The wide-scale introduction of large herbivores to the Arctic tundra to restore the ‘mammoth steppe’ grassland ecosystem and mitigate global warming is economically viable, suggests a new paper from the University of Oxford.
Grazing animals such as horses and bison are known to engineer the landscape around them, for example suppressing the growth of trees by trampling or eating saplings. When this process is harnessed to restore an ecosystem to a previous state it is called rewilding. It can also be used to change one ecosystem into a different but more desirable state. This is referred to as megafaunal ecosystem engineering.
In many parts of the world, forest ecosystems are considered the most important to restore due to their ability to store carbon. But in the Arctic tundra shifting the landscape from woody vegetation to grassland would enhance the protection of the carbon-rich permafrost, reduce carbon emissions associated with permafrost thaw and increase carbon capture in the soil.
This grassland ecosystem – called the ‘mammoth steppe’ – existed during the Pleistocene period, but was lost when large herbivores such as woolly mammoths went extinct. Horses and bison could act as eco-engineers to transform present day tundra back to grassland. By removing woody vegetation, enhancing grass growth, and trampling on snow in search of winter forage, large mammals increase the amount of incoming solar energy that bounces back to space – known as albedo. Grasslands also favour the capture of carbon in the deep roots of grasses, and enable cold winter temperatures to penetrate deeper into the soil. Altogether, these changes would have a net cooling effect on Arctic lands and delay permafrost melt.
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