The extinction of megafauna 10,000 years ago led to a reorganization of ecosystems, study says Sciences

The global extinction of large mammals such as mammoths and giant sloths, between 50 and 10 thousand years ago, left traces on the evolution of plant and animal species and the functioning of ecosystems. Seed sizes of plants and carnivores have decreased to adapt to a world without these large animals responsible for dispersing seeds and feeding large predators. Moreover, many plants, previously consumed by large herbivores, are now controlled only by fire. This is what suggests research from the State University of Campinas (Unicamp), published on Tuesday (12) in the scientific journal Annual Review of Earth and Planetary Sciences.

The conclusions are the result of a review of the latest available literature on this topic, to explain the direct and indirect impact of Pleistocene extinctions on plants and animals. These events have caused the disappearance of more than 70% of megafauna worldwide, and their consequences could go far beyond a decline in species richness, according to Mathias Mistretta Peiris, a researcher at Unicamp and author of the study. “Mammals we call megafauna can weigh more than 1,000 kilograms, consume a lot of food, disperse nutrients through their feces, and have the ability to move long distances. Extinction has caused a loss of these processes,” he explains.

The decline in plant seed size after the extinction of megafauna may have occurred as a result of the absence of large frugivores, since surviving species did not have sufficient body structure to consume and disperse large seeds. “Once the megafauna disappeared, the large seeds were no longer able to spread far from the plant, reducing their chances of germination,” says Pires.

The researcher also highlights that the lack of large mammals may have driven part of the evolution of plant species. According to him, “Little by little, the size of the seeds decreased, because smaller animals chose smaller seeds.”

It was not only the relationships between plants and herbivores that were affected. The extinction of large plant-eating animals also affected the survival of their predators, such as saber-toothed cats and cave lions. They became extinct, while the species that survived, such as the jaguar and puma, needed to incorporate smaller prey as main dishes into their new diet.

The research also indicates that changes in the relationships between plants, animals and the environment after the extinction of megafauna were crucial in determining the structure and functioning of current environments. “Since the Ice Age extinction, the location and importance of species in ecological networks has changed,” says Peiris. With fewer large herbivores, large-fruited plant species were removed from the center of ecosystem interaction networks, leaving smaller species to dominate the existing landscape. “The large predators that have survived are becoming more important, as there are far fewer species today than in the past,” he explains.

For the researcher, it is important to understand the past and create strategies to deal with new extinction events, as megafaunal extinctions have modified countless ecological interactions and processes. “The integration of the fields of paleoecology and conservation biology can help us develop strategies to restore functions performed by megafauna, such as the distribution of nutrients and seeds and the regulation of natural populations,” Peiris highlights.