Maybe better English would be There has always been immigration in the world?
Indeed. You would use "was" if referring to a past era now ended: "There was always immigration in the middle ages."
Duo accepts that.
"There always has been..." also accepted.
Il y a toujours eu de la guerre dans le monde.
why not the imperfect tense here so it is Il y avait toujours... ?
If you use imparfait, you're basically saying that immigration was an ongoing concern in the past, but not any longer.
This is because a basic rule for imparfait is that the action started and stopped in a past time.
A good comment
Thus the 'used to' construction duo loves for the imparfait?
...pistols at dawn gentlemen?.... By the way Brian your public hypocrisy and xenophobia do you no credit.
Shouldn't this logically be in the Present Perfect Continuous tense? "There has always been immigration in the world."
Really this should be "migration" not immigration.
Only if you insist that Duo always make accurate statements ....
... as a translation, "immigration" is correct.
Yes of course, the translation is fine. It was just an observation - there are plenty of non-native English speakers using this site to learn French and there are lots of examples of potentially misleading statements throughout Duo.
There has always been in UK English