What happens to all the animals if men were to disappear?

February 21, 2006 10:57 PM

EndOfTheWorldFilter: Biologists in the house? What happens to all the animals if men were to disappear?

I'm fascinated by end-of-the-world stories like The Stand, 28 Days Later and the terrorists plot in Rainbow Six. But I always wonder, what would happen to the flora and fauna?

Let's stipulate some facts: A science-fiction-ish worldwide disease wipes out all the humans in the course of a few weeks. What does animal and plant life on the planet look like one year later?

* Do pigeons and rats take over New York City?
* Do white-tailed deer take over Montana?
* Do feral cats wipe out several bird species?
* How long before grizzlies return to California and massive herds of bison return to the Great Plains?
* Do cod fisheries in the Atlantic return to normal?
* Is there any hope for the Florida panther?
* Does Australia buckle under the weight of all those darn rabbits with no natural predators?

Let the science run wild in our fictional thesis!

posted by frogan to science & nature (26 answers total)

When you said "men," I thought you were referring to the graphic novel series "Y: the Last Man," which is about a world in which all male creatures except for one man and his pet monkey are killed by a mysterious ... something.

Not that I'm a fangirl or anything. But if you like this sort of thing, pick it up.
posted by anjamu at 11:18 PM on February 21, 2006

No, I mean "all the people." As seen in The Stand, I Am Legend, Lucifer's Hammer, The Quiet Earth, etc.
posted by frogan at 11:21 PM on February 21, 2006

One year later? Not much different than now. Different species spread at different rates and you would still have the effects of things like dams, climate change and introduced species to factor in so it would be hard to predict. In general the recovery of a species would be related to the generation time and the size of the current population as well as things like corridors that allowed movement. Grizzlies and wolves would certainly come back to their former range but not as quickly as things like white tail deer that are already present in huge numbers. Salmon runs would be stymied by dams and when the dams finally went, they would be impacted by the huge amounts of sediment trapped behind the dams. Coastal wetlands would only fully recover when the levees eroded which could take a long time. Long lived plants like redwoods would probably take the longest to reestablish.

There would probably be a period of intense floods, firestorms etc. due to the cessation of human intervention and it could certainly drive small populations to extinction. Disease from feral domestics could wipe out genetically similar populations like the panther. Huge numbers of feral pigs, cows, horses, dogs and cats would be out there competing for resources too.

The results in the super long term would be easier to predict than the results in a year, methinks. Local effects would probably be the major factor.
posted by fshgrl at 12:08 AM on February 22, 2006

I'm sure that some real biologists will come along and correct me but I thought that there was some debate about how much of a role we (humans) had in the maintenance and creation of the great plains and the bison herds. Bison are pretty close to being cows. It would be a pretty weird ecological system where large herds of free roaming bovines ruled parts of the earth.
posted by rdr at 12:17 AM on February 22, 2006

This sort of question is what leads some people to join VHEMT, the Voluntary Human Extinction MovemenT.
posted by Ian A.T. at 3:15 AM on February 22, 2006

rdr - I think I read/heard that areas of the Great Plains were kept open by native burning, whereas European-American and Canadian settlement has allowed trees to reestablish themselves in these areas.

Many environments are dependent on humans for their continuation, such as heather uplands in Scotland (which are burned). New England was very park-like when the first European settlers arrived, due to native management of the area for crops and to increase wild grazing. In an opposite manner, areas of woodland in the woodland-savannah areas of West Africa (Guinea, etc) are created and maintained by local farmers, who plant the trees as wind breaks (establishing fire breaks for them), and who break up the soil and allow more trees to establish themselves in an otherwise harsh environment.

Things would change, and keep changing. I think I am generally skeptical of the static "climax" theory of environments (that they have natural climax conditions which maximise biological material interrupted by human activity or natural phenonmenon like fires), because it sort of assumes that forests are the most natural environment. Some areas would be more forested, some might be less. It would be all quite different, but in what manner would depend on the local situation.
posted by jb at 3:54 AM on February 22, 2006

As far as pigeons and rats taking over NYC, won't they have lost their primary source of nutrition? I'd think the cities would be pretty dead (esp a place like NYC) until some serious wear and tear makes it a more habitable place for plant life.
posted by shoos at 4:05 AM on February 22, 2006

What happens to the world's nuclear power plants and missile systems if all human operators disappeared? Something tells me that there might not be any animal life one year later. But maybe I've been watching "Lost" this season a little too much.

