Isn't this because humans killed and took the role of large grazing animals and large predators? After some time this can result in a new equilibrium, and when humans move out it's chaos again for a while. Question is not if nature will deal with it, but rather what we humans want — probably not some ecological desert for millenia.
I read the study. The "problem" with it is that it only examines biodiversity before and after abandonment, but without the abandoned areas being rewilded in any way.
Some areas are so destroyed by human activities that they need some help in rewilding, which is definitely possible. Of course, this study does point out that some management of the land that resembles previous human activities could help biodiversity. And of course, as the study mentions, they did not include "Mosses, lichens, mammals and invertebrates—including soil organisms such as nematodes and molluscs".
Keep in mind also that biodiversity is difficult to measure can be counterintuitive. Farmland and managed land creates edge habitats, or a confluence of habitats, where measured biodiversity is higher. Of course, when that edge habitat disappears the measurements can go down. But that does not imply that merging a huge number of farmland back ot a more contiguous wild are won't support biodiversity better in the long run.
Every ecosystem on the planet besides recent settlements like Hawaii or Antarctica are co-evolved with human beings. "Pristine wildness" is almost always a myth.
The Romans were deforesting the Mediterranean 2000 years ago. Aboriginal Australians continually burnt the land for 50,000 years creating the desert Australia you see today. Humans have been majorly changing the environment for a very long time.
That's not totally true. The way we have lived since the 1950s has made a lot of difference. Even where people have lived for a long time, highways and major roads since 1950 in terms of danger are a step change (or two) compared to earlier roads and have essentially walled off areas from wildlife traveling between them.
If you re-introduce certain keystone species, the rest follows automatically - the most well-known and well-studied example being the wolf in Yellowstone [1].
I suspect this is the opposite in areas of the USA that have seen population declines. There is virtually nowhere in the USA in the 2020s that looks like, say, Ogimachi Village. And even in, say, the 1920s, so much forest had been cut for agriculture, logging, mining, and soon thereafter for the first suburbs, that I can't imagine human development had any positive effects whatsoever on wildlife or biodiversity.
I wonder how much this is a factor of time. After significantly more than 1500 years of intensive human management, the ecology of Japan's countryside will have evolved for those conditions. America's ecology has not had a similar amount of time to adapt to the loss of the giant bison herds, et cetera.
I would probably agree Japans country side was populated and farmed to a larger degree than in the US.
While there definitely was some groups of people/tribes who farmed the land historically. In the US definitely was a smaller amount compared to Japan during that stretch of time before even the USA was around.
I's not that simple. Look at New England. Initially de-populated and left to grow over thanks to western agriculture then intentionally key that way by environmental policy. It's not inching toward anything resembling pre-colombian forests. It's turning into an impenetrable thicket. But hey, plenty of food for the asian long horned beetles and gypsy moths so that's a win. /s
There's a lot of bits of biodiversity you don't get without humans putting their thumb on the scale and forcing a different equilibrium.
The article mentions rice paddies, which tend to be almost entirely artificial constructs. It makes sense that if they aren't being maintained anymore, the species that relied on that maintenance would struggle.
Likewise, I don't know if Japan has to deal with wildly aggressive invasive species like I am right now with buckthorn, but there's lots of plants that will simply choke out most others and aren't very beneficial. If nobody's around anymore and they were actively grooming the pastures and such, that will also put a ton of pressure on previously flourishing species.
there is a phrase that reasonates with me and it goes something like this- all symbiotic relationships were once parasitic. There are plenty of caveats but i think the time regime is something we don’t really respect given that some of these processes are always happening at almost always on a timeframe that we don’t appreciate- naturally, being so briefly here.
Nobody knows. I'm serious - nobody knows. Japan has been populated by humans since prehistoric times; plenty of time for people and wildlife to adapt and coevolve.
Hard to imagine there's a way to extrapolate that far back in time.
California and North Carolina too. Back when I lived in Socal; we would have at two weeks of heavy rain during April-May with flooding. Now it's only a few days of lighter rain. The air used to be very dry since it would be so cold. Now it is becoming more humid before I left.
