Importance of our trees

The Roles of Trees in Urban Balance

Trees are an essential resource for our society. In this section, we will discuss the numerous advantages of trees in urban environments. The professions of arborist and horticulturist are vital for future generations, and we hope that through this short excerpt, we can raise public awareness about the importance of these trades.

Life on Earth became possible thanks to the appearance of plants over 420 million years ago. They represent a major milestone in the evolution of life. Cyanobacteria, by entering other microorganisms, are believed to have fused their chlorophyll (the pigment that enables photosynthesis), thereby creating plant cells. This pairing of microorganisms later allowed for the development of marine algae, making the conquest of dry land possible as algae washed up on shores. Plants thus conquered almost all terrestrial biomes, leading to the appearance of the first forests. In doing so, they facilitated the advent of animal life on Earth. Our planet has over 300,000 plant species that are necessary for all forms of animal life present on Earth.

One of the most current environmental issues being climate change, it is important to realize the significance of vegetation as a possible solution to the problem. According to a recent study published by the UN, the best way to fight climate change is to utilize the carbon sequestration performed by trees. A tree absorbs CO 2 during photosynthesis, which can greatly offset gas emissions in urban areas. Planting a trillion trees could limit the global temperature increase to 1.5 degrees by 2050, according to these specialists.

Unfortunately, plants were the first to be affected by urban development. Too many people still ignore their importance in our daily lives. Trees are essential for a good quality of life. For this reason, we wish to inform the public about their ecological, aesthetic, social, and economic benefits. Our goal is to increase the general knowledge of the population and thus ensure the conservation of current vegetation as part of our natural heritage.

Ecological Functions

Trees as Oxygen Producers and Sources of Life

Trees, like almost all plants, are autotrophic organisms. They manufacture their own food, allowing them to grow, reproduce, and pass on their characteristics to future generations through genes. They are primarily the only ones to produce organic substances from inorganic materials. Green plants are the base of the food chain, and non-chlorophyll plants, herbivores, and carnivores depend entirely on plant photosynthesis. Without them, many species could not survive. Photosynthesis thus allows the plant to transform light energy from the sun (inorganic matter) into glucose (potential energy for the plant organism) as well as to produce oxygen. This oxygen released into the atmosphere is vital to animal life on Earth. We depend on these trees, plants, and all vegetation capable of performing photosynthesis to produce the oxygen we need to live. A mature tree produces an average of 120 kg of oxygen per year, which corresponds to half the annual consumption of an adult.

Trees as Air Purifiers

Plants, specifically trees, are specialists in air filtration. The air absorbed by a tree contains a certain amount of pollutants and dust. This absorbed amount varies from one tree species to another. A mature maple can capture up to 20 kilograms of dust per year. A street lined with mature trees contains up to 4 times less atmospheric dust than a street without trees! Several species are renowned for their high pollutant filtration rates, such as elm, beech, alder, and willow, while other varieties such as bur oak, hop-hornbeam, and staghorn sumac can retain a larger amount of dust thanks to their fuzzy leaves.

It is also important to mention that mature plants in urban areas can capture approximately 800 kg of CO 2 per year.

Trees: Synonymous with Biological Diversity

The term biodiversity refers to all the species and ecosystems of a given region or natural environment. In the province of Quebec, there are more than 40,000 wild animal and plant species living in harmony, and many of these species depend on forest ecosystems. This diversity of organisms found in a given region is a fundamental measure of the health of the natural environment. The disappearance of a single plant species could alone cause the extinction of more than 30 animal species. Plants are primary producers in the food chain; they are therefore at the base of all animal life.

Trees Fight Against Soil Erosion

Trees help combat soil erosion, which frequently occurs in urban environments due to construction work and regular pedestrian traffic. Roots hold the soil in place on sloped land and prevent the collapse of banks into waterways. In addition to ensuring the regulation and stabilization of soil hydrology, trees also ensure the maintenance of the groundwater table level. When soil is directly exposed to rain due to the absence of plant cover, the impact of raindrops can have major long-term repercussions on soil structure, as well as a loss of minerals through gully erosion or runoff erosion, among others. This degradation is particularly pronounced on sloped soils, stream banks, cliffs, hills, and embankments.

Trees Improve Water Quality

Plants help limit the amount of pollutants flowing into waterways thanks to their roots, which absorb a large portion of the runoff volume. In this way, trees help protect our waterways and reduce damage caused by flooding. In addition to being very effective water filters—thus offering better water quality—forests serve to store water, thereby reducing soil evaporation. These forests also stabilize and delay snowmelt. Vegetation strips along waterways, lakes, or ponds are important for the balance and maintenance of the health of water bodies. Trees can absorb a large amount of runoff water, which is often loaded with fertilizers. The plant root system retains these fertilizers, preventing the over-fertilization of water bodies and thereby decreasing the development of algae and other aquatic plants

Trees Participate in Regulating Extreme Temperature Fluctuations

Through the process of evapotranspiration, trees release water vapor into the atmosphere, which influences the local humidity rate and helps temper extreme climate variations. Numerous scientific studies have shown that clearing trees from cities increases air temperature and wind speed.

