This is a really ambitious and important study. I was at the conference mentioned in the article and I was really impressed with the study design and the amount of resources they were able to muster for this experiment—way beyond anything anyone else has done. There is a lot of observational research on the health impacts of trees, and many people are arguing on that basis that we should be treating urban forests as not just decorations but as essential infrastructure like water treatment, sewers, etc. But some critics have pointed out that the research is not 100% definitive yet. I hope that this study will be the missing link in making the case for the essential nature of urban forests.