Raleigh used to have more snowy winters from what I was told. Now a days winters have a 1 in 4 chance of giving snow you might see in the morning for most of the area.
The problem is apparently the tall bamboo that is taking over and not letting native tree to grow. This bamboo does not have home grown competition although it is a native bamboo. The who thing probably needs some sort of automated tilling and panting or imported workers to remove the the giant bamboo and farm it somehow perhaps.
Wow the Spain is even more strange. It was over farmed and plowed so much that soil is degraded to become like concrete and barren because the water doesn't soak in.
For that type of devastation, I recall reading years ago that growing rye and then rolling it instead of plowing it and replanting rye again for multiple seasons can create moisture retaining top soil. They would also need to add ditches to have pools of water for wild life to make a come back.
It is a completely different phenomenon. In 500 years all these lands are going to have an ecosystem again even if they don't do anything but they have to live with it for 100s of years if they don't do anything.
If define biodiversity just by sheer number of sp, yes.
That's why biodiversity has so many definitions and the one used here is the most basic one which can lead to bad conclusions. I recall a study in an area affected by deforestation where plant "biodiversity" actually increased—but this was a natural, expected effect, driven by colonizing species that require more light to germinate from their seeds. The stable equilibrium one would expect, however, involves lower biodiversity.
Before so many people, Japans open wet habitats were mostly floodplains, with rivers that flooded and shifted around the way rivers do. Those rivers are now dammed, channelized, the floodplains are cities and fields, much the same as in the Eastern US. Rice paddies became the wetland for frogs, fireflies, dragonflies,wading birds. If the paddies go to forest, those species don’t return to floodplains, because the floodplains no longer exist.
This is surprising to hear. I lived in very remote kyushu for years and saw an incredible amount of wildlife. Badgers, hare, foxes, wild boar, deer, racoons (tanuki), monkeys. Roadkill everywhere all the time.
There are a lot of confounding factors in ecosystems at the edges of urban areas. I live in the Massachusetts exurbs, and have seen fluctuations in the population of deer, wild turkeys, and coyotes.
I've also seen some very well secured trash bins in Tokyo, so Japan clearly has wildlife even in urban areas that's very interested in the contents of trash bins.
I used to have a committee of four farm dogs visit my kitchen scrap pile every morning to sniff around. Now they are all in their separate invisible fence boundaries. So, more coyotes, fewer turkeys? I see more turkeys in some closer in suburbs and the neighborhoods of Boston.
> plant diversity peaked in the medieval era, when small farms created a patchwork of fields, pastures, and forests that supported a greater array of plants than either the closed forests that came before or the industrial farms that would follow.
That seems reasonable from a study from Europe they quoted. If farmed land, garbage left around, or brush clearing was helping certain species thrive it could mean they will struggle once farm plots and that other stuff goes away. It would be rather silly to have someone dump piles of rotting food in the woods to keep up the wild boar biodiversity that’s now declining.
Yes it was. Remember that we're animals and part of nature, too (even if that might offend some particularly religious folk).
A biosphere in relative equilibrium doesn't necessitate the absence of man.
I have bats, barn owls, half a dozen species of song birds, hedgehogs, several variants of mice and the occasional band of racoons (invasive species over here) living on my property. None of these are pets or domesticated in any way. They simply benefit from - and even rely on - the activities of me and my neighbours (I live in a rural community, my neighbours are farmers and I keep livestock myself).
There're just as "wild" as the foxes, storks, deer, cranes, herons, boars, wolves, and all the other critters that live in the area. You'd be hard pressed to actually find animals (and some plants for that matter) that aren't affected by or (sometimes indirectly) depend on human activity in most countries. Some benefit and thrive (like the examples from Japan), others struggle.
Not so long ago, maybe a couple of years, I heard that the trend was to go back to the countryside. Now it's emptying out again? Which one is it? Or does it change that quickly?
Not sure why you're being downvoted. That's a valid question.
First, I live in Japan. Been here for over 25 years. So, here's a first hand point of view, but anecdotal. So, take it as you like...
