I have a Minecraft save (SMP) that has a very sudden shift in terrain and biomes. To be exact, there is a long line along which the maps shifts from one block to the next in terms of natural terrain and biomes.

biome shift map biome shift live

This is looking terrible, especially on my world map. I've googled for this issue, but can't find any result where this issue is addressed. While looking for a solution, I read some mention that if you delete chunks in MCedit and let the game regenerate them, it will generate exactly the same blocks, so that is not an option. If MCedit can help in any other way, that's cool, I know my way with the program a little.

Some info: I think the world was generated in vanilla 1.7.1 or 1.7.2. I'm using mods now, but not at the time I started this world.

Is there any way to change/fix this?

  • 3
    Seems like your level.dat got corrupted and the seed got changed. When new pieces of the world were generated, the generation was altered and doesn't fit with the old pieces of the world anymore, because the seed that is used to generate the world has been changed. Unless you have the original seed, there's nothing you can do.
    – user79446
    Commented Jun 13, 2015 at 22:31
  • 2
    I was thinking the same. How can I get the original seed? When starting a game with a random seed, the game doesn't show you a seed string I believe?
    – paddotk
    Commented Jun 13, 2015 at 22:43
  • 3
    This also tends to happen whenever something changes in the way biomes are generated, often happens between major versions. Commented Jun 13, 2015 at 23:34
  • @poepje there is no way toget the original seed unless you have a backup of the world.
    – user79446
    Commented Jun 14, 2015 at 16:11
  • The seed is most likely the same. But when the mods were added they changed the world gen but were still using the same seed. Anytime a change is made to worldgen (update of game, adding of mods) this will happen at the edge of explored chunks and new generated chunks. If you want to fix this you can, but the method is not easy, and will destroy anything in the original chunks, but not in new generated ones.
    – ydobonebi
    Commented Sep 22, 2015 at 20:16

2 Answers 2


This is caused by starting the world without mods, and then adding mods that do something to the world gen (like for example adding new biomes or ores).

The part you explored before you added mods is still generated with the vanilla worldgen, the newly explored parts are generated based on the modded worldgen. Both are generated by using the same seed. But a slightly different worldgen.

If you are thinking that you never explored this far: that's normal, the game generates some area around wherever you are, so you came 5 chunks away from said area (or at least I think it was 5 anyway, might be more)

If you remove the chunks generated before you added mods with MCedit, they will be regenerated as new chunks with the new world generator.

I don't know which area of your world was made with the original worldgen and which part was not, but let's assume the bottom part is the old part. And the snowy area up top is generated once you had mods. Removing some of the birch wood forest area in MCedit should cause it to turn into snow forest biome (biome names are made up based on how it looks, they might actually have a different name). If my assumption is wrong, delete some snowy forest and it'll turn into birch forest.

  • Ok, though I don't understand why mods would alter the world generator of the game, it does make sense otherwise. The top/northern part of the map was the original part though. Anyway I'll give this a shot when I have time, so thanks.
    – paddotk
    Commented Sep 22, 2015 at 23:17
  • The world is generated based on some mathematical function, that uses the seed. Adding extra parameters(such as: an extra ore, a new biome option) to this equation changes the outcome of the function, and thus the resulting world. Some mods don't add anything to wordgen, and won't cause this behavior (for example: NEI). Others do add things and result in a changed world (for example: forestry adds some ore)
    – Arperum
    Commented Sep 23, 2015 at 10:11

You cannot directly reload the bad chunks, but you can restart the world, using the same seed but you will lose all items and structures you have built.

How you restart with the same seed:

First select the world you want to restart (In this case "TutorialWorld") enter image description here

Under "Create New World" You will see a setting called Re-Create. Click this, and from there it is just like creating a new minecraft world.

How Re-Create works:

Re-Create takes the world you selected and makes a new world, but using the same seed as the world you selected.

Just as reference:

You can do /seed in game to see the seed of the world you are in.

  • Then you will lose all your stuff! Commented Jun 14, 2015 at 12:46
  • "You cannot directly reload the bad chunks, but you can restart the world, using the same seed but you will lose all items and structures you have built." This answer is more replying to a comment by the op, "was thinking the same. How can I get the original seed? When starting a game with a random seed, the game doesn't show you a seed string I believe?"
    – user112881
    Commented Jun 14, 2015 at 13:42
  • If you are technical enough, you can delete the files for the bad chunks, delete level.dat and regenerate another world with the same seed Commented Jun 14, 2015 at 14:04
  • This won't regenerate the world as he originally had it though, as the seed is already changed. This isn't really any better than just starting a new world altogether.
    – user79446
    Commented Jun 14, 2015 at 16:10
  • It will use the new seed to generate the missing chunks, but keep the existing chunks Commented Jun 15, 2015 at 2:57

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