Origin of grasslands

Article By:

Retallack, Gregory J. Department of Geological Sciences, University of Oregon, Eugene, Oregon.

Last reviewed:2014

DOI:https://doi.org/10.1036/1097-8542.YB140813

Grasslands are the foundation of agriculture, providing the grains and proteins for a hungry world. Forty million years ago (MYA), there were no well-drained grasslands. However, today grasslands occupy approximately 40% of the land area of our planet. Grasslands have been considered to be adapted to areas of diminished precipitation on the downwind side of topographic obstacles that are created by mountain uplift and the tectonic reorganization of ocean currents. Now, there is an alternative hypothesis: Grasslands were a biological force for global change through the coevolution of grasses and animals that eat mainly grasses (grazers), creating cooler and drier conditions because of the light color of the grasses, limited evaporation of water from plants into the atmosphere, and deep organic soils. Organisms in coevolutionary trajectories adapt to each other rather than to their environments, so they can be forces for global change. For example, humans are a force for global warming and, by ploughing and harvesting, they have undone the cooling effects of grasslands. However, carbon farming techniques can offset human-induced global warming.

The content above is only an excerpt.