Western climate fires

The extent of the fires sweeping through the west this summer is sobering. As I perused an interactive map published by the New York Times earlier this week, zooming in and out on fire after fire, it dawned on me that several locations I have visited for recreation or traveled through in just this calendar year – in multiple states even – have now burned in the summer fires.

The extent of wildfires in the western US on 15 Sept 2020. Map from InciWeb.

During April, in one of my first hiking excursions since the coronavirus lockdowns began, with my daughter I hiked among and photographed flowers and oaks along the western shore of Lake Berryessa in Northern California. In the LNU fire to tear through that area this summer, most of the western shore of the lake burned. In fact most of the coast range hills down to Interstate 80 between Vacaville and Fairfield have burned.

Oak woodland and blooming lupines during April 2020 on the western shore of Lake Berryessa.

To the east of Lake Berryessa is a hiking location I visit often, the Stebbins Cold Canyon Reserve. It is a teaching and research reserve operated by the University of California, Davis but is open to the public for hiking. Like other places in California was closed for a time due to the coronavirus pandemic. Within a short time of opening back up this summer, I briefly hiked there on a warm day. Signs of a fire several years ago were still evident on the landscape, particularly on the western side of the canyon, but smaller shrubs and smaller plants have recovered. According to the maps though, it appears the whole canyon has burned again.

Also succumbing to the same complex of fires was an area to the northeast of Lake Berryessa, a hiking place I only discovered this spring in my search for more local hiking areas during the pandemic. Valley Vista Regional Park is a small county park located near the scenic Cache Creek and California highway 16 and it features grasslands and lovely oak woodland. This whole area too, it according to the maps has burned.

Oak woodland at Valley Vista county park earlier this year.

The extent of the LNU complex of fires in northern California during summer 2020. Asterisks mark approximate locations I had been hiking at earlier times in 2020. Map from InciWeb.

Finally, on my road trip through Wyoming and Colorado this July, I spent a night camping, and few enjoyable hours hiking in the Roosevelt National Forest north of Rocky Mountain National Park. I hiked into the Comanche Peak Wilderness near the headwaters of the Cache de Poudre River, a lovely valley of aspens and conifers. Virtually the whole wilderness was covered by a large fire.

The Roosevelt National Forest in July 2020. At left: Cache de Poudre River; at right: a grove of aspens. 

The Cameron Peak fire extent in the Roosevelt National Forest. Map from InciWeb.

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We increasingly see signs that climate change is here now. It is not just a phenomenon modeled to occur in the future. While scientists are often reluctant to attribute any specific natural disaster to changing climate, it is becoming more clear with each passing year that we may be entering uncharted territory. In the bigger picture, warming seas are making Atlantic hurricanes more intense. Sea-level rise due to warming and glacier melt is increasing the frequency of nuisance flooding in American cities. And for the last several years in the far western US, the fires have become worse and worse.

The summer fires of 2020 – some call these climate fires – have been everywhere in the western US. In addition to the very places I hiked or photographed or camped in this year, other western landscapes have burned. The beautiful, remote coast of Big Sur: a major fire. The Mendocino National Forest: a massive complex of fires that is still burning. The gorgeous Oregon Cascades: fires so bad they sent air quality levels in Portland and the Willamette Valley to extremely hazardous levels making the region have the worst air quality on Earth for a while. In the Sierra Nevada: several large fires. And northeast of Los Angeles, east of San Diego, and in eastern Washington: more fires.

With each passing year the most pressing question is less about the science and impacts of climate change (although science will always be crucial to monitoring, predicting, and responding to climate change), but rather whether society sees the accelerating pace of change and wants to seriously do something about it. Without reducing carbon inputs into our atmosphere, our future may becoming increasingly uncomfortable, costly, and even deadly.

Burned oak woodland just south of Interstate 80 near Vacaville and Fairfield in northern California. Photo: 16 Sept 2020. 

An early California spring

The last week has been rather warm in California, and today was exceptionally so. I admit that the warmth is very pleasant, but it is way too early for 70°F highs in northern California. Indications are that this warmth may persist for some time with California and the rest of the Southwest remaining quite dry for the month.

