Roadmap to renewables unites climate and sustainability goals

Vision and research gaps for a low-carbon, biodiverse future

UNIVERSITY OF CALIFORNIA - DAVIS

Research News

 

IMAGE: GREAT EGRETS SIT ATOP A FLOATOVOLTAIC ARRAY IN FLORIDA IN 2020. view more 

CREDIT: REBECCA R. HERNANDEZ, UC DAVIS

While the pressures of climate change bring a sense of urgency to renewable energy development, a new study serves as a roadmap toward uniting the goals of a low-carbon future with that of ecological sustainability and conservation.

The study, published in the journal Frontiers in Sustainability from the University of California, Davis, and John Hopkins University, aims to help decision-makers avoid the unintended environmental consequences of renewable energy development.

"Renewables aren't always sustainable, but they can be if we think proactively," said co-leading author Sarah Jordaan, an assistant professor at John Hopkins University's School of Advanced International Studies. "There is a huge misalignment between United Nations Sustainable Development Goals and climate goals. This is a call to action for leaders to come together to address it."

To develop the roadmap, the authors assessed public and private investments in renewable energy and analyzed the tradeoffs and synergies of clean energy. They also identified research themes drawn from a two-day workshop held by the Electric Power Research Institute in 2019 with 58 leading experts in the fields of renewable energy and sustainability from across academia, industry, government sectors.

MISSING THE FOREST FOR THE GHGs

Among the key research priorities identified for sustainable solar and wind developments include site selection and understanding interactions with wildlife.

For example, Florida's longleaf pine forests have, for centuries, helped store carbon, protect water quality and provide wildlife habitat. Now, only a fraction of the historical range of longleaf pine forests in the state remain. Yet a sliver of that remaining sliver is slated to be replaced by a solar installation.

Meanwhile, in the same state and just a few miles away, waterbirds squawk, preen their feathers, and hunt for food atop a floating array of solar panels - a "floatovoltaic" installation. Here, both wildlife and greenhouse-gas-reduction goals appear to coexist gracefully.

"We can't pursue climate change mitigation blindly," said co-leading author Rebecca. R. Hernandez, a UC Davis assistant professor and founding director of the Wild Energy Initiative in the John Muir Institute of the Environment. "We must consider the impacts of renewables on the few ecosystems we have left."

Other key considerations and priorities the scientists identified were public acceptance of clean energy projects and the study of end-of-life management for wind and solar. For instance, the composites in wind blades are not recyclable, and solar panels contribute to a growing electronic waste problem.

CAPTION

A heron stands beside a floatovoltaic array in Florida.

CREDIT

Rebecca R. Hernandez, UC Davis

PUSHING FORWARD

The authors said the work highlights how the field of sustainable renewable energy is in its infancy, with many of the questions and solutions unclear. The roadmap, they emphasize, is a living document, designed to change as the field matures.

"We're pushing forward into maturation something that is really just being born," Hernandez said of renewable energy. "Across its sectors, everyone is trying to figure things out as quickly as possible. This roadmap points to the fact that we all need to get organized and work together to share knowledge, innovation and results."

Jordaan said while the roadmap highlights problems, they are solvable.

"We need to research the things we don't know, implement solutions we do know, and develop technology as needed and ensure accountability," she said.

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Additional

Fire-resistant tropical forest on brink of disappearance -

Research on Indonesia shows effect of human modification

SWANSEA UNIVERSITY

Research News

 

IMAGE: A NEW STUDY LED BY SWANSEA UNIVERSITY REVEALS THAT ONLY 10% OF THE FOREST THAT IS LEFT ON TWO INDONESIAN ISLANDS REMAINS FIRE-RESISTANT. THE RESEARCHERS WARN THAT PROTECTING THIS... view more 

CREDIT: T. SMITH

A new study led by researchers in the Geography Department at Swansea University reveals the extreme scale of loss and fragmentation of tropical forests, which once covered much of the Indonesian islands of Sumatra and Kalimantan.

The study also reveals that only 10% of the forest that is left remains fire-resistant. The researchers warn that protecting this is crucial for preventing catastrophic fire.

Tropical deforestation exacerbates recurrent peatland fire events in this region. These release globally significant greenhouse gas emissions and produce toxic haze events across South East Asia.

An area of tropical forest and peatland larger than the Netherlands has burned in Indonesia in the past five years, according to Greenpeace.

Yet the study shows that contiguous tracts of undisturbed forests are not susceptible to burning even under current drought conditions.

Dr Tadas Nikonovas of Swansea University, lead author of the research, explained:

"Undisturbed tropical rainforests are naturally resistant to fire due to the humid and cool micro-climate they maintain, effectively acting as a fire barrier. Contrary to the widely-held perception that worsening droughts are threatening the remaining rainforests, tropical forests in Indonesia become susceptible to fire only after human disturbance."

However, the study also reveals that currently only a small fraction (~10%) of the remaining total tropical forest cover remains fire-resistant. The rest (~90%) has been severely fragmented or degraded and therefore is no longer able to maintain a fire-resistant microclimate.

Importantly, fire-resistant forests now cover only 3% of the region's peatlands, leaving large amounts of climate-critical carbon vulnerable to burning.