Trees Protect Against Heat

Trees cool the ambient air by offering us protection from the heat. Several studies show that air temperature in urban woodlands is generally cooler than in areas devoid of trees. The evapotranspiration of one mature tree that cools the ambient air is equivalent to 5 air conditioners running at full capacity! With their foliage, trees offer us protection against solar radiation by absorbing and reflecting this radiation, thus decreasing the intensity of solar rays and the perceived heat. Furthermore, they allow for the creation of shade on residential lots, offering cooler spaces during high temperatures.

Trees Protect Against Rain

Trees protect us from precipitation by intercepting droplets and snow. Conifers are the champions in this field since they can intercept up to 40% of precipitation, unlike deciduous trees of the same size, which intercept only 20%.

Trees Can Improve Arid and Disturbed Sites

Several nutrients are essential for plant survival, such as nitrogen, phosphorus, and potassium. Some plants, such as legumes, can fix nitrogen with the help of bacteria. They have the ability to take nitrogen from the air and, thanks to bacteria, return nitrogen to the soil at the root level so that other plants that cannot fix nitrogen can benefit from these nutrients. These nitrogen-fixing plants maintain a symbiotic relationship with Rhizobium bacteria, ensuring a benefit to both parties. The plant, by providing energy to the bacteria derived from photosynthesis, receives necessary amino acids from the bacteria. During this exchange, nitrogen is produced and will end up in the soil or be stored by the plant itself. When the plant dies, it decomposes and releases all the nitrogen it has stored over time into the soil, fertilizing it. This nitrogen fixation process allows plants such as those in the legume family (honey locust, Kentucky coffee tree, black locust) to live in poor and arid soils. Additionally, they enrich the soils with nitrogen for other plants growing in the same area. The grass family and the Cyperaceae family also have the ability to fix nitrogen.

Trees and Windbreaks

Wind is an element of great power, yet trees have the capacity to decrease wind speed. They create resistance to air movement, which results in a calm zone appearing behind them. Air velocity can be reduced by up to 50% when there is a dense screen of vegetation. The degree of velocity reduction will depend on the height of the vegetation, the density, and the permeability of the plants used. We find many windbreak trees along highways or straight streets for the purpose of controlling and reducing wind gusts and snowdrifts.

Trees are an Attraction for Wildlife

Several animal and plant species depend entirely on vegetation for their survival. Many mammals use trees as shelter, such as squirrels. Trees are also essential for birds and insects, offering them shelter, protection, and food. Many of these plants are essential for bird feeding in winter, such as mountain ashes and hawthorns, offering fruit during the winter period since these trees keep their fruit even during this time. Many other fruits produced by vegetation are part of the diet of various animal species, such as acorns, berries, and samaras. Additionally, vegetation offers protection to prey that hide among the leafy cover of trees to protect themselves from predators.

Trees Protect Against Noise

A belt of trees along roads can reduce ambient noise by 6 to 8 decibels. A sound sensation reduction of 50% corresponds to an attenuation of 12 decibels. The density of tree foliage is a good protective barrier against the ambient noises of the city and road traffic.

Aesthetic Functions

Trees: Architectural Elements (Enhancing the Landscape)

The urban environment is often a cold and lifeless landscape. The addition of vegetation such as trees breaks up this monotony and the linear aspect of structures. These trees allow for hiding unsightly places through their majestic structure of branches and leaves. When these natural elements are landscaped appropriately, these trees harmonize with the architectural elements created by man.

Trees as Privacy Screens

Trees are often used to define large outdoor spaces. In residential sectors, they are used to maintain privacy and the private aspect of homes. Plants such as various types of hedges offer this advantage. Trees also allow for the delimitation of residential zones from industrial zones and traffic zones, creating a natural screen against noise, thus providing insulation for areas that are a bit less attractive to us. Certain types of plants with thorns are planted in specific locations in parks to create a natural barrier blocking pedestrian access. By controlling pedestrian traffic, we preserve the diversity and conservation of our natural parks.

Social Functions

Trees and Their Psychological Effects on Humans

Trees in our cities constantly remind us that there is life all around us and that this life is affected by the immutable rhythm of the seasons. The sweet scent of lilac, cherry, and apple flowers at the awakening of spring; mature trees providing shade during summer heatwaves; the changing colors of leaves and their fall in autumn; as well as frozen vegetation during winter ice storms, all offer magnificent landscapes and are examples of phenomena that have an unconscious impact on us and our well-being.

Trees and Quality of Life

It has been proven by several scientific studies that trees are a source of well-being and mental health for city dwellers in a city with large green spaces and a significant amount of vegetation on its territory. The mere presence of trees near residences improves the quality of life of individuals. With their majestic appearance, trees evoke admiration and wonder. Trees and shrubs offer a more natural look to our urban cities and allow for the preservation of these natural elements necessary for our psychological balance. Vegetation in cities increases the desire to walk and enjoy these beautiful streets full of color and life.

