Exodus could hurt Scotland
His reaction follows Finn Russell's decision to leave Glasgow.
Flyhalf Russell, expected to join Racing 92, will join Greig Laidlaw and Richie Gray in France.
Players such as Sean Maitland and John Barclay play elsewhere in Britain – though Barclay is set to move back to Edinburgh.
There have long been difficulties with securing the release of players in France in time to join up with their international sides, and Townsend is keen to keep as many players playing in Scotland as possible.
"The better thing for the national team is more people playing in Scotland," he said.
"If more and more players leave Scotland, it will be much tougher. A huge reason Ireland have been successful is their players are in the same area, playing in Ireland and building up combinations and connections.
"Obviously we wish Finn all the best. We have two players currently injured in France who were likely to be in our squad – in Richie and Greig – and we'll now have a third but you've got to make sure there's not too many players leaving Scotland."
Townsend is preparing his side to take on Australia this weekend after suffering a narrow 22-17 defeat to New Zealand on Saturday.
Despite a hugely impressive performance, Townsend has demanded more from his players after making four changes, with Ryan Wilson, Maitland, Grant Gilchrist and Simon Berghan included in the starting XV.
He said: "We play the current number three team in the world, and arguably the best attacking team in the world.
"Australia beat New Zealand a few weeks ago, were very good against Wales and for a lot of the game on a wet day against England, so we know we're playing one of the form teams in the world right now.
"If we drop our standards, we're not going to win."
Maitland has been named on the wing in place of Lee Jones despite only being called up to the squad this week, while Ben Toolis drops to the bench as Gilchrist takes his spot.
Zander Fagerson and Alex Dunbar will face further tests this week following head injuries suffered against the All Blacks, but both are included in the 23 while Hamish Marshall has recovered from injury but Luke Hamilton misses out.
On the return of Wilson following a shoulder problem, Townsend said: "He feels in a much better place physically. It was a close decision last week on whether he'd be available, and the guys stepped in and did well.
"Ryan is a very important player for us."