Saturday, February 15, 2020

Blue Acceleration: Capitalism’s Growing Assault on the Oceans
By Ian Angus, originally published by Climate and Capitalism
“A new phase in humanity’s relationship with the biosphere, where the ocean is not only crucial but is being fundamentally changed”

Capitalism’s inherent drive to expand went into overdrive in the mid-20th century. Long-term socioeconomic and Earth System trends, graphed fifteen years ago and updated in 2015, show nearly simultaneous hockey stick upturns in about 1950.
GREAT ACCELERATION, 2015 update

Called the Great Acceleration, the speed-up is driving what Earth System scientists describe as “the most rapid transformation of the human relationship with the natural world in the history of humankind.”[1] It marks the beginning of a new historical and geological epoch, the Anthropocene — a time when “human activities have become so pervasive and profound that they rival the great forces of nature and are pushing the Earth into planetary terra incognita.”[2]
Long ago, Marx and Engels showed that capitalism can never stand still or rest content in one place. In obedience to its first commandment — Accumulate, accumulate! — “it must nestle everywhere, settle everywhere, establish connections everywhere.”[3] So it is not surprising that the trends identified in great acceleration research haven’t just continued, they have continued to accelerate. Capital, never content with expanding existing operations, constantly seeks new places and resources to exploit.
It is sometimes suggested that because capitalism has occupied the whole world, there are no more frontiers and no new sources of cheap resources — so peak appropriation has passed, sending the system into terminal decline. Such arguments misunderstand and underestimate the system’s compulsion to find new sources of profit. As Marx wrote, for capitalism, “every limit appears as a barrier to be overcome.” It always strives “to tear down every spatial barrier … and conquer the whole earth.”[4]
The world’s continents and islands may be fully occupied, but 71% of the planet is still mostly unexplored and underexploited. A new study by scientists associated with the Stockholm Resilience Centre shows that capitalism is now assaulting a new frontier — on, in, and under water.
Blue Acceleration
“The Blue Acceleration: The Trajectory of Human Expansion into the Ocean,” published in January in the journal One Earth, describes and graphs capital’s growing drive to industrialize the oceans and sea beds. Commercial activity in the oceans is expanding rapidly, and “considerable investments … are driving growth in existing industries and the emergence of new ones, spanning an increasingly diverse range of activities.”[5]
The authors believe that the blue acceleration marks the beginning of “a new phase in humanity’s relationship with the biosphere, where the ocean is not only crucial for sustaining global development trajectories but is being fundamentally changed in the process.”[6]
They illustrate that claim with 12 graphs that look much like the great acceleration graphs, but with the hockey-stick upturns occurring five decades later.

BLUE ACCELERATION. Global trends in (A) marine aquaculture production; (B) deep offshore hydrocarbon production, including gas, crude oil, and natural gas liquids below 125 m; (C) total area of seabed under mining contract in areas beyond national jurisdiction; (D) cumulative contracted seawater desalination capacity; (E) accumulated number of marine genetic sequences associated with a patent with international protection; (F) accumulated number of casts added to the World Ocean Database; (G) container port traffic measured in Twenty-Foot Equivalent Units; (H) total length of submarine fiber optic cables; (I) number of cruise passengers; (J) cumulative offshore wind energy capacity installed; (K) total marine area protected; (L) total area of claimed extended continental shelf.

The first two graphs are particularly powerful illustrations of efforts to overcome limits by moving capital and production to previously unexploited locations, and to obtain resources using new techniques and technologies.
Graph A, Marine Aquacultureshows the spectacular growth of fish farming, which was inconsequential in 1970, but now accounts for nearly 50% of all fish eaten by humans. In the open ocean, wild fish catches have been falling since the 1990s, but that decline has been more than offset by aquaculture, mainly located in coastal areas. Total fish production is larger than ever and fish processing is growing faster than any other food industry.[7]

Aquaculture grew 10% a year in the late 20th century, and is growing 5.8% a year now. UN Food and Agriculture Organization, The State of the World Fisheries and Aquaculture 2018, 2.

