One of humanity’s biggest problems at the moment is global warming; this is said to be mainly caused by the increase in carbon dioxide in the Earth’s atmosphere resulting from the burning of fossil fuels. Given how serious the consequences of global warming can be, its possible effects and the responses from human beings are being extensively analyzed.
It is precisely here that genetic studies are being used to analyze these effects, and maybe even predict them and find solutions and mitigating measures. Specifically, it is interesting to wonder whether the effects of climate change have reached deep into organisms, i.e. their genes.
Living beings are not defenseless against climate change. Specifically, they can present three types of responses.
Migrations in the face of climate change
First, there is migration from areas with increasing temperature levels to colder areas in terms of latitude or altitude. When we analyze several genetic markers (DNA segments with an identifiable physical location), we can see which colonization movements took place after the last glacial period (12,500 years ago), such as in the case of many sea and land organisms. It has also been possible to track the migrations after the Little Ice Age, (Middle Ages to mid-1800s). This was the case, for instance, of foxes on the islands in Northern Europe. And more recently, genetic studies of the skin of cod fished during the 19th century have helped to analyze the migration processes in the Greenland sea. These studies generate ideas that can be applied to the preservation and recovery of species that migrate due to global warming.
Acclimatization and adaptation
Organisms respond in two other ways to global warming: acclimatization and adaptation.
The role of omics techniques derived from genetics (genomics, transcriptomics, proteomics, etc.) are starting to divide phenotypic changes (morphology, physiology, behavior, etc.) derived from climate change into acclimatization (differences only in the number of certain RNAs and/or proteins) and adaptation (there are also DNA differences, and new types of RNAs and proteins may appear). At the moment, most research shows that possible changes in organisms due to climate changes represent acclimatization; there is little evidence of true adaptation. The appearance of these possible genetic adaptations due to climate change is being investigated in organisms with short life cycles. Such is the case of insects such as flies, mosquitoes and butterflies, whose populations have shown possible changes in genes related to heat stress, heat-shock or cell death apoptosis, although the changes appear to be polygenic.
Based on these provisional findings, some authors defend that there is not enough genetic information to support the existence of clear and sustained global warming over time. In other words, they argue that global warming is still not a strong enough factor to be able to select certain genetic variations and produce real adaptation. Until now, climate change would have determined how certain genes work, i.e. species acclimatization to the new climate.
Nevertheless and in opposition to the idea that acclimatization is a short-term response that cannot be inherited, there is the possibility that some types of acclimatization (those derived from epigenetic changes in DNA such as methylation) can be inherited and “used” to resist climate change, at least for several generations. Meanwhile, will real adaptation “arrive?”
Genetics against extinction
Today´s extinction rates of organisms are accelerating, although this effect cannot be attributed solely to climate change, since other factors also contribute to such changes (direct elimination, reduction and alteration of habitats, overfishing, etc.).
New techniques in genetics can be very useful to try to “revive-resurrect” species already extinct or in danger of extinction. This can be attempted by cloning them from well-conserved biological material-nuclei, DNA, or by editing the genome of related species with which it is intended to de-extinct using such current techniques as CRISPR. This is the case of mammoths where, on the one hand, it is a matter of finding well-conserved mammoth cells with which to carry out cloning in female elephants, or, on the other, it is a matter of editing the genome of elephants by bringing it closer to that of the mammoth.
But before reaching this point of difficult return, the new techniques of genetic analysis – omics – are being used to analyze a component as critical to avoid extinction as is the genetic variability that the populations of the species present. Thus, it has been determined, for example, that of the more than 64,000 species of vertebrates studied by the IUCN in 2012, more than 10 percent are in danger of extinction due to the set of factors already mentioned; and of them, the majority present a significant reduction in their genetic variability. It is necessary to take measures to stop this genetic deterioration. For this, the use of various tools of the so-called conservation genetics may be useful: in vitro reproduction of endangered species, freezing of embryos and ovules, introduction of reproducers in populations with few numbers, DNA banks, etc.
Global warming, disease and ecosystems
We should not forget the specific effect of climate change on human health and illnesses. In addition to its direct effects on human beings (such as breathing and allergic disorders), global warming can influence the dissemination of vectors of epidemic diseases such as the flu, plague, malaria and even Covid 19. Take for example in the bird, rodent and mosquito populations, genetics warns that in the case of the flu, for instance, some outbreaks (such as the “Spanish flu” in the early 19th century) may be related to a decrease in population size and genetic variability of the virus vector(s) such as in ducks, geese and other wild birds.
Furthermore, genetic studies may contribute to two other major aspects of climate change. Firstly, with regard to clarifying the response of many bacteria and microorganisms to climate change. For example, picoplankton: its metabolism was unknown until now, since the cultivation of picoplankton was not possible. Now, the “omics” make it possible to characterize its metabolism and its potential role in the response to climate change without requiring cultivation.Finally, genetically modified organisms (mostly bacteria and plants) can be used to fight against the effects of climate change such as drought or increased carbon dioxide in the Earth’s atmosphere, and even to recover deteriorated or altered ecosystems.
A special case of an ecosystem that is trying to recover through these techniques is the coral reef. They are currently being affected by the increase in sea water temperatures, along with their acidification, phenomena being linked to the increase in genetic evidence of climate change in the atmosphere and then in the ocean. The result of these processes is that large areas of such reefs are bleaching and degrading, mainly due to the fact that symbiotic algae that live with the coral cannot withstand such conditions and migrate or die. With this, the corals, in addition to losing their color, lose part of their food source and die as well. And with the death of the coral, the entire ecosystem it houses “dies with it”: various invertebrates, fish, plants, etc. In fact, an important part of marine biodiversity develops around coral reefs. To try to combat this deterioration, an attempt is being made to recover some areas already affected by “seeding” them with corals from other areas with genotypes resistant to the aforementioned effects of climate change. And likewise, the possibility of using CRISPR techniques to modify the genomes of corals themselves or those of algae is being studied to make them resistant to new environmental conditions.
Manuel Ruiz Rejón
Professor of Genetics at the Universities of Granada and Autónoma de Madrid