We all know that global climate change is occuring at a faster pace than ever, mostly as a result of human consumption of fossil fuels. With reason, this phenomenon is often interpreted negatively or pessimistically by those who cares for its consequences.
Personally, I am more concerned about biodiversity loss than climate change, since the latter seems reversible on a shorter timescale and many species show enough genetic and behavioural plasticity to survive major climactic disturbances. Feel free to provide counter-examples.
I realize that Iām rambling at this point so let me ask this one question:
Could the release of carbon locked away for millions of years in coal and other fossil fuels actually have a positive impact on biodiversity in the long term?
My reasoning is that more carbon for organisms to utilize = more organisms/biomass = higher potential for biodiversification through random mutation and natural selection
To put it simply, the āCā element (which is already insanely over-abundant across the whole ecosphere) has never been a limiting factor to Life on Earth (and its diversity or volume). However, alterations (man-made or not) to the cycling of this element - by forcefully/rapidly transferring copious amounts of it between its various reservoirs - is known to have harmed immensely (and durably) the global environment and its inhabitants, several times. Think Snowball Earth and Venus.
One aspect of CO2 emissions that fascinates me is the theory by the late Thomas Gold in his book āThe Deep, Hot Biosphereā, that the carbon from some of the so called āfossil fuelsā may never have been in the atmosphere to begin with.
Nobody can predict the future with certainty. Evolution is an amoral process. but Iām a human being, and Iām more concerned with my own survival and my familyās survival. If global warming is due to anthropogenic causes, then it is probably due to the increase in human population. The biodiversity of humans increases but with a decrease in the biodiversity of other creatures. Creatures that are not in direct competition with mankind or live in humans may increase. Such as the Covid and cold virus comes out more and more variants. or maybe rats and pigeons may increase. Humans have the ability to create varieties but not species. Species is an idea that comes from humans. Due to the evolution being amoral process, so I cannot associate it with āpositiveā or ānegativeā. Nature have a long time to work with. We donāt live long enough to see its impact, same as we couldnāt see a species coming into existence naturally. The noticeable impacts as predicted by scientists are that the droughts are more severe, and the floods, hurricanes are more severe. This causes crop failure, which lead to famine and migration of people into other places on earth, and that puts groups of people into direct confrontation which is the competition between organisms. There are times with heightened competition.
Biodiversity often stems from scarcity of available resources, so I wouldnāt assume more carbon means more biodiversity. Of course, large-scale extinction will ultimately allow for evolutionary radiation, so it is likely that biodiversity will return/increase in the long run, but that seems like a crappy reason to let existing species go extinct. The slower the rate of change, the more species will have a chance to adapt to new circumstances.
Interesting links! The Wikipedia article on the abiogenic hydrocarbon hypothesis hasnāt been updated in a long while, so Iām tempted to assume that the hypothesis has mostly been rejected by the wider scientific community. I found Researchers Map the Microbes Living Deep Beneath the Earthās Surface | Technology Networks and Microbes Deep inside the Earth. These articles (the first from 6 days ago and the other from 1996) make a decent introduction to the microbes inhabiting the Earthās crust, although I have not read them exhaustively.
āIf we store carbon dioxide underground, there are microbes that could metabolize it to make methane, for example. There is a biosphere underground that, depending on how itās perturbed, has potential to affect the surface.ā
itās kind of a miserable take, but humans at the top of the trophic web are a lot more vulnerable than many forms of multicellular life, such as cockroaches, coyotes, etc. The truth is climate change is more a risk to humans than many other species whereas ecosystem collapse and habitat loss are more a risk to other species (and then indirectly back to us). One could argue climate change may cause the human population to crash while at the same time warming temperatures to a level similar to past eras of the Earth where there was more tropical rainforest and such. So maybe in tens of thousands of years biodiversity would increase. Maybe even one could argue a āroleā of our species is to dig up all the carbon that was buried and causing ice ages, then die off, resulting in a refreshing of the global carbon supply.
I donāt actually believe this is the right approach to look at it, but i think it is kind of interesting.
