How Would You Design Large Forest Areas?

[siney]

Hi - I design a lot of maps that include large swaths of forested areas. I tend to leverage the Symbols / Spray tool but this creates very bloated files. Are there any "patterns" or textures that could handle the larger areas? I would love to hear some ideas and suggestions on what steps YOU would take to replicate an aerial photo in Illustrator like the one/s here:

Thanks guys! Can't wait to hear your approach / suggestions!