Is Gaia going to die of heat stroke?

 

Figure from the recent paper by Duffy et al. on "Science"

What is the maximum temperature that the Earth's Holobiont (aka "Gaia") can withstand before collapsing? Some data from a recent paper in "Science" indicate that we are not so close to the "Venus scenario" that would sterilize our planet. Nevertheless, the system is under stress

As you see in the figure at the beginning of the post, the optimal average temperature of planet Earth for the standard C3 photosynthesis (that of trees) is around 16 C, not far from the current value of around 18 C. (note that the graph takes into account not just temperature, but CO2 concentrations, supposed to be affecting temperature). Switching to the C4 mechanism (grass and others) moves the maximum to about 28 C;  10 degrees higher than it is now. 

So, we have a comfortable range in terms of plant life, and consider that the "zero" in the curve doesn't mean that all plants die; just that they are less efficient, especially in the hot equatorial zones. Note also how the "respiration" curve keeps growing as a function of temperatures; in the paper, they say that it keeps growing up to 60-70 C. 

Complicated story, but in any case, Gaia is not going to die soon. Note that during the Eocene, some 56 million years ago, the Earth's temperature was indeed some 8-10 degrees higher than it is now, and the planet was covered with lush forests. It is believed that C4 photosynthesis didn't appear on Earth before 35 million years ago. So, even an extra 10 C of warming will not destroy the biosphere: Gaia has a thick skin.

Eventually, the increasing solar irradiation will kill the Great Earth Holobiont but, hopefully, that will take a few hundred million years (at least). About humans, though.... well, it is another story. Do we still have a few decades left? Maybe. 

Of Mammophants and Holobionts

A question for you, space cadets, why did Mammoths go extinct, while elephants didn't? You have to detect a subtle clue that has to do with how the naked apes hunted them. You should be able to see it in this image. (Meuianga Mera, Chief Scientific Officer of the Reptilian Starfleet)

From "The Embryo Project"

Revive & Restore’s Woolly Mammoth Revival Project

By: Risa Aria Schnebly
Published: 2021-01-19
Keywords: mammophant, de-extinction, gene modification

Gratefully reproduced on "The Proud Holobionts" under this text's Creative Commons License 

In 2015, Revive & Restore launched the Woolly Mammoth Revival Project with a goal of re-engineering a creature with genes from the woolly mammoth and introducing it back into the tundra to combat climate change. Revive & Restore is a nonprofit in California that uses genome editing technologies to enhance conservation efforts in sometimes controversial ways. In order to de-extinct the woolly mammoth, researchers theorize that they can manipulate the genome of the Asian elephant, which is the mammoth’s closest living evolutionary relative, to make it resemble the genome of the extinct woolly mammoth. While their goal is to create a new elephant-mammoth hybrid species, or a mammophant, that looks and functions like the extinct woolly mammoth, critics have suggested researchers involved in the project have misled and exaggerated the process. As of 2021, researchers have not yet succeeded in their efforts to de-extinct the woolly mammoth, but have expressed that it may become a reality within a decade.

Researchers broadly define de-extinction as a method for reintroducing extinct species. However, the methods of de-extinction that researchers participating in the Woolly Mammoth Revival Project pursue would not lead to a perfect biological replica of a mammoth. The only chance to precisely recreate an extinct animal would be through cloning, a process of creating a genetically identical organism using the DNA of a host. DNA is the genetic information found in every living organism that carries the instructions an organism needs to develop, live, and reproduce. However, researchers cannot clone mammoths because cloning requires living cells, whereas other genome editing methods do not. Since one of the last species of mammoths went extinct around 4000 years ago, scientists are unable to acquire any living cells needed to clone the animal itself.

Because cloning is not an option in the case of the woolly mammoth, Revive & Restore researchers are attempting to use genome editing and engineering to make mammoth-like species instead of perfect replications of mammoths. Genome engineering is a technique that enables researchers to make changes to an organism’s genome, which is its set of DNA. There are many technologies that equip scientists to edit an organism’s genome and change how it will develop and function. Researchers from the Woolly Mammoth Revival Project are experimenting with CRISPR-cas9, a genome editing tool derived from bacteria that involves cutting out specific sequences of DNA and replacing them with other sequences. In the case of the de-extinction of the woolly mammoth, scientists would edit the Asian elephant genome to make it more similar to the genome from the woolly mammoth.

