CO2 and the return of the dinosaurs

The dinosaurs lived during the Mesozoic Era, which was divided into the Triassic, Jurassic, and Cretaceous Periods. Many of the iconic dinosaurs that we know and love such as Tyrannosaurus rex and Triceratops lived at the end of the Cretaceous while others such as Stegosaurus and Apatosaurus (formerly known as Brontosaurus) lived 80 or so million years earlier in the Jurassic. I used to picture all the dinosaurs co-existing simultaneously but the time span separating Stegosaurus from T. rex is larger than that between T. rex and the present! Dinosaurs also weren’t the only creatures alive at that time, just the most dominant ones. Technically, the term dinosaur only applies to land-based reptiles with certain features. The avian reptiles, such as Pteranodon, or the marine ones, such as Plesiosaurs, resembled dinosaurs but were not classified as such. Aside from those dinosaur-like animals, there were also invertebrates, fish, sharks, and a class of animals called Synapsids, defined by an opening in the skull behind the eyes, from which all mammals are descended.

Synapsids were small marginal creatures during the Mesozoic but came to dominate the land after the dinosaurs went extinct at the end of the Cretaceous (the KT extinction event). The consensus theory is that a large asteroid or comet strike in the Yucatan set off fire storms, seismic events and a cloud that blocked sunlight for up to a year. This caused plants to die globally, which collapsed the food chain.The only survivors were creatures that could go deep underwater or bury underground and survive long periods with little or no food. Survivors of the KT extinction include some fish, small sharks, small crocodiles and other cold blooded reptiles, small bipedal theropod dinosaurs, of which T-Rex is a member, and small rodent-like synapsids.

If the KT extinction event was a transient perturbation then it is reasonable to expect that whatever it was that allowed dinosaurs to become dominant would remain and the surviving theropods would come to dominate again. But that is not what happened. Theropods did survive to become modern birds but aside from a few exceptions, most are small and almost all are avian. Instead, the Synapsids came to dominate and the largest creature to ever live, namely the Blue Whale, is a Synapsid. Now this could be purely due to random chance and if we played out the KT event over and over there would be some distribution where either Synapsids or dinosaurs become dominant. However, it could also be that global conditions after the Cretaceous changed to favour Synapsids over dinosaurs.

One possible change is the atmospheric level of carbon dioxide. CO2 levels were higher than they are today for much of the past 500 million years, even with the recent rapid increase. The levels were particularly high in the Triassic and Jurassic but began to decline during the Cretaceous (e.g. see here) and have continued to decrease until the industrial revolution when it turned upwards again. Average global temperatures were also higher in the Mesozoic. The only other time that C02 levels and global temperatures have been as low as they are now was in the Permian before the Great Dying. During the Permian, the ancestor to dinosaurs was a small insectivore that had the ability to run on two legs while the dominant creatures were none other than the Synapsids! So, mammal-like creatures were dominant before and after the dinosaurs when CO2 levels and temperatures were low.

Perhaps this is just a coincidence but there is one more interesting fact to this story and that is the amount of stored carbon (i.e. fossil fuels) has been very high twice over the past 500 million years – the Permian and now. It had been believed that the rise in CO2 at the end of the Permian was due to increased volcanism but a paper from 2014, (see here), speculated that a horizontal gene transfer event allowed an archaea microbe to become efficient in exploiting the buried carbon and this led to an exponential increase in methane and CO2 production. The active volcanos provided the necessary nickel to catalyze the reactions. Maybe it was simply a matter of time before some creature would find a way to exploit all the stored energy conveniently buried underground and release the carbon back into the atmosphere. The accompanying rise in temperatures and increased acidification of the oceans may also spell the end of this current reign of Synapsids and start a new era. While the smart (rich?) money seems to be on some sort of trans-human cyborg being the future, I am betting that some insignificant bird out there will be the progenitor of the next dominant age of dinosaurs.

Cecil and the hunter

Like many others, I was first outraged when I heard about the death of the beloved lion in Zimbabwe at the hands of a hunter from Minnesota. But I then quickly realized that I am in no position to judge the man. Over the past week, I have dined on salmon, chicken, pork, tuna, and beef. Just because I don’t go into the brush to kill an animal I consume doesn’t mean that I am not directly responsible for its demise. The only difference between me and a hunter is that I do not find any sport in the shooting of animals. There are nearly a hundred million cows at any given time in the US waiting to be slaughtered. Is the life of a cow not as valuable as that of a lion? It is no fault of the cow that she is not an iconic symbol like the lion. Fish are wild animals and we are hunting them to extinction. Tuna can live very long lives and are partially warm blooded. Sharks exhibit very complex behavior and have live births. I would suggest that the death of a big fish is no less tragic than the death of a big cat.