Graph B, Deep Hydrocarbons, shows oil and gas production from more than 125 meters below the ocean surface. Off-shore extraction already comprises 30% of worldwide oil production, and “as shallow-water fields become depleted and novel technologies emerge, production is moving towards greater depths and new territories, including the Arctic where vast undiscovered oil and gas reserves are expected.” There is also growing industry interest in deposits of natural gas hydrates (crystalized methane) buried kilometers below the ocean floor, that “may represent twice as much organic carbon as the world’s coal, oil and other forms of natural gas combined.” [8]
Many of the blue acceleration trends involve new technology. A co-author of the report points out that “the marine biotechnology sector scarcely existed at the end of the 20th century, and over 99% of genetic sequences from marine organisms found in patents were registered since 2000.”[9]
More generally, as the One Earth article says, “the combination of increasing global demand, technological progress, and declining land-based sources have made extraction of a growing number of ocean materials not only feasible but economically viable.”
“Costly endeavors such as commercial mining of the deep seabed are now considered not only feasible but imminent. Likewise, the search for novel bioactive compounds to address antimicrobial resistance is increasingly focused on remote deep-sea microorganisms, whereas space constraints on land have contributed to the construction of large-scale offshore wind farms and investment in deep-water installations. …[10]
Today, offshore production of oil and gas is by far the most lucrative part of the ocean economy, while sand and gravel for construction are the most-extracted offshore minerals, by volume. Deep sea mining has yet to start, but the International Seabed Authority has already issued 29 mineral and metal mining licenses covering 1.3 million square kilometers of ocean floor.[11]
DeepGreen Metals, based in Canada, claims that the area of the Pacific Ocean seabed covered by its license is “one of the largest undeveloped cobalt, nickel, and manganese resources on the planet.”[12]

Deep-sea mining companies plan to use immense remote-controlled machines to scrape the sea bed, capture minerals, and dump the leftover sludge. The process will kill uncountable organisms in and beyond the mining zones.

The equipment used directly to extract or produce food, fuel and minerals is only part of the story. Blue acceleration industries also require ever increasing amounts of surface and coastal space for infrastructure, including port facilities, fishing boats, fish farms, offshore platforms, and deep-sea mining equipment. In coming years, such installations may be weakened, if not overwhelmed, by rising sea levels and increasingly powerful storms.
Accelerating Destruction
Of course, human societies have used ocean resources for thousands of years, but the blue acceleration appears to mark a new departure.
“The current rush for the ocean is unfolding with unprecedented diversity and intensity. … The multitude of claims that collectively illustrate the blue acceleration exhibit a phenomenal rate of change over the last 50 years, with a sharp acceleration characterizing the onset of the 21st century.”[13]
Three of the great acceleration trends identified in 2004 were ocean-related: aquaculture, ocean acidification, and marine fish capture. The first two continue to grow exponentially, while fish capture has begun to decline only because overfishing has all but wiped out major fish populations. Combined with greenhouse gas emissions and uncounted other pollutants, the impact of those trends has been dire. Noted conservation biologist Callum Roberts writes that we face “the prospect of seas so compromised that they no longer sustain the ecological processes that we take for granted and upon which our comfort, pleasure, and perhaps even our very existence depends.”[14]
The blue acceleration study shows that the great acceleration is receiving new impetus from ocean industrialization, which is “paving the way for new risks to emerge and regime changes to occur … [and creating] conditions for unknown thresholds to be crossed.”[15]
The danger of unpredictable and unpreventable damage is all the greater because so little is known about life and ecology in the deep sea. The far side of the Moon has been better mapped than 95% of the ocean floor, and only a tiny minority of sea-dwelling organisms have been identified, let alone studied.
Nevertheless, cheerleaders for deep ocean development promise all will be well. The World Bank, for example, says that the blue economy will “promote economic growth, social inclusion, and the preservation or improvement of livelihoods while at the same time ensuring environmental sustainability of the oceans and coastal areas.”[16] Fine words, but it has little to say about how the oceans can be protected in practice.
In fact, as Mark Hannington of the prestigious Helmholtz Centre for Ocean Research told the OECD, sea floor mining will inevitably cause environmental damage, and no one knows how to minimize it.
“Even the most careful deep-sea mining will disturb the marine environment. The generally held view is that industrial-scale mining will inflict a range of harm that will irreversibly alter the deep oceans, but as yet there is no clear picture of what those impacts might be. …
“It is difficult to know what regulatory regime should be put in place to address environmental impacts in areas that have never been mapped or even visited to protect them against harm that is still largely unknown and might not happen for decades to come.”[17]
A recent article in the journal Nature is more blunt: “The scarce data that exist suggest that deep-sea mining will have devastating, and potentially irreversible, impacts on marine life.”[18]
The danger of allowing profit-hungry corporations to dig for minerals and drill for oil in the deep ocean was shown dramatically in 2010, when the world’s deepest oil well exploded, killing 11 workers and releasing 4.9 billion gallons of oil into the Gulf of Mexico. As the Obama-appointed commission into the Deepwater Horizon disaster concluded, the actions of BP, Halliburton, and Transocean “reveal such systematic failures in risk management that they place in doubt the safety culture of the entire industry.”[19]
If past experience with mining and fossil fuel companies is anything to go by, no one should trust their pious promises of environmentally responsible behavior in deep water.
+ + + +
It is impossible to overstate the importance of the oceans to Earth’s life support systems. Ocean-based organisms produce more than half of the oxygen we breathe — far more than tropical forests. Almost all of the rain that makes plant life possible originates in the oceans, which contain 97% of the planet’s water. They help stabilize the climate by absorbing 50 times more carbon dioxide than the atmosphere, and by transporting warm water away from the tropics. They are the primary source of protein for a billion people, and an important source for three billion more. The great biogeochemical cycles at the heart of Earth’s global metabolism depend on healthy oceans.
A rational society, conscious of those facts, would carefully manage its relationship with the oceans, always applying the precautionary principle and giving top priority to the protection and regeneration of essential ecosystems.
But we don’t live in a rational society. As Michael Parenti writes, capitalism has very different priorities.
“The essence of capitalism, its raison d’etre, is to convert nature into commodities and commodities into capital, transforming the living earth into inanimate wealth. This capital accumulation process wreaks havoc upon the global ecological system. It treats the planet’s life-sustaining resources (arable land, groundwater, wetlands, forests, fisheries, ocean beds, rivers, air quality) as dispensable ingredients of limitless supply, to be consumed or toxified at will.”[20]
That is precisely what the blue acceleration represents: a drive to accumulate capital by enclosing, exploiting and commoditizing the oceans. For seventy years, Earth has been accelerating out of the Holocene into the Anthropocene, where environmental disasters loom. Now capitalism’s hell-bound train is speeding up, fueled by accelerating ocean development.
The case for ridding the world of this deadly system has never been stronger.