Iām not even sure whether a return to a non-glacial climate state would will prove so beneficial in terms of pure biodiversity. In retrospect, the recent climate fluctuations (of a bearable speed and amplitude) have proven remarkably effective at generating a smorgasbord of niches and taxa to occupy them.
To make a long story short: the hybrids between two species are sterile as a general rule, this means that separate species do have an objective reality.
I agree with you on that. Among not only mammals but all vertebrates, invertebrates, fungi and plants, fertile hybrids are rather common. The concept of hybridization is kind of irrelevant in bacteria and archaea since they have so many ways of transfering genetic information
I know it isnāt directly related to biodiversification, but here is a study on the apparent size decrease of mammals (mainly members of Equidae) during the Eocene Thermal Maximum (EMT2) that occurred about 2 million years after the PETM (approximately 53.7 Ma). Following are excerpts from that study (I didnāt read the Results section because I donāt understand the chemical mechanisms studied)
Mammal dwarfing has been observed, along with other changes in community structure, during the largest of these ancient global warming events, known as the Paleocene-Eocene Thermal Maximum
Statistically significant decrease in body size during ETM2 is observed in two of four taxonomic groups analyzed in this study and is most clearly observed in early equids (horses). During ETM2, the best-sampled lineage of equids decreased in size by ~14%, as opposed to ~30% during the PETM. Thus, dwarfing appears to be a common evolutionary response of some mammals during past global warming events, and the extent of dwarfing seems related to the magnitude of the event.
Much can be learned from the study of climate change in the geological past and its effect on contemporaneous biotas. Early Eocene global warming events, or āhyperthermals,ā are associated with large perturbations of the global carbon cycle and thus serve as analogs of modern-day global warming.
Terrestrial records of the PETM are also accompanied by significant mammalian turnover, including the abrupt introduction of several modern mammalian lineages (including perissodactyls, artiodactyls, and primates) and mammalian dwarfing in both immigrant and endemic taxa
Today, soil CO2 at depths greater than ~30 cm is dominantly a product of root respiration and within-soil organic matter decomposition because atmospheric CO2 has an insignificant direct influence at this depth
Using tooth size as a proxy for body size, evidence for mammalian dwarfing has been recorded in terrestrial records of the PETM (7, 8, 10). Teeth in adult mammals scale proportionally to body size. Of all tooth positions, the first lower molar (M1) tends to exhibit the strongest correlation between crown area and body weight across most taxonomic groups of mammals.
A high-resolution study focusing on the earliest equid Sifrhippus demonstrated a decrease of at least 30% in body size during the first 130,000 years of the PETM, followed by a 76% rebound in body size during the recovery phase of the PETM.
With only two early Eocene hyperthermals to compare to date, it is not yet possible to determine an empirical relationship between body size and CIE magnitude. However, it is clear that the smaller ETM2 CIE is associated with less extreme dwarfing, whereas the larger PETM CIE is associated with larger-magnitude body size change, suggesting a monotonic relationship
The dwarfing pattern is shown most clearly by A. pernix, the best-sampled taxon in our study (n = 57). Arenahippus decreases in size by ~14% going into the ā3.8ā° ETM2 CIE
Studies of modern animal populations have also yielded similar body size results. Soay sheep (Ovis aries), red deer (Cervus elaphus), and California squirrels (Spermophilus beecheyi) have all exhibited phenotypic responses to climate change (53ā55). The sheep and deer show a decrease in body size in response to increasing temperatures (53, 55), while the squirrels show a decreased body size in response to decreased precipitation
hydrological records of ETM2 suggest an increase in soil moisture during this event (15), perhaps mitigating the dwarfing response. In the same way that the fundamental carbon cycle causes of the PETM and ETM2 may be different (15, 63), the mechanism for body size change at the two events may also be different.
This suggests that dwarfing will be a likely natural response of some mammals to future global warming.
Note: CIE = ācarbon isotope excursionā = āchange in the ratio of stable isotopes of carbon in the ocean and atmosphereā
There are several factors that may cause dwarfism in mammals. Iāve read Island dwarfism. I read that the geological records are imperfect. The fossil bones in the soil Iām not very convinced on the information that can be derived from those.
