Researchers from the University of Helsinki and researchers representing Peking University and the Chinese Academy of Sciences in Shanxi province in China. This area is famous for its “red clay”, formed from material carried to the site by the wind, and containing numerous mammal fossils (dragon bones, as they are called) dating back 5.5 – 7.5 million years. By investigating these mammal fossils researchers are trying to discover how vegetation and climate have alternated from one region to another and over time. This information can be used in, for example, verifying the results gained  by paleoclimate models.

The paleontologists and geologists of the University of Helsinki have excelled during the last few decades as researchers on continent-scale climate changes and their biological consequences. One of the most significant research areas, studied since the 1980s, is the Miocene epoch that prevailed 7 – 11 million years ago. Miocene research is based on extensive field studies, the results of which can be used to collect a number of measurable quantities. The basic idea is that plant and mammal fossils can be used to determine global climate history indirectly. The regular patterns of the fossil material were also the starting point for the modeling collaboration with CSC.

”When we examined the fossil data and the calculated environmental estimates, we could not avoid the conclusion that weather phenomena, whether similar or different, occurring during the same era must have had the same causes. The cyclic phenomena prevailing today over wide areas, such as el Ninõ/La Nina, are examples of the atmospheric cycle”, explains Professor Mikael Fortelius, the initiator of the research project.

Dental crown height tells us about climate

This multidisciplinary project is working to find out how climate has affected the areal distribution, evolution and extinction of faunal and floral species, and vice versa. The project also investigates the cyclic atmosphere-ocean movement during the Miocene epoch.

One of the variables used in modeling is the dental crow height of herbivore mammals; this is important as an index of rainfall. ”Based on the wearing of the tooth we can conclude what kind of food the animal has been feeding on. Based on diets, we can make conclusions about the biological conditions in the area, since a certain plant requires a certain temperature and rainfall”, says Fortelius.

Once it became clear that the variable, in this case the dental crown height, does not depend on the species or the number of animals in the flock, it facilitated our understanding of paleoclimatic changes, their mechanisms, and consequences. ”This provided a window through which, as paleontologists, we were able to gain entry: would it be possible to use the material to explain why rainfall in China is increasing while the Mediterranean area is becoming more dry?”

Warm and humid

The climate during the Miocene epoch was warmer and more humid than today. The average temperature was 2.9 °C higher than today. Waterways stayed free of ice all year round even in the most northerly areas, and the North-South temperature fluctuations that we take for granted today were considerably less. For example, forest zones in the Miocene were extensive evergreen forests that extended much closer to the polar regions. The fauna in the Miocene forests and meadows was abundant, with species ranging from the three-toed horse, Hipparion to the saber- toothed cat, Machairodus. Over the past decades, one of the success factors for the project has been the information on extinct mammals saved in an international database by the University of Helsinki. The database called NOW (Neogene of the Old World) is extensive both with respect to time and regions: it contains information on the distribution, sites of discovery, and ecology of mammals found.

Mikael Fortelius’ group has calculated how extensive the effects would have been if the Sahara had become a desert during the Miocene epoch. Being light-colored,  a desert reflects heat and light back to the atmosphere many times more than darker-colored vegetation. According to the model, replacing the savanna with a desert would have led to climate cooling in the nearby regions of North Africa.

Chicken or egg?

The common idea is that climate has a one-way effect on vegetation, but according to paleontologists, things are not quite so simple. Research indicates that certain feedback mechanisms are involved. ”Plant transpiration has a direct impact on atmospheric humidity, and different vegetation regions reflect heat radiation in different ways. These effects are multiplied in the atmosphere”, says Fortelius.

The type of vegetation in certain areas can have a global effect. ”The Sahara used to be a savanna, and we have calculated the effects of this, and looked at how things would have been different had the Sahara become a desert during the Miocene period. Being light-colored, a desert reflects heat and light back to the atmosphere many times more efficiently than darker-colored vegetation. According to our model, replacing the savanna by a desert would have led to climate cooling and aridity in the nearby regions of North Africa, cooling in Central Asia, a slight increase in rainfall in South-Eastern and Eastern Asia (more powerful monsoons), and cooling in North America.

Among the important questions, relating even to our current climate are: how does the development of plant ecosystems affect sea surface temperatures and what are the extent and intensity of the effects on the ecosystem as a whole? In principle, the processes are universal, and the models can be applied just as well to the paleoclimate ten million years ago, as to today or the future. ”If we play a mind game, in which the current era is regarded as only a single time horizon within the period covered by the fossil data and we have the same level of knowledge on today’s species as we have on those of the Miocene period, we can use modeling to calculate various scenarios also for the future.”

”But of course, we have to be careful with what we say. I am not saying that our method is better at modeling the future than those of the major international projects that are specializing in this”, Fortelius says with a smile. ■


Samppa Haapio