The multiyear effort was conducted by researchers at University of California, Davis; Johns Hopkins University; University of Connecticut; and Northern Arizona University; and was funded by Save the Redwoods League. The research provides the foundation to better understand redwood responses to climate impacts and pathogens.

The research team previously made available the completed giant sequoia genome research in November 2020.

“It’s remarkable how far genomics research has come since we undertook this challenge in 2017,” said David Neale, plant sciences professor emeritus at UC Davis and lead author on the new coast redwood genome research. “Our work on the coast redwood and giant sequoia genomes will enable us to develop modern genetic tools that can be used in the restoration and conservation of these ecologically important tree species.”

The league and its research partners launched the Redwood Genome project in 2017. Project partners outlined an ambitious plan to fully sequence the coast redwood and giant sequoia genomes for the first time using new conifer genetic sequencing techniques.

The genomic resources and screening tools developed in this project will help researchers quickly assess evolutionary adaptive potential in these forests and ultimately inform forest restoration and management plans.

The coast redwood genome

The coast redwood is the world’s tallest tree, and its genome is among the most complex sequenced. Nearly nine times larger than the human genome, it is also the second largest genome sequenced. The redwood genome has 26.5 billion base pairs of DNA, and it is hexaploid, meaning redwoods have six sets of chromosomes. Humans have 3 billion base pairs of DNA and are diploid, with two sets of chromosomes.

When comparing the coast redwood genome sequence to that of other conifers, researchers found hundreds of gene families unique to the coast redwood. Many are genes that help the trees respond to and fight stress, resist disease and repair after injury.

The giant sequoia genome

The giant sequoia is the world’s largest tree species and among the oldest on the planet. As reported by the research team in 2020, its genome contains 8.125 billion base pairs of DNA. Similar to the human genome, the giant sequoia genome is diploid. The reference genome produced for this study represents the first genome sequenced in the Cupressaceae family, and it lays a foundation for using genomic tools to aid in giant sequoia conservation and management.

The genomes of conifers are three to 10 times larger than the human genome. They are highly repetitive and complex. The first conifer genomes ever sequenced were the Norway spruce in 2013 and loblolly pine in 2014, 10 years after the human genome was completed.

Sequencing conifer genomes was not previously feasible due to economic and technical limitations. With technological advancements that also reduced the cost, 10 conifer genomes have now been sequenced.

About the Redwood Genome Project

In the last 160 years, commercial logging and clear-cutting claimed 95% of the coast redwood range and about one-third of the giant sequoia range. In 2020, an estimated 10%-14% of giant sequoia died from high-intensity wildfires, and in some areas the seedbank also died.

Two wildfires also burned through large sections of the giant sequoia range in 2021, and mortality from those is currently estimated to impact another 5% of the mature trees. As a result, both forests have experienced significant losses in total acreage and genetic diversity.

With these significant impacts to both populations, the league is leading restoration projects in both forest ranges. It aims to use this and future genetic research to inform efforts to restore and maintain genetic diversity and bolster the resilience of these species in the face of rapid, unprecedented environmental change.

“This ambitious scientific research provides a critical foundation for the League and the entire redwoods community,” said Joanna Nelson, Ph.D., director of science and conservation planning for Save the Redwoods League. “It will ultimately help us understand the incredible range of responses that coast redwood and giant sequoia species have exhibited in the face of climate change and how native genetic diversity has informed these responses. The Redwood Genome Project helps us see, for the first time, the full genetic diversity that has allowed these forests to adapt and survive for millennia — and could protect them against a suite of conditions they have never experienced.”

The study was supported by grants from National Science Foundation, USDA, and National Institutes of Health. Save the Redwoods League donors contributed over $1 million to the Redwood Genome Project through Forever Forest: The Campaign for the Redwoods, including a significant lead gift from Ralph Eschenbach and Carol Joy Provan. Genomic services companies Illumina, Oxford Nanopore Technologies and Dovetail Genomics contributed in-kind.

