Sequoias in the California Drought

Speakers

Nathan Stephenson

USGS Research Ecologist, Western Ecological Research Center; former US Park Service Research Ecologist

Koren Nydick

USGS Science Coordinator and Ecologist; Sequoia and Kings Canyon National Parks tour guide

Adrian Zach

USGS Ecologist

Kings Canyon National Park, California - September 27, 2016

Introductory Note

On the National Park Service Centennial,
after visiting the Sierras in Yosemite,
NWNL went to Kings Canyon National Park
with SEJ/The Society of Environmental
Journalists. After a night of fresh air in our tent cabin, we heard how 4 years of drought had impacted the renowned Kings Canyon trees – especially Giant Sequoias, the world’s
biggest trees.

Concerned by climate change impacts,
NWNL joined several other awestruck and
worried journalists to hear park
ecologists describe the National Parks’
management efforts to save our nation’s
forest treasures using complex equations.
In so doing, they’ve also stumbled on new possible resources, such as water and climate refugia!

Outline

CHARTING DROUGHTS’ SUPPLY & DEMAND
LOWER MIXED-CONIFER FOREST LOSSES
BEETLES. DROUGHT & LIGHTNING KILL TREES
LEAF TO LANDSCAPE PROJECT
CLIMBING SEQUOIAS FOR RESEARCH
FIRE, FUELS & “CLIMATE ENVELOPES”
STRESSED TREES: SUGAR PINES & SEQUOIAS
SEQUOIA’S 2014 FOLIAGE LOSS
CLIMATE CHANGE & WATER REFUGIA
PROJECT TIMELINES & FUNDING

Key Quotes We have one of the nation’s most active programs of prescribed fires and allowing wildfires to burn, when feasible. Yet we still can’t get back to the natural variability before humans suppressed fires. We have limited dollars, so it’s a prioritization challenge. — Koren Nydick

To riff on Koren’s topic of a refugia as buffered from climate change and in terms of temperature—but this drought really drives home that there are also water refugia! Some places, like here, may be the most important water refugia. –Nate Stephenson

NATHAN STEPHENSON An interesting fact for me is that the White House called me to ask me the age of this giant Sequoia, which is 2020 years, plus or minus a couple of centuries.

JOURNALIST They didn’t call the Park Service for that information?

NATHAN STEPHENSON They did; but Park Service referred them to me because I had best estimated the age a few years earlier when George W. Bush gave a policy speech right here. They wanted him to be able to refer to this Sequoia.

JOURNALIST Nate, weren’t you with the Park Service, years ago?

NATHAN STEPHENSON Yes, but they viciously removed me from the Park Service in a reorganization. I’ve gone through 3 or 4 different agencies, but I’ve never left the desk I then worked at.

CHARTING DROUGHTS’ SUPPLY & DEMAND

NATHAN STEPHENSON Back to today! There are two components to a drought. The first is how much water falls out of the sky. If not much, you have the start of drought. The second component is how much evaporation is driven by the atmospheric temperature. Since temperatures have been going up, today’s drought – which looks normal – is a severe drought, typical of a once-in-a-century drought.

This drought has gone beyond that, due to temperature. There’s a supply side, and a demand side, which in this story is rising temperatures that drive up the demand side. A graph explains it better than words and there is some great work done by Clark Williams. This is for California as a whole. First, understand that PDSI is just a very commonly used drought index that incorporates supply and demand sides. On Williams’ graph, the axis notes the years, from 1900 to 2014. A background squiggly line shows how drought has changed through time. A blue line represents what droughts would be like if temperature had never changed.

I added a little blue, dashed line to show that if temperature had not changed, this drought would be about equivalent to California’s 1924 drought. However, the fact that temperature’s been increasing has added extra evaporation, the demand side of the equation. So, temperature (the orange line on top) has driven this drought down into uncharted territory on the historic record. So instead of a -3 on the drought index, there’s a -4, and that’s almost certainly per records, what happened back in 1924. They then saw many trees dying during that drought – mostly pines.

