What is it about?
In this far-reaching article, we combine continental growth models and climate models for synchronously and asynchronously rotating planets to gain a better understanding of their habitability. From this starting point we apply two biogeographical metrics to gain a better understanding of how life can be accommodated on different planets of varying mass and stellar type. Adopting different distributions of land area over time, we apply the well-used Species-Area Relationship for life on Earth in marine and terrestrial (land) environments. These relationships allow a good understanding of how life may be accommodated on these planets, given very different environmental conditions. Finally, we use a more generic relationship between Shannon Landscape Diversity Index and the Shannon species diversity and relate the diversification of the biosphere to an entirely different measurement by Lingham and Loeb of biological diversity on planets of differing land area.
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Why is it important?
Accompanying and extending the earlier work on Phytoclimatic Mapping of Exoplanets (IJA, 2020), this particular paper is the first quantitative assessment of habitability that clearly links ecological approaches to more generic measurements of habitability. Species Area Relationships (SARs) are a fundamental relationship of all life on Earth, irrespective of the organisms size or location. Microbial life, plant life and animal life all obey these relationships, therefore, it is critical that considerations of habitability elsewhere in the universe, incorporate this and other ecological relationships. While the inclusion of Shannon landscape and Species diversity is done in a very basic manner, that the result matches that in a separate analysis by Avi Loeb and colleagues, is very encouraging and suggests that once we are able to determine the geomorphology of alien worlds in more detail, application of SARs and Shannon diversity indices will provide far more detailed constraints on the kinds and diversity of life that these worlds will contain.
Perspectives
The article grew out of earlier discussion with Rodrick Wallace and an earlier, pair of qualitative papers published in 2018 in the International Journal of Astrobiology. I was looking for a means of quantifying habitability and the Species Area Relationship (SAR) and Shannon Diversity Index were natural choices. Putting together the models, to include continental growth, the role of plate tectonics in the emergence of continents and the effect of tidal-locking took some doing and we are very grateful to the patience of the editors and reviewers in producing this summative work.
Dr David Sinclair Stevenson
Carlton le Willows Academy
Read the Original
This page is a summary of: Biogeographical Modeling of Alien Worlds, Astrobiology, July 2021, Mary Ann Liebert Inc,
DOI: 10.1089/ast.2020.2304.
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