Wednesday, October 20

Large Pleistocene mammals were crucial to preserving plant diversity

A study published in the journal Frontiers in Ecology and the Environment proposes that the disturbances in vegetation generated by the Pleistocene megafauna provided the mechanism that many herbaceous species needed to thrive. According to the CSIC In this context, “mammoths and other large mammals, by walking or removing vegetation, created gaps between grasses (wild species similar to wheat, barley or oats), in which the soil was exposed to the sun.” This allowed herbaceous plants with showy flowers to germinate and establish themselves among the grasses.

“These herbaceous plants with flowers do not have a woody part and need direct sun to grow. That is why the role of large mammals was key to creating these spaces in which they germinated without being prevented by grasses, which are taller and overshadow the plants that are further down, making it difficult for them to flourish, “he explains Francisco I. Pugnaire, CSIC researcher at the CSIC’s Arid Zones Experimental Station (EEZA-CSIC) and co-author of the study. Thus, it is explained that before there was a higher proportion of herbaceous plants of this type with higher nutritional quality, and fewer grasses.

What did mammoths, mastodons, and other large animals eat during the Pleistocene, about 10,000 years ago? Due to their size, the animals known as megafauna required a large amount of energy, which is why they needed a large amount of food of high nutritional quality. However, “the plants that currently form the grasslands of any region of the world, dominated by grasses, do not contain enough nutrients to maintain this biomass of large animals of the Pleistocene.”

An ‘extra’ of energy

In other words, “the ‘extra’ energy was provided by non-grass herbaceous plants, annual or perennial species with showy flowers that store in their tissues the nutrients necessary for the development of large animals.” The study suggests that these herbaceous species flourished in the highly productive pastures of the Pleistocene, the so-called mammoth steppe, and “are, in many respects, superior to grasses in capacities such as growth rate, regrowth, anti-herbivore defense, etc. . ”

Therefore, the alterations of the vegetation cover provided empty spaces that these species occupied. The disappearance of the megafauna at the end of the Pleistocene due to climate changes and the appearance of the human species, gradually deprived these herbaceous species of the adequate areas to survive, causing the grasses to occupy the space and darken the ground, leading to the herbaceous non-grasses to lose their preponderance and maintain the secondary role that is observed in most of the current prairies.

In addition, “the evidence obtained in systems such as the current African savannas, where there are still large herbivores that cause great damage to the vegetation and provide places for the regeneration of non-grass species” support this interpretation, according to the CSIC researcher. From the study center, they point out that “the results of the study could contribute to improve the forage quality in cattle farms and increase the richness of species in natural and semi-natural grasslands”.