Repopulating the Mammoth Steppe
To keep the planet cool, you want grasses in subpolar regions, not trees, and you get grasses when you reintroduce herbivores. That is the driving logic for Sergey and Nikita Zimov, Russian father-and-son scientists working to protect the world’s permafrost.
Permafrost is a thick layer of perennially frozen, carbon-rich soil that covers 24 percent of the Northern Hemisphere. Perma indicates permanence, except it is thawing as the world warms, releasing greenhouse gases from defrosted ground. A vast grassland ecosystem called the mammoth steppe once spanned the regions where permafrost is found. Today, herbivores no longer roam and steppe has been replaced by taiga forest and mossy tundra.
The Zimovs created the Pleistocene Park in Siberia to demonstrate that by restoring grazers and grasslands, permafrost melting can be prevented. How so? When horses, reindeer, musk oxen, and other denizens of the frozen north push away snow and expose the turf underneath, the soil is no longer insulated and is 3 to 4 degrees Fahrenheit colder—perhaps just cold enough.
1.4 trillion tons of carbon are buried in permafrost—two times more than what is held in all the forests worldwide. Restoring the mammoth steppe might create the margin of safety needed to keep that carbon where it is.
Technical summaries for each solution will be available May 1, 2017.