A lot of these takes implicitly involve wizard population explosion, given colonization.

I know @Taure likes to have wizarding population be effectively stable w 2 kids/couple for hundreds of years.

Is that changing in this AU?

If so, lots of cool downstream results from that. For example I believe there's some evidence that big chunk of the population being young men tends to lead to more conflict so if the wizarding population is expanding and there's more young men as a fraction of the population, which you expect in a growing population, perhaps we see more magical conflict.

I guess I'm also skeptical that wizards wouldn't be able to handle global warming. Why can't they just make their cities float or cast cooling charms on a large scale? Perhaps to solve that problem we can introduce some magical consequences of global warming so for example some fire themed magical creature causes some high profile accidents and those are not as amenable to magical solution as mundane global warming would be.

 

You don’t even have to do that. A simple rocket engine is less complicated than a car or a motorcycle, and those canonically work just fine with magic.

 

I think the Idea here is less that wizard expand because of overpopulation, but more because they see an opportunityt to make a profit, make new magical discovereis or just want a place where they can enforce their own laws. Like how muggleborns immigrated to the Americas because they saw an opportunity to proper without blood purists there. Canonically the wizarding community seems mostly united because of the statute of secrecy, with the ministries we know coming into being because of it.

I have no problem imagining that once they have much more land avaiable and dont need to worry about muggles, there would be a lot more sub communities.

Wizards can solve the muggle's problems just fine, they just dont want to, thats why there is the statute of secrecy in the first place. Either way, they should be able to use magic to at least stop global warming from affecting them.

 

• Statute of Secrecy is still maintained, though there have been multiple “calamitous” breaches that have take weeks/months/years to fully clean up. As a result, the International Confederation of Wizards develops into a more powerful entity, with more control over individual Wizarding nations.

• Muggle sciences have advanced massively, obviously.
  
  
• Wizarding advancement has mostly been dedicated towards countering advancements in Muggle technology. So now you can, for example, protect a television against magic.
  
  
• Because of advancements in Muggle tech/sciences, there are calls to have less interaction with the Muggle world, because it is much easier to create anomalous behaviour in extremely sensitive technology Muggles perceive to be “perfected” (i.e. your Games Consoles should never crash, but the Muggleborn next door has never gotten his to work and people are asking questions).
  
  
• AS A RESULT: parents of Muggleborns are told that their child is magical ASAP. If they do not comply or seem to pose a threat, I think there will be severe consequences, likely the I.C.W. could enforce that the child be removed from “hostile” parents (they can’t afford to take chances with how easily it is to break the statute in the information age).
  
  
• The Wizarding population of the world is much larger. As a result of this, Wizards need more land, each Ministry has Departments dealing with acquiring new land for citizens to settle on (build their families or host their businesses).
  
  
• There is stricter control over which magic can be cast. And there are wide nets of magic over all nations, monitoring which spells are cast, where. This naturally creates tension and conflict with people who do not wish to have their every spell
  
  
• Wizards have gone from being amused/curious about Muggles, to being mildly wary of them. I would say there is greater anti-Muggle sentiment, though there are fewer “Dark” factions which capitalise on this.
  
  
• Global Warming has been/continues to be very destructive to the Muggle world. Wizarding world was largely unaffected. Some were forced to abandon their land because “the Muggles around you lost theirs too and it would look weird if only your land wasn't affected”. So people are forced to essentially absorb whatever damage their geography sustained, even if they lost nothing. As a result, many wizards are now in “mobile homes”, or else congregated closer together in larger wizard-only communities.
  
  
• Wizards rarely interfered with the Global Warming problems. Some Muggleborns are angry because they know how many ~millions of people have suffered from it. This is another point of conflict. Wizards are extremely isolationist at this point.
  
  
• The few times Wizards did interfere or aide in combating climate change, was if it would significantly impact a wizarding creature that they do not have space to re-home elsewhere. Also, beings like Faeries and Centaurs would complain and make a fuss and are very put-off by Muggle damage. So there may be magical creature vs. Muggle conflict that is always going on which Wizarding governments are always mediating on. Do they choose to appease the Muggle govs or magical creatures who might go on to break the statute later by trying to survive?
  
  
• Wizards do not care about advancements the Muggles make space travel, given that they have working astrophysical/astromagical models of every object in the night sky, they have no need for spaceships, and can monitor for any incoming cataclysmic asteroids, because if Muggles find it first and Wizards get it out the way, it’ll raise questions. They want to know things first so they can solve Global problems before they become problems for Muggles. They really don't want to leave Earth even if they would find it trivial to survive on the Moon/Mars etc.
  