Most people are growing up and moving to the bigger cities, because of education and because of jobs. If you want a very good job here in Japan, you need to try to go to a very good university.
If you are born just outside of a bigger town, or within 1 to 1.5 hr trip into a bigger town, then you'll likely travel to school by train and bus. You might even stay in this outer circle of homes when you get a job. That seems to be a kind of invisible "circle" where people tend to think "inside this circle, I can travel for school or work, but outside this circle, I'd be better off moving". Mostly that idea comes from two things: the time spent traveling and transportation costs -- you start to spend as much on trains and busses as you might for a cheaper apartment.
The further you are born outside that "invisible circle", you are much more likely to leave home for high school and then college, and then you are more likely to job hunt in bigger cities where there are more choices. It becomes too expensive to travel 2+ hours for every job interview.
So, in short, the countryside IS emptying out. The younger people are leaving for education and work, and the older folks continue to live there until they pass away... so the smaller towns and villages are emptying out. Thus the very large increase in "akiya", empty houses.
NOW, the "people are moving to the countryside" is a kind of YouTube influencer thing where there was a wave of non-Japanese people making videos about how cheap it is to buy one of these akiya in the countryside and improve them. So, those videos make it sound like people are rushing to the countryside to buy houses, but in fact, not many people are. Japanese people generally won't, because it's actually TOO expensive to renovate an old house, the yearly tax on houses is expensive, and then it's a nightmare to travel 30+ minutes every time you want to get groceries or look for new clothes. (I lived in one of these middle-of-nowhere villages for three years. Beautiful place, but took about 40 minutes to go get groceries, get to the nearest train station, or rent a movie!) Japanese people (well middle-age and up) start to worry about retirement and old age... and it's considered general knowledge that living in the countryside makes it extremely hard to visit the doctor, get medical help, get groceries, and such, especially when they are encouraged to turn in their driver's license (for people over 80) and there might only be one bus an hour into town! (Such as in the village I lived in.)
So, yes, there are two narratives on the internet about the Japanese countryside -- it's being bought up and renovated, CHEAP!, and it's emptying out. The later is the reality.
I feel like this has been studied before, and lots of times: nature is uncontrolled. Which really leads to constant (like every 10 years or so) disasters of one kind or another (usually an invasive species), destroying plant growth and biodiversity.
Humans built systems to prevent all this from happening, 1000s of little custom ones in 1000s of different little places with 1000s of different functions and kept those systems running. Irrigation. Bringing food (and edible trash). Preventing collapses. Building dams. Removing invasive species from specific areas. Those are probably the big ones. That's why there is the continuous nature across Europe. It's entirely artificial and it's due to farms being so incredibly widespread. Just look at the map. It's absolutely incredible how far and how much there are.
The "natural" Europe is really mostly steppe dotted with swamps and forests, usually next to each other, with vast open spaces, with very few animals, in between. That should be the situation one would expect to return.
I'm skeptical. Having been to some areas of rural Japan, I'd suggest that the macro cycle established by humans was irrigation related and the removal of the same causes deep challenges to former human-presence-biome members. A novel and restored biome, more suited to the natural hydrosphere of the area, will likely take decades to a century to re-emerge assuming its species survive and its preconditions haven't been ruined by concrete.
Note also in my limited experience there is typically a severe and sudden difference between flat land and mountains, the former being human managed with extreme prejudice and the latter being typically degraded/unnatural/replanted ("Japan's forests are ~44% dense post-war cedar/hinoki plantations with barren understories"). This is one of the most striking features of the Japanese landscape relative to other nearby countries. I would assume the current study focused only on flatland, as the forests are not going to empty out when proximal humans desist: quite the opposite.
The unstated truth here is that Japan apparently raped its physical environment for its war machine.
This is obvious to me in Southern California. I contribute nutrients to the land near me that would otherwise not be here at all. The compost alone has nutrients from fruit and vegetables that don't even grow here. I maintain fruit trees that the squirrels and rabbits eat and in turn the coyotes and red tailed hawks are able to sustain their population. It's pretty simple really. We add more energy into the system and it has more biodiversity in turn.