Notes
[1] Will Steffen et al., Global Change and the Earth System: A Planet under Pressure (Springer , 2005), 131. Will Steffen et al., “The Trajectory of the Anthropocene: the Great Acceleration,” Anthropocene Review, April 2015, 81-88.
[2] Will Steffen, Paul J. Crutzen, and John R. McNeil, “The Anthropocene: Are Humans Now Overwhelming The Great Forces Of Nature?” Ambio 38, no. 8 (2011), 614. The new epoch has not yet been formally recognized, but, as the Anthropocene Working Group points out, “the Anthropocene already has a robust geological basis, is in widespread use, and indeed is becoming a central, integrating concept in the consideration of global change.”
[3] Karl Marx, Capital, vol.1, (Penguin, 1976), 742; Karl Marx and Frederick Engels, Manifesto of the Communist Party.
[4] Karl Marx, Grundisse, (Penguin, 1973), 408, 539.
[5] Jean-Baptiste Jouffray, Robert Blasiak, Albert V. Norström, Henrik Österblom, and Magnus Nyström. “The Blue Acceleration: The Trajectory of Human Expansion into the Ocean,” One Earth, vol. 2/1, January 24, 2020
[6] Jouffray et al., “Blue Acceleration,”  46.
[7] FAO, The State of World Fisheries and Aquaculture 2018. Nearly half of the fish consumed by humans today comes from fish farms.
[8] Jouffray et al., “Blue Acceleration,” Supplemental Information , 3.
[9] Robert Blasiak, “Blue Acceleration: our dash for ocean resources mirrors what we’ve already done to the land,” The Conversation, January 24, 2020.
[10] Jouffray et al., “Blue Acceleration,” 45, 43.
[11] The International Seabed Authority was created in 1994 by the United Nations Convention of the Law of the Sea. It is supposed to both protect the deep sea environment and promote economic development. In practice it has given priority to development.
[12] DeepGreen, Media Release, September 24, 2018.
[13] Jouffray et al., “Blue Acceleration,” 46.
[14] Callum Roberts, The Ocean of Life: The Fate of Man and the Sea (New York: Penguin, 2013), 215.
[15] Jouffray et al., “Blue Acceleration,”  48.
[16] World Bank, The Potential of the Blue Economy (Washington, 2017), v
[17] quoted in OECD, The Ocean Economy in 2030 (Paris: OECD Publishing, 2016), 155.
[18] Olive Heffernan, “Seabed mining is coming — bringing mineral riches and fears of epic extinctions,” Nature 571 (July 25, 2019), 466.
[19] National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling, Deep Water: The Gulf Oil Disaster and the Future of Offshore Drilling, 2011, vii.
[20] Michael Parenti, Blackshirts and Reds, (San Francisco: City Lights Books, 1977) 154-55