The unfortunate hunter paid a lot of money to go on what he thought was a legal hunt. The guides he hired may have misled him and broken the law but hunting lions in Zimbabwe is not a crime. Remember that this is a country that was near economic collapse just a decade ago and could use an infusion of hard currency. I have argued before that hunting may ironically be a way to preserve wildlife and habitat. The interests of hunters and environmentalists could be aligned. Regulated hunting could be an antidote to illegal poaching. If the hunter broke a law then he should be prosecuted. Otherwise, his choice of recreation is protected by the First Amendment of the US Constitution.

Ideas on CBC radio

 

One of the most intellectually stimulating radio shows (and podcasts) is Ideas with Paul Kennedy on CBC radio. It basically covers all topics. Many of the shows span several hour-long segments. One inspiring show I highly recommend is devoted to landscape architect Cornelia Hahn Oberlander. She was a pioneer in green and sustainable architecture. She is also still skiing at age 93!

Did microbes cause the Great Dying?

In one of my very first posts almost a decade ago, I wrote about the end-Permian extinction 250 million years ago, which was the greatest mass extinction thus far. In that post I covered research that had ruled out an asteroid impact and found evidence of global warming, possibly due to volcanos, as a cause. Now, a recent paper in PNAS proposes that a horizontal gene transfer event from bacteria to archaea may have been the main cause for the increase of methane and CO2. This paper is one of the best papers I have read in a long time, combining geological field work, mathematical modeling, biochemistry, metabolism, and evolutionary phylogenetic analysis to make a compelling argument for their hypothesis.

Their case hinges on several pieces of evidence. The first comes from well-dated carbon isotopic records from China.  The data shows a steep plunge in the isotopic ratio (i.e ratio between the less abundant but heavier carbon 13 and the lighter more abundant carbon 12) in the inorganic carbonate reservoir with a moderate increase in the organic reservoir. In the earth’s carbon cycle, the organic reservoir comes from the conversion of atmospheric CO2 into carbohydrates via photosynthesis, which prefers carbon 12 to carbon 13. Organic carbon is returned to inorganic form through oxidation by animals eating photosynthetic organisms or by the burning of stored carbon like trees or coal. A steep drop in the isotopic ratio means that there was an extra surge of carbon 12 into the inorganic reservoir. Using a mathematical model, the authors show that in order to explain the steep drop, the inorganic reservoir must have grown superexponentially (faster than exponential). This requires some runaway positive feedback loop that is difficult to explain by geological processes such as volcanic activity, but is something that life is really good at.

The increased methane would have been oxidized to CO2 by other microbes, which would have lowered the oxygen concentration. This would allow for more efficient fermentation and thus more acetate fuel for the archaea to make more methane. The authors showed in another simple mathematical model how this positive feedback loop could lead to superexponential growth. Methane and CO2 are both greenhouse gases and their increase would have caused significant global warming. Anaerobic methane oxidation could also lead to the release of poisonous hydrogen sulfide.

They then considered what microbe could have been responsible. They realized that during the late Permian, a lot of organic material was being deposited in the sediment. The organic reservoir (i.e. fossil fuels, methane hydrates, soil organic matter, peat, etc) was much larger back then than today, as if someone or something used it up at some point. One of the end products of fermentation of this matter would be acetate and that is something archaea like to eat and convert to methane. There are two types of archaea that can do this and one is much more efficient than the other at high acetate concentrations. This increased efficiency was also shown recently to have arisen by a horizontal gene transfer event from a bacterium. A phylogenetic analysis of all known archaea showed that the progenitor of the efficient methanogenic one likely arose 250 million years ago.

The final piece of evidence is that the archaea need nickel to make methane. The authors then looked at the nickel concentrations in their Chinese geological samples and found a sharp increase in nickel immediately before the steep drop in the isotopic ratio. They postulate that the source of the nickel was the massive Siberian volcano eruptions at that time (and previously proposed as the cause of the increased methane and CO2).

This scenario required the unlikely coincidence of several events –  lots of excess organic fuel, low oxygen (and sulfate), increased nickel, and a horizontal gene transfer event. If any of these were missing, the Great Dying may not have taken place. However, given that there have been only 5 mass extinctions, although we may be currently inducing the 6th, low probability events may be required for such calamitous events. This paper should also give us some pause about introducing genetically modified organisms into the environment. While most will probably be harmless, you never know when one will be the match that lights the fire.

