When landscape dynamics shape biodiversity

The movement of rivers, mountains, oceans and sediments over geological time is central to the evolution of biodiversity on Earth. The study, published in Nature, involved the ISTerre [1] laboratory (a member of the OSUG federation) and the University of Sydney.

The Earth’s surface is the living skin of our planet, linking physical, chemical and biological systems. Over geological time, this surface evolves at the whim of rivers, which not only carve out canyons and form valleys, they are also the main vectors for the transfer of sediments and nutrients from mountains to continental plains and oceans.

This study proposes the hypothesis that it is neither geodynamics nor climate, but rather their interaction that, by regulating landforms and sediment flows, determines the long-term evolution of biodiversity.

To test this hypothesis, using reconstructions of ancient climates and plate tectonics, the research team has for the first time digitally reconstructed the evolution of the Earth’s landscape and sedimentary history over the last 540 million years. These unique sets of reconstructions (mapping relief, hydrographic networks, water and sediment flows over geological time) are now available to the scientific community.

The researchers then compared these results with paleontological reconstructions of marine and continental biodiversity over a very long geological period of 540 million years, and the results suggest that biodiversity is highly dependent on landscape dynamics, which determine at any given time the carrying capacity of the continental and oceanic domains, i.e. the maximum number of different species they can contain at any one time.

In the oceans, diversity has been closely aligned with the sedimentary flux of continental origin, which provides the nutrients needed for primary production. The increase in sediment flow that followed the break-up of Pangea explains the "Cenozoic marine revolution". Perhaps even more surprisingly, the mass extinction events in the oceans occurred shortly after the sediment flow had fallen sharply, suggesting that the nutrient deficit destabilized biodiversity and made it particularly vulnerable to catastrophic events, such as a volcanic crisis or asteroid impact.

On the continents, it wasn’t until their surfaces were gradually covered by sedimentary basins that plants were able to develop and diversify, thanks to the development of more elaborate root systems. This slow expansion of terrestrial flora was also stimulated by tectonic episodes, during which varied environments and habitats provided the right conditions for plant development.
For example, the advent of flowering plants some 100 million years ago, which Darwin described as an "abominable mystery", could be due to the fact that, at that time, the continents were covered by numerous sedimentary basins, but also that the landscapes became very varied with the formation of mountain ranges, which would have enabled the development of numerous species, each in their most suitable environment, without competing with one another.

References

T. Salles, L. Husson, M. Lorcery, B. H. Boggiani
Landscape dynamics and the Phanerozoic diversification of the biosphere, Nature, 2023
DOI : 10.1038/s41586-023-06777-z