This is something that the whole community could help with. Perhaps your local Youth Club or school could organise a litter pick one weekend. Even better if there is someone who could provide a drink and a biscuit at the end of the session. In my area, the Youth Club and the Parish Council worked together to design and paint a “graffiti” design on a wall that was constantly being graffiti’d and it turned into a really fun art project that a number of young people were able to get involved in. Is there somewhere in the park that you could suggest treating in the same way? If you and your friends could put some ideas together, you would need to talk to the Town Council, or ask your local County Councillor to raise it at a meeting called the Local Area Forum where there might be some funding available to help you. No promises, but it’s worth a try.