Weather of course is not climate, but as spring conditions trend towards occurring earlier year over year, this is a strong indicator of climate change in action. Out here in the western US, the exceptional warmth coupled with low rainfall may exacerbate drought conditions. California traditionally has highly variable rain patterns (of all states in the US it has the greatest year-to-year variation in precipitation), so swings from last winter (when precipitation was well above average) to this year (where we are rather below average) are to be expected.

I wanted to take advantage of the pleasant weekend and went on a short hike today to the Stebbins Cold Canyon Reserve in the coast range near Winters, California. Unsurprisingly a lot of other people had the same idea. Few plants were in bloom yet, but ferns and shrubs were thriving. A little ways up the trail into the canyon, there was a small amount of cool water in the creek, perhaps soon to dry up if February remains dry. I photographed water striders which posed on the surface tension of the water, active in the warm sun, leaving oversized shadows on the smooth rocks in the creek bed. 

Water strider shadows in the shallow creek.  

One of my newest favorite trees, the California bay laurel (Umbellularia californica) was in bloom along the trail! At the base of its spatulate leaves there were small clusters of yellow flowers. The flowers had a pleasant smell, different from the equally pleasant smell one obtains by rubbing the leaves of the plant through one’s fingers.

Blooming bay laurel.

It remains to be seen if an early spring is really here in California. If so perhaps we will begin to see blooms in short order on the almonds, peaches and other stone fruits prevalent in orchards of the central valley. Typically almonds will begin to bloom in mid February, shortly before my birthday, followed by other Prunus species. In the foothills, an assortment of wildflowers may soon be on display.

This coming April I’m hoping to take a road trip through the southwest, another version of the really memorable trip I completed in April of 2017 that took me to some exceptional national parks and monuments. If conditions are much drier this coming spring than last year, it will be interesting to see if the effect is noticeable. For example, last year I recalled seeing snow on the transverse ranges through central eastern Nevada, and a greener than expected landscape in that state. I experienced rain showers as I camped in Moab, Utah and backpacked in the Petrified Forest in eastern Arizona. 

One of the few blooming species at the reserve.
It superficially resembles a paintbrush, but I'm not sure
what this species is.

End of an (ice) age

Jackson Glacier at Glacier National Park.

Several National Parks, including Redwood, the Grand Canyon, and Glacier are named after their most iconic feature. They were established with an eye to the future to protect unique or superlative biological and geological features. In protecting a park’s namesake, whether that is old-growth redwoods or a pristine snowy peak, a whole ecosystem and its diverse components can also be protected from exploitation or excessive degradation. But at Glacier, the glaciers are disappearing.

A glacier is essentially a perennial slow-moving river of ice, formed from the long-term compaction of snow, flowing slowly down a mountainside. The weight of the glacier gradually propels it downslope, while its mass is renewed by new annual snowfall. Technically “official” glaciers have a minimum size of 25 acres. Glaciers are fantastic geologic agents: they carved out Puget Sound in Washington and the stunning Yosemite Valley in the Sierra Nevada for example.  

About a century and a half ago, there were estimated to be nearly 150 glaciers present in Glacier National Park. But by 2015, that number had declined to only 26. The trends at Glacier in northwest Montana track patterns elsewhere: glaciers are shrinking and snowpack is declining. Data from several benchmark glaciers in the northwestern US show mass loss of glacial ice over the last four decades. In the uneven distribution of climate change impacts across the globe, high latitude (particularly Arctic) and alpine regions appear to be warming to a greater degree than other regions.

Left: Map of some of the named glaciers in Glacier National Park and the adjacent Flathead National Forest. Right: Change in the area occupied by Chaney Glacier between 1966 and 2015. Map and figure from USGS.

Change in the Clements Glacier at Glacier NP.
Images from USGS Repeat Photography Gallery.

Glacial growth and retreat is a natural geologic cycle. Currently, the Earth is in an interglacial period, at the warm peak of an alternating cycle of cooling and warming that has alternated periodically over the last 2.6 million years. About 10,000 years ago the last major glacial period ended and the glaciers that covered much of the land in the northern hemisphere melted and retreated, sending sea-levels hundreds of feet higher.