The authors emphasize that the preventative role tropical forests play against fire is yet another important reason for the preservation and regeneration of the few remaining contiguous tracts of forests.

Dr Allan Spessa of Swansea University, the project leader, added:

"Protecting tropical forest is critical not only for biodiversity and carbon storage but also for preventing future catastrophic fire episodes. This is true for Indonesia, as well as for tropical forest in Africa and South America".

The research was published in a Nature group journal, Communications Earth and Environment

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This study is part of Swansea University-based Towards Fire Early Warning System for Indonesia (ToFEWSI) project.

Notes to editors

About the research: The DOI for this paper will be 10.1038/s43247-020-00069-4. Once the paper is published, it will be available to view online at
https://www.nature.com/commsenv/

For more information please get in touch with the project PI Dr Allan Spessa
(allan.spessa@swansea.ac.uk)

or the lead author Dr Tadas Nikonovas
(t.nikonovas@swansea.ac.uk).

Swansea University is a world-class, research-led, dual campus university offering a first-class student experience and has one of the best employability rates of graduates in the UK. The University has the highest possible rating for teaching - the Gold rating in the Teaching Excellence Framework (TEF) in 2018 and was commended for its high proportions of students achieving consistently outstanding outcomes.

Swansea climbed 14 places to 31st in the Guardian University Guide 2019, making us Wales' top ranked university, with one of the best success rates of graduates gaining employment in the UK and the same overall satisfaction level as the Number 1 ranked university.

The 2014 Research Excellence Framework (REF) 2014 results saw Swansea make the 'biggest leap among research-intensive institutions' in the UK (Times Higher Education, December 2014) and achieved its ambition to be a top 30 research University, soaring up the league table to 26th in the UK.

The University is in the top 300 best universities in the world, ranked in the 251-300 group in The Times Higher Education World University rankings 2018. Swansea University now has 23 main partners, awarding joint degrees and post-graduate qualifications.

The University was established in 1920 and was the first campus university in the UK. It currently offers around 350 undergraduate courses and 350 postgraduate courses to circa 20,000 undergraduate and postgraduate students. The University has ambitious expansion plans as it moves towards its centenary in 2020 and aims to continue to extend its global reach and realise its domestic and international potential.

Swansea University is a registered charity. No.1138342. Visit http://www.swansea.ac.uk

For more information:

Kevin Sullivan,
senior press officer,
Swansea University
k.g.sullivan@swansea.ac.uk

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Identifying where to reforest after wildfire

A future of fewer Christmas trees and other conifers

UNIVERSITY OF CALIFORNIA - DAVIS

Research News

 

IMAGE: A POST-FIRE AREA OF THE SIERRA NEVADA MOUNTAINS WITH VERY LITTLE CONIFER REGENERATION. view more 

CREDIT: JOSEPH STEWART, USGS/UC DAVIS

In the aftermath of megafires that devastated forests of the western United States, attention turns to whether forests will regenerate on their own or not. Forest managers can now look to a newly enhanced, predictive mapping tool to learn where forests are likely to regenerate on their own and where replanting efforts may be beneficial.

The tool is described in a study published in the journal Ecological Applications by researchers from the University of California, Davis; U.S. Geological Survey (USGS), Cal Fire and the U.S. Forest Service.

"Huge fires are converting forested areas to landscapes devoid of living trees," said lead author Joseph Stewart, a postdoctoral researcher at UC Davis and with USGS. "Managers need timely and accurate information on where reforestation efforts are needed most."

The tool, also known as the Post-fire Spatial Conifer Regeneration Prediction Tool (POSCRPT), helps forest managers identify within weeks after a fire where sufficient natural tree regeneration is likely and where artificial planting of seedlings may be necessary to restore the most vulnerable areas of the forest.

NOT SO EVERGREEN

Conifers, or plants with cones such as pine trees, dominate many forests in western North America. The study found that conifers are less likely to regenerate after fires when seedlings face drier climate conditions, especially in low-elevation forests that already experience frequent drought stress. Overall, fewer conifers are expected to grow in California's lower elevations following wildfire due to climate and drought conditions.

"We found that when forest fires are followed by drought, tree seedlings have a harder time, and the forest is less likely to come back," said Stewart.

A UC Davis team collected post-fire recovery data from more than 1,200 study plots in 19 wildfires that burned between 2004 and 2012, as well as 18 years of forest seed production data. Ecologists at USGS collected and identified over 170,000 seeds from hundreds of seed traps. The scientists combined these data with multispectral satellite imagery, forest structure maps, climate and other environmental data to create spatial models of seed availability and regeneration probability for different groups of conifers, including pines and firs.

Forest managers have used a prototype of the tool in recent years to better understand where to focus regeneration efforts. The new upgrade incorporates information on post-fire climate and seed production and includes an easy-to-use web interface expected to increase the tool's accuracy and use.

"This work is a great example of how multiple partners can come together to solve major resource management problems that are arising from California's climate and fire trends," said co-author Hugh Safford, regional ecologist for the USDA Forest Service's Pacific Southwest Region and a member of the research faculty at UC Davis.

