We will also cease, if the ecological balance is no longer present
A Jahr100Wissen / 100 years ago intervie with the biologist Professor Dr. Gela Preisfeld on the extinction of species and the Lazarus effect
100 years ago, the last Atlas lion was shot in Morocco. But scientists have been observing the extinction of species for centuries. What are the reasons for this?
Preisfeld: Panthera leo leo, the Atlas lion, was a very beautiful animal, and became extinct since the use of firearms increased and the lion was considered a popular hunting trophy. Another large, impressive animal that has also become extinct in the last hundred years is the pouch wolf, also called the Tasmanian wolf. This belonged to the marsupials like the koalas and the kangaroos, but was a predatory marsupial. The last animal to survive, for a relatively long time, of this species then became extinct in a zoo in the 1930s. However, these examples are due to anthropogenic changes such as habitat loss and poaching rather than major extinction events resulting from climate change.
There are many examples of species extinctions. In zoology, we call major species extinctions a faunal change. Right now, we are in a quaternary extinction wave that started about two million years ago and is still going on. Species extinction itself has been going on for millions of years. We actually know of at least five specific, major extinction events that we call the Big Fives. A Big Five includes an extinction event when at least 75% of the species have disappeared. That is quite a lot. In between, there are still small extinction events, where about 50% of the species are extincted.
I would like to point out these Big Five. The first took place in the Ordovician, 444 million years ago, due to long cooling events and associated glaciations. This, of course, leads to extinction for all organisms that cannot migrate. The second then occurred in the late Upper Devonian, 372 million years ago, due to a more rapid alternation of warm periods and glacial periods (ice ages), so that organisms could not adapt quickly enough. At the same time, there was also a lowering of the sea level, which had additional strong consequences. The third extinction event was then at the end of the Permian, 252 million years ago, when there was a drastic warming of 10 degrees. Of course, this had climatic consequences, also concerning the precipitation. The fourth was then about 200 million years ago at the Triassic-Jurassic boundary, where again the warming played a role. The fifth we know actually all, the large mass extinction in the Cretaceous-Paleogene boundary before approximately 66 million years, with which e.g. the dinosaurs also became extinct. And the extinction of the dinosaurs freed up many niches that could be used by mammals, which then diversified quite a bit.
Now, we are actually also in a mass extinction process. One might have to say 'The Big Six' in the near future. The only thing is that what we are experiencing now is different from the historical extinction processes in various aspects. It is much more dramatic, because it is happening much faster. That is the dangerous thing. Unlike the temperature changes in history and the water level changes, global warming is now happening a thousand to ten thousand times faster than it used to. Of course, no animal can keep up with that. In the last 50 years, you can see a 70% decrease in animal species, especially megafauna, large animals.
So far 1.5 million animal and plant species are known to science. Five to nine million animal and plant species are estimated to exist on earth. Of these, up to 58,000 species die each year before they are discovered and described. Many scientists are already talking about the 6th mass extinction in the history of the earth, but this time it is knowingly caused by humans through the destruction of habitats, pollution or the introduction of animals into foreign ecosystems. Is the situation hopeless, or do countermeasures also exist?
Preisfeld: Such organisms find a purely biological solution when they can simply leave their habitat and find other niches. But of course, not all of them can do that. The question is, what can we do to change things? After all, according to the Climate Change Convention, the focus is on limiting damage to two degrees of global warming in order to minimize further extinction processes. Unfortunately, not even Germany reaches this target, although, even the Corona pandemic contributes to it, since the CO2 emission declined a bit as a result. Actually 30% of the areas on the land and on the oceans should be conserved. Here, conserved means protected and preserved. However, this is prevented by monocultures and the use of large amounts of harmful pesticides as well as the further degradation of near-natural areas on a huge scale worldwide. There are small spots where something happens, but the extinction risk for organisms is simply enormous when a habitat changes abruptly. All those that cannot adapt lose out, do not reproduce effectively, cannot use the available resources for themselves. Sustainable handling and sustainable use of nature is becoming more and more urgent.
We have too few scientists and too few independent advisors in politics. There are so-called conservation plans to minimize the risks of extinction, but these only apply to certain regions, such as the tropics or the Great Barrier Reef. The Convention on Biological Diversity has been signed and recognized by 196 nations and, in addition to preserving biodiversity, also aims at sustainability and fair distribution of genetic resources. That really is the only way we can make a difference across national borders. If we protect one species here, that is good, but it does not bring the progress we need. This 30% that is to be protected, with that you could actually ensure successful biotope protection, if you keep to the two degrees of global warming. According to projections, you could save 50% of the species with that. So if we kept to the conventions, we could massively curb the extinction of species.
There are, of course, other consequences, such as the melting of the permafrost, which you do not even want to think about, but it is happening. And the bad thing is that everything we do now will only have an impact on the climate in 30 years. The conversion processes in the atmosphere or the rebuilding of the ozone layer simply take a very long time.
