Scientists hope a new method will pave the way to provide insights into the impact of climate change and habitat loss on biodiversity.
In a study published in Systematic Biology, researchers from Imperial College London, UCL, Dalhousie University and the United Nations Environment Programme World Conservation Monitoring Centre described how their new simulation methods improve understanding of how patterns of biodiversity emerge across the globe.
This new simulation acts like a global weather forecast for all species on Earth, calculating how many species of animal live on land, and how quickly new species evolve. The scientists used their method to estimate that there are between 1 million and 3 million species of animal life on land, including all the species not yet known to science.
How quickly do species evolve?
Professor James Rosindell, Professor of Biodiversity Theory in Imperial's Department of Life Sciences, and lead author of the research, explained, "The two main questions we wanted to answer were how many species of terrestrial animals there are on the planet and how quickly do new species of terrestrial animals evolve."
"The purpose of the study was to uncover those differences in terms of how fast new species evolve and to get some answers of many species there are in total – including all the ones that are not known to science." Professor James Rosindell Professor of Biodiversity Theory
Terrestrial animals are all the animals that live on land. The study found that the animals with smaller bodies speciated at a higher rate, meaning that new species of smaller animals develop more rapidly. When comparing the differences between carnivores, omnivores and herbivores of roughly the same size, the scientists found that carnivores evolved at the highest rate. They also estimated that the total number of terrestrial species is in the range of 1–3 million, aligning with previous estimates, showing that this new method generates results that are consistent with already established methods.
Developing the new method
The team created their simulation method by combining two concepts. The Madingley model is a simulation model that can be used to predict how many individual organisms of different kinds there are in each part of the globe. Neutral theory describes how many species exist in an environment by connecting the number of species, how quickly new species come into existence, and the number of individual organisms. By combining the Madingley model and neutral theory for the first time, the team created a new method for creating a simulation of the diversity of species across the globe.
"A key novelty of this study was that we plugged together the Madingley model and neutral theory for the first time, and I think that's significant because of the huge potential that type of combination has moving forward," said Professor Rosindell.
"The exercise enabled us to estimate the number of terrestrial species of life on earth, including all the numbers unknown to science, but it has great potential beyond this in future work."
Forecasting future biodiversity
With their new simulation method, the scientists say further models of species diversity can be created at a global scale, helping them to make long-term forecasts about changes in biodiversity even where data is missing.
"Everyone is trying to guess at this question that's going to be almost impossible for us to ever know the true answer to, but our findings show we're moving science in the right direction." Professor James Rosindell Professor of Biodiversity Theory
Speaking about his hopes for what future research this study opens up, Professor Rosindell said:
"The end result will be a model of all life on earth that has the ecological and environmental elements necessary to answer questions around what will happen under different climate change and habitat loss scenarios. How many and what kind of species will go extinct? Where on the planet will this happen? Ultimately, this will enable us to steer toward the more favourable scenarios for the future of life on earth."
Fernandes, L. D., Hintzen, R. E., Thompson, S.E.D, Barychka, T., Tittensor, D., Harfoot, M., Newbold, T., and Rosindell, J. (2025) Species Richness and Speciation Rates for all Terrestrial Animals Emerge from a Synthesis of Ecological Theories, Systematic Biology, 2025; syaf006, https://doi.org/10.1093/sysbio/syaf006
