Adding a forum may hurt SEO Traffic?

I have a WordPress blog(blogging and technology niche) with 10,000 monthly SEO traffic(95% from Google).

I have decided to add forum using bbPress to that blog( I can't maintain a high quality content on forum. Yes, I can remove spam posts. But still their may be lots of thin low quality content on forum.

So it can hurt SEO traffic? Will it lose current SEO traffic also?

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