Large trees are essential for healthy cities

Large trees are essential for healthy cities

Trees are important elements of our urban landscape. Given that more than 50% of the world’s population lives in cities, it is difficult to imagine urban areas without the numerous services and advantages that trees offer to locals and ecosystems.

This was demonstrated when COVID-19 regulations were the most stringent: urban park utilization skyrocketed. This is no coincidence. One of the main reasons city dwellers felt the need to spend time in green spaces was that the presence of trees promotes both physical and mental health.

In addition to providing numerous environmental and climate regulation advantages, the trees we see every day on public or private property, in cities, or in parks also reduce city noise, sequester carbon, and slow soil water infiltration rates.

Although the total number of trees in a city affects the quantity and quality of ecosystem services, not all trees are equally capable of providing these services or have the same characteristics. It is crucial to consider which trees are best at providing these advantages, why, and what behaviors would encourage them.

We are a component of the Laval University Research Chair on Urban Trees and their Environment, which seeks to identify approaches to aid the long-term survival of trees in urban settings.

Which trees provide the most benefits?

Large trees typically have better ability to capture and store carbon from the air, lessen atmospheric pollution, and stop stormwater runoff.

Larger trees can store more carbon than smaller trees because they have higher woody biomass (amount of wood) in their trunks. In a similar way, larger canopy size—the tops of dominant trees—and total leaf area—the total area of all leaves—both of which are related to larger overall tree size—increase plants’ capacity to capture precipitation and air pollutants. Because of this, larger trees often provide necessary regulating functions for urban areas more effectively than smaller ones, especially in a changing climate.

Planting huge tree species also offers considerable economic benefits. One study reports that the annual net benefit of planting large tree species is 44 per cent higher than that of a medium tree species and 92 per cent higher than that of a small tree species.

The same study found it takes less than five years for the net benefits of these trees to outweigh the net costs. This can be explained in part by the fact that large trees increase real estate prices and land values, in addition to reducing energy costs for heating and cooling by regulating the microclimate.

However, it is not always possible to plant big trees in urban areas due to the limited overhead or underground space. In these conditions, smaller trees can also make a significant contribution.

Large trees are essential for providing ecosystem services. But the ability to deliver these services is conditional on one thing: the trees must be in good condition. Those in poor condition have less capacity to deliver ecosystem services, since poor conditions impede growth, slow carbon sequestration and can also lead to canopy die-back.

In urban settings, hostile environments can impede the growth and proper development of trees. The survival of newly planted trees is threatened by factors such as inadequate root space, soil compaction, insufficient soil moisture, use of de-icing salts, and air pollution. In view of this, several management practices have been developed to encourage the growth and development of trees. Here are some examples:

1. Plant the right tree in the right place. For example, some tree species are better adapted to certain climates or more tolerant than others to limited amounts of space. There are guides available for planting choices that are based on environmental characteristics, including soil conditions.

2. Large trees should not be frequently pruned as this greatly reduces the leaf area and woody biomass of individual trees. Selecting a tree species that is suited for a particular location is one of the keys to reducing the need for pruning.

3. In order to introduce policies that support their conservation, it is necessary to formally acknowledge the value of the ecosystem services that large trees provide.

The importance of concrete actions

In spite of the fact that expansive trees are for the most part more compelling than little ones in giving certain biological system administrations, within the setting of a changing climate, and where timberland flexibility is foremost, it is imperative not to put all our eggs in one wicker container and solely plant huge tree species.

In reality, at the woodland scale, a few characteristics are emphatically connected with the generation of biological system administrations, counting vertical heterogeneity (the sum of vegetation strata, extending from blossoming plants to overwhelming trees) and bush differing qualities, which is the number of distinctive species show.

At long last, the key things to keep in mind are that expansive trees are amazingly imperative, which we advantage from endeavors to protect them. Additionally, planting huge tree species ought to be energized, since there’s a inclination to plant little species in cities. Concrete activities can be taken right away to induce the foremost out of urban trees presently and over the long term.

It is up to us to create them happen

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