THE FOSSIL, PROPHET OF THE FUTURE
The industrial age has cost humanity a profound climate change, which is occurring at an unprecedented rate. This process resembles the rapid changes that have affected the Earth’s ecosystems in its geological past and which – therefore – can help us prophesy and direct future choices. Or, at the very least, to tell us why certain choices may have dire consequences, based on the experience of millions of years of Earth’s history.
Over the past 500 million years, our planet has experienced at least five catastrophic periods, which led to the extinction of more than 90 per cent of the organisms living on Earth at the time. According to palaeontology, i.e. the scientific study of prehistory, the last ‘mass extinction’ occurred 66 million years ago, marking the boundary between the Cretaceous and the Palaeocene, and wiping out about 76% of all living species on the planet, including non-bird dinosaurs.
As mentioned, palaeontology studies the living world of past ages in an attempt to reconstruct its history, natural laws and development. One of the most important tasks of science is to reconstruct the natural conditions under which life developed on Earth at various times in its history, and it does so through the study of the remains of organisms and rocks, because they bear the marks of the time in which they were produced, and today we know that climate is an important factor influencing life and the formation of minerals and rocks. The world of palaeontology is constantly being enriched by new discoveries that help us understand the present and think about the future.
A threat to biodiversity
Animal species are dependent on each other to ensure existence and thus biodiversity
With increasing anthropogenic pressures (the effect the human race has on the planet), diversity within the biosphere (the habitable part of the Earth, on the ground and in the air) is decreasing at a rapid rate and is the most serious environmental problem we face today. In a study, entitled ‘Integrating Conservation Biology and Palaeobiology for Biodiversity and Ecosystem Management in a Changing World’, scientists emphasise the importance of palaeontological data from deep time (more than 2 million years ago) for establishing conservation priorities for species and implementing effective conservation measures.
Scientists suggest that palaeontological data from fossils have great power to predict the future and may offer more advice on the preservation of life than is currently known, giving us information on the reasons why species are prone to extinction. Scientists are comparing deep time events with human-induced processes. This comparison can determine the likely long-term response of species and ecosystems to abiotic stressors (non-animal stressors such as drought, salinity, frost and excessive heat).The rate at which plant communities disappeared or changed following a mass extinction event 66 million years ago can be used, for example, to develop a reforestation programme in regions heavily degraded by anthropogenic pressure (environmental modifications produced by human activities).
Studying the reduction in body size in mammals during periods of prolonged high temperatures can be usedto predict changes in the composition and function of future animal communities in response to climate change. Understanding the extinction mechanisms of pelagic sharks at the beginning of the Miocene, for example, could reveal the abiotic factors that cause the decline of sharks in the open ocean today. Deep time analysis is therefore a valuable source of information for predicting the response of species to changing environmental conditions. However, some caution is needed in interpreting the conclusions, as they cannot take into account all aspects of our natural response.
In the footsteps of the dinosaurs
Time pattern of the age of the Earth
It was previously believed that the warm, flat climate of the early Mesozoic was the most suitable environment for dinosaurs. But new research shows that they were perfectly adapted to cold conditions and successfully survived freezing winters, a decisive factor in their survival in the late Triassic. According to many scientists, the mass extinction event, which wiped out more than three quarters of all terrestrial and marine species, including crustaceans, corals and all large reptiles, was triggeredlater by widespread volcanic eruptions, the result of tectonic plate movements.
In addition, the eruptions may have triggered an explosion of carbon dioxide into the atmosphere, which would have raised its already prohibitive levels, causing deadly temperature spikes on land and making ocean waters too acidic for many creatures to survive. The authors of the new study suggest that the most intense phases of the eruptions emitted sulphur aerosols that reflected so much sunlight that they caused repeated global volcanic winters that could last a decade or more; even the tropics could experience prolonged frosts. This killed off non-isolated reptiles, but isolated, cold-adapted dinosaurs were able to survive.
Resistance to cold is due to the probable presence of proto-pearls (forerunners of modern bird feathers, horny skin formations that some dinosaurs presumably had) in many members of the species, as well as a warm-blooded system and a high metabolism, allowed dinosaurs to survive the darkness and cold of volcanic winters and expand to dominate the Earth for the next 135 million years.
Contemporary climate change research focuses on the phenomenon of global warming, especially in polar regions. Scientists are trying to simulate life in a warmer world and mitigate the possible consequences. The changes are very complicated and research on the ancient Arctic can be very useful, especially to understand how precipitation and temperature affect vertebrate populations .