We don’t have quantitative data, but we see no indication that they saw anything quite like what we’re seeing here now. So, when we talk about climate change, I think its important to know these graphs showing a gradual increase in temperature. That shows there will be a gradual change in our natural environment. Species will move to adjust to climatic change. But what gets less attention is that many of those temperature changes will probably be sudden jolts to the system. Our species will reach a threshold. The effect of higher temperatures will amplify a normally typical drought and then create something we’ve never seen before.

We must use this drought as a preview of the future. They’re calling this a hotter drought;, but I call this one a “baby hotter drought” because things could be much worse if temperatures keep increasing. So let’s take advantage of this “baby hotter drought” to try to understand which parts of the landscape are most vulnerable and then be proactive managerially to make forests more resilient in the vulnerable areas. That’s how we’re trying to use this drought.

LOWER MIXED-CONIFER FOREST LOSSES

NATHAN STEPHENSON We’re looking at mayhem. For listeners and readers of this tour conversation, we are looking at a suite of lower mixed-conifer forest. There is still much green out there; but there are also orange and brown trees that have died during this drought. Close-up, you can see some here that are being killed right now.

This Jeffrey pine is going yellow now. As we first walked up here, I went, “Oh, no!” because I’ve liked that Jeffrey pine for 37 years; but now it’s on its way out. The shrubby, little black oak in front of us here, is a drought related victim. We can see trees in all stages are dying out there. Some are just barely turning yellow, and there are those that are thoroughly orange/yellow, and one that died last year that retained its needles, so it’s just browner.

NATHAN STEPHENSON Adrian, describe what we’ve been doing in this zone vis a vis all these dead trees and what we’ve found?

ADRIAN ZACH We have a long-term research project here where we have some established plots with trees about 100 years that we track through time. Tree mortality has generally happened at lower elevations, and we only lost a couple out here. I like to describe scientists as folks who just pay attention in a systematic way. So, when you see something like this, where there are many dead trees compared to what you’d normally see, it is very dramatic for those of us who live here.

We come, see a lot of trees, and ask, “Which trees are dying? What size are the trees that are dying? Does this change by species? Is it just the big trees or the small trees dying? How does that vary, and why does that matter?’ Folks in the Park Service want to understand. As climate changes, and we get potentially more of these droughts, we wonder which parts of our landscape will be more vulnerable? How do we tell where to put limited resources for protection. We talk in terms of triage. We have hypothetical models based on many assumptions; and we do our best.

But when a drought like this happens, as tragic as it is to see this many trees die, another way to look at it is that it’s an opportunity. If you want to know what areas are more vulnerable and under a lot of stress, this system is under great stress right now. There are many trees down. The trees themselves tell us what parts of this landscape are more vulnerable. It’s where trees are dying more often.

What factors are driving this? Originally, we only had a couple of plots in this zone. This past year we’re putting out more plots and doing some simple data collection. We’re asking which trees are dead, which are alive, how big are those that are surviving? We have some very preliminary results from that, and we’re see some interesting differences. Looking around here, there’s many dead pines. In all the plots we’ve looked at so far at pines over 50 centimeters – the big ones that are up in the canopy. Many white firs are here – more than pines. No matter whether a fir tree is big or small, about a quarter of them are dying. With the pines, it’s clear that the largest trees have died – but the smaller trees are dying at a higher rate. With incense cedar, another common species out here, some of the bigger trees are dying, but a great majority of those dying are of a smaller size and under the canopy.

BEETLES. DROUGHT & LIGHTNING KILL TREES

The next question, of course, is why do we see these differences? What’s the biology that’s going on? Is it an inherent difference in physiology of the trees; or, as we suspect, are there other things going on when a tree dies. It’s not just about the water. Almost every single one of these pines if you walk up to it, you’ll see bark beetle signs – their pitch tubes. Now people are asking, “Are the bark beetles the problem, or is it the drought?” Wrong question. The drought makes this tree susceptible, then the bark beetles have taken it out.

