Thoughts on fauna populations if people all disappeared
In Alan Weisman’s book, The World Without Us, the author ponders “a world from which we all suddenly vanished. Tomorrow.”
This week, people who study Alaska’s wildlife donate some thought to the subject.
Alaska’s lack of people has benefited many species, including caribou, which still outnumber Alaskans, and salmon, which torpedo up our rivers with a staggering, wonderful density that was once seen all over the west coast of North America.
Mark Wipfli has spent many hours on salmon streams throughout Alaska, and the University of Alaska biologist has thought many times of mankind’s impact on salmon. If people were to disappear, Wipfli envisions a slow healing of damage done to salmon habitat. In Alaska, that means the recovery from logging and mining of streamside forests that provide everything from fish food in the form of insects to the contribution of dead trees to waterways (for erosion control and creation of eddies and other features good for salmon).
Old-growth forests (with trees aged from 50 to 200 years) provide ideal conditions for salmon, just as those same trees have benefited us with stout building materials. The mining of minerals we use every day has also disrupted life for salmon.
“If we vanished . . . there would no longer be harvesting or overharvesting,” Wipfli said. “Mining impacts to watersheds would slowly diminish, but would probably take a lot longer. And dams would eventually crumble and tumble, allowing rivers to flow like they once did.”
The bottom line is salmon - and the marine, freshwater and terrestrial ecosystems that support them - would be better off without us, he said. “We continue to create barriers and stressors that collectively make it more difficult for salmon to thrive like they historically did, especially in the Lower 48.”
Along a robust population of salmon, Alaska also is not yet experiencing a bird shortage.
“Birds from six of the seven continents come to Alaska to breed each year – that’s billions and billions of birds,” said biologist Sue Guers of the Alaska Bird Observatory in Fairbanks. “These numbers are estimates from now. Imagine what it was like before our time.”
Alaska’s many million acres of un-peopled river valleys and tundra plains would continue to attract birds if we were gone, but some species would miss us, Guers said. Ravens and gray jays that pick at what we leave behind in cities and towns would revert back to following wolf packs, and the pigeons that live in Fairbanks might find life impossible at 40 below without the warm exhaust of heated buildings.
“Most other species would most likely benefit from humans disappearing,” Guers said. “Think about all the habitat destruction going on in the Lower48 and in Central and South America - loss of habitat is one of the major causes of species loss and biodiversity.”
As years passed without humanity, nature will take down other bird barriers, including wind turbines, cellphone towers, and what Wiesman cited as mankind’s most damaging invention to birds, window glass. But he also wrote that housecats, the expert hunters that kill billions of songbirds worldwide each year, would do quite well without us.
Large mammals like moose and caribou on far-away hilltops might not miss us at all, said biologist Tom Paragi with the Alaska Department of Fish and Game.
“I don’t think the remote portions of Alaska would be much different than we see today, because of intact habitats,” Paragi said. “In contrast, if you “re-wilded” Iowa or Manhattan, you’d have smaller populations of white-tailed deer and raccoons after wolves, bears and cougars come back.”
One of the biggest differences between Alaska and the rest of the world is that we have cleared so little of the landscape for farming here, Paragi said. That has allowed moose their willows and caribou their lichen, as well as the space to breed and move around.
Hunters and predator-control programs affect local populations of moose and caribou, but Paragi said he doesn’t think either would change much in abundance if people were to disappear.
“Moose density near urban Alaska would almost certainly go down as human disturbance of vegetation ended and predators increased, but one lightning-caused fire could change the landscape in a few days more than even a large amount of logging,” he said.
Each biologist in this story also mentioned the lingering affects of a warmer climate and how that may endure after people checked out.
“If we generally have milder winters, species like wood bison, mule deer and fishers will likely continue to spread westward into Alaska, along with deer ticks and others along for the ride on the mammals,” Paragi said.
“A huge unknown is how long human-induced climate-change effects, including ocean acidification, will linger and continue to impact and change ecosystems once we’re gone,” said Wipfli, the salmon expert. “Undoubtedly at least hundreds, more like thousands, of years.”
“Problems like climate-change, pollution and introduction of exotic species all over the world means migrant birds are getting impacted by humans during all aspects of their life cycle,” Guers said.
(This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Ned Rozell is a science writer at the institute.)