One of the biggest that I can think of is the global cut flower industry.
Is there anything positive to offset the negatives?
Farmland not used to produce food or feed. Shipping… air freight to rapidly fly the flowers around the world. Refrigeration… flowers need to be refrigerated constantly. Temporary… they get thrown away after viewing.
The only positive I could think of would be food for the bees but this could easily be compensated for by growing flowering food or feed.