Space in trunk by the fenders - trash

Was there originally anything in the trunk to keep things from falling down into the spaces by the fenders?
It's amazing what you can find down there, but on the driver's side it felt like a kid's sandbox. There was a lot of dirt and little bits of stuff that falls off trees.
What can be done to keep things from going down in there?
I'm worried about dirt and water getting in there and causing some major rust.
Also, is there an easier way to clean it out? I've got a long plastic thing that goes on the vacuum cleaner, but it doesn't get down there far enough.
Thanks!

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