As the others have said, it unscrews. I have nothing meaningful to contribute, so I'll spin this yarn instead:
For the first time, I took my full birding rig with me on my last motorcycle trip. If you need to undo a recalcitrant filter from the end of your lens barrel I advise you just chuck it in your motorcycle luggage. The vibrations, most likely from some stints of off-road riding, unscrewed the filters on all of my lenses inside my camera case. Strangely enough it did not knock off any of my lens caps in the process.
Insofar as I'm able to determine this experience did not break any of my in-lens image stabilizers or autofocus motors.