But the relationship between fire and ice, in terms of Earth’s climate, is not quite as “either or” as Frost depicted. In the case of a study presented today at the 2021 AGU Fall Meeting in New Orleans, that relationship is more “give and take.”

The team of researchers behind the recent study describe a link between dwindling sea ice and worsening wildfires in the western United States. As sea ice melts from July to October, sunlight warms the increasingly iceless, surrounding area. This ultimately brings heat and fire-favorable conditions to distant states like California, Washington, and Oregon later in autumn and early winter.

The researchers describe this relationship — its existence previously known, but its underlying mechanism now described for the first time — as similarly influential as climate patterns like the El Niño-Southern Oscillation.

“It’s not a perfect analogy, but teleconnections like this are a bit like the butterfly effect,” said Hailong Wang, an Earth scientist at the Department of Energy’s Pacific Northwest National Laboratory and coauthor of the new study. He references the popular feature of chaos theory where a butterfly’s flapping wings are thought to influence the formation of a distant tornado.

“Climate conditions in one part of the world can, over time, influence climate outcomes from thousands of kilometers away,” said Wang. “In our case, we find the Arctic region and the western United States are connected by this relationship. Regional land and sea surface warming caused by sea ice loss distantly triggers hotter and drier conditions in the West later in the year.”

Wang presented his findings virtually at an AGU press conference that explored wildfire in a changing climate on Dec. 16.

A tale of two vortices

Wang and his fellow authors found that, as Arctic sea ice melts and the surrounding land and sea surfaces warm, a vortex strengthens in the atmosphere above the heated area. This vortex, spinning counterclockwise like a cyclone, is spawned by differences in air pressure.

The powerful vortex constantly pushes the polar jet stream out of its typical pattern, diverting moist air away from the western United States. With the now wavier jet stream nudged off its usual course, a second vortex, spinning clockwise, forms under the ridge of the polar jet above the western United States. This second vortex — similar to the vortex responsible for the Pacific Northwest’s extreme heat earlier this summer — brings with it clear skies, dry conditions and other fire-favorable weather.

As the Arctic continues warming, it can sharpen the contrast between these two distantly connected systems, further exacerbating conditions in an already fire-ravaged region. More than three million acres have burned across California alone during the 2021 wildfire season.

“This dynamics-driven connection warms and dries out the western United States region,” said Yufei Zou, lead author and data scientist who was a postdoc at PNNL when the study was conducted. “By uncovering the mechanism behind that teleconnection, we hope those in charge of managing forests and preparing for wildfires will be more informed.”

Less ice, more heat

To probe the influence of Arctic sea ice in forming fire-favorable climate conditions, the study’s authors called upon the past four decades of recorded sea ice levels. The team isolated the mechanism at play through modeling conducted at the National Energy Research Scientific Computing Center, a DOE Office of Science user facility at Lawrence Berkeley National Laboratory.

Arctic sea ice has continually declined since scientists began measuring its loss in the late 1970s. End-of-summer sea ice cover has diminished by 13 percent each decade relative to the 1981-2010 average, according to the National Oceanic and Atmospheric Administration.

Arctic sea ice is projected to continue declining, eventually leading to periods of iceless Arctic waters before the 2050s. Today, even the older, thicker ice that persists year-round is now thinner and more fragile.

In addition to Wang and Zou, authors from PNNL include Philip J. Rasch and Rudong Zhang.

The new research on these unique soils, being presented on Wednesday, 15 December at AGU Fall Meeting 2021, marks the first attempt to quantify carbon capture by canopy soils. The work highlights another way old-growth forests are rich, complex ecosystems that cannot be quickly replaced by replanting forests.

Tree branches collect fallen tree leaves and other organic material over hundreds of years, like the ground does. On top of the branches, the plant litter decomposes as it accumulates, forming a carbon-rich layer that can be several inches thick. The researchers climbed up into the rainforest canopy in Costa Rica, instruments in hand, to find out just how much carbon canopy soils can contain.

