you have a saving chance even with climate warming on the horizon. Maybe putting in barriers
where you have populations that are threatened, maybe opening them where you don’t. These
are complex trade offs that managers need to make in this uncertain future translocating
species, thinking out of the box, looking at areas where you’re going to put them at
safeguards or refugia into the future, or areas where you’re reintroducing them into
formerly occupied habits. And finally, protecting, restoring, and reconnecting these critical
habitats such as we’ve done with working with our partners in Canada to really fully understand
how these relationships interact with healthy environments and how we can bring them back
to provide healthy ecosystems and habitat conditions for fish populations and aquatic
species to grow and survive and persist in this changing future.
I always leave a talk with “Give fish a chance.” I think there’s hope. I want to thank you
all for attending this webinar today. I’d be happy to take any questions.
Ashley: We have one. It’s from Donald. It says, “What are some of the management decisions
that need to be considered, less commodities extraction?”
Clint: I think that management decisions have shifted. The paradigm’s shifting. I think
in the past it’s been reactionary. In the case of native trout management, for example,
managers are reacting to annual events like a collapsing stream bank and going out and
repairing that at a very small scale. I think in the context of climate change,
managers are now thinking over broader landscapes and over longer periods of time and understanding
that there’s going to be winners and losers in the equation, and being able to anticipate
the change and put the biggest bang for the buck where you’re going to get it into the
future. I showed some examples of management activities
that could bolster some fish populations into the future here. I think context matters.
It depends a lot on what the current situation is in the system. For example, in the case
of cutthroat trout, if a manager only has a few populations left that are genetically
pure and they’re at high risk of hybridization, a manager might have to put in a temporary
barrier to protect the last remaining genetic strongholds for that species so then they
can work on invasive species, habitat conditions, to try to re found them to their historic
habitats. I think habitat management and protection
of riparian zones is going to be very important into the future. Monitoring those habitats
over time is going to be key because we have to evaluate change and how we’re manipulating
the environment to understand how species are responding and is adaptive management
working? Space and time and context matters. These
are going to be difficult decisions in the face of uncertainty, but I think in a lot
of cases it’s back to the basics. Like I showed in my first couple slides, these fish have
adapted to persist in a changing climate over thousands of years. More recently, they’ve
declined dramatically to the point they’re greatly depressed and the resiliency is greatly
reduced. We have to build back that resiliency in areas where we can have hope.
I don’t know if that answered that. Ashley: We have another question from Donald,
and it was just referring to “Could hybridization also be a survival strategy?”
Clint: I guess the verdict isn’t out on that. It can be. Natural hybridization can lead
to evolutionary novelty, adaptive radiation, and can actually create new species. From
an evolutionary standpoint, natural hybridization is a key mechanism to promote persistence
of different characteristics and even create new ones. It’s a lot different than anthropogenic
hybridization, human mediated, where we’ve translocated fish in nearly every watershed
in the United States. In some cases, there’s been irreversible change.
I would argue that invasive species are the trump card for aquatic ecosystems. We can
do everything to build back habitat, but hybridization is a one way street. In the case of the cutthroat
trout, that fitness slide that I showed, that’s the first study that I’m aware of that has
linked different levels of non native genetic admixture with performance on the landscape.
In this case, we looked at fitness in terms of reproductive success, and we related that
to how hybridization may proceed or how it might increase in individuals. We found a
strong negative effect there. We found out breeding depression occurring
where anthropogenic hybridization is occurring in native trout. Over time, however, will
those deleterious alleles or genes get purged and recombination take place and fitness will
improve? The verdict’s not out yet. I would argue though is that if you look across the
entire range of all these cutthroat sub species across the Western United States, hybridization,
genetic in aggression is by far the leading threat and has dramatically declined the genetic
distribution of cutthroat. In the case of westslope cutthroat, we only
know of about less than 10 percent of their historic distribution. Now it contains non
hybridized populations. Again, those unique genes and gene complexes are linked to those
adapted traits that allow these species to persist. Hybridization occurs it jumbles them
up. Ashley: And then a follow up with that. “Has
there been an effort to remove the invasive species in the hybridized zone to tip the
balance back in favor of the cutthroat, despite conditions favoring the rainbows?”