So is the loss of glaciers today part of a normal cycle? Probably not, because today’s rate of atmospheric CO₂ increase (due to human production of greenhouse gases) is unprecedented in recent geologic history. A global increase of 1 to 2°C that may have occurred over centuries or millennia in the past is now on our doorstep in a matter of decades. And because large-scale biological and geological processes can temporally lag the events that drive them, we have probably locked in additional warming for years even were we to cease all additional greenhouse gas emissions tomorrow.

The glaciers and snowfields of Glacier National Park provide the source waters for rivers that flow to the Pacific Ocean, the Gulf of Mexico, and Hudson Bay. The park straddles the continental divide, the cross-roads of the watersheds that collectively cover most of North America. Glacial melt is a particularly important source of water to mountain ecosystems in the late summer when the non-glacial snowfields have already melted.

Long-term change in snowpack throughout the western United States. Red circles indicate areas
 with snow decline. Image from EPA.

Change in the size of the Grinnell Glacier at Glacier NP.
Images from USGS Repeat Photography Gallery.

Driving through the park this month, I saw the lingering snowfields of the higher peaks, with perhaps a glacier or two tucked into the mountains. The melting water fed rapidly flowing streams, waterfalls, and lakes. The only glacier I definitively saw was Jackson Glacier from a viewpoint along the “Going-to-the-Sun” road. Views of other glaciers required more committed backcountry hikes that I didn’t have the time for on the trip.

By emitting so many greenhouse gases into the atmosphere in such a short time, we may be ushering in an era of unprecedented warming across the planet that may affect everything from species distributions to ocean acidification and sea-level rise. The threats to glaciers are a global phenomenon, requiring global action to address. More locally, at Glacier NP and other alpine ecosystems, it remains to be seen how the loss of glaciers will affect ecosystem processes over the coming centuries.   

References

Glacier National Park website

National Snow and Ice Data Center. 2017. All About Glaciers.

US Geological Survey. Retreat of Glaciers in Glacier National Park. 

US Geological Survey. Repeat Photography Gallery.

Snowfield and Bird Woman Falls as seen from the
"Going-to-the-Sun" road at Glacier National Park.

Oregon tidal wetlands and climate change (pt. 4)

In the previous post, I discussed our attempt to understand how salinity and flooding affect tidal wetland plant growth. A final question I’ll describe in this series of posts was the effect of salinity on seed germination and the first days of seedling growth. Climate effects, whether manifest as higher temperatures, increasing salinity, or greater flooding could impact young seedlings, not just adult plants. Such effects on seed germination could impact the population sizes of species in wetland habitats.

Plantago maritima seeds in a germination experiment.

To address this question, we planned a simple series of experiments in the lab. Using one to several species per experiment, we put seeds collected from the field into lab dishes moistened at a series of salinity levels. Our treatments ranged from freshwater conditions (0 ppt) to 20 ppt, a level about 2/3 the salt strength of full seawater. From our measurements of soil salinities in the region’s tidal wetlands, we found that wet season salinities really didn't exceed about 20 ppt, even in the saltiest marshes. 

It is very well established that salt is physiologically stressful for vascular plants. It presents a challenge for intracellular osmotic balance, requiring plants to expend energy to maintain acceptable levels of ions in their tissues. Species living in salt marshes have various mechanisms for handling salt much better than most other plants. These "salt-lovers" are known as halophytes. Most plants cannot live in salty environments and are known as glaucophytes. To cope, halophytes may extrude salt from their leaves, store salt internally, or have other means of dealing with these unneeded ions.

We collected seeds in the field from perhaps some two dozen species and ultimately worked with 13 species that showed promise of germination under lab conditions. The species in our tests included grasses, some annual and perennial forbs, a rush, and a shrub (twinberry, Lonicera involucrata) that forms scrub-shrub wetland in some parts of Oregon estuaries. Unfortunately, we found that sedges did not germinate well under our basic lab conditions, so we were unable to examine salinity effects in this important group of wetland plants. With species from a variety of tidal marsh habitats and taxonomic groups, we were able to see which plants were more or less tolerant of high salinity at their earliest life history stage.