Active carbon, a short-term storage pool of organic carbon, was three times higher in canopy soil compared to soils underfoot, the researchers found.

“We knew these would be really organic-rich soils, but we didn’t expect the extremely large amount of carbon compared to mineral soils,” said Hannah Connuck, an undergraduate researcher at Franklin and Marshall College who will be presenting the study results.

The researchers are still calculating the total concentration of organic carbon at their research site, but other research has found canopy soils to have up to 10 times higher concentrations of organic carbon, according to soil scientist Peyton Smith, a study co-author and Connuck’s soil science mentor at Texas A&M University.

Connuck and Smith also measured how much carbon dioxide was being released by microbial organisms living in the canopy soils, which is critical for knowing whether soils are storing or releasing carbon overall. They found that even though the microbes were releasing higher volumes of carbon dioxide than ground soils, their rate of carbon storage was rapid enough to compensate, likely making canopy soils a net carbon sink that has not been considered in carbon models yet.

“It could be a substantial carbon sink, and we need to account for it,” Smith said.

Like other soils, canopy soils take a long time to form, and therefore take a long time for a forest to recover if an area of old growth is cut down. The soils also host unique microbiomes, including highly diverse microbial organisms and canopy-specific plants like epiphytic orchids.

“It’s a good argument for keeping primary and other old-growth forests around, rather than harvesting and replanting with secondary growth forests,” Connuck said.

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To conserve these species, scientists must first know where they are. While the distributions of some plant and animal groups have been extensively mapped, comparatively little is known regarding the whereabouts of the world’s insects.

In a new study, researchers created the most detailed distribution map to date of butterflies in the American tropics, showing that areas of highest diversity coincide with regions most threatened by deforestation and development. The study specifically focused on Ithomiini, or glasswing butterflies, a large group with nearly 400 species that occur throughout much of Central and South America. Their ubiquity may make them a good indicator for the fate of other insects in the region.

“If we want to understand the diversity of insects in general, then one approach is to concentrate on groups that likely reflect the diversity of all insects and for which we have good knowledge, like butterflies,” said study co-author Keith Willmott, curator and director of the Florida Museum of Natural History’s McGuire Center for Lepidoptera and Biodiversity.

Mimicry both helps and hinders glasswings

Glasswing butterflies get their namesake from their unusual, transparent wings marked with colorful spots of alternating hues and patterns. As with many other butterfly species, such as monarchs, these markings serve as a warning. Male glasswing butterflies feed on the nectar and tissue of poisonous plants, concentrating the toxins in their abdomen and passing them on to females when mating. These toxins, a type of alkaloid, give the butterflies and their eggs a bitter taste that makes them unpalatable.

But would-be predators aren’t born innately knowing not to eat these butterflies, instead learning through trial and error. As a result, many glasswing species have evolved similar wing patterns that give them strength in numbers.

“Since different species share the same warning color patterns, they share the overall cost per species of educating predators to avoid them,” Willmott said.

This type of resemblance, called Müllerian mimicry, has helped glasswing butterflies survive and diversify in the varied habitats of the tropics, but it also comes at a cost. While this strategy is effective when all species resembling one another are thriving, the extinction of any one species could jeopardize the survival of others, Willmott explained. “This is particularly true if one of the more common species goes extinct, because all the others lose the benefit they gained from being involved in Müllerian mimicry with those butterflies.”

Glasswing butterflies are most diverse and most vulnerable at high elevations

Willmott and his colleagues have spent the last several decades trekking across mountains and forests in search of glasswings, describing new species and documenting their natural history along the way. By combining the data they’ve collected over the years with information gleaned from specimens in more than 60 museums and private collections, the researchers compiled nearly 30,000 distribution records. They used this extensive dataset to map the diversity of glasswings and the interactions between lookalike species throughout the American tropics.

Their results indicate glasswings are highly diverse in particular parts of their range, including the Amazon River basin, where their transparent wings help them blend in against the backdrop of forest gloom. But the majority of species cluster together in mountainous biodiversity hotspots. The eastern slopes of the Andes Mountains contained the top 5% of glasswing diversity, while secondary hotspots included the highlands of Central America and the Atlantic coastal forest of Brazil.