On the other hand, in the very early 80s, there was a book that addressed how animals might evolve after the end of the human race, but I can't think of its name. Any ideas? Note that it was more of an artist's speculation and paintings rather than the writings of biologists.
posted by kimota at 4:25 AM on February 22, 2006

After Man. Kinda pricey these days
posted by kimota at 4:50 AM on February 22, 2006

Richard Jefferies' book After London, or Wild England (1885) is a fantasy novel about the after-effects of a disaster which wipes out most of the population of England. In the first few chapters he discusses the effects on the animal population: (1) the crops are left unharvested in the fields, attracting swarms of mice (leading in turn to a big increase in the number of hawks, owls and foxes); (2) domestic pets run wild, leading to packs of wild dogs roaming the countryside; (3) most farm animals die off, leaving only a small population of wild cattle, pigs and horses; (4) some zoo animals escape, but die off within a few years; (5) deer and other woodland animals increase in numbers, as England gradually turns back into an enormous forest.

I still find this a very plausible scenario. The two points that particularly strike me are, first, that there would be rapid and unpredictable fluctuations in the animal population in the first few years, before the whole situation gradually began to stabilize, and secondly, that human civilisation would quickly pass the point of no return (e.g. Jefferies suggests that the swarms of mice would roam the countryside like locusts, eating any crops they found and preventing the surviving humans from keeping any fields under cultivation). It's as though Jefferies intuitively grasped the principle of the 'tipping point' -- not bad for someone writing in 1885.
posted by verstegan at 5:40 AM on February 22, 2006

I know I read something about what would happen to nuclear power plants after the Rapture, but I can't find it now. I'm pretty sure it was linked from MetaFilter, too. I'll keep looking...
posted by MrMoonPie at 6:15 AM on February 22, 2006

Very quickly there will be lots of big dumb animals walking around, all the farm animals, all the fairly harmless ones. And all the pets -- lots of dogs and cats munching on smaller animals and one another.

But then the larger predators start to catch up. Herds of dairy cows are easy picking. Herds of chihuahuas are easy snacks. (And tasty!) By the end of the year, the populations of all the large carnivorous mammals we've been controlling will already be fattening on the heaps of stupid animals we've been encouraging.

In Asia and Africa, the lions and tigers and elephants and rhinos would come back.

In North America, in addition to mountain lions and bears, there could be escaped zoo animals from other continents. Most zoo captives might die in their cages, but if the world were ending for humans and it looked as though zoo animals would not be cared for, animal lovers probably would release them. Within a year, pairs of lions and tigers could be raising offspring in the wilds of North America and hippos might be wading southern rivers.

The wooden suburbs within a year would start to overgrow, spring open, rot, and fall to the rats and all the animals that follow the rats into the holes they chew. In a year, you wouldn't know where the lawns end and the roads begin, no unless you scraped the cover off the roads.

Cities would very quickly start to support all sorts of birds and smaller mammals. Leaves and dust collect and mulch quickly, and that turns all the horizontal surfaces green. The rivers running through most large cities would have plenty of fish to support birds and shore-dwellers. And very soon, plants would push up through the undriven roads and parking lots.
posted by pracowity at 6:18 AM on February 22, 2006

BTW, the movie version of Aeon Flux uses the premise of plants going wild w/o humans around as a plot point.
posted by smackfu at 6:19 AM on February 22, 2006

people are the top predator of most things on the planet. we kill more of most things than many natural causes do. so i figure if we were all gone in one year you wouldn't notice much difference, but in two years or three you would see a massive increase in the amount of birds and fish, as we kill billions of these each year with our cars and boats.

i would guess that in 50 years almost all cities and major settlements on the planet would have been recaptured by plants, and 50 years after that you would see most major cities infested with local fauna again.

in all i would say it would take about 200-300 years before all that would be left of us is plastic and ruins.
posted by stilgar at 6:48 AM on February 22, 2006

This actually has happened. I have been listening to Charles Mann's book 1491, much of which looks at the changes in North American ecosystems when Eurasian disease epidemics wiped out the vast majority of American Indians in the early 1500s. He points out that a lot of what we think of as the "natural" environment of North America before contact, (including your "massive herds of bison") were actually unnatural and perhaps unsustainable fluorescence of species that had been kept at much lower numbers by human predation.

