i may have a problem

[irishQ]

seems to be an erosion issue which could be very easily solved with more dirt, but... i
just want to check with the experts as to whether or not this is an easy fix.

see the pic of my backyard. i have a bunch of christmas palms, some foxtails and a few royals which all have root exposure. they are growing just fine. they have been in the ground about 10 years.

my concern is whether i can leave these alone or should i bring in lots of top soil to replace the erosion. if i refill the area, is there any chance of killing the trees if it is done wrong?

thanks