Rarity is surprisingly common – University of Copenhagen

28 November 2019

Rarity is surprisingly common among land plants -- and that may be a problem in a changing world

Naia Morueta-Holme, assistant professor at Center for Macroecology, Evolution and Climate, was part of a team of scientists who took on the mammoth task of counting the number of species of land plants. One of the unexpected outcomes was the realization that rarity is common among plants. 

The scientists, lead by professor Brian Enquist, University of Arizona, had to go through 200 million observations of plant distributions. The number of species in the database turned out to be as high as 435.000. Almost 40 percent of these -- more than 150.000 species -- have been recorded less than five times in nature.

The frequency of these very rare species is particularly high in the Northern Andes in South America, Costa Rica, South Africa, Madagascar and Southeast Asia. Apart from being hotspots for biodiversity these areas are also some of the places on Earth most threatened by climate change and human exploitation.

Unless something is done about it. The paper by Enquist et al. is part of a collection of papers from Science Advances made accessible during the COP25 meeting in Spain 2-13. December. Another paper, co-authored by Neil Burgess, professor at CMEC, describes the challenges and principles of dealing with nature in a changing world. In order to reach the goals set by the Paris Climate Agreement, at least 30 percent of the land area will have to be protected, and 20 percent to be designated as climate stabilization areas.


  1. J. Enquist, X. Feng, B. Boyle, B. Maitner, E. A. Newman, P. M. Jørgensen, P. R. Roehrdanz, B. M. Thiers, J. R. Burger, R. T. Corlett, T. L. P. Couvreur, G. Dauby, J. C. Donoghue, W. Foden, J. C. Lovett, P. A. Marquet, C. Merow, G. Midgley, N. Morueta-Holme, D. Neves, A. Oliveira-Filho, N. J. B. Kraft, D. S. Park, R. K. Peet, M. Pillet, J. M. Serra-Diaz, B. Sandel, M. Schildhauer, I. Šímová, C. Violle, J. J. Wieringa, S. Wiser, L. Hannah, J.-C. Svenning, B. J. McGill, The commonness of rarity: Global and future distribution of rarity across land plants. Science Advances (2019).




  1. Dinerstein, C. Vynne, E. Sala, A. R. Joshi, S. Fernando, T. E. Lovejoy, J. Mayorga, D. Olson, G. P. Asner, J. E. M. Baillie, N. D. Burgess, K. Burkart, R. F. Noss, Y. P. Zhang, A. Baccini, T. Birch, N. Hahn, L. N. Joppa, E. Wikramanayake, A Global Deal For Nature: Guiding principles, milestones, and targets. Science Advances (2019).