  
• There may be concerns that Muggle genetic engineering will either detect that Muggleborns exist, or they may somehow inadvertently start turning any would-be Muggleborns into Squibs. This could be a LARGE point of conflict in any story.
  
  
• Very few people have cybernetics. There are fringe weirdos who cut off fingers/hands etc. to get them, but most others have "heard the horror stories" and don't want to risk it.
  
  
• The average wand is no more powerful than they were in the 1990s.
  
  
• Mind magic means nothing to anyone. If anything, it would be considered Dark, as it would allow people to keep Secrets from the Ministry/I.C.W. and likely signify that the practitioner of Mind magic was working against the efforts of the Wizarding world.
  
  
• Alchemy means nothing to anyone. It is a curious branch of magic that offers little value. Anyone who might be capable of creating something like a Philosopher’s Stones are carefully monitored. If something big is created, they will order the inventor to destroy it to avoid someone i.e. accidentally turning a building into solid gold, and attracting Muggle attention.
  
  
• Point of conflict: many branches of magic are more stringently controlled. It is difficult to be an academic/researcher.

• Some spells are refined and easier to learn/cast due to refinements in teaching perhaps. But how good you get at magic is entirely based on your effort.
  
  
• Harry Potter is a mythic figure rivalling Merlin and Hogwarts Founders’. Hermione Granger and Ronald Weasley are also household names. People say “She’s a right Hermione, that one” if they were to casually refer to a child as being smart. Similar to someone calling another “Einstein.”
  
  
• There are no other realms / alternate realities.
  
  
• Some weirdo Wizards do go to live on the moon etc. Maybe this creates advancement in magic where people can transfigure i.e. rock into breathable air, which gives them unlimited supply of oxygen anywhere they go. Combined with nice clothes and a handy variety of Charms at their disposal, some adventurous wizards consider it quite fun. Though they will find themselves tracked down later to be charged for risking the Statute.
  
  
• Muggle-baiting is rife. Someone put a wizard hat on a space station’s antenna and it was a huge scandal. Apparently “he’d forgot he'd taken it off when he’d stopped for a rest”, but he still went to prison for it.
  
  
• There have been new Goblin Wars. Gringotts is viciously anti-Muggle, but there is nothing the Wizarding world can do because Gringotts is too powerful of an institution.
  
  
• Most Wizards still just use Apparition or the Floo Network or Portkeys, though they are all tightly monitored and restricted. There are black-market resurgences in things like Vanishing Cabinets etc., but they are heavily penalised.
  
  
• Many “old families” despise the new way of things and absolutely want nothing to do with it. They are penalised for trying to go “unmonitored”.
  
  
• Owls are outlawed. It is too easy for them to be tagged/followed by AI-piloted drones which have caused problems in the past.
  
  
• Oddball idea: The Wizarding governments enjoy the impact of Global Warming, because it distracts the Muggles -- and in the confusion, they are able to orchestrate a land-grab. They may even intentionally worsen the weather so Muggles think some areas of land are inhospitable.
  
  
• There are no aliens. Give it ten-thousand years and maybe we’ll find some. Intelligent life is uncommonly rare. Space travel is only worth it for Muggles, because they have greater need of the materials in i.e. asteroids.
  
  
• Oddball idea: Wizards want to lower the Muggle population without saying they want to lower the Muggle population. This idea seeds in the culture until someone new causes drastic amounts of Muggle deaths. Maybe Wizards worsen Global Warming intentionally in order to “kill off” Muggles.
  
  
• Magicals have adopted Television/screen-casting. So you have real-time Quidditch, duelling, chess, gobstones etc. Celebrities become much more celebrated. People wonder what it would have been like to see Harry Potter in his prime. They have a much greater impression of Harry than exists in reality.
  

Story Ideas:

I’d probably write about “older” Wizarding families like the Longbottoms, and how they have grown into prominence as their Herbology products have global reach. They are wealthier than the Malfoy’s could ever have hoped to become (conversely, many forget Malfoys were followers of Voldemort, instead they are now considered well-renowned Potioneers and Enchanters. They still have pointed faces, silver-blonde hair, and grey eyes).

But despite the Longbottom’s influence, they are feeling tightly controlled. The ICW is a formidable adversary and can easily crush their family if they don’t play ball; they cannot put out inventions they have made, because the I.C.W. don’t permit them to sell or export it. So for generations they feel their efforts are being squandered by “less able wizards” of the Ministry/ICW.

You’d have a young, talented witch/wizard surrounded in anti-Muggle sentiment, whose ancestor was the Neville Longbottom, but who deeply dislikes Muggles because of how much strife its caused his/her family.

Moral of the story: it’s all really complicated, and you don’t need to be a Dark Lord to want to do some particularly heinous things.