The lab tests we conducted generally confirmed what is already known about many estuarine species: though often tolerant of elevated salinity, most species germinated most readily in freshwater. These species are thus not really true "salt-lovers", but rather salt-tolerators. Also, unsurprisingly, we found that species varied in their tolerance of higher salinity conditions. Two species - pickleweed (Sarcocornia perennis) and Douglas' aster (Symphyotrichum subspicatum) - appeared to act the most like true halophytes. These results alone did not shed any profound light on seed germination biology, but did provide valuable data for plants found in the Pacific Northwest.

Germination responses (means and SE) for three Oregon tidal wetland species across a range of salinities.

 In the final part of our study, however, we tried to take our work one step further. We asked how salinity effects on germination matched, or failed to match, patterns of plant distribution in the field. To explore this, we returned to the data set described in parts 1 and 2 of this series of blog posts. We looked at the full range of summer soil salinities found in our research (~1 to 44 ppt) and assessed how each species was distributed along this gradient.

For about half of the species we looked at, the answer seemed to be that adult distributions didn't match predictions based on seed tolerance. In this group of species, seed germination was usually greatly reduced at salinities of 10 or 20 ppt, but they were commonly found in soils with salinities of 30 (even up to 44 ppt) as adults in the field. Because we didn't conduct additional experiments, we could not account for the reasons underlying this mismatch in these species, but one idea is that their seeds may be adapted to germinate under conditions of low salinity. These periods of low salinity are most likely to occur in late winter or spring when the Pacific Northwest is very rainy. As plants continue growing into the summer, they presumably become more tolerant of elevated salinities during dryer summer months in the Pacific Northwest.

Our germination study was relatively simple, but it highlighted the fact that we still have much to learn about even common species in our coastal habitats. Each species might be affected by salinity, temperature, changing carbon dioxide concentrations and other environmental factors differently. Moreover, each life stage of each species could have different responses to these factors. Add in the fact that species interact with other species, and the complexity of community ecology grows exponentially. With dozens of plant species in coastal marshes and swamps, there is much to learn about species relationships with the coastal environment and how these may be altered with climate change.

Reference

Janousek CN, Folger CL. 2013. Inter-specific variation in salinity effects on germination in Pacific Northwest tidal wetland plants. Aquatic Botany 111:104-111.

Oregon tidal wetlands and climate change (pt. 3)

Our survey work in Oregon's coastal wetlands showed patterns of species distribution suggesting how and which species might be vulnerable to climate change on the Pacific Northwest coast.  In previous posts, I discussed some of our findings relative to wetland algae and plants. However it was important to extend our knowledge of climate impacts by conducting controlled experiments too. During the summer of 2012 I was fortunate to work with an enthusiastic summer intern who participated in an EPA program that gives undergraduate students from smaller liberal arts colleges opportunities to work in federal research labs.

Seedlings.

The project we conducted was a short-term experiment to assess the dual effects of salinity and flooding on wetland plant productivity. We used seven species that were easily grown from seed; most are commonly found in Oregon tidal marshes. The species we used also differed in apparent tolerance to salinity and flooding based on their field distributions. We grew several hundred seedlings at the lab starting in the spring.

Some of the experimental pots placed at three tidal
elevations at one of our sites. A blue salinity sensor
can be seen at bottom center; a tall white stilling well
with a water level sensor is at the right.

To conduct the experiment with a range of salinities, we planned to work at three sites in the Yaquina estuary - one near the mouth of the estuary and two farther inland. We placed salinity/temperature sensors in the field track conditions over the course of the experiment and the data time confirmed that our sites had quite different salinity profiles.

To create differences in flooding intensity among treatments, we planned to set out plants at three tidal elevations at each site. We used mean higher high water (MHHW) as our baseline, which is about a mid-marsh elevation on the Oregon coast. We placed other plants at 25 and 50 cm below this elevation. We synchronized positions in the tidal frame across the three sites (to within about 5 cm) with high accuracy GPS. Our approach followed efforts in marshes in other parts of the US that have used "organ pipe" arrays to vary flooding intensity. However, instead of actually building an apparatus to hold plants at different elevations, we simply used the sides of tidal channels in the marshes to provide the needed elevations for the study.