Would those trees have died if those bark beetles weren’t in the system? Our suspicion is that many fewer of these trees would now be dead. So, there’s a biotic interaction going on. Pines have a very aggressive bark beetle that tends to prefer larger trees. Firs are dying evenly across the size classes. They have bark beetles in them too, but they behave differently.

In the incense cedar, which in some ways is the more interesting, there’s a native bark beetle. It’s been in the system the whole time. Once in a while, we’d find them in our plots. But during the drought they’ve been much, much more prevalent. This bark beetle tends to be restricted to small diameter branches or trunks, so it’s possible the differences we’re seeing are partly physiologic, but there are also biological issues. Other organisms in the system may be involved. And so, we’re learning many very interesting things that we hope will translate into being able eventually to provide quantitative and qualitative information about how this landscape works and how it may change as the climate changes.

JOURNALIST Do you think this could be nature adjusting itself since fire has been suppressed? Maybe there’s not been as much fire as the forest needs, so trees are dying, since there are too many of the? Or maybe that in addition to the drought?

ADRIAN ZACH That’s a very good question – and one we’re asking. With other projects we’re involved in, we’re asking why some are areas in this landscape have burned, and not others. Fire suppression, increased density and some results suggest that areas that have burned seem to have less mortality. That’s preliminary. On the other hand, there may be some thresholds here. So, I say “Thinking this is the system adjusting anthropomorphizes the issue and maybe doesn’t work since places that are denser, whether due to fire suppression or other historical factors, likely will be more at risk, given more competition for resources.

But, at some point, even in areas that burn, we’ve had preliminary evidence that at some point, if the droughts are intense enough, past burns may not matter. So, we don’t know where we are with the drought. We had a relatively normal water last year. If this trial keeps going on, we may find that if even an area burned, it is okay. That will be true in some places and less in others. It’s just one more factor for the equation.

KOREN NYDICK Adrian was telling you about the different size classes, to me that’s important, because the major effect of a fire is to kill the smaller size classes, not the larger. With the pines, it’s the opposite effect. That signals to us that something else is going on. Some aspects of this drought may act like a fire, yet some do not. I think that’s important.

ADRIAN ZACH Koren makes a very good point. Often I hear that when fire programs here tried to restore things to a more historical state, they burned to favor pines. If we’re being simplistic, there are a lot more firs. There are shade-specific species that are more vulnerable to fire. If you watch what goes on during this drought, firs die at a higher rate; but the big pines die at a dramatically higher rate. That’s quite different than what we’d expect in a system that has burning regularly.

In a regular year, mortality rates of forests trees dying is 1 to 2%. In the last several years we’ve potentially over 50% of trees in the canopy have died. It’s not an annual rate, but it’s still much higher than 1%. In one analysis we’ll ask “What does a fire do? What are the differences of impacts on varying species? What will that mean for the forest?

JOURNALIST Is there any evidence that with changes in precipitation, there’s a change in lightning, which, of course, causes the fires?

NATHAN STEPHENSON I don’t know of any evidence of long-term changes in lightning strikes; but lightning ignitions have gone down. That may mean there are fewer lightning strikes as a long-term trend over decades – not just this drought.

JOURNALIST Does that include human ignitions? We have a rising number of human starts.

NATHAN STEPHENSON I don’t think we know. I don’t think we have a rising number of human starts here within this forest, but ignitions have been going down, per our fire data. I don’t know of any opinions on why that’s happening – and we’re too busy to explore it.

LEAF TO LANDSCAPE PROJECT

NATHAN STEPHENSON Now Koren will talk about a project to join these threads together.

KOREN NYDICK So Nate told you about the exceptionality of this drought. He called this a “baby hot drought” and asked how it can help us learn to prepare better for a future of grownup hot droughts and mature hot droughts that are likely to occur. You can think of this drought as a dress rehearsal for what’s to come. This drought is unprecedented in the last 120 years, but it’s also unprecedented in terms of what we as scientists can learn. We haven’t had the opportunity to study something like this before. So we created our Leaf to Landscape project to understand the vulnerability of the forest to hotter droughts.

