The cleaner clootie campaign

Many people choose to interact with sacred sites by leaving clooties - small bits of cloth tied to trees.

Unfortunately these cause problems for wildlife, because small birds can get tangled in them, animals can choke on them, and they can damage the tree that they are tied to.

Clooties on a tree (source: Cleaner Clootie Campaign)

That's why the Cleaner Clootie Campaign was started, to try to get people to use biodegradable clooties. My personal preference would be for people not to leave any kind of clootie, but if you feel you have to, at least use biodegradable fabric. It is more in keeping with the folklore anyway, as the traditional view was that you left a clootie as an offering to take your illness away, and as the clootie rotted away, the illness faded too.

If you want to perform a meaningful service or offering for a sacred site, clean up the litter. 

In the 1990s a group of local Pagans (including me) cleaned out the litter from Nine Wells near Cambridge, and it stayed tidy for years afterwards, because it seems that if people see a tidy site, they don't drop litter.

You could also do the site a favour by removing the clooties that other people have left.