Homeless people in next door neighbour's backyard

[Changseok Kim]

Hi BP members, 

I have an issue with my rental property, and wish to ask for your guidance. I have a rental property and currently occupied with renters. Recently, the new neighbour next door let homeless people (his friends, I guess) stay in his backyard, currently there are three tents.  Unfortunately there are no barriers between his backyard and our rental property, and campers location is very close to the kitchen of our rental property. Also, the new owner cut down trees between our property and his, which exposes the campers more to our property. Our renters are uncomfortable with the current situation and feels insecure about their privacy, requesting for installation of tall fence, which will cost lump sum money. 

How would you approach this situation? Any recommendation will be appreciated. 

Thank you.