Leaf to Landscape is meant to help us prepare for and manage the future. There are two parts. One focuses on the giant Sequoia, because they’re our iconic species and people love and care about them so much. Part two is broader and mainly about the lower elevation montane forest, as opposed to the subalpine forest. So, it’s broader and includes 9 species of trees,, but it also has 3 different spatial scales.

We have a partner, Greg Asner, at the Carnegie Airborne Observatory. He has state-of-art sensors on an airplane that record very fine spatial resolution. Using the broadest spatial scale, it uses remote sensing, with lidar laser imaging, and hyperspectral imagery. It’s fine scale in terms of resolution on the ground getting you within a fine scale of about two meters. But it’s also finely resolved in terms of the spectrum of radiation reflected off these trees. That’s what this hyperspectral sensor measures.

And if you cut it up very coarsely, you get less information than if you finely cut up the wavelengths. His sensors look at those wavelengths, I think, in 5 nanometer bands, that are then averaged into 10 nanometer bands. Think of it as satellite imagery with a very fine resolution fingerprint that tells us about the spectral signature, but it at a coarser spatial scale. We’ve asked him to fly over our landscape and share the kind of indicators of drought stress – mainly moisture stress on these trees.

One indicator is water canopy content. That’s the amount of water in a square meter, for example, based on wet wavelengths of light returned. Water has a signature, so there’s a lot of technology built around that.. There could be other signatures that tell us about differing carbohydrates in the trees that are critical to the health of those trees. There’s a suite of signatures that he’ll look at with us as part of this Leaf to Landscape Project. Those signatures can be linked to the species and to the condition of the canopy. But the species signature is strong enough that we now have preliminary canopy species maps of the area he flew over in five days. It’s expensive, but it gathers data on many trees.

How do you know if your recording and your interpretation is what’s going on? That’s in the other scale of the project. There’s a leaf scale and a population scale. With the leaf scale, a giant Sequoia, is almost 50 trees.

CLIMBING SEQUOIAS FOR RESEARCH

Our sequoias are in giant forests in 4 different areas. We’re working with University of California-Berkeley, Anthony Ambrose and others who climb the trees – a very big production that is technically and physically challenging. They rig the trees with ropes with a crossbow. That takes from 1 to 8 hours, depending on how the shots go. They rig them all the way to the top so that when we return for sampling, a climber can go up and sample foliage. They sample at the base and the top of the crown. At the top of the crown, they’re sticking out of the tree basically cutting limp foliage. They take their samples, cut the foliage, bring them down, and get a variety of different measurements.

We do water potential measurements that look at stress around the midday period when trees actively photosynthesize and lose water through their stomata, since it’s the higher stress time of day when they lose water as they photosynthesize. But they also take samples at pre-dawn when trees are more relaxed – before the sun comes up. That comparison is helpful in understanding stress. Those samples go to the lab to assess water content, differing pigments, different carbohydrates, nitrogen, carbon and such that can tell us how a tree is doing.

We’re also working with Greg at the Carnegie Airborne Observatory to collect samples from the other tree species. For Giant Sequoias, they need a special climbing technique, because they’re so huge. They can’t use traditional techniques to climb Sequoias, since other tree species are much smaller; and they don’t do pre-dawn samples. We can learn from those samples and compare it to what we’re seeing in the remote sensing.

Getting very accurate GPS locations of those trees is important to make that connection. The mid-scale is a piece that USGS is doing, and it’s different for the Sequoias. For Sequoias, the mid-scale looks at foliage dieback. In 2014, Nate was looking for dead seedlings, on the working hypothesis then that for Sequoias, the seedlings would be in the biggest trouble in a drought. But what was noticed was dieback of foliage in the Sequoias – not dead trees, but rather, dead foliage in living trees. That hadn’t been noticed before.

NATHAN STEPHENSON I have a map of that dieback.

KOREN NYDICK Their survey looked at a subset of groves. The map is of Giant Forest with its red areas showing the most significant dieback. That helped us pick areas for our giant Sequoia climbing. We picked areas that had low dieback and some areas of high dieback, to get a good representation of stress.