Clint: That’s a great question. There’s only a couple examples in open connected stream
systems one in Idaho and one in the Flathead. I’ve been a part of the one in the Flathead
when we first discovered hybrids in the stream network. Montana Fish, Wildlife & Parks at
the time, they have a dual mission providing recreational opportunities as well as protecting
native species. We found hybridization was increasing in this
interconnected stream network. In the face of uncertainty, the managers went out, and
we surgically implanted transmitters into the body cavities of these hybrids. They led
us to the hybrid source population. It’s like the Judas fish approach. We identified where
these hybrid sources were on the landscape, and the managers, in the early stages of invasion,
got on it and started suppressing and attempting to eradicate these sources.
Over time, over the last decade or so, we’ve seen a dramatic reduction in the number of
hybrids at these sites, and we’ve seen a slowing of the spread of hybridization and a reduction
in the percent genetic admixture in cutthroat populations that we’ve been monitoring in
the system. In this case, it worked or it’s working even with climate change because managers
got on it in the early stages. Ashley: “How does your work dovetail into
or complement Dan Isaak’s work with the US Forest Service?”
Clint: We’ve worked with Dan and his group on several projects. One good example of how
our research programs are complementary is with Dan’s temperature sensor network that
he set up all over the Pacific Northwest, the NorWeST program.
That’s been an amazing program, one, in my opinion, for people to gain an understanding
of how climate change is affecting aquatic habitats over broad scales, and even at local
scales. So for one, gaining a better understanding has been key, and then understanding that
change by instituting and setting up a temperature sensor network across this broad landscape
is very key for monitoring how warming impacts are occurring over these broad scales.
So that’s been very important. We can link that to great models to predict occurrence
and changes in species distributions, for example, into the future. That’s going to
be very key for management. An example of how our approaches with the daily models are
complementary is that we can again look at different scales of fish performance, for
example. Not only these seasonal means and averages
to look at changes over these scales, but we can actually link daily time step simulations
with responses of fish populations, such as changes in growing days or emergence or the
timing of spawning. I think that these different temperature modeling approaches are actually
very complementary in a lot of cases. Ashley: A couple more questions. One is from
Elise and it says, “It’s not uncommon to have one endangered fish species move into another
endangered fish species’ habitat where it previously did not occur. Do you have any
thoughts about managing this?” Clint: [laughs] Is that Alisa Wade?
Ashley: Kelley. Clint: Oh, OK, I’m sorry. If an endangered
species moved into another endangered species, so if there was a shift, how would we manage
that? Is that the question? Ashley: Yes, I think so.
Clint: Well, I’m not a manager. I’m a researcher. So what I would try to do is understand what’s
driving those interactions. I would say that if that’s the case, that would be an area
where you’d probably want to protect or conserve biodiversity, because we’ve got two species
that are now asympatric, and if we’re going to do adaptive management on the landscape,
you’re going to benefit two species. If one species is negatively impacting one
another, again, we’re going to have to go back to “the context matters” and to understand
the relative distributions and abundances and the genetic diversities of those species
across the landscape. See where they overlap. See where maybe one species might have a broader
range, the other doesn’t, and try to develop approaches to hang on to the one that’s declining.
Again, I think my job is to provide data for managers. Those are difficult questions. I’m
really not familiar with that happening on the landscape, although I could be wrong.
That’s a tough question. Those are difficult decisions. If anyone has examples, I’d love
to hear about that. Ashley: Another question from Janelle. It
says, “Would you be able to address the Jarbidge River population in light of your climate
change predictions?” Clint: At the watershed metapopulation scale,
yes. Right now, with the blue temperature and flow model, we can look at the vulnerability
of those systems to change. We also have genetic data from the Jarbidge area. That was one
of those populations that had low levels of genetic diversity. In the face of climate
change in areas that are already on the southern limit of the range, such as that system, that
might be an area where adaptation is going to be even more important. What we know now
is that the genetic diversity is at its lowest there.
