All but one of the photos shown here, taken during our exercise around the perimeter of the park this morning, need no explanation.‡
Most of the litter bins are emptied regularly, but their mere presence seems to encourage the stuff. Animals might play a role as well in distributing it, if not depositing in the first place. I am also well aware that there are some who regularly remove these blots on the landscape, but you do need a proper litter picker† and bag (handling the stuff with your hands is not recommended). One lady, well known to locals, can often gather ten or so bags of the stuff in one session. Others focus on the benches in the orchard garden, which seem to attract a particular type of detritus. The Greenwayers specialise in the waterways for which you need training and protective clothing, but due to a combination of weather and lockdown, have not had a chance to meet this year yet.
Meanwhile, if only the stuff that is brought into the park were to be taken away by the same people, we would not be able to take photos such as the above.
‡No, tarantulas are not native to the park. †There is an enormous selection.