While large tracts of the Amazon rainforest remain relatively undisturbed, glasswing diversity in the tropical Andes frequently overlapped with areas at the highest risk of habitat loss due to land conversion for agriculture. This was especially true for species with restricted distributions, highlighting the pressing need for conservation efforts in these areas.

Mountainous regions create a variety of small, localized environments as they climb in elevation. The relatively young Andes, which are among the world’s highest mountains, support a correspondingly large number of species. The differences in topography, temperature and rainfall also make the Andes an ideal place to grow a variety of crops. “At the moment, loss of habitat is the most significant threat,” Willmott said. “It is just an unfortunate coincidence that areas that are good for people to live are also areas that support high animal and plant diversity.”

Lead author Maël Doré, a doctoral student at the National Museum of Natural History in Paris, also worries that climate change may further limit the range of already restricted species on the slopes of tropical mountains. As temperatures increase, species may cope by shifting their distributions to higher elevations, but whether glasswing communities will move fast enough to keep up with climate change is uncertain.

Far from the Andes, the lower and older mountains along the Brazilian Atlantic coast are home to a number of rare and endemic glasswing species, which also face threats from habitat destruction. “This region has experienced almost five centuries of human occupation, but it was also here that pioneering initiatives to protect Neotropical butterflies and their habitats were born almost 100 years ago,” said co-author André Freitas, a professor at the Universidade de Campinas in São Paulo, Brazil.

Still, Willmott and his colleagues remain optimistic. With a detailed map of where butterflies occur, conservation efforts can be directed to preserve environments and communities under threat, as well as those that are still untouched by humans.

“With more accurate maps of butterfly distributions, we can identify species and communities that currently lack protection, to more effectively focus limited resources where they are most needed,” Willmott said.

However, there has been little research into how extreme events develop in the world’s oceans. Beginning in the early 2000s, first scientific studies pointed out the significance of marine heatwaves and their impact on ecosystems. A wake-up call came in 2011 in the form of a persistent marine heatwave off the west coast of Australia that destroyed the species-rich kelp forests there. Probably the most prominent example of a marine heatwave is the “Blob,” as it is known — a giant bubble of warm water that spread in the northeast Pacific Ocean and along the US West Coast from Alaska to the equator from 2013 to 2015. It killed millions of marine birds, fish and other creatures.

Researchers at ETH Zurich, the University of Bern and the University of Tasmania used a high-resolution ocean model to analyse this extreme weather event from a new perspective. Led by Nicolas Gruber, Professor of Environmental Physics at ETH Zurich, the international team concluded that it was not solely the high water temperatures that caused the mass die-off, but probably a combination of extreme events that occurred simultaneously.

A combination of extreme events is particularly dangerous

The researchers used their model to reconstruct the Blob’s development over time, and in doing so, they analysed for the first time the combination of temperature, acidity and oxygen concentration of the ocean water. Their simulations show that, at the peak of the heatwave in July 2015, extremes in acidity and low oxygen had also spread extensively throughout the affected region in the northeast Pacific.

From this, the ETH researchers concluded that what occurred off the coasts of Oregon, Washington and British Columbia was not merely a heatwave but a compound extreme event. “When marine life is confronted with multiple stressors at once, it has difficulty acclimatising,” Gruber says. “For a fish species that’s already living at the upper end of its optimal temperature range, an added oxygen deficiency can mean death.”

That’s why, in their study — which was just published in the journal Nature — the researchers called on the scientific community to pay greater attention to compound extreme events in the ocean. “To assess the risks of these kinds of events, we urgently need to study the chain of different environmental factors leading to such extremes more closely — and not only in individual regions, but also at the global level,” Gruber says.

Global distribution analysed for the first time

The authors of this study have already taken a first step in this direction. In addition to the Blob, they used a global climate model to investigate where and how often extreme events — separated into heatwaves and situations involving anomalously high acidity and low oxygen — occur and how severe they are.

