In the landscape of Yellowstone National Park, bison play a transformative role in the grasslands. A recent study reveals that these large herbivores, when moving freely, enrich the soil without damaging it, improving forage quality and keeping soil carbon intact.
The role of bison in improving grass
Contrary to popular belief, bison herds do not devastate the land. In their natural habitat, they allow for a 150% increase in the crude protein of plants. This increase is due to an accelerated nitrogen cycle, facilitated by soil microbial activity and constant grazing.
The study, led by Chris Geremia and his team, covered the period from 2015 to 2022, analyzing 16 grassland areas. Using fenced plots, they compared excluded zones with those of free grazing, measuring vegetation, carbon, and nutrients in the soils.
The findings highlight that areas of intensive grazing not only maintain productivity but also retain soil carbon. This “green factory” produces more nutritious grass, essential for the herbivores that depend on it during the winter.
The constant movement of the herds creates a mosaic of habitats. In some areas, the grass is short and dense, rich in nitrogen, while in others, it grows tall and accumulates biomass. This diversity favors plant and animal biodiversity, providing shelters and microhabitats.
Historically, Yellowstone has been a continuous refuge for bison. Although the population drastically reduced at the beginning of the 20th century, today it has recovered significantly. Recently, it was determined that Yellowstone bison form a single genetic population, which strengthens their adaptation and survival.
Besides their ecological value, bison have a profound cultural significance for the indigenous nations of North America. Initiatives like the Bison Conservation and Transfer Program aim to restore these cultural and ecological connections, benefiting local communities.
In a context of climate change, the case of Yellowstone offers vital lessons. Bison, by facilitating nutrient recycling and creating diverse habitats, act as an “ecological insurance” against extreme climates. This highlights the importance of allowing large herbivores to migrate and complete their natural cycles.
The study on Yellowstone bison was published in the journal Science.
