The fact that someone is an investor or operates an Air BnB out of their property doesn’t mean they have a conflict of interest. They may have a particular reason for wanting to remove the trees and plants that aligns with their interests, all owners have an interest in the outcome of a decision, but that doesn’t mean they have a conflict of interest.
A conflict of interest is where someone has a material personal interest in the outcome of something – for example if an OC was looking at engaging a contractor and an owner had a financial interest in the contractor, then they should recuse themselves from any decision in that regard because the two interests conflict.
That doesn’t mean that I don’t sympathise with you, I like gardens. But if you want to have a chance of success make sure you have a solid argument.