To demonstrate the impact of climate change, the researchers simulated the extreme events for the period from 1861 to 2020 and compared the current situation with pre-industrial times. The results speak for themselves: globally, the number of hot days on the ocean surface each year has increased tenfold, from around 4 days to 40. The number of days on which the ocean depths are characterized by anomalously low oxygen has increased fivefold.

With regard to acidity extremes, the situation is even graver. Compared with pre-industrial times, what has now established itself is almost a permanent extreme situation. “This shows how far climate change has already advanced in the ocean,” says Thomas Frölicher, Professor at the University of Bern and co-author of the study.

The researchers also show on a world map which ocean regions see the most intense extreme events — both at the ocean surface and 200 metres below it. The spatial resolution of these events within the water column is important because this further limits the possibilities for the affected marine life to escape, as the study’s authors highlight.

Huge knowledge gaps

The researchers cannot assess the ecological consequences of extreme events in detail, but one thing is clear: compared with climate change, which progresses slowly, the effect of extremes on ocean life is generally stronger. The sudden occurrence of environmental changes makes many kinds of adaptation strategies impossible.

Current model simulations can replicate the response of these ecosystems to extremes only to a limited extent — they cannot yet do justice to the complexity of biological and ecological processes. “For example, our models are still extremely limited in their ability to distinguish between different groups of algae and zooplankton,” says Meike Vogt, a senior researcher in Gruber’s group. But this differentiation is important, as different species differ greatly in their ability to withstand extremes.

“We know from Swiss forests that beech trees are less drought-tolerant than, for instance, pines,” Gruber says. By contrast, far too little is known at present about the marine ecosystems. “We lack broad understanding of the ecosystem structure and function in the various ocean regions. Only when we have this foundation will we be able determine the impact of climate change and extremes,” Vogt says.

But there’s no doubt about this: if climate change continues extreme events will increase — individually and in combination with others. A better data basis and extensive research work would pave the way for more suitable action to protect the ocean. “Much like there are already international protected areas on the high seas, we could, for example, establish a fishing ban to protect areas affected by extreme events,” Gruber says. This has already been done in the case of the Blob. However, a fishing ban alone will hardly be enough; further measures are urgently needed, emphasizes the ETH professor. “Time is short!”

The study, funded by the European project ERC-CoG TRADITION, assessed the stable isotope composition of over 300 human individuals and more than 400 radiocarbon dates from archaeological sites on the southern Brazilian coast. Most of the sites are collective cemeteries built by fishing communities that flourished in the region between 7000 and 1000 years ago. Thousands of sites have already been recorded by archaeologists, who usually find hundreds of human burials, carefully deposited among enormous quantities of fish and shellfish that were consumed and used as grave goods in funerary rituals.

The researchers found a sharp decline in the frequency of archaeological sites from ca. 2200 years ago, which coincided with a major reorganisation of coastal environments in response to a fall in the relative sea level. According to Alice Toso, ICTA-UAB researcher and lead author of the study, “sea level change around 2000 years ago possibly caused a turning point in the carrying capacity of coastal environments that for thousands of years had sustained large indigenous communities along the southern coast of Brazil. The shrinking of coastal ecosystems such as bays and lagoons caused aquatic resources to be less abundant and less predictable, forcing groups to disperse into smaller social units.”

André Colonese, ICTA-UAB researcher and senior author of the paper, commented that “the radiocarbon density distribution of these sites suggests the human population declined along Brazil’s Atlantic Forest coast around 2000 years ago. Interestingly, instead of abandoning fishing due to less predictable resource distribution, the remaining populations intensified fishing, exploiting in particular species of high trophic level, including sharks and rays. We believe that a fundamental shift in subsistence practices occurred at that time, from community-based (large sharing) to family-based (limited sharing) fishing.” The study thus reveals that millennial-scale resilient coastal societies are vulnerable to the societal and economic impacts of environmental thresholds.

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