When the environment changes and we convert forests to farms or urban centers, wildlife of course disappears. Then over time the surviving creatures will evolve and adapt to become suited to living around these urban centers.
When you remove these urban centers the same thing happens. You are changing the environment. So of course there is an initial culling as the selection process activates.
We tend to think of depopulating actions in a single unidirectional way. Nature -> Urban = Bad and depopulating. The reality is that nature is neutral. It's Not unidirectional and nothing is bad or good. Believe it or not I'm sure species do go extinct from the conversion from urban to more wild environments. It happens both ways and again, extinction isn't inherently bad either.
this will inevitably prompt the usual litany of "without immigration, Japan will not survive", so I'd like to point out the elephant in the room: no one wants to live in the countryside anymore, for a number of good reasons. those reasons are mostly cultural, and there's nothing any government can do about it.
Isn't this because humans killed and took the role of large grazing animals and large predators? After some time this can result in a new equilibrium, and when humans move out it's chaos again for a while. Question is not if nature will deal with it, but rather what we humans want — probably not some ecological desert for millenia.
I read the study. The "problem" with it is that it only examines biodiversity before and after abandonment, but without the abandoned areas being rewilded in any way.
Some areas are so destroyed by human activities that they need some help in rewilding, which is definitely possible. Of course, this study does point out that some management of the land that resembles previous human activities could help biodiversity. And of course, as the study mentions, they did not include "Mosses, lichens, mammals and invertebrates—including soil organisms such as nematodes and molluscs".
Keep in mind also that biodiversity is difficult to measure can be counterintuitive. Farmland and managed land creates edge habitats, or a confluence of habitats, where measured biodiversity is higher. Of course, when that edge habitat disappears the measurements can go down. But that does not imply that merging a huge number of farmland back ot a more contiguous wild are won't support biodiversity better in the long run.
[dead]
Every ecosystem on the planet besides recent settlements like Hawaii or Antarctica are co-evolved with human beings. "Pristine wildness" is almost always a myth.
That’s a strong assertion. It was less of a myth 200 years ago (prior to the Industrial Revolution) and even less of one further back.
People may have generally existed in these regions, but the scope of ecological impact & evolutionary pressure is more recent.
The Romans were deforesting the Mediterranean 2000 years ago. Aboriginal Australians continually burnt the land for 50,000 years creating the desert Australia you see today. Humans have been majorly changing the environment for a very long time.
That's not totally true. The way we have lived since the 1950s has made a lot of difference. Even where people have lived for a long time, highways and major roads since 1950 in terms of danger are a step change (or two) compared to earlier roads and have essentially walled off areas from wildlife traveling between them.
The thing is a lot of these rural areas were farms before 1950 or if we got back further before even the Meji Restoration in Japan.
It's actually more of a recent phenomenon that a lot these small villages and towns now becoming basically vacant in Japan.
People have been in Japan for many thousands of years at this point.
> "Pristine wildness" is almost always a myth.
Which is half true, half not.
If you re-introduce certain keystone species, the rest follows automatically - the most well-known and well-studied example being the wolf in Yellowstone [1].
[1] https://www.yellowstonepark.com/things-to-do/wildlife/wolf-r...
what?
I suspect this is the opposite in areas of the USA that have seen population declines. There is virtually nowhere in the USA in the 2020s that looks like, say, Ogimachi Village. And even in, say, the 1920s, so much forest had been cut for agriculture, logging, mining, and soon thereafter for the first suburbs, that I can't imagine human development had any positive effects whatsoever on wildlife or biodiversity.
I wonder how much this is a factor of time. After significantly more than 1500 years of intensive human management, the ecology of Japan's countryside will have evolved for those conditions. America's ecology has not had a similar amount of time to adapt to the loss of the giant bison herds, et cetera.
I would probably agree Japans country side was populated and farmed to a larger degree than in the US.