As the woolly mammoth’s closest living relative, the Asian elephant is ninety-nine percent genetically identical to the mammoth without any genetic editing interventions. Genetic engineers can use CRISPR-cas9 to cut out and remove precise sequences of elephant DNA and replace them with the DNA sequences that make up specific genes in the woolly mammoth’s genome. The genes they add into the elephant genome code for features that can make an elephant more mammoth-like, such as promoting the development of thicker layers of fat and longer hair. Researchers will not have created a biological woolly mammoth once an organism with that genome develops. However, it would theoretically be a mammoth-like creature which some have researchers have called a mammophant. They speculate the organism will be able to survive in the Arctic, where woolly mammoths once lived to promote biodiversity in that area. Researchers at Revive & Restore expect the introduction of their hybrid species can help prevent the melting of permafrost, the thick layer of soil and bedrock that stays frozen year-round in the Arctic, thereby preventing the release of greenhouse gases.

Stewart Brand and Ryan Phelan founded Revive & Restore in 2012, launching its inception with a project designed to de-extinct the passenger pigeon, a species of bird that went extinct in the early twentieth century due to overhunting. The extinction of the passenger pigeon was one of the catalysts for the US conservation movement because it demonstrated how human action alone could entirely eradicate a species that was once extremely abundant. For Revive & Restore, the passenger pigeon was a model candidate for de-extinction not only because of its fame within the conservation movement, but also because the passenger pigeon was an important species in the forests of the eastern US. Its foraging and migration patterns helped to create areas within forests that allowed other species to populate.

Revive & Restore’s next species of focus was the woolly mammoth, which was an important species in the Arctic, where the mammoth would trample plants and trees which would enable the arctic permafrost to remain frozen by exposing it the cold air. In 2012, Brand and Phelan hosted a meeting of international scientists interested in the project to discuss the feasibility of reintroducing the woolly mammoth, or a species very similar. Two of the project’s key figures, scientists George Church and Sergey Zimov, met at that meeting and discussed its practicality. Church, a professor of genetics at Harvard Medical School in Boston, Massachusetts, had the scientific expertise needed to engineer a mammophant. Zimov, a researcher of ecology from Russia, could provide a place the mammophants could live, and suggested the potential role of the mammophant in combatting global warming.

In 1996, Zimov founded Pleistocene Park, a fifty square mile wide nature reserve in the remote Siberian Arctic where mammophants may eventually roam. Some of the goals of Pleistocene Park include restoring the area’s ecosystem, protect the permafrost, and prevent further global warming. Zimov had already reintroduced large grazing animals into the park to replace the wildlife that existed in that region in the late Pleistocene era, which was a span in Earth’s history that ended about 12,000 years ago. Zimov believes that reintroducing large species like mammophants could mitigate the effects of global warming in the Arctic by helping to prevent the thawing of arctic permafrost.

During the late Pleistocene era, mammoths and other large animals trampled and scraped snow away from the ground, exposing the permafrost to cold winter air that could penetrate the ground and keep the deep layers of the permafrost frozen. Without the activity from large animals, there is nothing to disturb the snow that covers the ground, which means the colder air cannot reach and freeze the permafrost during the winter. That means that the permafrost can melt more easily upon the arrival of seasonal warm weather, especially as global temperatures rise due to global warming. When arctic permafrost thaws, it can release greenhouse gases that have been trapped within it for centuries. Those greenhouse gases can trap heat inside the earth’s atmosphere and researchers predict its impact will be greater than any other factor contributing to global warming. However, according to Zimov, the reintroduction of large grazing animals into Pleistocene Park has already seemed to help keep deeper layers of the permafrost frozen. After Church visited Pleistocene Park himself in 2015, Church and Zimov launched the Woolly Mammoth Revival Project with Revive & Restore.

