For most of the last 300 million years, Earth’s ecologies were shaped by enormous, plant-eating animals: first dinosaurs and later mammals, clearing vegetation and distributing nutrients and generally making habitats more resiliently abundant. Then along came humans, and we know how that story, so often told, turned out.
But might another story yet be written — of how people can replicate the life-nourishing impacts of megaherbivores? Is it possible for us to enrich the world in ways woolly mammoths and giant sloths once did? It’s worth trying. “Ecosystems would certainly become much more diverse and bountiful,” says Hervé Bocherens, a paleobiologist at the University of Tubingen, “and probably more stable when facing climate change.”
In a paper published in Frontiers of Ecology and Evolution, Bocherens chronicles the rise and fall of megaherbivores, opining briefly on debates over what caused their Ice Age extinctions — human hunting, says Bocherens, pushed the climate-stressed animals over a tipping point — and describing how Stone Age societies actually performed many of their ecological roles.
As had the giant creatures whom they drove extinct, so did our ancestors create openings in forests, redistribute nutrients across landscapes, and plant seeds that smaller animals struggled to process. It was only a “partial restoration,” notes Bocherens, and there were some animals humans didn’t replace: woolly mammoths, for example, whose activities produced the so-called mammoth steppe, a sort of Arctic prairie that was once Earth’s most widespread biome.
That partial restoration was better than nothing, though, and in those few areas today where megaherbivores — mostly elephants — still exist in ecologically meaningful numbers, the importance is clear. “Where they have disappeared,” says Bocherens, “there is a clear decline in diversity for plants and animals, with increase of fire and a less stable ecosystem to external disturbances.”
No longer, however, do humans fulfill the roles of megaherbivores. Industrial land-clearing and seed-dispersal and nutrient-cycling is conducted in ways that mostly precludes other animals from partaking in the bounty. Could that change? Perhaps, says Bocherens. We might yet learn to share agricultural landscapes with the megaherbivores who remain, and contemplate reintroducing others to wilder places, and think about how our ecological roles compare to our ancestors.
It won’t be easy, but we know it’s possible.
Source: Bocherens, Hervé. “The Rise of the Anthroposphere since 50,000 Years: An Ecological Replacement of Megaherbivores by Humans in Terrestrial Ecosystems?” Frontiers in Ecology and Evolution, 2018.
Image: Mauricio Antón / Wikipedia