The book is not without its problems (Mann is a science journalist, not a scientist or historian). But overall it is pretty sound and a good introduction to exactly the phenomenon you are interested in.
posted by LarryC at 6:50 AM on February 22, 2006

Rats would not take over. Between falcons and feral cats and dogs, that population would be controlled. You don't find rats in ghost towns do you?

Cows, sheep and chickens would die, they are too dependent on humans. Horses could go wild on the plains. Pigs would tear up much of the forests. That is if the pigs and horses were to be freed and disease did not wipe them out. Goats would be just fine.

Bears and wild canines would enjoy feeding on deer, cats and other small game, though the coyote and coy-dog populations would probably be too much competition for bears and wolves to spread much.

Invasive species of plants are so prevalent all over the world that the real competition would be between the natives and the invaders. Green, invasive, eastern hemisphere grasses would begin to be killed off in North America by the combination of expanding forest and the unrestricted return of prairie grasses. Where the forest and prairie met would be the most fascinating point for evolutionary biology.
posted by Pollomacho at 7:09 AM on February 22, 2006

I guess the women would take over. I think the animals could deal with that.
posted by caddis at 7:12 AM on February 22, 2006

kimota:
I think there's little likelihood of nuclear missiles spontaneously launching without human intervention.

Powerplants have numerous safety mechanisms to prevent meltdowns, but as history has shown, they aren't failure proof. Some varieties require water circulation. So if all redundant systems failed before the fuel was sufficiently spent, there could be a meltdown.

Still I think general flaura and fauna populations in the longterm would survive the outcome of a nuclear power plant disaster.
posted by justkevin at 8:44 AM on February 22, 2006

In a year, you wouldn't know where the lawns end and the roads begin, no unless you scraped the cover off the roads.

no ... it would take longer than that ... where i live there have been areas that were, for some time, effectively abandoned ... roads and parking lots that haven't been maintained for 30 years are still mostly intact ... broken up a bit and ragged, but still distinct

it would probably take at least 100 years for a real break up and even then there'd still be substantial signs of a road having been there ... jagged rocks of cement and asphalt

i think buildings would last a good long time too ... it takes awhile for things like that to totally disappear ... longer than a lifetime ...
posted by pyramid termite at 8:54 AM on February 22, 2006

I did laugh at the "men" disappearing - luckily, women will still be around to take up the slack.
posted by agregoli at 8:57 AM on February 22, 2006

For at least a little while.
posted by agregoli at 8:58 AM on February 22, 2006

Smithsonian this month has an interesting article on urban coyotes. It's worth picking up just to read that.
I never knew that coyotes were originally found only between the Rockies and the Mississippi. Obviously they've spread.

Coyotes can breed with dogs or wolves. My own pup is quite likely part coy-dog. She was originally a feral dog along the Mexican border and displays many of the characteristics of a coy-dog.

In the Northeast thay have found coyotes that are 68 lbs. Far larger than the 15 lb. average on the Plains. They have also found that Northeastern coyotes almost all carry some wolf genes. (I apologize, this is all from memory)

I guess my point is that we have altered natural systems significantly. How they will react if/when we disappear is hard to determine.

However, I like to think of hippos in the southern Mississippi River and tigers hunting tasty, tasty wild pigs through the South. Better than that "Only The Cockroaches Survive" scenario. But then, I have a closer tie to warm-blooded animals.
posted by Seamus at 9:55 AM on February 22, 2006

Discover Magazine had an article on what would happen to the environment if humans suddenly went extinct, with a really fascinating timeline. Not finding it in my stack, however.
posted by adamwolf at 10:16 AM on February 22, 2006

Discover Magazine had an article on what would happen to the environment if humans suddenly went extinct, with a really fascinating timeline.

Rad! I'll look for it.
posted by frogan at 2:35 PM on February 22, 2006

Found it -- Earth Without People, February 2005 issue. Thanks!
posted by frogan at 2:59 PM on February 22, 2006

I'd swear there was recently an ask.me about how long it would take for the power to fail, in the event of some all-the-people-are-gone catastrophe, but my search-fu is failing me. There were some interesting facts about fuel-storage vs runtime. I swear, it was a real thread.
posted by nomisxid at 3:05 PM on February 22, 2006