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Additional co-authors include Phillip van Mantgem, Adrian Das, Nathan Stephenson, Jon Keeley and Micah Wright of USGS; Derek Young and James Thorne of UC Davis; Kristen Shive of Save the Redwoods League; Haiganoush Preisler of U.S. Forest Service; and Kevin Welch of California Department of Forestry and Fire Protection.

The study was funded by the USGS' Southwest Climate Adaptation Science Center, Ecosystems Mission Area and Land Change Science Program.

Climate warming linked to tree leaf unfolding and flowering growing apart

BRITISH ECOLOGICAL SOCIETY

Research News

 

An international team of researchers from the Chinese Academy of Sciences, Zhejiang A & F University and the University of Eastern Finland have found that regardless of whether flowering or leaf unfolding occurred first in a species, the first event advanced more than the second over the last seven decades.

In the four European tree species the researchers looked at: horse chestnut, scots pine, alder and ash, the time interval between leaf unfolding and flowering increased at a rate of 0.6 to 1.3 days per decade between 1950 - 2013. Similar trends were seen geographically, with the time interval between the two life-cycle (phenological) events being greater in trees in warmer areas of Europe.

Although leaf unfolding and flowering have both been shown to be happening earlier with climate warming, this is the first large scale study to examine both phenological events together and show that they are not advancing at the same rate in response to climate warming.

Leaf unfolding and flowering are key annual events for trees with each signalling the start of growth and reproduction, respectively. The timing of these events is crucial for maximising fitness.

"The unequal advances of leaf unfolding and flowering may alter trees' partitioning of resources between growth and reproduction and could leave flowers or leaves vulnerable to late spring frost damage if they appear too early" said Dr Jian-Guo Huang, the corresponding author of the study. "This could have impacts on tree species health and further affect ecosystem structure and function."

Species that produce flowers before leaves, like ash, could suffer losses in seed production if flowers were damaged by late spring frost. For species that produce leaves before flowers, like horse chestnut, late spring frost damage to leaves could reduce growth and carbon uptake.

Dr Qianqian Ma, lead author of the study said "The timing of phenological events is very sensitive to environmental factors, with temperature being particularly important in temperate plants. The changes in phenology we observed in our study may affect both growth and reproductive development in tree species and ultimately affect the ecosystem, nutrient cycles and carbon storage."

Tree species have evolved an optimal timing for growth and reproduction based on historic climate conditions. Changes to flowering times could disrupt interactions with pollinators, impacting the survival of both species with knock-on consequences for the ecosystem. Changes to when trees are able to grow in the year can have further consequences to their survival and carbon uptake.

The triggering of these phenological events is closely linked to temperature changes in the seasons. "Plants often require an exposure to chilling temperatures during winter as a cue for rest before the bursting of leaf buds or flowering can be triggered by a sufficient exposure to warmer temperatures in spring." explained Dr Qianqian Ma.

For each tree species, leaf unfolding and flowering have evolved to occur in a predetermined order. Although leaf unfolding occurs first in most species, those pollinated by wind, like alder and ash, flower first so that leaves don't inhibit pollen dispersal.

To collect the data on the four tree species, the researchers used the Pan European Phenology (PEP) network. This database contains annul observations of the date when leaves first unfold (or separate for evergreens) and the date when flowers first emerge for tree species across Europe. With this data the authors calculated the time intervals between first leaf date and first flower date between 1950 - 2013 and assessed this with corresponding temperature data.

Dr Qianqian Ma said: "Using long-term phenological records in Europe, we examined simultaneously the responses of both leaf unfolding and flowering of four common temperate tree species: ash, alder, horse chestnut and scots pine to climate warming."

These trees were chosen to give a mix of deciduous and evergreen trees with different orders of leaf unfolding and flowering.

Ideally more species would have been included in the study, but the researchers could only look at tree species with data on first leaf, first flower date and temperature. Only four tree species had sufficient data records over long enough time periods and large enough geographic areas.

Dr Jian-Guo Huang said: "Further studies that simultaneously monitor the timing of phenological events and the allocation of resources within plants are needed to better evaluate the consequences of altered phenology under climate warming."

COVID-19: what strategies are beneficial to the state

Competing benefits: economic theory and COVID constraints

NATIONAL RESEARCH UNIVERSITY HIGHER SCHOOL OF ECONOMICS

Research News

 

Those who consider themselves healthy will be more willing to comply with COVID restrictions if they believe, according to their own estimations, that the expected losses from the disease will be significant, suggest researchers of the Faculty of Economic Sciences at HSE University.

Based on the classic Prisoner's Dilemma, HSE researchers modeled human behavior strategies in the face of COVID restrictions. Their model showed that unequal access to medical care both contributes to irresponsible behavior in some citizens and the independent acceptance of restrictions by others, without any government intervention. The study was published in the journal Public Administration Issues.

During the first wave of infections of the coronavirus pandemic, government decisions were often made at random, based on common sense or epidemiological calculations. Very quickly, implemented measures came into conflict with societal ideas of efficiency and fairness--i.e., economic issues. Meanwhile, simple classical models that economists usually use in their studies can tell a lot about the motives behind citizens' behavior when restrictions are implemented, and about possible options for public policy.

