[Valley] Trees = framerate drop

[NightFire275]

Whenever I play on a map that has trees (for example, A06), my framerate suddenly takes a huge drop. I can play everything else fine at a stable 60 FPS at the highest settings with plenty of cars (Canyon, Stadium and any Valley map without trees), but as soon as I see trees, my framerate drops to as low as 35 FPS even with only my car on screen. My GPU rises to 100% usage after it sits around 60-70% elsewhere.

I've experimented with settings and I've found this problem happens worst on the Very Nice shader setting, and the only way to get rid of it is to change it all the way down to Very Fast. Even so, I doubt this is running as intended.

My specs:

CPU: Intel Core i5-2500K @ 4.5 GHz
GPU: Sapphire Radeon HD 7850 2 GB (Overclocked to 1225 MHz/1375 MHz)
Memory: 8 GB DDR3 @ 2133 MHz
PSU: 750 W
OS: Windows 8

I'm thinking this is either an issue that needs addressing through an AMD driver, or through a patch for the game. Just seems odd to me!