According to Nabu, the porpoise and the green lizard, among others, are acutely endangered in Germany. The populations of farmland birds have declined by 34 percent since 1980. Almost a third of the mammal species in Germany are endangered. This is the result of the current Red List of Mammals presented by the Federal Agency for Nature Conservation (BfN) and the Red List Center (RLZ). Can science help to stop this development with its know-how?
Preisfeld: Science can provide data, it can develop strategies. Biotope and habitat protection instead of species protection would be two different ways of looking at how to go about something like this. Science plays a major role here. But the implementation has to be done by politicians and the economy has to join in. If we always pursue a policy that is in line with the economy, then we simply will not do justice to the threats to our environment and ecology. Both are not possible, the economy must rethink and be ready. It must not just threaten to leave with their companies here and look for their tax havens if the burden and the requirements become too great. At the moment, companies are then relocated to Africa or Asia, where there are, so to speak, no environmental regulations at all, in order to finance our luxury products. Instead, it must recognize that there are also natural limits to its growth.
And we, too, have to take a look at our own noses and rethink our actions.
Another reason for species extinction are non-native, invasive species. What do we mean by this, and which ones are there in our country, for example?
Preisfeld: According to WWF (World Wild Fund For Nature), there are over 260 animals and over 600 plants that have been introduced to us. But not all of them are dangerous and thus qualify as invasive. The only organisms of invasive concern are those that either threaten native species or pose a health or economic threat to humans. For example, the ragweed (Ambrosia artemisiifolia) is a health concern because it is highly allergenic. The pollen and also the contact with the plant can cause severe allergic reactions. It actually comes from North America, and could survive well in Southern Europe for a while. Only the seeds could not tolerate frost, which prevented it from ripeness. Then apparently, about 20 years ago there was a mutation and now the seeds are frost resistant and can spread better. That is how this can happen. Or also the giant hogweed (Heracleum mantegazzianum), which pretty much displaces our own hogweed and is also a contact allergen. The milky sap causes allergic reactions and contact with it can also cause burns. On the other side, we enjoy the summer lilac (Buddleja), which is becoming established on fallow land. It too is an invasive species. In terms of animals, we have the American crayfish, the camber crab. That is displacing our own crayfish (Astacus astacus) because it is bigger and stronger. It also transmits a fungus called crayfish plague, to which it itself is immune. But our native crayfish are not immune to it and are being displaced. Conservationists are lifting the invaders out of the rivers en masse or setting traps. There are others, of course: the ornate turtle, the American bullfrog, which eats small birds and even small mammals, which in turn are food sources for other organisms. The raccoon is also an invasive species. But there, I think it is all too late by now. It has already become a permanent fixture here. You cannot eradicate it anymore.
If man upsets the balance of nature too much, he deprives himself of his livelihood. Could man not become an endangered species himself one day?
Preisfeld: Absolutely. If we continue like this, it will be only possible to survive in very small special niches, if at all. Nature is not bothered by major climate changes, it adapts. We have seen this with the Big Five, forty thousand years of continuous rain, no human being can survive, nature can. We humans are adaptable, but there are limits. If we are deprived of our livelihood, if nothing grows properly, if the ecological balance no longer exists, then we will also extinct.
Animals are often particularly adaptable. Sometimes the so-called Lazarus effect occurs in extinct species. What is that?
Preisfeld: This goes back to the resurrection of Lazarus by Jesus, that is a figure that was believed to be dead and was resurrected. With it, exactly this is meant, i.e. that allegedly extinct species come back, that one finds them suddenly again. Such a phenomenon could have two causes. First, the historical, fossil record could have been incomplete, so that they were effectively always there, but that one did simply not have the evidence for it. Or, a few organisms could have retreated into nearly invisible niches and recovered there, becoming more prominent again. An example of this is Wollemia (Wollemia nobilis). This is a coniferous tree that belongs to the Araucaria family. Wollemia was firstly rediscovered in Australia in 1994 in remote gorges in the Blue Mountains. It was then genetically verified. Therefore we know that this tree has always survived. This is such a typical Lazarus effect. In the animal area there is the Lazarus effect with many rats and mice and also with birds, of which one thought they there became extinct. However, this is, above all, due to incomplete dating.
Perhaps I am painting a gloomy picture here. We will certainly still be able to experience positive aspects in our lives if the efforts of politics and business continue hand in hand. America is now also back on board, since climate protection is extremely linked to the extinction of species. Maybe something will change now, hope remains in any case.
Uwe Blass (Interview on January 21, 2021)
Professor Dr. Gela Preisfeld studied, received her doctorate and habilitated at the University of Bielefeld. After short research stays in Australia and a substitution at the Goethe University Frankfurt/Main, she accepted the appointment to the Chair of Biology and its Didactics, Zoology at the University of Wuppertal in 2006.