Before genetic engineers can begin to add mammoth genes into the elephant genome, they first have to identify which genes are the most critically involved in the features they hope to emulate. The mammoth genome was first sequenced in 2008 by a team of biologists at Penn State University in State College, Pennsylvania. The team used samples of mammoth hair found in two mammoth specimens buried in the Siberian permafrost, one that was 20,000 years old and another that was 60,000 years old. Though most DNA specimens that old would be too degraded for scientists to sequence, the mammoths had been frozen and preserved in the Siberian permafrost. However, the mammoth’s DNA sequence does not specifically communicate the associated genes. To determine those genes, researchers have tested and compared the sequences of the woolly mammoth to those of the Asian elephant.

Scientists can reprogram the cells they edit to become different kinds of cells in the body, such as red blood cells, hair cells, or tissue cells. By pushing the edited reprogrammed cells to develop, the team can then see what the outcome of the genome edits they make will be. For example, if the researchers splice in a gene meant to give the elephant longer, mammoth-like hair, they can then push the group of cells they edited to develop into actual hair cells through genetic engineering without ever having to create an actual organism. They can then see what the creature’s hair will actually look and feel like, how long it will grow, and how thick it will be, among many other things. Then researchers can see whether the edits they made will really make the elephant more cold-resistant or not. After testing to confirm that the gene edits have the outcome the researchers wanted, the researchers can then combine all their successful edits into one genome sequence that they will use to create an animal.

As of 2020, Church continued to lead one of the teams working to identify the important genes within the woolly mammoth genome with the use of CRISPR-cas9. One of the most recent updates from Church’s lab in 2017 announced that they had successfully located forty-five genes that code for traits to make the hybrid more resistant to cold weather. Though there are several thousand genetic differences between the genome of the mammoth and Asian elephant, Church has hypothesized in some interviews that his team may only need to splice in fifty of the mammoth genes to create a mammophant capable of surviving in the Arctic.

Out of concern for animal welfare, Church and his team have stated they plan to avoid forcing Asian elephants to act as a surrogate for the mammophant by growing the mammophant embryo in an artificial womb outside of the body instead. Additionally, the team can test the physical effects of changing and combining the genomes without having to produce an actual animal. Asian elephants are an endangered species as of 2020, so scientists have used genome editing technologies for early investigations into proving the feasibility of the concept. Additionally, critics such as Matthew Cobb, a professor of zoology at the University of Manchester in Manchester, England, doubt that scientists can achieve the capability to produce a functional artificial womb within the next decade. Cobb explained that an artificial womb would deprive a fetus from many important pre-birth interactions with its gestational carrier that help the fetus to properly develop. However, Church and his lab have conducted early experiments attempting to grow mouse embryos ex vivo, or out of a uterus, rather than in vivo, meaning in a uterus, and have suggested the technology will become possible within the next decade.

Even if the technology may soon be feasible, many critics question whether we should be trying to de-extinct the mammoth at all. For example, David Ehrenfeld, a professor of biology at Rutgers University in Camden, New Jersey, has raised concerns that the mammophants may not be able to survive in the Arctic because they are genetically different from the extinct mammoths and will not be able to learn survival skills without a herd. He suggests those factors could also lead the mammophants to behave unpredictably in their environment and possibly even cause more destruction than help. To avoid that problem, Revive & Restore has stated plans to raise eventual mammophants with captive Asian elephant families in zoos who may teach them survival and herding behaviors so the mammophants can one day form herds of their own.

