Friday, April 22, 2022

The value of trees

 An appreciation of trees

Trees in our yards and in our communities add to the global
population, which is crucial for slowing down climate change.

Here are just some of the many ways that trees are important not only in our urban and suburban neighborhoods, but also for the whole planet:

- Trees actually cool the air through transpiration. A mature deciduous tree like an oak will transpire more than 400 liters of water on a hot summer's day. In the process of liquid water evaporating (going from liquid to gas) the air is cooled. At 68˚F each gram of water that evaporates, cools the air by 585 calories. Transpiration: Forests' most important service

- Trees sequester carbon, by absorbing carbon dioxide (CO2) a long-lasting greenhouse gas, through the process of photosynthesis where they remove carbon dioxide from the air to make sugars, which are then stored in the various plant tissues. A typical hardwood tree can absorb as much as 48 pounds of carbon per year. This means it will sequester approximately 1 ton of carbon by the time it reaches 40 years old. Carbon sequestration

- Trees produce oxygen through photosynthesis, but trees and all the other organisms in the forest absorb most of that oxygen to live. Also read Transpiration: Forests' most important service where I talk about three cycles in the forest: Carbon, Oxygen, and Water.

- Trees remove carbon monoxide (CO) and other air pollutants from the air. They are absorbed primarily through stomata (pores) on the leaves where they diffuse into intercellular spaces and may be absorbed by water films to form acids or react with inner-leaf surfaces. Trees can remove significant amounts of air pollution in cities, where it is often concentrated. More information on this from the EPA.

- Trees, especially a variety of native trees, provide important habitat for birds and other wildlife. See below.
- Trees reduce soil erosion with their extensive root systems. 
- Trees remove pollutants and sediments from stormwater runoff and then slowly release the water back into waterways and underground aquifers.
- Trees reduce stress levels in people.
- More trees around schoolyards correlates to higher educational performance levels. Link to study.
- Trees increase property values. "Good tree cover increased property prices by about 7 percent in residential areas and 18 percent for building lots. Quality landscapes with healthy trees can increase retail spending from 9 to 12 percent. Tree-filled office properties can expect 7 percent higher rents than those without trees or quality landscaping." Three huge benefits big trees offer you

Baltimore: Over the life of a single tree, it is not unreasonable to conclude that $57,000 in economic and environmental benefits are provided.

- $3.3 million a year in energy savings by shading buildings from the summer sun and blocking winter winds;
- $10.7 million a year storing 527 tons of carbon. Carbon is a harmful gas that contributes greatly to the greenhouse effect;
- $3.8 million a year by removing 700 metric tons of air pollution (carbon monoxide, nitrogen dioxide, sulfur dioxide etc);
- $1.6 million a year by removing 244 metric tons of ozone. Ground-level ozone is the main ingredient in smog and a leading contributing factor of asthma."
Current value of services provided by Baltimore’s trees

More cities and communities need to emulate Baltimore's stance on the intrinsic value of their canopy trees, because when each tree has a value of $57K, then city crews are much less likely to remove mature trees for superficial reasons such as, "They shed too many leaves." or "They need to be trimmed too often." Even if those removed trees are replaced by new trees, those smaller trees won't begin to replicate the benefits of the mature trees for fifteen or twenty years!

Wildlife habitat

Native trees are extremely important for building local habitat. Doug Tallamy has changed the narrative about why native plants are so important. His arguments are compelling and easy to understand. He pointed out that "a single pair of breeding chickadees must find 6,000 to 9,000 caterpillars to rear one clutch of young and the vast majority of those caterpillars will hatch on native plants."

He says that home landscapes can help wildlife survive. His newest initiative is his "homegrown national park." He urges people to replace half of their lawns with native trees and native understory habitat. This way we could go from 40 million acres of lawn to a 20-million acre national park.

This is an easy concept and we can bring in people who have not thought about habitat before by making it easy for them to obtain native plants and helping them be successful in attracting pollinators and birds to their yards.

For more information and details, here are articles on things that live in or on trees:
Resurrection ferns
Spanish moss 
Birds of prey

Resurrection ferns (Pleopeltis michauxiana) are epiphytes (air plants) and are often found on the broad live oak branches. They increase the habitat values of the trees.Lichens are 3-way symbiotic organisms and are often found on trees, but they do not harm them in any way.

Spanish moss (Tillandsia usneoides) is a flowering plant in the pineapple family, which provides additional habitat values and does not need to be removed trees.Trees provide habitat for a wide variety of
wildlife such as these cute raccoon cubs. 

We love having Barred Owls (Strix varia) in our non-poisoned, wooded yard. Even dead branches provide habitat and food for birds such as these Crested Flycatchers.

Trees are being removed

Despite all their benefits, trees are being removed at an alarming rate. Not just in our rainforests, but in our communities and neighborhoods and often for no discernable reason except perhaps to grow more lawn. Here are two examples from my neighborhood, but examples like this are found in all over Florida and beyond. People don't seem to have enough respect for the value of trees and all their benefits.

There were two beautiful mature native sycamore trees (Platanus occidentalis) in this front yard and now only one badly mutilated tree is left. They were perfectly placed to soak up the moisture from the swales next to the roads--this is a corner lot. They were not too close to the house and not too close to the wires. Now, the new owners of this house have planted knock-out roses around the base of this poor tree. These trees were important and cooled the whole yard, which have made that house more comfortable in the summer. While the remaining tree will leaf out and send out new shoots, severe over-trimming and topping of this tree will significantly shortens its lifespan. 

A beautiful live oak (Quercus virginiana) and a bunch of other trees were taken down for no reason. This was two years ago, and this tree and others were chopped up and stacked up as firewood. What's left now is a larger lawn area between the road and the house. Now, the whole yard will be hotter in the summers and support fewer birds.

And more views on trees...

From The Nature Conservancy:
 Six ways trees benefit all of us.
Even aliens know that trees are valuable!

Sunrise in a beautiful, treed yard.

So, plant a wide variety of native trees in your yard and in your community to build more biodiversity, but more importantly, keep and maintain mature trees so they can continue to provide habitat for wildlife and ecosystem services for us and the whole planet. We all need to work to help people living in our neighborhoods and those working for all levels of our government understand how valuable trees are on so many levels.

Green Gardening Matters
Ginny Stibolt


  1. A person cannot love a plant after he has pruned it, then he has either done a poor job or is devoid of emotion