Scientists discover largest bacteria-eating virus. It blurs line between living and nonliving.

An illustration of bacteriophages invading a bacteria.
(Image: © Shutterstock)
Huge bacteria-killing viruses lurk in ecosystems around the world from hot springs to freshwater lakes and rivers. Now, a group of researchers has discovered some of these so-called bacteriophages that are so large and so complex that they blur the line between living and nonliving, according to new findings.
Bacteriophages, or "phages" for short, are viruses that specifically infect bacteria. Phages and other viruses are not considered living organisms because they can't carry out biological processes without the help and cellular machinery of another organism.


That doesn't mean they are innocuous: Phages are major drivers of ecosystem change because they prey on populations of bacteria, alter their metabolism, spread antibiotic resistance and carry compounds that cause disease in animals and humans, according to the researchers in a new study, published Feb. 12 in the journal Nature
To learn more about these sneaky invaders, the researchers searched through a DNA database that they created from samples they and their colleagues collected from nearly 30 different environments around the world, ranging from the guts of people and Alaskan moose to a South African bioreactor and a Tibetan hot spring, according to a statement.
From that DNA, they discovered 351 huge phages that had genomes four or more times larger than the average genome of phages. Among those was the largest phage found to date with a genome of 735,000 base pairs — the pairs of nucleotides that make up the rungs of the DNA molecule's "ladder" structure — or nearly 15 times larger than the average phage. (The human genome contains about 3 billion base pairs.)
These phages are "hybrids between what we think of as traditional viruses and traditional living organisms," such as bacteria and archaea, senior author Jill Banfield, a University of California, Berkeley, professor of Earth and planetary science and of environmental science, policy and management, said in the statement. This huge phages' genome is much larger than the genomes of many bacteria, according to the statement. 
The authors found that many of the genes coded for proteins that are yet unknown to us. They found that the phages had a number of genes that are not typical of viruses but are typical of bacteria, according to the statement. Some of these genes are part of a system that bacteria use to fight viruses (and was later adapted by humans to edit genes, a technique called CRISPR-Cas9). 
Scientists don't know for sure, but they think that once these phages inject their DNA into bacteria, the phages' own CRISPR system strengthens the CRISPR system of the bacteria. In that way, the combined CRISPR system could help to target other phages (getting rid of the competition).
What's more, they found that some of the phages had genes that coded for proteins necessary for the functioning of ribosomes — a cellular machine that translates genetic material into proteins (the proteins are the molecules that carry out DNA's instructions). These proteins aren't typically found in viruses, but they are found in bacteria and archaea, according to the statement. 
Some of these newfound phages may also use the ribosomes in their bacteria host to make more copies of their own proteins, according to the statement. 
"Typically, what separates life from nonlife is to have ribosomes and the ability to do translation; that is one of the major defining features that separate viruses and bacteria, nonlife and life," co-lead author Rohan Sachdeva, a research associate at UC Berkeley, said in the statement. "Some large phages have a lot of this translational machinery, so they are blurring the line a bit."

This bizarre virus has genes never seen before

 
The newly discovered "Yaravirus" contains genes that have never been seen in any other viruses. (Image: © IHU Aix Marseille University and Microscopy Center/UFMG)

Our planet is teeming with mysterious microbes. Now, in the waters of an artificial lake, scientists may have discovered one of the most mysterious of all: a brand-new virus with genes that have never been seen before.