Additionally, many ethicists have expressed concern over de-extinction being an immoral endeavor. De-extinction, if successful, may eventually undermine the conservation movement by making extinction seem like less of a problem. If extinction suddenly seems reversible, the public may feel less responsible for behaviors and actions that contribute global warming and biodiversity loss. For example, Ben Minteer, a professor of environmental ethics at Arizona State University in Tempe, Arizona, has noted that the premise of de-extinction may teach people that technology alone can reinforce the idea that human will remain unaccountable for changing their behaviors to prevent such damage from occurring in the first place. Other conservationists like Stuart Pimm, a professor of conservation ecology at Duke University in Durham, North Carolina, worry that the time, money, and effort dedicated to de-extinction efforts like the Woolly Mammoth Revival Project could divert important funds dedicated to protecting the many endangered species and ecosystems still around today. Additionally, journalists have suggested the notion of the topic entirely became manipulated with aggrandized and sensationalist headlines without regard to the restrictions and hindrances scientists will need to overcome before making it a reality.

As of 2021, the Woolly Mammoth Revival Project was still in the process of revising the elephant genome. Whether or not the project is ultimately successful, the scientific and public discussion on de-extinction has prompted questions that consider how far humans should be allowed to interfere with nature. Although humans may be responsible for behaviors that have led to global warming, the risks and uncertainty surrounding de-extinction may outweigh the benefits of correcting such mistakes.

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Campagna, Claudio, Daniel Guevara, and Bernard Le Boeuf. “De-Scenting Extinction: The Promise of De-Extinction May Hasten Continuing Extinctions.” Hastings Center Report 47 (2017): 48–53. https://onlinelibrary.wiley.com/doi/pdf/10.1002/hast.752 (Accessed July 26, 2020).
Clayton, Susan. “Preserving the Things We Value.” Center for Humans & Nature, 2015. https://www.humansandnature.org/conservation-extinction-susan-clayton (Accessed July 26, 2020).
Devlin, Hannah. “Woolly Mammoth on Verge of Resurrection, Scientists Reveal.” The Guardian, 2017. https://www.theguardian.com/science/2017/feb/16/woolly-mammoth-resurrection-scientists (Accessed July 26, 2020).
Ehrenfeld, David. “Resurrected Mammoths and Dodos? Don’t Count On It.” The Guardian, 2013. https://www.theguardian.com/commentisfree/2013/mar/23/de-extinction-efforts-are-waste-of-time-money (Accessed July 26, 2020).
Hawks, John. “How Mammoth Cloning Became Fake News: George Church, Artificial Wombs, Elephant Embryos, and a Gullible, Science Media.” Medium Science, 2017. https://medium.com/@johnhawks/how-mammoth-cloning-became-fake-news-1e3a80e54d42 (Accessed July 26, 2020).
Hysolli, Eriona. “An American-Russian Collaboration to Repopulate Siberia with Woolly Mammoths… Or Something Similar.” Medium, 2018. https://medium.com/@eriona.hysolli/an-american-russian-collaboration-to-repopulate-siberia-with-woolly-mammoths-or-something-similar-9cbac4e985cb (Accessed July 26, 2020).
Minteer, Ben, The Fall of the Wild: Extinction, De-Extinction, and the Ethics of Conservation. New York, New York: Columbia University Press, 2019.
Nijhuis, Michelle. “Don’t Think of a Mammophant.” Last Word on Nothing, 2017. https://www.lastwordonnothing.com/2017/03/07/dont-think-of-a-mammophant/ (Accessed July 26, 2020).
Novak, Ben Jacob. “De-Extinction.” Genes 9 (2018): 548. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6265789/ (Accessed July 26, 2020).
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Riederer, Rachel. “The Wooly Mammoth Lumbers Back Into View.” The New Yorker, 2018. https://www.newyorker.com/science/elements/the-wooly-mammoth-lumbers-back-into-view (Accessed July 26, 2020).
Shapiro, Beth. How to Clone a Mammoth: The Science of De-Extinction. Princeton: Princeton University Press, 2015.
“The Great Passenger Pigeon Project.” Revive & Restore. https://reviverestore.org/about-the-passenger-pigeon/ (Accessed July 26, 2020).
“What We Do.” Revive & Restore. https://reviverestore.org/what-we-do/ (Accessed July 26, 2020).
Wood, Charlie. “We Can Clone a Mammoth: But Should We?” Christian Science Monitor, 2017. https://www.csmonitor.com/Science/2017/0216/We-can-clone-a-woolly-mammoth.-But-should-we (Accessed July 26, 2020).
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How to citeSchnebly, Risa Aria, "Revive & Restore’s Woolly Mammoth Revival Project". Embryo Project Encyclopedia (2021-01-19). ISSN: 1940-5030 http://embryo.asu.edu/handle/10776/13209.

