I believe there have been studies on the value of real estate next to parks. They found that real estate values increased if they were along the park, but the homes behind them, away from the park edge, did not see an increase in value. I don’t remember who did the study but perhaps if you search for “real estate value along park space”, you will find it.
There have also been some studies on the amount of pollution absorbed by trees. This was a study done in China and again I don’t recall the scientist names or affiliation.