One of the most famous models in game theory is the Prisoner's Dilemma. Two people caught while trying to escape are faced with a choice: to be silent or betray the other? Neither of them knows how the other will act. Both face punishment in the form of an additional term of imprisonment, but its severity depends on how the captured fugitives behave. If one of them testifies against the other, his term will be shortened, and the term of the silent fugitive will be as severe as possible. If both testify against each other, then both will be punished with serious sentences. If both are silent, then each prisoner's punishment will be mild. The benefits of cooperation outweigh the benefits of pursuing one's own interests. Despite this, people do not always agree to mutually beneficial cooperation due to imperfect information.

In the case of pandemic-related restrictions, the logic remains: for example, if everyone voluntarily self-isolates at home, then one person who violates the restriction wins, since they will not get infected and, moreover, retain their usual lifestyle. But, if everyone starts to ignore the restrictions, the increase in the rate of infection leads to a worsening of the situation for everyone (at the very least due to the decrease in the availability of medical care).

However, restrictive measures do not always find support among populations. In a lockdown, even vulnerable citizens ('at-risk groups') will be inclined to violate the bans if they consider freedom of movement important and are confident that they will receive adequate medical care. Individuals who suffer large losses under restrictive measures (quarantine, self-isolation, or bans on work or movement) and, at the same time, have high incomes and access to high-quality health services, will be willing to accept the risks of infection, even if their behavior results in an escalation of the epidemic. Only when citizens consider the likelihood of their receiving quality assistance to be low do they consider following restrictions to be more advantageous.

'Together with my colleagues Ludmila Zasimova, Marina Kolosnitsyna, and Natalia Khorkina, we consistently modeled situations in which all people support or, conversely, violate the imposed restrictions,' says Alexey Kalinin, first author of the study and Associate Professor of the Faculty of Economics at HSE University. 'If there is a significant lack of equal access to medical care in a given state, this can contribute not only to irresponsible behavior among some citizens, but also to the ready acceptance of restrictions by other citizens, without any government intervention.'

Convincing at-risk groups for whom the probability of becoming infected is close to 1 or those who are currently sick to stay home is pointless, the researchers say. The disease is already embedded in their behavior. But there is a clear rationale for conducting information campaigns aimed at healthy populations to convince people of the risk of infection: those who consider themselves healthy will be more willing to comply with restrictions if, according to their own estimations, the expected losses from the disease are significant.

In addition to analyzing individuals' behavior, the HSE researchers examined the model's results in terms of the welfare of society as a whole.

From the standpoint of utilitarianism, that is, maximizing total social welfare, it turns out that the general acceptance of restrictions (all forms of lockdowns) is not advantageous. If there is a sufficiently effective way to distinguish a carrier of the disease from a healthy person, then from the point of view of society, it is enough to isolate only one group, and it does not matter which one. This is what happens in the case of local quarantine bans: if it is known that a certain group is sick or at higher risk, it is sufficient to isolate that group without introducing bans for society as a whole.

At the same time, such an approach does not at all guarantee that partial or even more general restrictions will be better for society than abandoning them, which led to epidemic. This situation develops when the total loss of welfare from restrictions is estimated to be higher than the total damage from the massive spread of infection. This explains the rationality of the decisions of individual states that abandoned the policy of prohibitions as such, as well as the conscious acceptance of epidemics with low mortality--as in the case of seasonal ARVI diseases. This was done, for example, by Sweden (in the first wave of the pandemic), Japan, and South Korea, whose restrictions were advisory in nature.

An alternative approach to public welfare is the Rawlsian approach, where the welfare of the worst-off individuals is important. It unexpectedly leads to a situation where it is beneficial for the state to impose restrictions on the healthy, and not the sick or vulnerable population (which already 'will find a way' to get sick and suffer losses from illness in addition to losses from isolation). The fact that in practice, instead of this approach, general bans are chosen is explained by the impossibility of separating sick and healthy individuals with perfect accuracy: it is more effective to isolate everyone rather than to allow a sharp deterioration in the situation of at least one person.

'In general, the desire for maximum, complete isolation of all groups of the population from the standpoint of social welfare and the effectiveness of public administration turns out to be untenable,' says Kalinin. 'The main issue is whether the restrictions applied in order to divide society into groups that are as isolated and homogeneous as possible are sufficient to prevent direct contact between them (simultaneously being on the street or in public places). A similar approach was used, for example, at the beginning of the epidemic in the Netherlands, where isolation requirements were aimed at the high-risk group--the elderly--and no formal restrictions were introduced for other groups of the population.'

In the absence of reliable quantitative information about the scale of the pandemic, theoretical conclusions drawn from the classic Prisoner's Dilemma and focused on determining how, in principle, people can adjust their behavior, can be useful in justifying decisions made at both the individual and the state level.

Key building block for organic molecules discovered in meteorites

NASA/GODDARD SPACE FLIGHT CENTER

Research News

 

IMAGE: PHOTO OF A PIECE OF THE MURCHISON METEORITE THAT WAS USED IN THIS STUDY. view more 

CREDIT: NASA

Scientists from Japan and NASA have confirmed the presence in meteorites of a key organic molecule which may have been used to build other organic molecules, including some used by life. The discovery validates theories of the formation of organic compounds in extraterrestrial environments.

