It is just not possible to ascribe enough value to our urban forests. The trees that ornament and protect our environment are absolutely critical to our well-being. Eco-systems suffer when trees are absent. And any paved-over environment like a city with its emphasis on the prevalence and reliance on motorized roadways and its de-emphasis on natural green is one that has failed to recognize the primary function and importance of the flora, particularly trees, for our well-being.

Trees are carbon sinks, they give off oxygen while absorbing atmospheric carbon dioxide. They cleanse the air we breathe. Above their function in this way they are beautiful growing flora, some of which species can grow for hundreds, even thousands of years. They shelter us, their harvesting produces lumber that is used in manifold ways from building homes to producing wood pulp for use in newspapers, books, magazines, all adding to the quality of our lives.

In Ottawa, the urban forest is 25% represented by ash trees, and ash trees have, for the last few years, come under threat by the ash tree borer. The trees that live serenely among us, allowing us to breathe healthily, satisfying our aesthetic with their large green, cooling presence, and which comprise such a large portion of our growing tree stock are under threat. And by extension, so are we.

• In the Netherlands studies have shown that people in areas with more greenery suffered lower rates of a multitude of health problems, and in particular anxiety experienced by children.
• Children living in New York City in areas with greater numbers of trees thriving on the streets appear less likely to suffer from asthma.
• Researchers in Portland, Oregon, found that pregnant women living where more tree canopies exist within 50 meters of their homes or living close to open green spaces, are less likely to bear underweight babies.

"You want them because they are beautiful, natural cleaners (of air) and protectors of us. I see a lot of asthma, a lot of emphysema, a lot of pneumonia. It's on the rise and I think it's largely related to pollution", explained Dr. Curtis Lavoie of the Children's Hospital of Eastern Ontario. "It's only because we've got amazing drugs out there that we are able to save lives and stop major disaster. But it's still a huge load, and it's parents and kids who suffer."

Drugs, a poor compromise solution to losing our natural immunity to illnesses that plague our communities, and which could be ameliorated if we were more committed to the health of the trees surrounding us. The threat to the urban ash trees posed by the ash borer, the devastation of wonderful old elms by Dutch elm disease, the threats that are posed to pines from pine beetle infestations all impact us deleteriously.

 Many municipalities, like Ottawa, have undertaken programs to emphasize the necessity to plant more trees. And funding set aside in the city budget to mount tree-planting blitzes by the city itself, along with offers to supply trees gratis, to those people who have the room for them on their properties and contact the city for that purpose, have been an assist in ensuring the urban forest does not fail.

The United States began to experience the devastation caused by the emerald ash borer invasion before Canada did. The insect invasion, over the years, has killed tens of millions of trees in 15 states. It arrived in Ottawa by 2008; first detected as an invidious invader in Michigan, in 2002, although it's highly likely its presence went undetected for years previous to the recognition of its deleterious presence.

The U.S. Forest Service undertook a measurement of death rates in 1,300 counties across the 15 states that have experienced ash borer infestations. The infestation represented "an unprecedented opportunity to study the impact of a major change in the natural environment on human health". And, in county after county the scientific investigators found that human death rate rose as those ash trees disappeared from the bio-environment.

The greatest jump in deaths appeared in communities where people had higher-than-average incomes and greater education foundations. Those attributes just happen to be the places where trees appear more prevalently. Still, said lead researcher Geoffrey Donovan, "...We saw the same pattern repeated over and over in counties with very different demographic makeups".

And Ottawa's Dr. Lavoie believes that a new U.S. study published in the American Journal of Preventive Medicine  proves without equivocation that the link between the death of wide tree swaths like the Ash, is responsible for "excess deaths" from heart problems for adults, as well as from lower respiratory problems.

Asthma, he emphasizes, remains the single biggest cause of children being admitted to hospital. And the rate increases as tree die-back occurs. Apart from the fact that trees have a calming effect on people. A stroll in a woodland setting is a deep-seated pleasurable outing, one that makes us more content, happier, at one with nature.