While there definitely was some groups of people/tribes who farmed the land historically. In the US definitely was a smaller amount compared to Japan during that stretch of time before even the USA was around.
I's not that simple. Look at New England. Initially de-populated and left to grow over thanks to western agriculture then intentionally key that way by environmental policy. It's not inching toward anything resembling pre-colombian forests. It's turning into an impenetrable thicket. But hey, plenty of food for the asian long horned beetles and gypsy moths so that's a win. /s
There's a lot of bits of biodiversity you don't get without humans putting their thumb on the scale and forcing a different equilibrium.
Seems counter-intuitive and definitely warrants research to understand the mechanism. The most unintuitive part being local plants not returning.
The article mentions rice paddies, which tend to be almost entirely artificial constructs. It makes sense that if they aren't being maintained anymore, the species that relied on that maintenance would struggle.
Likewise, I don't know if Japan has to deal with wildly aggressive invasive species like I am right now with buckthorn, but there's lots of plants that will simply choke out most others and aren't very beneficial. If nobody's around anymore and they were actively grooming the pastures and such, that will also put a ton of pressure on previously flourishing species.
there is a phrase that reasonates with me and it goes something like this- all symbiotic relationships were once parasitic. There are plenty of caveats but i think the time regime is something we don’t really respect given that some of these processes are always happening at almost always on a timeframe that we don’t appreciate- naturally, being so briefly here.
I believe the Japanese Knotweed fulfills that function.
I highly recommend Robin Wall Kimmer's Braiding Sweetgrass. She reckons academia and science with indigenous knowledge.
What was the primeval state of these places, and how long has it been since it looked like that?
Nobody knows. I'm serious - nobody knows. Japan has been populated by humans since prehistoric times; plenty of time for people and wildlife to adapt and coevolve. Hard to imagine there's a way to extrapolate that far back in time.
I can't help wondering if their consideration of climate change as a covariate factor has been rigorous enough.
Climate change is happening everywhere but it is quite noticeable in Japan with summers getting hotter and winters getting milder.
California and North Carolina too. Back when I lived in Socal; we would have at two weeks of heavy rain during April-May with flooding. Now it's only a few days of lighter rain. The air used to be very dry since it would be so cold. Now it is becoming more humid before I left.
Raleigh used to have more snowy winters from what I was told. Now a days winters have a 1 in 4 chance of giving snow you might see in the morning for most of the area.
The problem is apparently the tall bamboo that is taking over and not letting native tree to grow. This bamboo does not have home grown competition although it is a native bamboo. The who thing probably needs some sort of automated tilling and panting or imported workers to remove the the giant bamboo and farm it somehow perhaps.
why do you say that?
I didn't see it in the article nor the 2025 study https://www.nature.com/articles/s41893-025-01578-w
Additionally, the article points to Spain and Lake Constance in the Alps exhibiting similar effects.
Wow the Spain is even more strange. It was over farmed and plowed so much that soil is degraded to become like concrete and barren because the water doesn't soak in.
https://www.youtube.com/watch?v=ZUzZk_uqSWc&t=107s
For that type of devastation, I recall reading years ago that growing rye and then rolling it instead of plowing it and replanting rye again for multiple seasons can create moisture retaining top soil. They would also need to add ditches to have pools of water for wild life to make a come back.
It is a completely different phenomenon. In 500 years all these lands are going to have an ecosystem again even if they don't do anything but they have to live with it for 100s of years if they don't do anything.
I looked at few documents about japan and I believe it was conclusive.
https://www.nippon.com/en/articles/-/14855
I will look up spain when I get time and get back to you. I have to be somewhere now.
If define biodiversity just by sheer number of sp, yes.
That's why biodiversity has so many definitions and the one used here is the most basic one which can lead to bad conclusions. I recall a study in an area affected by deforestation where plant "biodiversity" actually increased—but this was a natural, expected effect, driven by colonizing species that require more light to germinate from their seeds. The stable equilibrium one would expect, however, involves lower biodiversity.
