Raising the "Terrain" setting increases not only its intended effect of raising level geometry detail, but also increases grass density and render distance.
It is imperative that grass detail and draw distance has it's own indepenent setting or possibly two separate independent settings for distance and density, as Very High/Ultra level geometry can be run easily while grass density and distance at those settings can lower framerate much more. Meaning it would be optimal if you could have moderate grass settings and Ultra/Very High Terrain which can be run well for those rigs where having the current Terrain setting above High is unplayable.