Yes, this is a real sign
Nope, we aren't pulling your leg. This is an honest-to-goodness sign put up at a local campground by the good old USDA Forest Service. See anything wrong with this picture?
The small print in the box toward the bottom is a liability disclaimer: "With respect to the identification and removal of all tree hazards found in a forested recreation setting, neither the United States Government nor any of its employees makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness, of the information contained herein, or actions that may be taken by a visitor to the National Forest."