 

 

Saving large animals

One  story in the news lately is the dramatic increase in the poaching of African elephants (e.g. New York Times). Elephant numbers have plunged dramatically in the past few years and their outlook is not good. This is basically true of most large animals like whales, pandas, rhinos, bluefin tuna, whooping cranes, manatees, sturgeon, etc. However, one large animal has done extremely well while the others have languished. In the US it had a population of zero 500 years ago and now it’s probably around 100 million.That animal as you have probably guessed is the cow. While wild animals are being hunted to extinction or dying due to habitat loss and climate change, domestic animals are thriving. We have no shortage of cows, pigs, horses, dogs, and cats.

Given that current conservation efforts are struggling to save the animals we love, we may need to try a new strategy. A complete ban on ivory has not stopped the ivory trade just as a ban on illicit drugs has not stopped drug use. Prohibition does not seem to be a sure way to curb demand. It may just be that starting some type of elephant farming may be the only way to save the elephants. It could raise revenue to help protect wild elephants and could drop the price in ivory sufficiently to make poaching less profitable. It could also backfire and increase the demand for ivory.

Another counter intuitive strategy may be to sanction limited hunting of some animals. The introduction of wolves into Yellowstone park has been a resounding ecological success but it has also angered some people like ranchers and deer hunters. The backlash against the wolf has already begun. One ironic way to save wolves could be to legalize the hunting of them. This would give hunters an incentive to save and conserve wolves. Given that the set of hunters and ranchers often have a significant intersection, this could dampen the backlash. There is a big difference in attitudes towards conservation when people hunt to live versus hunting for sport. When it’s a job, we tend to hunt to extinction like  buffalo, cod, elephants, and bluefin tuna. However, when it’s for sport, people want to ensure the species thrives. While I realize that this is controversial and many people have a great disdain for hunting, I would suggest that hunting is no less humane and perhaps more than factory abattoirs.

Weather prediction

I think it was pretty impressive how accurate the predictions for Superstorm Sandy were up to a week ahead.  The hurricane made the left hand turn from the Atlantic into New Jersey just as predicted.  I don’t think the storm could have been hyped any more than it was.  The east coast was completely devastated but at least we did have time to prepare.  The weather models  have gotten much better from even ten years ago. The storm also shows just how vulnerable the east coast is to a 14 foot storm surge.  I can’t imagine what a 20 foot surge would do to New York.

We need Google genome

I listened to two Long Now Foundation talks on my way to Newark, Delaware and back yesterday for my colloquium talk.  These podcasts tend to be quite long, so they were perfect for the drive.  The first was by environmental activist and journalist Mark Lynas and the second by National Geographic photographer Jim Anderson.  Both were much more interesting than I expected.  Lynas, who originated the anti-genetically modified organism (GMO) food movement in Europe in the 1990s, has since changed  his mind and become more pragmatic.  He now advocates for a more rational environmental movement that embraces technological solutions such as GMO foods and nuclear energy.  He argues that many more people are killed by particulate matter from coal-fired generating plants in a year than over the entire history of nuclear use.  I have always felt that nuclear power is the only viable technology to reduce carbon emissions.  I have also argued previously that  I’m more worried about the acidification of the ocean due to CO2 than an increase temperature.  I think we should start building CANDU reactors now and head towards fast breeder reactors.

Jim Anderson talked about the loss of diversity of domesticated plants and animals and how they are essential for the survival of humans.  For the first 9,900 years of agriculture, we increased the diversity of our food stuff.  For the last hundred, we have gone in the other direction. We used to have hundreds to thousands of varieties of fruits and vegetables and now we’re down to a handful.  There are at most 5 varieties of apples I can buy at my local supermarket, yet a hundred years ago, each orchard would produce its own variety.  This leaves us extremely vulnerable to diseases.  The world’s banana supply is dominated by one variety (the Cavendish) and it is under siege by a fungus that threatens to wipe it out.  The Irish potato famine was so severe because they relied on only two varieties that were both susceptible to the same blight. Our fire wall against future blights are seed banks, where we try to preserve as many varieties as we can.  However, not all seeds can remain viable forever.  Many have to be planted every few years from which new seeds are harvested.  This replanting is often done by amateur horticulturists.  The podcast made me think that with the cost of genome sequencing dropping so rapidly, what we need now is for someone, like Google, to start sequencing every living being and making it publicly available, like Google Books.  In fact, if sequencers become cheap enough, this could be done by amateurs.  You would find some plant or animal, document it as well as you can, and upload the sequence to the virtual seed bank.  This can be a record of both wild and domesticated species.  We can then always resurrect one if we need to.  There could also be potential for mischief with highly dangerous species like small pox or anthrax, so we would need to have a public discussion over what should be available.