The chemistry of life runs on organic compounds, molecules containing carbon and hydrogen, which also may include oxygen, nitrogen and other elements. While commonly associated with life, organic molecules also can be created by non-biological processes and are not necessarily indicators of life. An enduring mystery regarding the origin of life is how biology could have arisen from non-biological chemical processes, called prebiotic chemistry. Organic molecules from meteorites may be one of the sources of organic compounds that led to the emergence of life on Earth.

Associate Professor Yasuhiro Oba from Hokkaido University, Japan, led an international team of researchers who discovered the presence of a prebiotic organic molecule called hexamethylenetetramine (HMT) in three different carbon-rich meteorites. Their discovery validates models and theories that propose HMT as an important molecule in the formation of organic compounds in interstellar environments.

"HMT is a key piece of a puzzle which draws the whole picture of chemical evolution in space," said Oba, lead author of a paper about the research published December 7 in the journal Nature Communications. "To explain the formation of meteoritic organic molecules such as amino acids and sugars, two easily vaporized (volatile) molecules, formaldehyde and ammonia, are necessary in asteroids, the parent bodies of many meteorites. However, since they are easily lost from asteroidal environments due to their high volatility, scientists question how enough could have been available to build the meteoritic organic molecules being found. HMT does not vaporize even at room temperature, and it can produce both molecules if it is heated with liquid water inside asteroids. Finding HMT in meteorites confirms the hypothesis that it is a stable source for ammonia and formaldehyde in asteroids."

Early in the solar system's history, many asteroids could have been heated by collisions or the decay of radioactive elements. If some asteroids were warm enough and had liquid water, HMT could have broken down to provide building blocks such as formaldehyde and ammonia that in turn reacted to make other important biological molecules which have been found in meteorites, including amino acids. Some types of amino acids are used by life to make proteins, which are used to build structures like hair and nails, or to speed up or regulate chemical reactions.

"These results shed light on the various ways amino acids can form in extraterrestrial environments," said Jason Dworkin, a co-author of the paper at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "This can be explored further when comparing the samples from Japan's Hayabusa2 and NASA's OSIRIS-REx missions. These spacecraft collected material from asteroids with what appears to be different histories of liquid water. If there is a mission to return a sample from a comet nucleus someday, perhaps we can see if there is a connection between HMT in comets and asteroids."

While the diversity of organic compounds in meteorites is well-documented, many questions remain about the processes by which these compounds were formed. The most important meteorites in this area of research are carbonaceous chondrites, stony meteorites that contain high percentages of water and organic compounds. Experimental models have shown that a combination of water, ammonia and methanol, when subjected to photochemical and thermal conditions common in extraterrestrial environments, give rise to a number of organic compounds, the most common of which is HMT. Interstellar ice is rich in methanol. Hypothetically, HMT should be common in water-containing extraterrestrial materials, but, until this study, it had not been detected.

HMT is likely to break apart when exposed to processes commonly used in the analysis of organic compounds in meteorites, and therefore, may not have been detected in other studies even though it was present. The scientists developed a method that specifically extracted HMT from meteorites with minimal breakdown. This method allowed them to isolate significant quantities of HMT and HMT derivatives from the meteorites Murchison, Murray and Tagish Lake.

Since Earth has abundant life, the researchers had to be confident that the HMT found in the meteorites was in fact extraterrestrial, and not just from contamination by terrestrial life. "The Murchison fragment used in this study was from the Chicago Field Museum that had been stored for many years inside a sealed container, and is the least contaminated and most pristine piece of Murchison we have ever studied for amino acids, giving us more confidence that the HMT detected in this meteorite is in fact extraterrestrial in origin," said Daniel Glavin of NASA Goddard, a co-author on the study.

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This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (JP15H05749, JP16H04083, JP17H04862, JP20H00202), the National Aeronautics and Space Administration (NASA) Astrobiology Institute through the Goddard Center for Astrobiology (13-13NAI7-0032), NASA's Planetary Science Division Internal Scientist Funding Program through the Fundamental Laboratory Research (FLaRe) work package at NASA Goddard Space Flight Center, and the Simons Foundation (SCOL award 302497).

Yasuhiro Oba is part of the Astrophysical Chemistry/Ice & Planetary Science Group at the Institute of Low Temperature Science, where he studies chemical evolution of compounds at scales from molecular clouds to planetary systems.

Land ecosystems are becoming less efficient at absorbing CO2

NASA/GODDARD SPACE FLIGHT CENTER

Research News

 

Land ecosystems currently play a key role in mitigating climate change. The more carbon dioxide (CO2) plants and trees absorb during photosynthesis, the process they use to make food, the less CO2 remains trapped in the atmosphere where it can cause temperatures to rise. But scientists have identified an unsettling trend - as levels of CO2 in the atmosphere increase, 86 percent of land ecosystems globally are becoming progressively less efficient at absorbing it.

Because CO2 is a main 'ingredient' that plants need to grow, elevated concentrations of it cause an increase in photosynthesis, and consequently, plant growth - a phenomenon aptly referred to as the CO2 fertilization effect, or CFE. CFE is considered a key factor in the response of vegetation to rising atmospheric CO2 as well as an important mechanism for removing this potent greenhouse gas from our atmosphere - but that may be changing.