Before so many people, Japans open wet habitats were mostly floodplains, with rivers that flooded and shifted around the way rivers do. Those rivers are now dammed, channelized, the floodplains are cities and fields, much the same as in the Eastern US. Rice paddies became the wetland for frogs, fireflies, dragonflies,wading birds. If the paddies go to forest, those species don’t return to floodplains, because the floodplains no longer exist.
Give it 20 more years, it takes time for ecosystems to rebuild.
This is surprising to hear. I lived in very remote kyushu for years and saw an incredible amount of wildlife. Badgers, hare, foxes, wild boar, deer, racoons (tanuki), monkeys. Roadkill everywhere all the time.
There are a lot of confounding factors in ecosystems at the edges of urban areas. I live in the Massachusetts exurbs, and have seen fluctuations in the population of deer, wild turkeys, and coyotes.
I've also seen some very well secured trash bins in Tokyo, so Japan clearly has wildlife even in urban areas that's very interested in the contents of trash bins.
I used to have a committee of four farm dogs visit my kitchen scrap pile every morning to sniff around. Now they are all in their separate invisible fence boundaries. So, more coyotes, fewer turkeys? I see more turkeys in some closer in suburbs and the neighborhoods of Boston.
> plant diversity peaked in the medieval era, when small farms created a patchwork of fields, pastures, and forests that supported a greater array of plants than either the closed forests that came before or the industrial farms that would follow.
That seems reasonable from a study from Europe they quoted. If farmed land, garbage left around, or brush clearing was helping certain species thrive it could mean they will struggle once farm plots and that other stuff goes away. It would be rather silly to have someone dump piles of rotting food in the woods to keep up the wild boar biodiversity that’s now declining.
If something is dependent on human intervention for survival in a specific environment, was it ever even wild?
Yes it was. Remember that we're animals and part of nature, too (even if that might offend some particularly religious folk). A biosphere in relative equilibrium doesn't necessitate the absence of man.
I have bats, barn owls, half a dozen species of song birds, hedgehogs, several variants of mice and the occasional band of racoons (invasive species over here) living on my property. None of these are pets or domesticated in any way. They simply benefit from - and even rely on - the activities of me and my neighbours (I live in a rural community, my neighbours are farmers and I keep livestock myself).
There're just as "wild" as the foxes, storks, deer, cranes, herons, boars, wolves, and all the other critters that live in the area. You'd be hard pressed to actually find animals (and some plants for that matter) that aren't affected by or (sometimes indirectly) depend on human activity in most countries. Some benefit and thrive (like the examples from Japan), others struggle.
Mildlife.
Not so long ago, maybe a couple of years, I heard that the trend was to go back to the countryside. Now it's emptying out again? Which one is it? Or does it change that quickly?
Not sure why you're being downvoted. That's a valid question.
First, I live in Japan. Been here for over 25 years. So, here's a first hand point of view, but anecdotal. So, take it as you like...
Most people are growing up and moving to the bigger cities, because of education and because of jobs. If you want a very good job here in Japan, you need to try to go to a very good university.
If you are born just outside of a bigger town, or within 1 to 1.5 hr trip into a bigger town, then you'll likely travel to school by train and bus. You might even stay in this outer circle of homes when you get a job. That seems to be a kind of invisible "circle" where people tend to think "inside this circle, I can travel for school or work, but outside this circle, I'd be better off moving". Mostly that idea comes from two things: the time spent traveling and transportation costs -- you start to spend as much on trains and busses as you might for a cheaper apartment.
The further you are born outside that "invisible circle", you are much more likely to leave home for high school and then college, and then you are more likely to job hunt in bigger cities where there are more choices. It becomes too expensive to travel 2+ hours for every job interview.
So, in short, the countryside IS emptying out. The younger people are leaving for education and work, and the older folks continue to live there until they pass away... so the smaller towns and villages are emptying out. Thus the very large increase in "akiya", empty houses.
