Our Earth is full of life. There are many species of animals living at the tops of mountains, in the depths of oceans and in the thickets of jungles. However, what is the biggest possible number of species that could live on the planet? A new research from the University of Southampton provided first statistical evidence that environmental changes determine the number of species that can exist on Earth.
One may imagine that there could be an infinite number of different species living in our planet. However, scientists from different fields, such as evolutionary biology, ecology and palaeontology, have been debating if the upper limit of species diversity exists.
Now scientists analysed the fossil record of microscopic aquatic creatures called planktonic foraminifera to prove that this upper limit depends on the environmental conditions. In other words, it is changes in the environment that determine how many different species can live on Earth. This may look like common sense – the better the conditions, the more wildlife can survive in a particular area. But scientists say it is not all that simple.
Dr Thomas Ezard, lead author of the study, said: “analyses of how species numbers have changed over time have assumed that any limit has always been the same, even through periods of massive climate upheaval. Our data reject this idea of fixed rules for competition among species and instead show that the limit to the number of species that can co-exist on Earth is much more dynamic”. In other words, it is changes more than anything that puts a cap on species richness.
Team analysed 210 evolutionary species of macroperforate planktonic foraminifera in the past 65 million years. They found that not only their populations were regulated by competition among themselves, but also had a finite upper limit. Mathematical models revealed that it is the changes of environmental conditions that alter the outcomes of the competition. Scientists are glad to finally find a good method to research diversity of species. Usual fossil records are incomplete, but microfossils provide a strong basis for such analysis.