For a new study published Dec. 10 in Science, researchers analyzed multiple field, satellite-derived and model-based datasets to better understand what effect increasing levels of CO2 may be having on CFE. Their findings have important implications for the role plants can be expected to play in offsetting climate change in the years to come.

"In this study, by analyzing the best available long-term data from remote sensing and state-of-the-art land-surface models, we have found that since 1982, the global average CFE has decreased steadily from 21 percent to 12 percent per 100 ppm of CO2 in the atmosphere," said Ben Poulter, study co-author and scientist at NASA's Goddard Space Flight Center. "In other words, terrestrial ecosystems are becoming less reliable as a temporary climate change mitigator."

What's Causing It?

Without this feedback between photosynthesis and elevated atmospheric CO2, Poulter said we would have seen climate change occurring at a much more rapid rate. But scientists have been concerned about how long the CO2 Fertilization Effect could be sustained before other limitations on plant growth kick in.

For instance, while an abundance of CO2 won't limit growth, a lack of water, nutrients, or sunlight - the other necessary components of photosynthesis -- will. To determine why the CFE has been decreasing, the study team took the availability of these other elements into account.

"According to our data, what appears to be happening is that there's both a moisture limitation as well as a nutrient limitation coming into play," Poulter said. "In the tropics, there's often just not enough nitrogen or phosphorus, to sustain photosynthesis, and in the high-latitude temperate and boreal regions, soil moisture is now more limiting than air temperature because of recent warming."

In effect, climate change is weakening plants' ability to mitigate further climate change over large areas of the planet.

Next Steps

The international science team found that when remote-sensing observations were taken into account - including vegetation index data from NASA's Advanced Very High Resolution Radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments - the decline in CFE is more substantial than current land-surface models have shown. Poulter says this is because modelers have struggled to account for nutrient feedbacks and soil moisture limitations - due, in part, to a lack of global observations of them.

"By combining decades of remote sensing data like we have done here, we're able to see these limitations on plant growth. As such, the study shows a clear way forward for model development, especially with new remote sensing observations of vegetation traits expected in coming years," he said. "These observations will help advance models to incorporate ecosystem processes, climate and CO2 feedbacks more realistically."

The results of the study also highlight the importance of the role of ecosystems in the global carbon cycle. According to Poulter, going forward, the decreasing carbon-uptake efficiency of land ecosystems means we may see the amount of CO2 remaining in the atmosphere after fossil fuel burning and deforestation start to increase, shrinking the remaining carbon budget.

"What this means is that to avoid 1.5 or 2°C warming and the associated climate impacts, we need to adjust the remaining carbon budget to account for the weakening of the plant CO2 Fertilization Effect," he said. "And because of this weakening, land ecosystems will not be as reliable for climate mitigation in the coming decades."

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More than half of Hudson River tidal marshes were created accidentally by humans

Resilient Against Sea Level Rise UMass Amherst geologist and team studied marshes from Wall Street to Albany

UNIVERSITY OF MASSACHUSETTS AMHERST

Research News

 

IMAGE: THE ARRIVAL OF THE RAILROAD AND ASSOCIATED STRUCTURES IN 1850 ALONG THE BANKS OF NEW YORK'S HUDSON RIVER TIDAL ESTUARY IN SEVERAL AREAS CREATED THE CONDITIONS FOR MARSHES TO FORM.... view more 

CREDIT: COURTESY OF THE DAMS AND SEDIMENT IN THE HUDSON PROJECT

AMHERST, Mass. - In a new study of tidal marsh resilience to sea level rise, geologist and first author Brian Yellen at the University of Massachusetts Amherst and colleagues observed that Hudson River Estuary marshes are growing upward at a rate two to three times faster than sea level rise, "suggesting that they should be resilient to accelerated sea level rise in the future," he says.

Writing in Earth Surface Processes and Landforms, Yellen and colleagues documented that more than half of Hudson River tidal marshes formed since 1850. That year, the channel was straightened and a riverside railroad, berms, jetties and human-made islands of dredged soil were built. This all trapped sediment and created backwaters that often - but not always - turned into marshes, an "unintended result of early industrial development," they state.

"In one case, historical aerial photos document this transition occurring in less than 18 years, offering a timeframe for marsh development," they point out. Yellen's co-authors are colleagues Jonathan Woodruff, Caroline Ladlow and undergraduate Waverly Lau at UMass Amherst, plus Sarah Fernald at New York's department of environmental conservation and David K. Ralston of Woods Hole Oceanographic Institution.

Yellen notes that for this "very collaborative" study, the researchers took advantage of "an experiment that has already happened over decades or centuries. Many of these accidental tidal marshes worked; they protect the shoreline and provide one of the richest ecosystems in terms of direct ecological and human benefits."

Further, marshes are "really useful," he adds - as a first line of defense against coastal flooding, essential habitat for juvenile commercial fish species, they store huge amounts of carbon that mitigates climate change, they provide habitat for migratory birds, filter nutrients coming off the land "and they're beautiful."

Yellen and colleagues write that these tidal wetlands "currently trap roughly 6% of the Hudson River's sediment load. Results indicate that when sediment is readily available, freshwater tidal wetlands can develop relatively rapidly in sheltered settings. The study sites serve as useful examples to help guide future tidal marsh creation and restoration efforts."