In mid June, with some welcome help from another summer intern, we excavated terraces from the channel banks to place several hundred potted seedlings into the field. It was two long and very muddy days of field work!

Our plants grew under different salinities and flooding levels for five weeks. This was a relatively short length of time - constrained by the limited period of the internship - but long enough to assess treatment effects on the seedlings. We checked on the plants about every week and some were lost to the vagaries of field experimentation. (I think a few were uprooted by birds.) During our checks we noted which plants browned, probably due to physiological intolerance of environmental conditions.

Above ground dry mass (means and SE) of Grindelia stricta seedlings grown at 3 tidal elevations in low, moderate and high salinity wetlands. Like Grindelia, most species we investigated had lower above- and below- ground growth with greater flooding and/or greater salinity.

By mid summer, the experimental results were pretty unequivocal. All species, including one that we expected to be most tolerant of flooding and salinity stress based on its field distribution, grew less with higher salinity and/or greater flooding. Species seemed to differ in terms of their sensitivity to one experimental factor or the other, but all showed the same trend.

One concept we explored in the study was idea that "salinity exposure" - the combined effects of both flooding and salinity - could account for differences in plant productivity. In other words, we tested whether plants exposed to low salinity for long periods of time might be stressed as much as plants exposed to higher salinity for shorter periods of time. We created a simple index to quantify this total exposure and found that it correlated reasonably well with plant biomass for a number of species in the study.

Change in shoot dry mass in Plantago maritima seedlings with increasing salinity exposure. Our salinity index combined the length of exposure to flooding with absolute levels of local salinity. The index would be 0 in wetlands that are never flooded by salt water and ~33 for at a site continuously submerged in full seawater. Intermediate values could be due to long exposure to low salinity water or brief flooding by higher salinity water.

In terms of future sea-level rise, the overall results seemed pretty clear: for the species we investigated, if vertical marsh growth cannot match sea-level rise, plant production is expected to decline. Of course any increase in flooding or salinity at a given site would occur over the scale of decades, not the short time scale of our study. Yet declines in plant production in future wetlands might result in less food for marsh consumers and less detritus for the formation of new wetland soils.

I really enjoyed conducting this study. I was nervous about whether our seedlings would grow in the lab or whether they would quickly get destroyed once transplanted in the field. But the plants were hardy enough (or we had enough luck) to give us a good data set. Conducting this research, I had an opportunity to think about plant physiology and environmental stress. I read about some basic ideas in plant ecology such as how plants may trade off allocation of resources to above (shoot) or below-ground (root) production.

Though exciting, manipulative field experiments are challenging! The goal is to isolate factors to determine cause and effect, but at the same time maintain conditions that are as realistic as possible. Also, ecologists often want to be able to derive broad conclusions about such experiments, but various constraints often mean it is necessary to work at a single site, with a limited number of species, or only for a limited period of time. After conducting experiments such as these, it is important to ask: would different species or locations or seasons give different results? Extracting generalities from such complex ecosystems is a rewarding, but heavy intellectual challenge.

Reference

Janousek CN, Mayo C. 2013. Plant responses to increased inundation and salt exposure: interactive effects on tidal marsh productivity. Plant Ecology 214:917-928.  

Oregon tidal wetlands and climate change (pt. 2)

Which factors affect the distribution of tidal wetland
plants? Will these gradients shift with climate change?

In the last post, I began to describe some of the work I conducted as an ecologist with the EPA. Our initial investigation was a regional survey to quantify plants, algae and environmental characteristics in wetlands scattered throughout four estuaries along the Oregon coast. After working through the algae, a second goal of the regional survey was to relate vascular plant species abundance, composition and diversity to the major environmental gradients present in these wetlands (link to the paper). Salinity and elevation relative to tides (this determines when and how long plants are flooded) were of particular interest. With future sea-level rise, both flooding and salinity exposure are expected to increase.

It is already well known that factors like elevation and salinity impact wetland vegetation in a general sense (e.g., Watson and Byrne 2009), but the specific relationships between plant communities and their local environment are less well known in the Pacific Northwest. Additionally, it is useful to know which environmental factors have the greatest effect on plant communities.

