Graphical box glitch arround big grass

[togg]

I'm playing on a Mac 10.11.6 (15G1004). I think this started with the latest update but I'm not sure.
This happens basically everywhere. It isn't the best screenshot possible but as you can see there're some lines like this -  -  -  -  -  -  -  - that delimit the grass space.

[togg]

I shouldn't had resized the screenshot, anyway, that's the part of the bug.