A team of scientists led by Anthony Fiorillo, a palaeontologist at Southern Methodist University in Dallas, Texas, has conducted a study on the Cretaceous period of the northern region of the American continent. The significance of the period and the terrain is that the Earth was in a state of shrinking habitable areas at the time and allows us to model what we might see if global warming continues and the climate becomes as warm and humid as in the Cretaceous period.
Scientists identified two crucial climatic parameters and demonstrated their role in shaping animal and plant populations in Arctic Alaska using two families of herbivorous dinosaurs (Hadrosauridae and Ceratopsidae), which were crucial to the health of the ecosystem in which they lived. The study suggests that mean annual precipitation played a more important role in determining the distribution of herbivorous dinosaurs than mean annual temperature.
The study examined the animal and plant life and ancient climatic conditions of Alaska’s terrestrial ecosystem. It is impossible to analysethe rate of change, which may have been very different during the Cretaceous period, but it is possible to reconstruct the appearance of an ice-free coastline and to see how rivers and floodplains would respond to the spring melting of the mountains if everything did not freeze over, as well as to observe the distribution of plants and animals.
Biodiversity is sensitive to any climate change and is currently in a critical state. Given the commonality of events such as hyperthermic events, habitat loss, and pollution, the question arises: can the risk of species extinction during past mass catastrophes help us in attempting predictions of the current biodiversity crisis? The study, published by the Royal Society, is based on an extinction risk model using a machine learning algorithm based on a series of marine fossils that testify to the extinctions of the Late Permian, Late Triassic and Late Cretaceous (252, 200 and 66 million years ago).
It is worth noting that the mass extinctions of the Late Permian and Triassic periods are associated with the eruption of large igneous regions (areas characterized by extremely large accumulations of magmatic rocks), which led to cascading changes in the environment, such as warming due to greenhouse gas emissions, deoxygenation and ocean acidification. The Cretaceous period is not so clear, as the massive volcanic eruptions coincided with the impact of a large meteorite on Earth, which led to thermal stress in the form of an extreme regional warming pulse around the impact site and extreme global climate cooling in the short term (ten years), followed by ocean acidification and a reduction in organic matter growth over longer timescales. In other words, the initial conditions cannot be said to be the same as those we know with more certainty.
The analysis shows that although there is some similarity in the patterns of extinction selectivity between ancient crises, the selectivity is not constant, resulting in poor predictive performance. As with meteorology, we can hazard a guess, but we cannot predict reality with certainty.
Furthermore, the difficulty of prediction is related to differences in the way threats to biodiversity manifested themselves in the geological past, compared to how they manifest themselves today. For example, anthropogenic pollution today has a much larger scale and includes synthetic substances, while introduction (the deliberate or accidental removal by humans of members of the living world outside their natural habitats) is likely to occur on a much larger spatial scale and at a much faster rate. The size of the geographical area and the richness of species within it undoubtedly offer advantages in terms of survival, but are less decisive in the face of mass extinctions.
The effect of continental drift
Two billion years ago an asteroid hits the Earth, changing the environmental balance for millions of years
At the beginning of Earth’s history, atmospheric oxygen dominated over dissolved oxygen in the oceans. However, an international team of scientists now offers an alternative view of this reconstruction, emphasising the importance of the horizontal movement of tectonic plates and the uneven distribution of dissolved oxygen at the surface and on the ocean floor in the diffusion of oxygen in the soil, sea and air.
The study shows that the oxygen content in the world’s oceans is unstable and fluctuates at intervals of several thousand years. Presumably, such fluctuations could play a key role in the sharp increase in biodiversity, as happened at the beginning of the Palaeozoic, when there was the so-called Cambrian explosion (i.e. the huge increase in finds of fossil remains of living beings in deposits from the early Cambrian period, which is dated to the beginning of the Palaeozoic, around 538.8 million years ago). The movement of the continents could be to blame for this instability.
Although continental drift seems slow, imperceptible and seemingly incapable of causing dramatic changes, it directly affects the movement of ocean waters. Surface waters become colder and heavier as they approach the poles and sink downwards, along with the oxygen they contain, stimulating the development of a biome (a specific terrestrial environment characterised by a particular vegetation) and climate at the bottom. The force of the updrafts lifts organic matter to the surface, triggering the growth of plankton. This cycle is a key factor in shaping the diversity and distribution of marine life.
