Thirteen thousand years ago North America was home to more than fifty species of megafauna–animals that weigh more than one hundred pounds. If you think the United States has a weight problem today, try reconciling the fact that the continent was once home to a four hundred pound beaver, a six hundred pound armadillo, and a nine ton mammoth.
There is a growing body of interest around using megafauna to achieve conservation goals and slow climate change. Megafauna are potent “ecosystem engineers”– a species that has a dramatic influence on the functioning and diversity of its environment. For example, African elephants strip the bark off trees, browse woody vegetation, and deposit nutrient rich dung across their ranges. Elephants’ behavior is necessary to maintain the Savannah ecosystem that supports springbok, antelope, lions, and many others. If elephants were not there, the landscape would revert back to forest. Most continents except for Africa have lost the majority of their megafauna, and as we shall see, some scientists believe that the reintroduction of megafauna into specific areas of the globe could play a role in improving nutrient cycling, advancing conservation goals, and even promoting carbon sequestration.
Given how much of an impact elephants have on their ecosystems, it makes sense to assume that creatures as large and powerful as wooly mammoths had proportionally large impacts on vegetation. Until recently, it has been difficult to know for sure how they affected the landscape, but advances in paleoecology is bringing new data.
A recent study published in the Proceedings of the National Academy of Sciences shows that the decline of North America’s megafauna between eleven and fourteen thousand years ago had widespread and lasting effects on the continent. UC Berkeley’s Anthony D. Barnosky and his team of biologists showed that the loss of mammoths and mastodons coincides with a significant increase in the abundance of deciduous woody tree species– the preferred food source of many large herbivores. By analyzing the relative abundances of ancient pollen in particular areas they were able to detect a pronounced increase in alder, ash, birch, and oak pollen during the time when massive browsers were going extinct. What makes these vegetation changes particularly attributable to the loss of mammoths and mastodons is that they took place during a pronounced cooling phase of the planet– exactly the climate conditions that should have repressed alder, ash, birch, and oak.
So why would an environmental pragmatist care about these ecosystem engineers? Megafauna change the flow of carbon and other elements between the soil, the oceans, and the atmosphere. Studies have shown that “mammoth-steppe ecosystems”, whose grassy plains dominated circumpolar regions until the mammoth’s extinction, supported a much greater abundance of life than today’s arctic tundra. “The average per square kilometer of pasture included one mammoth, five bison, six horses, and 10 reindeer” (http://www.pleistocenepark.ru/en/background/). More importantly in the context of climate change is that some scientists believe that returning large tracts of land to mammoth steppe would slow down the thawing of permafrost by creating colder ground temperatures and higher albedo, thus reflecting more light back into space. Unlike mammoth steppe, as tundra thaws, it releases the potent greenhouse gas methane. Although it is far from scientific consensus, many scientists entertain the idea that “re-wilding” northern latitudes with Pleistocene megafauna such as the wooly mammoth would convert the landscape back to an ecosystem that is better equipped to mitigate climate change. Needless to say, this idea is riddled with unknowns at this time.
Regardless, “Pleistocene Park” has already been established in 160 square kilometers of northern Siberia with the goal of bringing back the mammoth-steppe ecosystem. Researcher Sergey Zimov and his team have already successfully introduced many large animals with the goal of re-engineering this ecosystem: bison, musk ox, moose, horses, and reindeer are among the animals currently living there. Will Zimov stop just there? He has already had discussions with the Harvard Woolly Mammoth Revival team which is currently using CRISPR gene splicing technology and the genome of Asian elephants to make mammoth “de-extinction” a scientific reality.
Even if bringing back the mammoth isn’t the most straightforward way to tackle the issue of climate change, it definitely sounds like the most fun. In the meantime, studies such as that done by Barnosky and his team help lay the groundwork for our understanding of how megafauna have shaped, and continue to shape, the planet.
Full citation for the scientific article:
Barnosky, A. D., Lindsey, E. L., Villavicencio, N. A., Bostelmann, E., Hadly, E. A., Wanket, J., & Marshall, C. R. (2015). Variable impact of late-Quaternary megafaunal extinction in causing ecological state shifts in North and South America. Proceedings of the National Academy of Sciences . http://doi.org/10.1073/pnas.1505295112
Featured image- Mauricio Antón via Wikipedia
Giant Beaver- Dantheman9758
Mammoth vs. Mastodon- Dantheman9758 via Wikipedia
Pleistocene Park- ShaneP via boards.theforce.net