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PublisherArizona State University. School of Life Sciences. Center for Biology and Society. Embryo Project Encyclopedia.
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Copyright Arizona Board of Regents Licensed as Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported (CC BY-NC-SA 3.0) http://creativecommons.org/licenses/by-nc-sa/3.0/
Last modified Monday, June 28, 2021 - 04:06
TopicTheories, Technologies, Organizations, Ethics
SubjectExtinction, Biological; Extinction, Species; Genetic Engineering; Genetically Engineered Organisms; Genetically Engineered Animals; Genetically Modified Animals; Cloning, Organism; Mammoths; Woolly Mammoth; Mammuthus primigenius; Mammuthus; Conservation; Animal diversity conservation; Animal conservation; Gene Editing; Bioethics; Life sciences--Moral and ethical aspects; Conceptniversity, 1711 South Rural Road, Tempe Arizona 85287, United States

Those Pesky Savanna Monkeys: The New Large Igneous Province

 

This is the second part of a short series dedicated to the "Savanna Monkeys," aka "homo sapiens". In the previous post, I described how they evolved and how they changed Earth's ecosystem in the process. Here, we take a peek at the future. The monkeys could really do a lot of damage. 

The giant volcanic eruptions called LIPs tend to appear on our planet at intervals of the order of tens or hundreds of million years. They are huge events that cause the melting of the surface of entire continents. The results are devastating: of course, everything organic on the path of the growing lava mass is destroyed and sterilized, but the planet-wide effect of the eruption is even more destructive. LIPs are believed to warm coal beds at sufficiently high temperatures that they catch fire. These enormous fires draw down oxygen from the atmosphere, turning it into CO2. The result is an intense global warming, accompanied by anoxia. In the case of the largest of these events, the End-Permian extinction of some 250 million years ago, the whole biosphere seriously risked being sterilized. Fortunately, it recovered and we are still here, but it was a close call. 

LIPs are believed to be the result of internal movements of the Earth's core. For some reason, giant lava plumes tend to develop and move toward the surface. It is the same mechanism that generates volcanoes, just on a much larger scale. From what we know, LIPs are unpredictable, although they may be correlated to a "blanketing effect" generated by the dance of the continents on Earth's surface. When the continents are clustered together, they tend to warm the mantle below, and that may be the origin of the plume that creates the LIP

Of course, if a LIP were to take place nowadays, the results would be a little catastrophic -- possibly more catastrophic than the fantasy of Hollywood's movie makers can imagine. They have thrown all sorts of disasters at hapless humans, from tsunamis to entire asteroids. But imagine the whole North American continent becoming a red-hot lava basin, well, that's truly catastrophic!

Fortunately, LIPs are slow geological processes and even if there is one more of these events in our future, it won't happen on the time scale of human lifetimes. But that doesn't mean that humans, those pesky Savanna Monkeys, can't do their best to create something similar. And, yes, they are engaged in the remarkable feat of creating a LIP-equivalent by burning huge amounts of organic ("fossil") carbon that had sedimented underground over tens or hundreds of millions of years of biological activity. 

It is remarkable how rapid the monkey LIP has been. Geological LIPs typically span millions of years. The monkey LIP went through its cycle over a few hundred years: we see it developing right now. It will be over when the concentration of fossil carbon stored in the crust will become too low to self-sustain the combustion with atmospheric oxygen. Just like all fires, the great fire of fossil carbon will end when it runs out of fuel, probably less than a century from now. Even in such a short time, the concentration of CO2 is likely to reach, and perhaps exceed, levels never seen after the Eocene, some 50 million years ago. It is not impossible that it could reach more than 1000 parts per million. 

