Why do these stripes appear when creating a city?

[tranquil knot]

Here i have a city i just created using the largest region size, And these stripes always appear (look at the minimap)

This happens in every seed btw

[lofty imp]

Check your plugins

For anything that alters terrain

[tranquil knot]

Are there such plugins?

[lofty imp]

Yes

And you have one installed that does

I can't think of the name

It's likely one by KingTut though

[hushed cape]

is that the nature+ plugin