There are several ways of answering this question.
First, as described in an earlier post, a mature tree can add thousands of dollars to the value of a property, in addition to saving the occupants money on utility bills.
Second, trees provide measurable value to a city through their role in absorbing and filtering stormwater, cleaning the air, and improving human health. New York City has calculated that its street trees are worth $122 million a year, and that every dollar spent on improving this urban forest generates a return of $5.60.
Third, a recent study found that adding ten trees to a city block produces benefits to the health of nearby residents that are equivalent to giving those residents an extra $10,000 a year of household income.
Urban trees have also been found to decrease childhood obesity, improve ADHD symptoms, deter crime, reduce traffic accidents, improve memory, speed recovery from illness, and even lower the rates of suicides and premature births.
Trees are usually the last thing to be considered in development projects, getting treated as nice-to-have amenities that are added at the end if there’s any money and space left. Experts on urban trees, however, say that the presence of trees in our neighborhoods is crucial to our wellbeing. Their true value, these experts say, is effectively incalculable.