NOW, the "people are moving to the countryside" is a kind of YouTube influencer thing where there was a wave of non-Japanese people making videos about how cheap it is to buy one of these akiya in the countryside and improve them. So, those videos make it sound like people are rushing to the countryside to buy houses, but in fact, not many people are. Japanese people generally won't, because it's actually TOO expensive to renovate an old house, the yearly tax on houses is expensive, and then it's a nightmare to travel 30+ minutes every time you want to get groceries or look for new clothes. (I lived in one of these middle-of-nowhere villages for three years. Beautiful place, but took about 40 minutes to go get groceries, get to the nearest train station, or rent a movie!) Japanese people (well middle-age and up) start to worry about retirement and old age... and it's considered general knowledge that living in the countryside makes it extremely hard to visit the doctor, get medical help, get groceries, and such, especially when they are encouraged to turn in their driver's license (for people over 80) and there might only be one bus an hour into town! (Such as in the village I lived in.)
So, yes, there are two narratives on the internet about the Japanese countryside -- it's being bought up and renovated, CHEAP!, and it's emptying out. The later is the reality.
Thanks for that reality-on-the-ground report/description.
I feel like this has been studied before, and lots of times: nature is uncontrolled. Which really leads to constant (like every 10 years or so) disasters of one kind or another (usually an invasive species), destroying plant growth and biodiversity.
Humans built systems to prevent all this from happening, 1000s of little custom ones in 1000s of different little places with 1000s of different functions and kept those systems running. Irrigation. Bringing food (and edible trash). Preventing collapses. Building dams. Removing invasive species from specific areas. Those are probably the big ones. That's why there is the continuous nature across Europe. It's entirely artificial and it's due to farms being so incredibly widespread. Just look at the map. It's absolutely incredible how far and how much there are.
The "natural" Europe is really mostly steppe dotted with swamps and forests, usually next to each other, with vast open spaces, with very few animals, in between. That should be the situation one would expect to return.
Maybe they weren't wildlife but roomates just like the pigeons and the rats.
I'm skeptical. Having been to some areas of rural Japan, I'd suggest that the macro cycle established by humans was irrigation related and the removal of the same causes deep challenges to former human-presence-biome members. A novel and restored biome, more suited to the natural hydrosphere of the area, will likely take decades to a century to re-emerge assuming its species survive and its preconditions haven't been ruined by concrete.
Note also in my limited experience there is typically a severe and sudden difference between flat land and mountains, the former being human managed with extreme prejudice and the latter being typically degraded/unnatural/replanted ("Japan's forests are ~44% dense post-war cedar/hinoki plantations with barren understories"). This is one of the most striking features of the Japanese landscape relative to other nearby countries. I would assume the current study focused only on flatland, as the forests are not going to empty out when proximal humans desist: quite the opposite.
The unstated truth here is that Japan apparently raped its physical environment for its war machine.
https://japansociety.org/news/japans-forests-good-days-and-b...
This is obvious to me in Southern California. I contribute nutrients to the land near me that would otherwise not be here at all. The compost alone has nutrients from fruit and vegetables that don't even grow here. I maintain fruit trees that the squirrels and rabbits eat and in turn the coyotes and red tailed hawks are able to sustain their population. It's pretty simple really. We add more energy into the system and it has more biodiversity in turn.
When the environment changes and we convert forests to farms or urban centers, wildlife of course disappears. Then over time the surviving creatures will evolve and adapt to become suited to living around these urban centers.
When you remove these urban centers the same thing happens. You are changing the environment. So of course there is an initial culling as the selection process activates.
We tend to think of depopulating actions in a single unidirectional way. Nature -> Urban = Bad and depopulating. The reality is that nature is neutral. It's Not unidirectional and nothing is bad or good. Believe it or not I'm sure species do go extinct from the conversion from urban to more wild environments. It happens both ways and again, extinction isn't inherently bad either.
I wonder if this is somewhat specific to Japan or has been observed elsewhere
In your face depopulators!
"People are bad, except when they aren't."
this will inevitably prompt the usual litany of "without immigration, Japan will not survive", so I'd like to point out the elephant in the room: no one wants to live in the countryside anymore, for a number of good reasons. those reasons are mostly cultural, and there's nothing any government can do about it.