I can’t help the impulse. Whenever I’m hiking through the western forests, prairies, and deserts, my mind conjures up images of Ice Age beasts. I guess I keep engaging in the fantasy because I know I just missed them. Ten thousand years is nothing from a geologic perspective. Shasta ground sloths wouldn’t seem out of place shuffling through groves of Joshua trees, mastodons should still be cracking conifer boughs in the woods, and the grasslands were so recently the place where deer, antelope, and camels played.
But the places I scuff my boots aren’t the same as they were back in the heyday of North America’s enormous herbivores. While there have only been a few clicks of the Cosmic Clock since the end of the Pleistocene, the world hasn’t remained in stasis as if waiting for the return of our missing megafauna.
In fact, as Elisabeth Bakker, Jacquelyn Gill, and others argue in a recent review, the extinction of the great Ice Age beasts has created a world dramatically different than the one roamed by shaggy proboscideans and enormous sloths.
Herbivores are plant predators. It might be strange to think of them that way. A horse plucking up grass or an elephant chawing a mouthful of leaves isn’t as violent or gory a spectacle as a pack of wolves taking down an elk. Yet ecologists call the feeding habits of herbivores “predation” for good reason. The interactions may be slower and harder to see, and there is cooperation in addition to competition, but there are still arms races between herbivores and the plants they rely on. And this constant shuffle is what helps create the landscapes we see all around us.
Consider the American mastodon. This “bubby toothed” elephant was a browser, preferring tree branches and other woody vegetation to the diet of grass enjoyed by its distant cousin, the woolly mammoth. But the mastodon didn’t just eat trees and shrubs. The beast would have trampled down paths through the woods and scraped its tusks against tree trunks, further altering the landscape around it by stamping out some young plants and hindering the growth of others. Mammut americanum wasn’t just a big vegetarian.
The beast, Bakker and coauthors write, was an ecosystem engineer.
The same was true of many other herbivores that lived around the world until very recently. Up until about 600 years ago, for example, giant, flightless birds called moas browsed in the forests of New Zealand, helping to create openings in the woodlands that allowed light-sensitive plants to thrive in the patches they opened up. Since their disappearance, however, the forest has closed, with wire plants—whose springy anatomy made them resistant to moa depredations—spreading in greater numbers.
Modern, short-term experiments have shown the same pattern. When big herbivores or either eliminated or excluded from an area, Bakker and colleagues write, the woodlands start to close up. Not as many young plants are being pulled up and fewer adult plants are having to struggle to put out leaves against the onslaught of big browsers.
For example, experimental studies have shown that areas where African elephants have been excluded can host 42% more trees than when the mammals are stripping them and pushing them over. Through extinction and the restriction of our last few megaherbivores to parks and game reserves, we’re playing out a miniature version of what happened when the Pleistocene’s major plant predators went extinct.
So when I set out from my Salt Lake City apartment and climb up above the level of the Lake Bonneville shoreline, to where my Ice Age inspirations used to roam, I need to do more than picture Harlan’s ground sloth or a mastodon trundling through the stands of oak and aspen. I need to think about what those herbivores did. Of branches stripped bare, toppled trunks, and wide paths through the woods pressed down by the hungry herbivores.
The lost megafauna weren’t just charismatic characters from a closed act in Earth’s history. They helped make the world what it was. I am only sorry that I can’t see what they created.
Reference:
Bakker, E., Gill, J., Johnson, C., Vera, F., Sandom, C., Asner, G., Svenning, J. 2015. Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation. PNAS. doi: 10.1073/pnas.1502545112
Go Further
Animals
- Octopuses have a lot of secrets. Can you guess 8 of them?
- Animals
- Feature
Octopuses have a lot of secrets. Can you guess 8 of them? - This biologist and her rescue dog help protect bears in the AndesThis biologist and her rescue dog help protect bears in the Andes
- An octopus invited this writer into her tank—and her secret worldAn octopus invited this writer into her tank—and her secret world
- Peace-loving bonobos are more aggressive than we thoughtPeace-loving bonobos are more aggressive than we thought
Environment
- Listen to 30 years of climate change transformed into haunting musicListen to 30 years of climate change transformed into haunting music
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- U.S. plans to clean its drinking water. What does that mean?U.S. plans to clean its drinking water. What does that mean?
- Food systems: supporting the triangle of food security, Video Story
- Paid Content
Food systems: supporting the triangle of food security - Will we ever solve the mystery of the Mima mounds?Will we ever solve the mystery of the Mima mounds?
History & Culture
- Strange clues in a Maya temple reveal a fiery political dramaStrange clues in a Maya temple reveal a fiery political drama
- How technology is revealing secrets in these ancient scrollsHow technology is revealing secrets in these ancient scrolls
- Pilgrimages aren’t just spiritual anymore. They’re a workout.Pilgrimages aren’t just spiritual anymore. They’re a workout.
- This ancient society tried to stop El Niño—with child sacrificeThis ancient society tried to stop El Niño—with child sacrifice
- This ancient cure was just revived in a lab. Does it work?This ancient cure was just revived in a lab. Does it work?
Science
- The unexpected health benefits of Ozempic and MounjaroThe unexpected health benefits of Ozempic and Mounjaro
- Do you have an inner monologue? Here’s what it reveals about you.Do you have an inner monologue? Here’s what it reveals about you.
- Jupiter’s volcanic moon Io has been erupting for billions of yearsJupiter’s volcanic moon Io has been erupting for billions of years
- This 80-foot-long sea monster was the killer whale of its timeThis 80-foot-long sea monster was the killer whale of its time
Travel
- How to plan an epic summer trip to a national parkHow to plan an epic summer trip to a national park
- This town is the Alps' first European Capital of CultureThis town is the Alps' first European Capital of Culture
- This royal city lies in the shadow of Kuala LumpurThis royal city lies in the shadow of Kuala Lumpur
- This author tells the story of crypto-trading Mongolian nomadsThis author tells the story of crypto-trading Mongolian nomads