There is always the possibility that such a high carbon concentration in the atmosphere will push Earth over the edge of stability and kill Gaia by overheating the planet. But that's not a very interesting scenario: we all die and that's it. So, let's examine the possibility that the biosphere will survive the great carbon pulse generated by the savanna monkeys. What's going to happen?

The savanna monkeys themselves are likely to be the first victims of the CO2 pulse that they generated. Without the fossil fuels they have come to rely on, their numbers are going to decline very rapidly. From the incredible number of 8 billion individuals, that they recently reached, they are going to return to levels typical of their early savanna ancestors: maybe just a few tens of thousands. Quite possibly, they'll go extinct. In any case, they will hardly be able to keep their habit of razing down entire forests. Without monkeys engaged in the cutting business and with high concentrations of CO2, forests are advantaged over savannas, and they are likely to recolonize the land, and we are going to see again a lush, forested planet (arboreal monkeys will probably survive and thrive). Nevertheless, savannas will not disappear. They are part of the ecosystem, and new megaherbivores feeding on them will evolve in a few hundred thousand years. 

Over deep time, the great cycle of warming and cooling may restart after the monkey LIP is over, just as it did for the "natural" geological LIPs. In a few million years, Earth may be seeing a new cooling cycle that will lead again to a Pleistocene-like series of ice ages. At that point, new savanna monkeys may evolve. They may restart their habit of exterminating the megafauna, burning forests and building things in stone. But they won't have the same abundance of fossil fuel that the monkeys called "Homo sapiens" found when they emerged into the savannas. So, their impact on the ecosystem will be smaller, and they won't be able to create a new monkey-LIP. 

And then what? In deep time, the destiny of Earth is determined by the slowly increasing solar irradiation that is going, eventually, to eliminate all the oxygen from the atmosphere and sterilize the biosphere, maybe in less than a billion years from now. So, we may be seeing more cycles of warming and cooling before Earth's ecosystem collapses. At that point, there will be no more forests, no more animals, and only single-celled life may persist. It has to be. Gaia, poor lady, is doing what she can to keep the biosphere alive, but she is not all-powerful. And not immortal, either. 

Nevertheless, the future is always full of surprises, and you should never underestimate how clever and resourceful Gaia is. Think of how she reacted to the CO2 starvation of the past few tens of millions of years. She came up with not just one, but two brand-new photosynthesis mechanisms designed to operate at low CO2 concentrations: the C4 mechanism typical of grasses, and another one called crassulacean acid metabolism (CAM). To say nothing about how the fungal-plant symbiosis in the rhizosphere has been evolving with new tricks and new mechanisms. You can't imagine what the old lady may concoct in her garage together with her Elf scientists (those who also work part-time for Santa Claus). 

Now, what if Gaia invents something even more radical in terms of photosynthesis? One possibility would be for trees to adopt the C4 mechanism and create new forests that would be more resilient against low CO2 concentrations. But we may think of even more radical innovations. How about a light fixation pathway that doesn't just work with less CO2, but that doesn't even need CO2? That would be nearly miraculous but, remarkably, that pathway exists. And it has been developed exactly by those savanna monkeys who have been tinkering with -- and mainly ruining -- the ecosphere. 

The new photosynthetic pathway doesn't even use carbon molecules but does the trick with solid silicon (the monkeys call it "photovoltaics"). It stores solar energy as excited electrons that can be kept for a long time in the form of reduced metals or other chemical species. The creatures using this mechanism don't need carbon dioxide in the atmosphere, don't need water, and they may get along even without oxygen. What the new creatures can do is hard to imagine for us (although we may try). 

In any case, Gaia is a tough lady, and she may survive much longer than we may imagine, even to a sun hot enough to torch the biosphere to cinders. Forests are Gaia's creatures, and she is benevolent and merciful (not always, though), so she may keep them with her for a long, long time. (and, who knows, she may even spare the savanna monkeys from her wrath!). 

We may be savanna monkeys, but we remain awed by the majesty of forests. The image of a fantasy forest from Hayao Miyazaki's movie, "Mononoke no Hime" resonates a lot with us.