The Sept. 18 referendum in Scotland regarding whether it will become a country independent of the United Kingdom already has roiled British stocks and the pound.

As for the impact on Scotland, it won't be pretty whichever way the vote turns out, says Harvard economist Ken Rogoff, former chief economist of the International Monetary Fund.

"It's certainly a disaster for Scotland. First and foremost, it's going to be a horrible adjustment," he told CNBC.

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"Even if it doesn't pass, people are not going to want to invest there, because they might do it again. People will migrate out of there."

The ramifications are negative for the European Union too, Rogoff said. That's because it may inspire other autonomous regions, such as Catalonia in Spain, to seek independence.

"Other places in Europe [will] say, 'Hey, we can do that too.' So it's certainly quite a wild card there," he noted.

Recent polls show a tight race in the Scotland vote.

Rogoff isn't the only one concerned about far-reaching implications from the referendum. "There is just massive uncertainty," Mujtaba Rahman, European director for the Eurasia Group, a political and economic consulting firm, told The New York Times.

"From what an independent Scotland would look like to the currency, the financial system and even Britain's membership in the European Union."

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