Time to strategically plant trees
With one natural disaster after another in the month of December for two consecutive years, the city is still reeling with the after effects of cyclone Vardah.
With one natural disaster after another in the month of December for two consecutive years, the city is still reeling with the after effects of cyclone Vardah. Many parts don’t have power or communication restored as yet and the one thing all of us have seen is the scale of damage seemingly exacerbated by the trees. Across the city trees toppled or broke off big branches, injuring people and animals, crashing into homes and cars, blocking roads and ripping down power lines. It is estimated that over 10,000 trees (and counting) have been uprooted by the storm in the city, but it doesn’t really take winds of over a 100KMPH to get a tree to fall.
That then prompts the question - Why do some trees fall during storms and others don’t? How do we ensure we have trees in our city but still have a plan for times like this?
The first thing to know is that all trees have the potential to fall at some level of force from nature – be it wind, snow, ice, either singly or in combination due to a phenomenon known as “windthrow” which uproots a tree. This can be described as the lever action of force from wind applied to the roots and trunk. This force increases with height making taller trees more susceptible to windthrow.
Tree roots usually extend 1-2.5 times the radius of the branches and many urban areas do not allow this extensive development. With so many buildings being developed in urban areas in the city, any type of infrastructure works including compacting soil, changing gradation and digging for any service lines can kill roots and cause decay to set in. Trees planted in a single file – without a buffer or grove as a backup are also vulnerable to wind forces - this is typically the case in trees planted in line along boundary walls or along road avenues.
Now, that the city has lost an extensive number of trees, it is time to re-plant in a smart and strategic manner. Many cities around the world invest in an Urban Tree Management Plan – which forms the key basis for greener future-ready cities. The purview of the plan covers tree selection, planting, care and protection and the overall management of trees as a collective resource. Most urban areas already have some mature trees present, the plan should include Tree preservation and planning for additional trees as well.
While adding trees to an urban area, it is paramount to select species based on the features and requirements based on various conditions – including but not limited to the potable water consumption, height, size of crown and canopy etc. Another important aspect is to identify hazard trees through assessment and have some form of mitigation in place for these. Poor structure in the crown will result in limb breakage, splitting and tearing as well and existing trees identified with such conditions should be planned around. Urban forestry is a field of its own with arborists and tree biologists that can contribute to the correct selection and management of trees in urban areas.
Lastly, governance and management aspects of urban trees need to be managed. With regular pest control and hazard assessments it is possible to identify and plan ahead for times such as these. Stay safe, and lets get our city green again in 2017 – with a comprehensive urban tree plan for Namma Chennai!