A couple of years ago, the group collected water samples from the creeks of Lake Pampulha, an artificial lagoon in the city of Belo Horizonte in Brazil, in search of giant viruses — or those with massive genomes — that infect single-celled organisms called amoebas. But when the team went back to the lab and added these samples to amoeba cells to try to catch giant viruses in their attempt to infect the cells, they found a much smaller intruder.

"It was really a big surprise since so far we only know giant viruses infecting amoebas, not small viruses," said senior author Jônatas Abrahão, an associate professor in the microbiology department of the Federal University of Minas Gerais in Brazil. This new virus was only around 80 nanometers in diameter, but all amoeba-infecting viruses that we know of to date are much larger, at more than 200 nanometers, Abrahão told Live Science

The researchers named the tiny virus the "Yaravirus" after "Yara," the mother of waters — an important character in the mythological stories of the Tupi-Guarani indigenous tribes, according to the study.

When the researchers analyzed the microbe's genome, they found that most of them had never been seen in any other viruses. They searched for the Yaravirus' gene signature in thousands of environmental genomic data and found no hint, "indicating how rare this virus is," Abrahão said.

Only six out of 74 genes showed some degree of similarity to other known genes, he added. Some of the known genes are also known to be present in giant viruses — but because Yaravirus is both small in size and genome, it's not a giant virus, Abrahão said. Yet, it infects amoebas like giant viruses do.

"This is one of the reasons why this new virus is so intriguing and we claim that it challenges the classification of DNA viruses," Abrahão said. What's more, DNA viruses are classified based on the protein that makes up their shell, or capsid. The Yaravirus' capsid doesn't resemble any previously known protein. It's also unclear when and where this virus originated and evolved.

"It would be necessary to isolate new viruses similar to Yaravirus to improve our analysis and try to define their origin," he said. Though they isolated the virus only recently, it is possible this virus has been circulating on Earth for ages, Abrahão said.

In any case, Yaravirus doesn't infect human cells.

"If we consider all known viruses by now, we can say that most of them do not represent any threat for our health," Abrahão said. But that doesn't mean we shouldn't care about them. "Viruses are extremely important in [the] environment," helping with nutrient recycling or controlling pests, Abrahão said.

The group hopes to further analyze the features of the virus in an effort to understand how it interacts with amoebas and other potential hosts, and to figure out the microbe's origin and how it evolved. And this study shows "we know only a very small fraction of this diversity" of viruses present on our planet, Abrahão said. "There is still a lot to explore."

This study has not yet been peer-reviewed and was posted online Jan. 28 to the BioRxiv database.

A mysterious 80 nm amoeba virus with a near-complete “ORFan genome” challenges the classification of DNA viruses

Paulo V. M. Boratto, Graziele P. Oliveira, Talita B. Machado, Ana Cláudia S. P. Andrade, Jean-Pierre Baudoin, Thomas Klose, Frederik Schulz, Saïd Azza, Philippe Decloquement, Eric Chabrière, Philippe Colson, Anthony Levasseur, Bernard La Scola, Jônatas S. Abrahão

Abstract
Here we report the discovery of Yaravirus, a new lineage of amoebal virus with a puzzling origin and phylogeny. Yaravirus presents 80 nm-sized particles and a 44,924 bp dsDNA genome encoding for 74 predicted proteins. More than 90% (68) of Yaravirus predicted genes have never been described before, representing ORFans. Only six genes had distant homologs in public databases: an exonuclease/recombinase, a packaging-ATPase, a bifunctional DNA primase/polymerase and three hypothetical proteins. Furthermore, we were not able to retrieve viral genomes closely related to Yaravirus in 8,535 publicly available metagenomes spanning diverse habitats around the globe. 

The Yaravirus genome also contained six types of tRNAs that did not match commonly used codons. Proteomics revealed that Yaravirus particles contain 26 viral proteins, one of which potentially representing a novel capsid protein with no significant homology with NCLDV major capsid proteins but with a predicted double-jelly roll domain. Yaravirus expands our knowledge of the diversity of DNA viruses. The phylogenetic distance between Yaravirus and all other viruses highlights our still preliminary assessment of the genomic diversity of eukaryotic viruses, reinforcing the need for the isolation of new viruses of protists.

