Tree planting is about good design, not green cover

The city has a diversity of habitats, land use conditions and varying intensities of human use and manipulation. Most critically, Chennai being a coastal city on the shores of the warm Bay of Bengal, is naturally vulnerable, more so as we move towards the Anthropocene era. This vulnerability varies spatially and temporally and the coastal character of the city is both its natural buffer as also the zone of vulnerability. 

Greening a mega city is a complex and daunting task. In addition to human centric parameters such as avenue planting, planting within parks and other public areas, median planting, planning in home gardens etc., there are certain other parameters that are more critical. 

The first of these is the recognition that tree planting and greening are not synonymous in their concept, scope or purpose. That trees alone contribute to greening as a notion, despite being much cherished, needs to be revalidated. It is only when the effort is more holistic or in other words, an apt simulation of natural systems, that greening becomes worthwhile. In simpler words, only when tree planting is buffered by planting of associated palms, shrubs, herbs and grasses (including bamboo) that the city can experience the critical ecological services that nature provides such as moderating local temperature, releasing oxygen, improving groundwater recharge, and providing habitat to birds and other animals. It is also probably the right time to acknowledge that many birds that are typical of urban areas prefer shrubs for nesting. 

For easier understanding, trees may be broadly grouped into two: slow-growing hard wood trees and fast-growing soft-wood trees. Coastal ecosystems, given their harsh conditions and limited availability of freshwater, are typified by slow growing hardwood trees. When this fundamental is compromised upon to fulfil the ‘immediacy’ of planting trees, the results can only be disastrous. 

Some of the trees which had a strong cultural association provide the much needed testimony to this notion. For example, the Indian Laurel or Punnai maram (Calophyllum inophyllum), whose fragrant white flowers are used during Krishnashtami is a native of coastal parts of India and is a hardy tree with a beautiful canopy. Keeping company to the Punnai in festivity is the Jamun (Syzigium cumini), which is yet again a tree recommended for coastal regions. Likewise, the much revered Banyan, Peepal, Neem, Palms (Panai), Poovarasu, Pungam and Arjun are trees that are recommended for Chennai. 

In contrast, the showy and fast growing soft-wood trees like Delonix regia, Silk cotton etc, have buttresses and very superficial and sprawling roots which, when pruned, make the trees very unstable. 

The critical point is that the choice of tree species for Chennai is limited, and hence tree planting needs to be strengthened by a planting design that accommodates shrubs and grasses as well. The metrics for greening Chennai is certainly not in the numbers or records that we aim to break, but is in the grounded approach that we commit ourselves to over the next decade.