Trees are trees, so why would diversity matter?


by Gary Balcerak

You may have heard people bemoaning the lack of diversity among the species that make up the urban forest of your community and thought, why would it matter? It turns out there are numerous reasons why it matters. Protection from a single pathogen killing off a large portion of the urban forest in a short amount of time is one. Using a few species, or worse yet a single species, is a recipe for disaster. Dutch Elm Disease and the devastation to the American elm across America being perhaps the most famous case.

Deodar Cedar

Cedrus deodar (Deodar Cedar)

Purpleleaf Plum

Prunus cerasifera (Purpleleaf Plum)

Photos by Gary Balcerak

There is even new evidence that the greater the tree diversity in a community the greater the diversity of bacteria and fungi. It is the exposure to these natural pathogens, at a young age, that impel the human immune system. Simply put greater tree diversity equates to a healthier human population!

The health benefits extend to many living organisms, the greater the number of species of trees the greater number of wildlife that can use the trees as habitat (food, protection, housing). Different wildlife species provide different ecological niches. This not only increases the interest for birdwatchers, it makes for an overall healthier environment.

Eucalyptus sideroxylon (Rediron Bark)

Eucalyptus sideroxylon (Rediron Bark)


Syagrus romanzoffiana (Queen Palm)

Photos by Gary Balcerak

Species diversity is also a hedge against climate change. With greater diversity, as the climate changes the urban forest can be used as a living laboratory, where successful and unsuccessful species can be evaluated for continued use. We know the climate is changing, what is less clear is what the changes will mean. The diversification of the urban forest increases the chances that some of our urban trees will not only survive but thrive in our changing world.

If you are a birdwatcher you know the joy of seeing a particular bird for the first time. There are people who derive the same excitement about seeing a new tree, I know I am one. It is possible you have this inside you and may not even realize it! By looking more closely at the trees around you, even before you know their name, you will start to recognize the common ones as being the same species. As you move about your daily life become aware of the trees around you and start to notice the ones that are of the same type, you are now Tree Spotting! I hope you find this activity is as enjoyable and rewarding as I do.


Maytenus boaria (Mayten Tree)

Photo by Gary Balcerak

Given the technology of today finding the name for your tree is not very difficult. The Arbor Day Foundation has the What Tree Is That? which is a simple and effective tree guide, this is probably the best for true beginners. Oregon State University offers Tree Key which is a slightly more advanced key, although it only covers the pacific northwest. Virginia Tech Dendrology offers ID Keys which provides several different ways to identify the tree you are looking at. Virginia Tech has the largest data base which means you are more than likely to find your tree, but it will probably take more steps.

My experience is that once some of the mystery is removed, looking at trees and wanting to know more about them is a natural process. Children are naturally curious, when asked "what tree is that?", just know that the answer is far more available than most people think. Trees are all around us, and provide a connection to nature, even in our fast paced, technology driven society. The urban forest is a constant reminder that we are a part on nature, if we would just take the time to notice. Trees provide many benefits and joys, look a bit closer and see how trees effect you. Who knows, as you become more involved with trees you may even end up being a tree advocate!

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