Significance statement Most of the known viruses of amoeba have been seen to share many features that eventually prompted authors to classify them into common evolutionary groups. Here we describe Yaravirus, an entity that could represent either the first isolated virus of Acanthamoeba spp. out of the group of NCLDVs or, in alternative evolutive scenario, it is a distant and extremely reduced virus of this group. Contrary to what is observed in other isolated viruses of amoeba, Yaravirus is not represented by a large/giant particle and a complex genome, but at the same time carries an important number of previously undescribed genes, including one encoding a novel major capsid protein. Metagenomic approaches also testified for the rarity of Yaravirus in the environment.



A Climate of Emergence
By Jasmine Dale, originally published by Permaculture Association

February 14, 2020

A version of this article originally appeared in Permaculture Works, adaptation issue. Permaculture Works is the membership journal of the Permaculture Association – one of the many benefits of membership.
A combination of forces has now brought the ‘climate emergency’ to mass public attention. Banks, corporations and governments are climbing on board daily as I write, lining up to fight the War on Carbon.
Suddenly, we find ourselves in a situation, where moments ago ecological concerns were sidelined and now it’s official: there is an emergency; “our house is on fire”. How do we adapt to this change?
Hear the language of the emergency? Is it to galvanise progressive change or engender fear? I’ve been in a few emergencies. I’ve even been in a house on fire. Clear thinking and quick strategic action were required. Fear and panic are highly contagious and are not helpful in an emergency. I’m noticing even committed permies around me are doubting whether our methods and principles are enough to avert catastrophe.
For some years, within climate negotiations, powerful corporate interests have cited the need to stimulate an emergency through social media to release huge public investment for their solutions and to create new markets.1 For campaigners, it makes sense to be aware of the policies and ecologically disastrous technologies on the negotiating table to achieve a zero-carbon world by 2025. Many proposals for the Beijing summit in 2019 were the polar opposite to the work the permaculture movement is committed to.
So, how are we to adapt to a ‘climate emergency’ in the face of such overwhelming forces? A key permaculture attitude of turning a problem into a solution seems useful. Rising awareness is germinating a climate of emergence, a new sensitivity to ecological crises, which insists on new ways of doing everything, very fast. With social media and television flooded by the issues, many people are awakening to the fragility of our life support systems and may be unaware of existing viable solutions. Let’s work with this edge, help people to adapt and not panic. Clear thinking, discernment and strategic action. The kind of designing and creating we’ve all been doing.
Nationally, CTRLshift is connecting up many like-minded groups, working hard to form a co-ordinated policy voice. It’s making an impressive leap towards integrating hundreds of grassroots groups into an effective ecosystem, strengthening the social mycelia that can support an alternative system at scale.
Closer to home, keep talking to people, strengthening a clear vision (a 2020 Vision!). Imagining the possibility of a route out of this crisis and that another world is possible, is vital to designing it and overcoming despair. Encourage people to engage in local projects that work practically towards positive outcomes. Within ourselves, stay centred and connected to the living earth all around us.
In an era of fake news and a context of a multi-trillion dollar market being created, interrogate climate strategy and policy. Query how will it create thrival for people and ecosystems? Ask who profits? I don’t know what complex processes that feedback over millennia will do in the future, although I do know that permaculture works.