Their research involved seven sites spanning more than 100 miles of the Hudson Estuary, "from Wall Street up to Albany," Yellen says. The bays where tidal marshes developed started out six to seven feet deep and have steadily grown vertically. "One concern for marshes globally is that they will be drowned by rising sea level, but this case study shows how marshes can be created and it gave us some timing benchmarks for what is considered a tricky ecosystem restoration," he adds.

The researchers used two main methods to investigate the river's history and resilience in the face of sea level rise - sediment cores that shed light on how fast sediment accumulated and historical maps, charts and aerial photos to determine how the sites have changed over time. Yellen summarizes, "As long as there is space for sediment to accumulate, new marshes can develop. There is a community of land trusts up and down the river who are planning now for future sea level rise and considering where new marshes can form. This research will help them and state agencies guide land acquisition and land conservation strategies adjacent to the river to 2100 and beyond."

The research, part of the Dams and Sediment in the Hudson (DaSH) project, was supported by a grant to Ralston from NOAA's National Estuarine Research Reserve Collaborative, plus the U.S. Geological Survey and the Department of Interior Northeast Climate Adaptation Science Center at UMass Amherst.

Also, Lau received a Polgar Fellowship from the Hudson River Foundation for her senior thesis project. She took the lead on one of the sites and made a short film about tidal marshes around the world and the Hudson River marsh near her home in Queens.

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NASA finds what a glacier's slope reveals about Greenland Ice Sheet thinning

NASA/GODDARD SPACE FLIGHT CENTER

Research News 

IMAGE: GIF SHOWING THE POTENTIAL DISTANCES OVER WHICH THINNING CAN SPREAD INTO GREENLAND'S INTERIOR. GLACIERS IN REGIONS OF HIGHER ELEVATION, TEND TO PERVADE LESS INLAND THAN THOSE IN REGIONS OF LOWER... view more 

CREDIT: CREDITS: DENIS FELIKSON

As glaciers flow outward from the Greenland Ice Sheet, what lies beneath them offers clues to their role in future ice thinning and sea-level rise contribution.

Outlet glaciers are rivers of ice flowing within the cracks of the bedrock and draining into the surrounding sea. They retreat and start to thin as climate warms, and this thinning works its way toward the center of the ice sheet. Now, by looking at the bed topography beneath the ice, scientists have a better understanding of which glaciers could have a significant impact on the Greenland Ice Sheet's contribution to sea-level rise in coming years. They found that some glaciers flowing over gentler slopes could have a greater impact than previously thought. The gentle slopes allow thinning to spread from the edge of the ice sheet far into the interior, whereas glaciers with steep drops in their bed topographies limit how far into the interior thinning can spread.

The research, which was published December 11th in Geophysical Research Letters, analyzed 141 outlet glaciers on the Greenland Ice Sheet to predict how far into the interior thinning may spread along their flow lines, starting from the ocean edge.

"What we discovered is some glaciers flow over these steep drops in the bed, and some don't," said lead author Denis Felikson with NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the Universities Space Research Association (USRA). "For the glaciers that do have that steep drop in the bed, thinning can't make its way past those drops." Borrowing a term from geomorphology - the study of Earth's physical features - they coined these steep drop features "knickpoints."

When a river flows over a knickpoint, it often results in a waterfall or a lake. But for glaciers, steep is a relative term which in reality translates to just about three degrees of incline. "It's not like the ice is going over a cliff," said Felikson. "But in terms of glacier dynamics, they are very steep - an order of magnitude more steep than a typical bed that the ice flows over."

The researchers were able to identify these "steep" changes in topography using digital elevation models of the ice sheet bed and surface topography. Surface topography came from the Greenland Ice Mapping Project, created using NASA's Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument that flies aboard NASA's Terra satellite, in conjunction with data from NASA's Ice, Cloud, and land Elevation Satellite (ICESat) mission. The bed topography digital elevation model, known as the BedMachine data set, is a high-resolution model of the bed beneath the Greenland Ice Sheet, created using data from NASA's Operation IceBridge airborne surveys of polar ice.

"This bed topography data set was critical to us doing our work," Felikson said. "And it is thanks to NASA remote sensing, namely the Operation IceBridge surveys, that we were able to do this." Using the remote sensing data, scientists were able to compare topography measures to produce a single metric along a glacier's flow line. This helped them identify a break point between the upstream and downstream parts of the glacial ice.

Ice below the knickpoint is susceptible to thinning from the glacier's edge. But the thinning does not extend beyond this point upstream, so the interior of the ice sheet is not impacted.

Of all the glaciers observed, a majority (65 percent) had discernable knickpoints. Especially steep knickpoints are prevalent in the more mountainous regions of Greenland, where several of the biggest and fastest moving glaciers also show knickpoints that are relatively close to the coast. By sheer size alone these glaciers could contribute significantly to ice sheet thinning and melt, but because their knickpoints are near the coast, thinning is not expected to spread far inland.