NATHAN STEPHENSON That map is called our “gummy-worm” map, because the colors are all in gummy-worm shapes. The crew had to be speedy and safe as they followed the main trail system and they could only look so far to either side. They’re out doing it again now, so we may encounter them when we go to Crescent Meadow, but maybe not.

This will be the third time we’ve done this. We did it in autumn 2014, autumn 2015, and the Giant Forest August in 2016 at the end of summer. That’s when the trees really show their dead foliage.

JOURNALIST Are you correlating these to aspect and elevation?

NATHAN STEPHENSON We’ve done that. Lower elevations tend to have higher probability of foliage dieback.

JOURNALIST Did you find any surprises there?

NATHAN STEPHENSON I thought, for various reasons, elevation would be weakly correlated, but it’s quite strongly correlated. This might be non-intuitive at first, but areas where there are only a few big Sequoias had the most dieback. When the Sequoias are all packed together cheek to jowl, there’s almost no foliage dieback. We think that means those sparse areas of Sequoias are sparse because it’s just not a very good habitat for Sequoias.

JOURNALIST So density has to do with growing conditions, not community.

KOREN NYDICK Yes.

NATHAN STEPHENSON Or, probably not.

KOREN NYDICK This whole project is based on the premise that not all forest locations, or all Sequoia grove locations, are “created equal” – so to speak. Some are just better habitats. There’s prime Sequoia habitat, but there’s also more fringe Sequoia habitat. A variety of factors will make some areas more vulnerable to droughts like this and worse than others and the same with forests. The forest is kind of spread out, and we’re only looking at one area. If you look across the landscape, it’s patchy. If we can understand the patchiness, for Sequoias and the rest of the forest, it can help us direct management.

FIRE, FUELS & “CLIMATE ENVELOPES”

KOREN NYDICK Have you heard of “The Fire and Fuels Management Program”? It’s one of our most powerful tools to manage the forest. We have one of the nation’s most active programs of prescribed fires and allowing wildfires to burn, when feasible. Yet we still can’t get back to the natural variability before humans suppressed fires. We have limited dollars, so it’s a prioritization challenge.

JOURNALIST One speaker today talked about the changing climate space as a climate envelope. Is that what we see happening here?

KOREN NYDICK When people talk about changing” climate envelopes” or climate space, they’re talking about gradual change, a shift over time. Let’s say the pines are where the climate is no longer suitable, and then punctuated droughts for a period of time could kick them way out of that climate envelope. There’s the gradual aspect to that. Then you have a hot drought that changes that envelope. You can then get pulse responses like we see here. We’ve done modeling using climate envelopes for different vegetation types to try to predict which areas will be more stressed than others.

It’s a good tool to use as a reference for planning, but it’s a model. It doesn’t have all the information you need to know about hydrology, soil and a myriad of other factors. A project asking the trees how they are doing in the drought is a way to indicate vulnerable spots. We can have models and empirical-based methods collecting data right then – and we want to use both, This project compares both approaches and ask, “Okay, how do they differ, and which gives us a better picture?” It may be that models tell us one aspect of the story, and empirical data tell us another aspect.

STRESSED TREES: SUGAR PINES & SEQUOIAS

JOURNALIST With this concept of triaging areas or species, do you have any sense now of what area of the forest or species in this area you might have to let go because they may not be manageable?

KOREN NYDICK Well, we’re not at the point of letting go right yet, but one species of concern is sugar pine, one of the pines that Adrian was talking about, that were dying in the drought. Even in Giant Forest, you see the giant sugar pinecones on the ground, and you ask, “Oh, where’s the sugar pine?” As I walk around Giant Forest, I often look up and see that the parent to those cones is dead or dying, although the seedlings might still be nice and green.

Even before this drought, there was a declining trend in sugar pine. They fight the drought. They have beetles. They also have white pine blister rust, a fungal disease hitting five-needle pines. They have some complex interactions with fire, so it’s a species we’re concerned about.

JOURNALIST Do you manage preferentially for the giant Sequoias?

KOREN NYDICK Yes. As we triage, those groves get more attention. We use a landscape analysis that brings in differing factors, called FRID – Fire Return Interval Departure.