A first step was to look at different environmental factors as relative predictors of plant occurrence. From the plant surveys we had a simple dataset showing whether each species was present or absent at each location we sampled. We also had quantitative data at each location for five gradients of potential importance to plant distribution: tidal elevation, soil salinity, soil nitrogen content, soil grain size, and a hydrologic index that quantified the degree of marine versus river dominance for the estuary from which the data were collected. The plant and environmental data were put into logistic regression models for many of the common species. The exciting next step - which I learned about after encountering a study on butterfly habitat use - was to apply a technique called hierarchical partitioning. This statistical technique enables a researcher to assess the relative strengths of effects (independently and jointly with other factors) of different variables in a statistical model. Like all statistical methods, it has its limitations (for instance, it doesn’t perform well with non-linear relationships between dependent and independent variables), but it seemed like a promising technique to quantify the relative importance of selected environmental factors on plant distribution.

I ran the analyses for 20 of the more commonly-occurring species and obtained some interesting results. First, for quite a few species, soil salinity was the most important variable in explaining the presence or absence of the species in the wetlands. In the figure below, for instance, salinity was positively related to the presence of perennial pickleweed (Sarcocornia perennis). Pickleweed occurrence was also positively correlated with tidal elevation, estuarine river-dominance, and soil clay content, though less strongly. (The positive correlation with river flow seems somewhat counter-intuitive for this salt-loving species, but may be due to its high frequency of occurrence from low marsh at our most river-dominated site.)

Relative strength of abiotic factor effects on the occurrence of pickleweed (Sarcocornia perennis) in Oregon tidal wetlands. All factors had statistically significant effects, but soil salinity appeared to have the greatest effect in the statistical model.

Elevation turned out to be the most important variable predicting the presence or absence of some other species. And, more rarely, soil nitrogen stood out as a key environmental gradient. Grain size (percent clay) of the soils generally only weakly correlated with species presence and absence.

The logistic regression models enabled a species-by-species look at environmental correlates of plant occurrence, but wetland plant communities in the Pacific Northwest are very diverse and species associations occur in complex patterns. We used another exciting statistical technique, non-metric multidimensional scaling (NMDS), to investigate overall plant composition in our dataset. In a nutshell, NMDS is a computational technique that aims to represent all of the differences between pairs of samples in a simple 2 or 3 dimensional graphical display. Its value lies in its ability to take a complex multi-dimensional dataset and summarize that information in a visually-intuitive manner from which patterns can be deduced.

The plot below shows the results of our NMDS analysis based on the abundance of 20 common plant species. Points closer to each other are more similar in terms of species composition. In the figure, the samples are colored based on their tidal elevation. Brownish points are plots from lower wetlands (e.g., below mean higher high water, MHHW) and greenish points are plant assemblages from high tidal marsh that is less frequently flooded. The analysis shows that plant communities separate out on an elevation gradient, similar to the patterns of vertical zonation one would see with invertebrates and algae on a typical rocky shoreline.

Non-metric multidimensional scaling plot of vascular plant communities in Oregon tidal wetlands. Plots are colored according to their height above or below local mean higher high water (m). Plot stress = 0.11.

Below I’ve shown the same NMDS plot, but with points coded by summer-time soil salinity. Plant composition differs between more saline and fresher wetlands, but there is a gradual gradient as with elevation.

An observational study like this is valuable for generating hypotheses about which environmental factors affect the distribution of different wetland species. However, we know that species are affected my more than environment itself – interactions with other species matter too. To more clearly determine causality, and not just patterns in the data, controlled experiments are needed. With dozens of species in the tidal wetland flora of Oregon and many potential abiotic and biological factors of importance, comprehensive study of this question would be a massive undertaking! In the next two posts, I’ll discuss some limited experimentation we performed to assess the effects of a few abiotic factors on plant growth and germination.

References

Janousek CN and Folger CL. 2014. Variation in tidal wetland plant diversity and composition within and among coastal estuaries: assessing the relative importance of environmental gradients. J. Vegetation Science 25:534-545.

Watson EB and Byrne R. 2009. Abundance and diversity of tidal marsh plants along the salinity gradient of the San Francisco Estuary: implications for global change ecology. Plant Ecology 205:113-128.