However, glaciers that flow through gentle topography are found to either have gradual knickpoints, or no knickpoint at all. Such glaciers are of interest, and concern, because even those that are smaller in size have the potential to let thinning expand hundreds of kilometers inland, eroding the heart of the ice sheet.

"They could be impactful in terms of sea level rise, not because they are big and deep, but because they have access to more ice that they can eat away," said Felikson. "It will take them a lot longer to respond, but over the long term they could end up contributing just as much to sea level rise, maybe, as the big glaciers."

Over the gentle topography of the northwest coast of Greenland, nine of twelve neighboring glaciers are predicted to thin more than 250 km (155.3 miles) into the interior of the ice sheet, over a ?140-km (86.9 mile) wide region. The northwest sector of the ice sheet is also the only region experiencing an ongoing increase in ice discharge over the last couple decades, and Felikson predicts that it will continue to do so given the characteristics of these glaciers.

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This work was started at the University of Texas as part of Felikson's dissertation and has continued throughout his time at NASA Goddard. The origins of knickpoints and their implications for long-term thinning, as well as Greenland's overall contribution to sea level rise, remain the basis for future research.

The data used in this study is available at:
https://zenodo.org/record/4284759

Ice sheet uncertainties could mean sea level will rise more than predicted

IMPERIAL COLLEGE LONDON

Research News

 

Sea level could rise higher than current estimates by 2100 if climate change is unchallenged, according to a new assessment.

Its authors say understanding the way strong global heating affects polar ice sheets will be crucial to projecting sea level rise over the next century. However, uncertainties remain and current knowledge about ice sheets suggests sea-level rise under continued strong warming could be higher than the Intergovernmental Panel on Climate Change (IPCC) 'likely' range by 2100.

The authors of the study, published today in the journal One Earth, also suggest ways scientists can make predictions more certain, by improving our understanding of ice-sheet dynamics, such as how they interact with warming oceans and how they fracture and break apart.

Lead author Professor Martin Siegert, from the Grantham Institute - Climate Change and Environment at Imperial College London, said: "Greenhouse gas emissions are still on the rise, and strong heating, of more than 4°C by 2100, is well within the realm of the possible if emissions continue unabated.

"Currently, hundreds of millions of people live in regions susceptible to coastal flooding, and the likelihood of even worse flooding will significantly increase with severe sea-level rise. The sea-level rise we have already faced has been somewhat mitigated by flood barriers and other measures, but we are unprepared for higher rates of rise that could overwhelm these measures. If we don't do more to avert dangerous global heating, we may reach a point where we can no longer protect people."

The team reviewed current models of the effect of warming on ice sheets that the IPCC's 2019 report on sea-level rise relies on. For the strong heating scenario of more than 4°C of temperature rise by 2100, the report gave a 'likely' range for sea-level rise of between 0.61 and 1.10 metres above 1950 levels.

However, the team's analysis showed that ice sheet models do not include sufficient detail on key processes that may lead to significant mass loss under strong warming, meaning sea level rise above the IPCC's likely range is far more possible than below it.

Co-author John Englander, President and Founder of the Rising Seas Institute, said: "Sea-level rise will be one of the most challenging issues faced by society in the coming decades. We need to recognize that we cannot stand by and wait for clarity about actual sea-level rise to begin planning for it.

"Waiting for better confidence in predictions is not a reason to delay building a margin of safety, for example into building codes and zoning, recognising the inevitability of sea-level rise and its catastrophic implications."

There are two main ways sea level can rise substantially at a global level. Throughout the twentieth century, rise has been dominated by thermal expansion - added heat driving water molecules apart, expanding the volume of the ocean water. In the twenty-first century, however, the second mechanism has become dominant: the addition of water from melting ice sheets and glaciers.

While sea-level rise due to thermal expansion can be predicted using relatively simple relationships between the temperature and the expansion, ice sheets and glaciers respond to rising temperatures in complex and interconnected ways that make prediction more fraught.

Researchers looking ahead to the next century of climate change and its increasing impact on human society, nature and the environment often look back at previous episodes of natural climate change for clues as to how various earth systems will react.

At the end of the last ice age, there is evidence that ice sheets responded to warming by rapidly losing mass at rates that at times were higher than currently observed, leading to several metres of sea-level rise per century.

The team say this means current projections of sea-level rise may be underestimates, as the ice sheets may lose mass faster over the coming century than our current models predict.

To improve models and predictions, the authors identify key areas of research that are needed to fill in our gaps in knowledge. These include better mapping of the ground beneath glaciers and ice sheets, collection of data at the margin where glaciers meet the ocean, and improved coupling of models of the atmosphere, oceans, and ice sheets.

While the network of existing observations of ice sheet dynamics already gives scientists a very strong warning signal and causes for concern, the authors say these improvements could lead to a next-generation 'early warning system' focused on signals of rapid change in sea level, such as increases in ocean water temperature along the margins of ice sheets.

Professor Siegert said: "We already have a good start on an early warning system for dangerous sea-level rise, with satellites, airborne platforms, robotic devices, field investigators, and expert knowledge. While this network is growing and getting stronger, it has major weaknesses at ice-sheet boundaries that require urgent action. We need to develop an array of robotic devices in key parts of Antarctica and Greenland that are most vulnerable and capable of rapid sea-level rise in the future."

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