Just look at these pictures.
It is depressing looking at all that. Look at the general demographic. They are young, the ones some of are trying to save the planet for, yet here they are trashing it! It's not unique, either. We have had the beaches and beauty spots, protests and marches.
They had the means to take all that crap there so they had the means to take it away again - no excuses.
I have been a bit more than mildly interested in environmental issues for all my adult life, though not a zealot, but scenes like these make me wonder 'why bother?'
Honestly, I would use water cannon with indelible dye on these idiots so that they can be identified and made to put in many hours of cleaning up littering of all descriptions. Get them out on the roads, rivers, canals, hills and fields and make them work. Do it in all weathers as well.