I don’t know if that answers your question or not. I would say that the peripheral populations
are important for evolution and climate warming. The more we can learn about how those species
are under selection. Those selection pressures are greatest at those southern limits of the
ranges. If we can learn more about the adaptive capacity and how certain regions of the genome
are linked to temperature and flow, we can better understand how species elsewhere are
going to respond. In the case of Jarbidge, we do have some data. Again, it’s at the watershed
scale. I would say that with Dan’s temperature work coming online soon, linking that with
VIC, you could probably get a better high resolution analysis of the impacts in the
Jarbidge system. I would then add we’ve got abundance in genetic data. You could then
look at how those might change into the future. Ashley: Thank you. We’re running low on time.
We do have about four more questions. I’m going to take up two right now. “In your scaling
up analysis, what do you think would change in your assessment if you considered other
local characteristics, such as stream temperature, over air temperature, or flow gauged on that
specific stream?” Clint: I didn’t catch the first part of that.
Ashley: “In your scaling up analysis, what do you think would change in your assessments
if you considered other local characteristics?” Clint: I guess the way I’d answer that is
that at the smaller scale, we’ve found that the alluvial valley bottoms are going to provide
critical areas for thermal refugia. Again, those are the areas with ground water, hyporheic
flow. Those are the cold spots on the environment now and likely into the future. There’s still
a lot of things that we don’t know about those areas.
What I would say is that scaling up, we’d want to be able to quantify where those areas
occur, so we can build them as covariates into our models to better predict temperature
responses. When you look at relationships of observed temperature to expected, there’s
a strong correlation there with our temperature models. The extremes, those outliers, tend
to be those groundwater influenced areas. I think if there’s one area that we need to
learn more about, and build that understanding into our modeling. It’s understanding those
groundwater influences and how those might change into the future. Nagle, with the Forest
Service, developed an algorithm to predict that. I didn’t show it in my slideshow, but
using our daily stream temperature model and looking at a groundwater site, it predicted
again, this is an algorithm we can apply to different landscapes that site actually showed
up right in those alluvial valley bottom areas that were predicted by our model. We’re trying
to account for that in our stream temperature models.
For flow, I would say the biggest demand right now, or weaknesses, are that a lot of the
flow gauge stations are in large rivers. We need to get a better understanding of what’s
going on at the local scale in smaller order streams to get a better understanding of how
flow influences fish populations, because truly, flow is a master variable.
Ashley: Thank you. Last question. It says, “I noted with interest your description of
RCP 4.5 as a ‘middle of the road climate forecast.’ In contract, our PCIC climate specialist described
A2 and RCP 8.5 as ‘roughly as business as usual,’ B1 and RCP 4.5 as ‘roughly half the
emissions of business as usual,’ and RCP 2.6 as ‘aggressively optimistic greenhouse gas
reduction scenarios.'” Do you care to comment? Clint: Well, I’m not a climatologist, I’m
a fisheries ecologist, for one. I can speak to that just in the case of our work, using
RCP data. We compared RCP 4.5 to 8.5 predictions in the crown ecosystem, which I showed you
at the beginning of our show, as well as the climate vulnerability work that Alisa has
been working on. We haven’t seen a lot of differences in changes in temperature and
relative vulnerabilities across these different scales. But again, that’s a broad statement
from a naive scientist that relies on my climatologist to feed me those data to build into our biological
assessments. Ashley: Excellent. Thank you, Clint. And Shawn,
did you have any closing remarks? Shawn: I’m tempted to comment on that last
question, but in the interest of time, I will say thank you very much, Clint. It was an
excellent presentation. Clint: Well, thank you all. It was a pleasure
to be involved with the webinar series. I appreciate your time and attention. It’s been