If you think of how long since there’s been a fire, compared to what it would have been historically before pre-settlement times, that’s a big factor. So we try to get fire frequency more within the range of what we think will help the forest stay resilient, based on what past variability was. But there are other factors like: ignition risk, how difficult it will be to control a fire, “flame link,” whether there’s development or Sequoias. In this analysis we also need to add in climate vulnerability.

JOURNALIST I read that other trees that were not Sequoias but were around Sequoias competing with water use, then those other trees could be removed if a Sequoia was struggling with dieback. Is that right?

KOREN NYDICK In the park we mainly use fire as our tool to thin the forest. But it’s not feasible to use fire around developments or the General Sherman tree, so they use certain mechanical prescriptions to mimic what the fire would have done -that is, we cut down those smaller size classes, and firs could be involved, as could some pines or incense cedars.

NATHAN STEPHENSON Those big Sequoias are incredibly fire-resistant, so little trees around them often get cleared out by the fire – and the Sequoia starts growing faster than ever.

KOREN NYDICK The main thing is to try to mimic what a fire would have done.

We’re right next to the Central Valley, which collects air pollution from as far away as San Francisco. As the air heats during the summer, it comes up here, and we can get severe air pollution issues here – ozone especially which affects our visibility – as do other types of particulates and gases in the atmosphere.

Ozone also can injure trees and other vegetation. Jeffrey pine is especially susceptible to foliar damage. Now, generally ozone’s not going to kill a tree; but it can weaken a tree, making it more susceptible to the other factors we’ve talked about.

SEQUOIA’S 2014 FOLIAGE LOSS

KOREN NYDICK We haven’t mentioned what we’ve learned about the Sequoias from a 2014 foliage dieback. There was a lot of concern: “What does this mean? What’s happening to the Sequoias?”

In 2015, the dieback was much, much less than normal. That was one piece of information. Also, those water potential measurements I mentioned showed that some of the Sequoias were more stressed than in any previous measurements not during the drought. But there seemed to be a threshold they weren’t going beyond.

Our working hypothesis now is that the loss of that foliage helped reduce stress and kept them in a good hydrologic status. If you think about it, foliage is how they photosynthesize, how they get their sugars, so they need it, especially over the long term. But it’s also how they lose their water. So if over the short term, they can get rid of some of that foliage, that stops some of their water loss and basically keeps their hydraulics working.

NATHAN STEPHENSON Can I add to that smart response the Sequoias had to the drought? It looks like they weren’t stressed to the point of being damaged, and they got to “think about it” The foliage they dropped was their old foliage – and that’s the smart thing to do, because it’s less productive than the new young foliage. Again, they said, “We’ve got to reduce our leaf area. What foliage shall we drop? The old stuff! We’ll keep the young, productive stuff.”

And so, they did well. I’ll add that I’m now in my 37th year working here. Until this drought, I’ve seen only 2 Giant Sequoias die standing. They usually die as they fall over.

With the 2 I saw die, their crowns turned brown while on their feet, so to speak – like these pines here. During this drought, there’ve been a couple dozen. So the Sequoias have probably done the best of any tree species here. Yes, a couple died, but not any big famous ones. The ones that did die were a couple of odd quirks, that were right at the edge of a meadow. You’d think, “Oh, my gosh, they have more water! What’s the deal here?” We’re not sure, so we have the ‘Spoiled Sequoia Hypothesis” since they had ready access to water.

KOREN NYDICK There are many potential applications for science. At Whittaker over near Redwood, is an experimental forest area owned by University of California-Berkeley. They did some preliminary testing and data collection that Nate saw.

NATHAN STEPHENSON Yeah. On the topic of Sequoias doing better than other species, it’s worth pointing out that where trees are dying the most, Sequoias just don’t grow there. Plus, the trees growing near the Sequoias are doing well – sugar pines excepted. There is the question, “Are the Sequoias doing better, because they’re inherently a sturdier species, or are they just growing in nice spots?”