According to the study, this cyclical process could be interrupted or even stopped altogether, with a major impact on the evolution of marine life on a global scale, if humanity’s impact on the planet proves to be too severe. The University of Sydney study was designed to determine the impact of global warming on the rate of circulation in the deep ocean – the so-called ocean conveyor belt rate (i.e. constant underwater currents). Scientists believe this is very important in predicting the dynamics of ocean temperature and carbon dioxide dissolution.
So far, about a quarter of the carbon dioxide created by human activity (and more than 90% of the excess heat associated with it) has been absorbed by the ocean without major problems. Small organisms drifting in the water use dissolved carbon dioxide to build skeletons and shells. At the end of their life cycle, the organisms fall to the bottom, taking with them the carbon they have collected during their lives. This is how a mass of sediment constantly accumulates on the ocean floor, a global store of carbon.
The so-called ocean conveyor belt, thanks to which today, using the tools of palaeontology and geology, major climate changes can be predicted
Thanks to the geological documentation of the ocean floor, knowledge of its shape and analysis of the bottom sedimentation cycle, scientists were able to understand when and where sedimentation stopped. The scientists concluded that sedimentation was virtually uninterrupted for 13 million years, corresponding to a drop in the planet’s average temperature and the growth of ice caps on land. This suggests that the conveyor belt of the oceans has gradually slowed down, compared to the time when temperatures on Earth were three to four degrees higher than today and deep ocean flows were much faster.
Independent studies using satellite data show that large-scale ocean circulation and ocean vortices have become more active during the last two to three decades of global warming. This is also shown by a study of the seabed around New Zealand, which showed that the production of preserved sea shells in the form of carbonate sediments was greater during ancient periods of global warming, despite the acidification of the oceans at that time. The combination of these results leads to the conclusion that warmer oceans not only have a more active deep circulation, but potentially store carbon more efficiently. But to be certain, a more complete analysis of the geological history of ocean basins is required.
Another interesting proposal has been put forward by an international team of scientists led by researchers at Trinity College School of Science in Dublin. By chemically analysing ancient mud sediments from a 1.5 km deep well in Wales, the scientists were able to link two key events that occurred around 183 million years ago (the Toar period) and led to a sudden warming of the Earth’s climate and subsequent global ecosystem changes. This period is characterised by catastrophic volcanic activity, the so-called Great Eruption Provinces (LIPs), and associated greenhouse gas emissions in the southern hemisphere, where southern Africa, Antarctica and Australia are located today.
Global models for reconstructing tectonic plates and their movement, as well as mercury concentrations in Lower Taurus sedimentary rocks, helped the team discover a fundamental geological process. When the speed of continental plates slows to near zero due to a change in direction, flows of hot magma moving from the base of the mantle, close to the Earth’s core, can rise to the surface, causing large volcanic eruptions and related climate disruptions and mass extinctions. In other words, a normal rate of continental plate movement of a few centimetres per year effectively prevents magma from penetrating the Earth’s continental crust.
A model linking changes in plate motion to surface magmatism
To understand past climate formation processes and to be able to predict future changes and mitigate their consequences, an integrated approach from all scientific disciplines is essential. In this context, palaeontology can offer a unique perspective on past biological changes. In particular, palaeontology makes it possible to systematically assess the effects of past climate changes and parallels with current changes, e.g. by predicting the response of biota (the complex of plant and animal organisms living in a given ecosystem) to climate change, helping to predict r and species shifts, local extinctions, biome changes, and more.
Nevertheless, the Intergovernmental Panel on Climate Change (IPCC) believes that palaeontology is currently unable to provide policy-relevant information on climate change impacts. According to climate experts, palaeontology looks at much longer time scales than those considered relevant in the context of the work of climate protection organisations.
Using the example of studies on mass extinctions of species under varying degrees of warming, the scientific group acting on behalf of the United Nations believes that improving the reliability of claims and quantifying projected losses should be a priority for palaeontologists’ research. One of the main objectives of the IPCC working group is to identify the vulnerability of different systems to climate change, whereas most palaeontological research to date has focused on a single aspect of vulnerability rather than investigating the issue more fully.
According to the IPCC, the contribution of palaeontology to policy-relevant climate impact research could be enhanced by more focused research, explicit consideration of time scales and, above all, better structure and reporting. The fossil record is undoubtedly of great importance for understanding the mechanisms of our planet’s life cycle, with knowledge of long time series of environmental changes that can help scientists predict future environmental responses.
But it is worth noting that most studies and conclusions are indirect and hypothetical, relationships punctuated by the words: probable, possible, predicted, predictable, probable. The world around us is not a closed and predictable system, but a large living organism that is constantly in an active and dynamic state, where predictions remain predictions.There is still a long way to go.