An article published in the Nature Communications journal establishes the extent to which the current characteristics and geographical distribution of South American vegetation are determined by the presence of megafauna already extinct in the Late Pleistocene, more than 10,000 years ago. Besides the Desertification Research Centre (CIDE), other parties involved in this paper are the joint centre of the Universitat de València, the Spanish National Research Council (CSIC) and the Valencian Government.

The results of this paper highlight the importance of considering the previous evolutionary history in the explanation of the current ecosystems’ dynamics. The current ecosystems’ diversity can be explained not just by the present environmental factors, but also by those that influenced the communities that populated our planet thousands of years ago.

According to Juli G. Pausas, CIDE researcher and co-author of this study, “we estimate that, in South America, savannah occupied about 10 million square kilometres during the Pleistocene”. Based on the estimates published by researchers, 63 % of them turned into forests after the extinction of the megafauna and 37 % remained as savannah.

“This suggests that South America was a continent dominated by savannah, much more similar to Africa than it is today, and that a significant proportion of South American forests are the result of megafauna extinctions”, concludes Juli G. Pausas.

To comprehend the origin of current landscapes and how those depend on, among others, plant-animal interactions and disturbances they have suffered, the research goes back more than 10,000 years, when a large part of the planet was inhabited by large mammals: the megafauna. The majority of these animals went extinct between the late Pleistocene and early Holocene; however, their impact is still present in the distribution and dynamics of current vegetation.

Anachronisms as indicators of the history of the megafauna

The paper analysed data collected in Central and South America and included data related to plant defence traits (wood density and presence of thorns), climate, soil and forest fires, as well as those related to the historical distribution of the extinct megafauna of herbivorous mammals. The results show that a significant proportion of the geographical distribution of these defence-related features (wood density, leaf size and presence of thorns) is explained by the diversity and size of the megafauna that inhabited these neotropical regions.

Woody plants that live in ecosystems with abundant herbivores are characterized by morphological and physiological adaptations that reduce the damage caused by large herbivores (antiherbivore defence traits). The results of this study suggest that these traits may persist as anachronistic characteristics for thousands of years and be an indicator of megafauna’s history.

“These anachronisms offer us a valuable opportunity to comprehend past megafauna distribution patterns and megafauna-plant interactions, and thus understand the dynamics that have occurred in our ecosystems”, explains Vinicius L. Dantas, a researcher at the Institute of geography of the Federal University of Uberlândia (Brazil) and co-author of the paper.

Reference:

Dantas V. & Pausas JG. 2022. The legacy of Southern American extinct megafauna on plants and biomes. Nature Communications 13: 129.