CLIMATE CHANGE & WATER REFUGIA

KOREN NYDICK There’s another working hypothesis that the groves themselves could be a climate change refugia for the forest. A climate refugia is an area on the landscape that’s relatively buffered from climate change compared to other areas. There is a publication that discussed that and how we can use and learn from such a refugia.

NATHAN STEPHENSON Koren is a co-author.

KOREN NYDICK Yes, that’s another aspect: the groves might be the epicenter of the forest – more broadly, where we can keep the healthiest ecosystems going. In the future, they could be where reforestation could come from – if we ever get a handle on what’s going on globally with our environment!

NATHAN STEPHENSON To riff on Koren’s topic of a refugia as buffered from climate change and in terms of temperature—but this drought really drives home that there are also water refugia! Some places, like here, may be the most important water refugia. We’ve known for decades that Sequoias get more water than the surrounding forest. With this drought, we think maybe they also get more reliable water.

There may be some underground reservoirs above grove elevations. This is all speculation…, but there may be centuries-old water that just keeps trickling down through cracks in the bedrock that keeps the grove area better watered than the surrounding forest. We’re now investigating this concept to see if it’s valid, or not.

KOREN NYDICK We have preliminary results from our remote sensing – including for the Giant Forest, which had the gummy-worm map. On that map, the giant Sequoias were identified by their hyperspectral signature. The colors show where the canopy has more water: red is less water, and there are patches. We hope to use the identified general patterns to help us better manage the forest.

ADRIAN ZACH I said there are many less trees down in the Giant Forest, and that’s true. But we’ve seen some preliminary [data ?] this year showing mortality in Giant Forest. So how many years can that go on?

KOREN NYDICK We haven’t done this research, but it’s interesting to think about Nate’s comment about the Sequoias dropping their foliage. He was using an anthropo-medic frame to explain that, but what does cause a tree to drop its foliage? Is it a chemical signature that they send out? Is it that the hydraulics of a little branch reach a threshold, and then they drop off? It’s probably a chemical cue, but we don’t know that. So that’s something we haven’t studied related to this drought in Sequoias.

PROJECT TIMELINES & FUNDING

JOURNALIST What’s your timeline for all these research projects? You mentioned several you’re working on now.

NATHAN STEPHENSON Is it next week we’re going to be done? [Laughter]

KOREN NYDICK It started with the 2014 foliage dieback. In 2015 the full campaign started with remote sensing, climbing the trees, collecting the samples and putting a few sensors in trees to be removed in October. Next year we’ll see. Right now, we don’t have resources for another full campaign – only a small portion. But then the year after that, we’re slated to get more resources to keep the project going.

We’ll either be studying what happens when the drought is even more prolonged – or, hopefully, we’ll be studying the initiation of post-drought conditions.

NATHAN STEPHENSON On the human side of things, it takes time to get funds when you work for the government. We saw these changes happening and were in the third year of drought in 2014 when we started talking about it. We just said, “This is too important. This is perishable information. We can’t wait several years to get funds to study this.” We got people interested and excited and received emergency pots of funds. I think it was pretty amazing.

KOREN NYDICK The initial funds came from Sequoia and Kings Canyon National Parks with a little partnership money from the Forest Service. Our money came from an emergency request to our superintendent.

This drought is happening. We really needed to study it. At the same time, we have proposals in the works, and some money is coming. But it takes a long time to get funding for these kinds of efforts. Yet, we’re stringing it together, and there are a variety of sources. One thing that’s really fun about this project is that it’s a huge collaboration of different parties working on different aspects. The different funding that’s coming shows that a variety of agencies are interested in knowing answers to these questions.

JOURNALIST How much does it cost?

KOREN NYDICK This year, we have a $250,000 grant to cover many aspects we talked about.

ADRIAN ZACH There’s some leveraging going on.

NATHAN STEPHENSON The Park Service chipped in, and I went to the USGS office in Washington and said, “This is too important.” They gave us extra funds, so now Adrian and I have more money to work with.

Posted by NWNL on August 10, 2025.
Transcription edited and condensed for clarity by Alison M. Jones.

Sequoias in the California Drought California Megadrought