Some examples of living organisms. The Siberian tiger is bigger in size than Bengal tiger or Sumatran tiger. Iāll also mention fish species. Fish are not mammals but are still animals which may have related patterns. Fishes such as guppies and tilapias are prolific, able to double the population quickly. These fishes are tropical in origin and can be grown in temperate regions. In the tropics, male guppies are often naturally of a small size. When the fish reaches Germany or USA, they managed to isolate big varieties, and these went back to tropical countries, and we now have both big and small varieties. The tilapias in the canals are of a smaller size than farm raised fishes. This is due to them being able to breed freely. Breeding increases when the water gets warm. Fish are sluggish until the water has a suitable temperature. then the fish start expending energy. The females generally are smaller than males, and the males are longish in body shape. Some fishes will be taken by predators. Tilapias are limited by the oxygen in the water. As temperature rises, the dissolved oxygen in a pool of water gets lower, Tilapias are species that adapted to that together with anabantoids.Same for animals. As temperature gets warmer, animals may have less fur and fat. and animals probably breed more and live a shorter lifespan compared to creatures in temperate regions. Some creatures hibernate in winter, some donāt. There are other factors, such as genetic factors in a population. Predation and availability of food source, competition in an environment and chance mutation. However some creatures like elephants grow big due to the opposite of island dwarfism. and reptiles may potentially grow big in warmer temperatures.
Fossil bones in the soil are prone to contamination - which is why geochemists, palaeoecologists, sedimentologists, geochronologists, stratigraphers, and palaeontologists routinely work together; they are trained in the study of whole-rock samples, carefully-picked minerals in them, and/or best-preserved fossil parts, and only then perform relevant analyses and statistics, accounting for record biases and associated uncertainties. The study examplifies all this routine in its āResultsā section.
Fascinating post frontyardscientist. I believe there are 2 possible explanations why animals in general are smaller than they were in the ice ages. 1. a larger animal has less surface area, (loss of body heat is a function of surface area, smaller animals have a a larger surface are ration to mass), so larger animals do better in cold environments. E.g. whales who spend half the year in Arctic or Antarctic waters.
2. Human hunting. Although it may be more hazardous and difficult to kill a large animal than a small one, there is benefit in obtaining much more food from a mammoth than a rabbit. A modern example is the hunting of kangaroos in my home country Australia. About are a million or so kangaroos per years are legally āharvestedā for food and skins. This is actually a an ecologically sustainable industry with less environmental impact than raising domestic livestock. what scientists have noticed however, is that the a number of kangaroo species have reduced in size over the last century or so. They have theorised that this is due to the fact that, because hunters are paid on weight, there is an economic benefit in hunters using a cartridge on a larger kangaroo than a smaller one.
On the topic of body size in relation to climate, cf. Bergmannās rule and Temperature-Size rule (TSR). This age-old subject has been recently reinvigorated by the issues of climate change and overexploitation (e.g. overfishing). Obviously thereās hardly a universal, one-size-fits-all āexplanationā; as is usual with contingent historical processes, different settings at different times produce different results in different natural objects. Trying to derive rules and make sense of itā¦ is part of the fun. (āWhat about the evolution of body size in insular creatures from different taxonomic groups subjected to varying hunting pressure during the Late Glacial-Early Holocene under various latitudes?ā )
In any case, itās unrelated to the mere amount of carbon at hand.
I donāt actually think we are heading for more than an extended interglacial. I think between feedback loops and other factors we will go back to an ice age in the next few tens of thousands of years. I mean i donāt know for sure. And this isnāt in any way dismissing human caused climate change, which i think is a huge issue. I think we overstate our impact on the planet relative to the impact to our species. We will adapt or die in the next few decades. Or probably something in between. Either way, the earth will then regulate.
Of course this is all speculation on my part. The one thing for sure is these are very complex systems and will do things we canāt anticipate.
Feeling optimistic eh? Although certainly not the most likely scenario, an RCP8.5-like world (roughly: zero policy and an ice-free Antarctica) remains plausible and possible. (Ice)sheet happens.
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