Trees and Ornamentation

Trees in cities improve the overall aesthetics of a city, bringing a variability of colors, textures, and forms. Vegetation enormously beautifies our urban landscapes and is highly valued by citizens. Ornamental trees such as Canadian serviceberry (Amelanchier canadensis), Japanese tree lilac (Syringa reticulata), sweet cherry (Prunus avium), as well as decorative crabapples (Malus cv) are good examples of trees with spectacular flowering, bright colors, textures, and superb foliage that greatly improve the aesthetic of the landscape in our cities.

Trees and Recreation

Wildlife reserves, national parks, urban parks, and outdoor centers are all places where vegetation dominates, and many are protected zones. These are privileged locations for city dwellers, offering recreation and gathering places for the population. Citizens can practice sports there such as hiking and mountain biking. These green spaces also offer the possibility of observing the nature that fascinates us so much.

Trees and Environmental Education

Several municipal parks in large cities offer observation points for flora and fauna. These sites help raise public awareness about the importance of conserving these natural environments. Interpretation networks are also available in some cities, allowing citizens, tourists, and students to be in contact with all the riches of the natural world, as they are accessible to everyone.

Trees and Medicine

It is not only in recent decades that we have used extracts from different plant species to craft powerful remedies. Indigenous peoples, among others, already knew at the time the extent of the benefits that plants could bring them. They used them to make soothing rubs from various herbs, treatments for certain diseases, and for prevention. More than 500 different plants were used to heal, prevent, and treat various diseases, and these remedies were administered in multiple ways. Many were drunk as herbal tea, some had to be chewed, and others inhaled. Even today, these peoples have recourse to this medicine. In our society, plant organisms are used to create a good number of medications. Willow bark, for example, is used to develop aspirin, and Taxus, commonly called Yew, has virtues that can serve in the treatment of certain types of cancer. We must protect our ecosystems so that future generations can also benefit from their medicinal virtues just as we have during our generation.

Economic Functions

Trees and Fruit Production

Trees that produce fruit, such as pear, apple, plum, and cherry trees, have significant economic value for local producers. Several property owners in cities, suburbs, or rural areas have the chance to have these fruit trees on their land and take advantage of their yield for their own consumption.

Trees: Economic Engine

Trees have great economic value in urban environments. These types of plants generate thousands of jobs in the fields of arboriculture and horticulture. In most municipalities, particular importance is given to these fields with the goal of preserving, conserving, and enhancing these resources.

Trees: Tourist Attraction

Inhabitants of large cities are well aware of the parks, woodlands, and neighborhoods filled with magnificent trees. The enthusiasm for such sites sparks the interest of a large number of individuals. Woodlands and urban parks with high woody potential also attract tourists. This is a significant economic asset for a municipality.

Trees: Energy Savers

Trees located on the north side of a residence help reduce heating costs in winter because they act as a protective barrier against cold winter winds. During periods of extreme heat in the summer season, trees close to the house lower the temperature, which allows for reduced use of air conditioning.

Trees and Woody Material

Trees are used in several fields as an important and indispensable resource. In forest environments, this resource is used to create construction materials, lumber, firewood, or paper pulp, and all are essential to our country's economy. Every consumer uses products daily that come from the transformation of woody material. The management of this resource is therefore paramount if we want to continue exploiting it in the long term.

Trees and Sugar Production

The sugar maple is an emblematic tree of Quebec. Throughout the St. Lawrence Valley, it is possible to see clusters of sugar maples and recognize them easily by their large development as well as their flamboyant color during autumn. In the spring, the sap of these trees provides sugar and syrup with a sweet, rich, and distinctive taste. Products derived from this sap are highly sought after and have significant economic value for the local producers who process them.

Trees: Accident Inhibitor

Plants located in specific areas help reduce the number of road accidents. Trees lining highways, for example, help decrease wind gusts, prevent glare when the sun is near the horizon, and reduce blowing snow during the winter.

Trees and the Financial Value of a Property

The presence of trees on a property's land can increase the house's value by 10% to 23%, and in some cases, this increase can go as high as 30%! The presence of trees and greenery tends to increase the value of neighboring residences. Properties located on the periphery of parks, golf courses, and green spaces sell for more on the real estate market because buyers are often willing to invest more for a residence near these soothing and peaceful spaces.

"Wherever the tree has disappeared, man has been punished for his short-sightedness."

These words by Chateaubriand summarize the vital contribution of trees to our lives.

"We see into what regrettable extremes this attitude, this exploitation mentality has led us. The tree is not only an economic contribution; it is also a precious contribution to our well-being."

Sources

Deloeuvre, Guy. The Tree of Life. E-book. Published in 2018.

Reece, J.B., Urry, L.A., Cain, M.L., Wasserman, S.A., Minorsky, P.V., Jackson, R.B. Campbell Biology, 4th edition. ERPI, Éditions du Renouveau Pédagogique Inc. 2012. (Subsequent editions accepted, previous editions subject to tutor approval).

Zimmer, C. (2011) Introduction to Evolution: This Wonderful Tinkering. De Boeck, Brussels.

Raven, P.H., R.F. Evert, and S.E. Eichhorn 2014. Plant Biology. 3rd edition. Translation of the 8th American edition. de boeck.