Nitrogen-fixing trees help tropical forests grow faster and store more carbon

Tropical forests are allies in the fight against climate change. Growing trees absorb carbon emissions and store them as woody biomass. As a result, reforestation of land once cleared for logging, mining, and agriculture is seen as a powerful tool for locking up large amounts of carbon emissions throughout the South American tropics.
But new research published in Nature Communications shows that the ability of tropical forests to lock up carbon depends upon a group of  that possess a unique talent—the ability to fix nitrogen from the atmosphere.
The study modeled how the mix of tree species growing in a tropical forest following a disturbance, such as clearcutting, can affect the forest's ability to sequester carbon. The team found that the presence of trees that fix nitrogen could double the amount of carbon a forest stores in its first 30 years of regrowth. At maturity, forests with  took up 10% more carbon than forests without.
Sarah Batterman, a Research Fellow at Cary Institute of Ecosystem Studies and coauthor on the paper, explains, "We want to use this work to guide tropical reforestation to optimize carbon uptake and resiliency. This requires understanding what mix of trees is needed to maximize long-term carbon storage while withstanding future climatic conditions. Our findings suggest that nitrogen-fixing trees are a key ingredient in the reforestation recipe."
Nitrogen-fixing plants partner with soil microbes to turn atmospheric nitrogen gas into a form of nitrogen that is available to fuel plant growth. Through these interactions, nitrogen fixers are able to self-fertilize. This adaptation gives them an edge in recently cleared, early succession tropical soils that are nitrogen-poor. Fixers also help fertilize nearby plants when they shed their leaves and return nitrogen to the soil.
In the tropics, nitrogen-fixing trees are common, but they can be relatively rare in newly recovering forests. Their large, nutrient-packed seeds are often dispersed by wildlife. Having animal dispersed seeds is a disadvantage in the early stages of forest regrowth, when animals that once lived in the forest have not yet returned. Planting fixers as part of reforestation efforts could boost forest development and carbon accumulation.
Batterman says, "To understand the function of nitrogen-fixing trees in a tropical forest, we need to isolate their effects. We can't do that in a real forest because adding or removing trees would alter other aspects of the ecosystem, such as light availability, which would skew findings. It would also take decades to centuries to measure. Instead, we developed a model to quantify ecosystem processes, like nitrogen cycling, that affect forest growth and carbon sequestration."
A patch of pasture next to rainforests at different stages of recovery from deforestation in Panama. To maintain pasture in this area, tree seedlings must be cut back by hand several times a year. This image shows how quickly trees can recover if they are given the chance and nitrogen-fixing species are present. Credit: Sarah Batterman
Nitrogen-fixing trees help tropical forests grow faster and store more carbon
Using data collected at 112 tropical forest plots in Panama—a record which includes data on over 13,000 individual trees ranging in age from five to 300 years post-disturbance—the research team developed a model that represents interactions among soil, plants, and nutrients at the scale of individual trees. The model accounts for competition between plants for light and nutrients, nutrient cycling between plants and the soil, and tree-level nitrogen fixation.
Trees were classified into four groups that are unique to different stages of forest regrowth, including early-, mid-, and late-successional species, plus nitrogen fixers. By changing the ability of trees to fix nitrogen in their model, the team was able to predict how fast carbon accumulated in a forest and how much carbon it was able to store.
Batterman explains: "Forests with nitrogen-fixing trees grow more rapidly in early succession and have a higher carbon storage potential than forests without nitrogen fixers. They also recover faster when confronted with disturbances."
To quantify nitrogen cycling in tropical forests, many existing models use ecosystem-wide parameters such as evapotranspiration and net primary production to estimate nitrogen fixation fluxes. These models tend to overestimate the amount of nitrogen in the system.
Lead author Jennifer Levy-Varon, who worked on the study while a Postdoctoral Research Associate at Princeton University, says, "Our model is unique because instead of looking at ecosystem-wide processes and using those to estimate nitrogen fluxes, we're honing in on individual trees. This gives us a more accurate understanding of nitrogen-fixers' contributions to the  nitrogen budget and associated carbon sequestration."
To put the importance of nitrogen-fixing trees in context, the team used their model to predict how much additional carbon could be stored in reforested areas in tropical countries based on acreage pledged under the Bonn Challenge.
"The Bonn Challenge is an international effort to reforest 350 million hectares of land by 2030. We found that by including -fixing trees in these efforts, tropical countries could sequester an additional 6.7Gt of carbon dioxide over the next 20 years. To give that number some context, 6.4Gt was the total amount of CO2 equivalents emitted in the US in 2017. It's comparable to driving 15.6 trillion miles, which is about 5 years of US vehicle emissions," says Batterman.
Coauthor Lars Hedin, Professor of Ecology and Evolutionary Biology at Princeton University, concludes, "This model gets us closer to understanding the importance of  in the global carbon cycle, and their role in removing the greenhouse gas  dioxide from the atmosphere."Ecologists find how forest age affects the accumulation of carbon in the soil

More information: Jennifer H. Levy-Varon et al, Tropical carbon sink accelerated by symbiotic dinitrogen fixation, Nature Communications (2019). DOI: 10.1038/s41467-019-13656-7