M ore than cyclone Vardah, or its velocity, it’s the city’s green cover that’s being discussed lately. As a tree researcher and academician, I’ve been keenly following news reports that have been reporting quite a few general and amateur statements: ‘Exotic trees cause damage’, ‘Trees planted in pavements, choked by concrete uproot easily’, ‘Trees should be planted for more fresh air’, ‘Trees should not be planted as they cause damage to people and property’.
I wish to record some of my experiential observations regarding the city’s green cover – before and after the cyclone. There were many mixed feelings after the cyclone. Some blamed the cyclone, some were angry with authorities, some were furious with the debris, some became emotional with the loss, some questioned God, some turned judgemental.
Vardah broke all ground rules regarding our basic understanding of trees. There was no specific pattern in the types of trees that were lost; both exotic and indigenous species got uprooted. Trees along pavements and those within spacious boundaries were equally damaged. It’s very difficult or rather even impossible to predict the intensity, characteristics, and consequences of natural disasters. Judiciousness and thoughtful planning, however, will always mitigate the impact of such disasters.
Exotic species
Gulmohrs and Copper Pods are consistently the major casualties during squalls, including Vardah. Gulmohr (Delonix regia) was introduced to India more than 150 years ago when British foresters and garden superintendents found the copious, scarlet flowers attractive. It is native to Madagascar and thousands of them were planted in Madras Presidency with seeds outsourced from Calcutta Botanic Gardens. This was at a time when the Madras Agri-Horticultural Society enjoyed a cordial relationship with the curator of Calcutta Botanic Gardens. The Copper Pod (Peltophorum pterocarpum), native to Thailand, Malaysia, Indonesia, Philippines, Papua New Guinea, and Australia is another exotic tree that is widely grown in Chennai. Both these trees have shallow roots and are not wind-resistant. Either their branches snap or the entire tree can get uprooted even at slight provocation. So in the statistics of lost trees during Vardah, about 75 per cent are Gulmohrs and Copper Pods. Both these trees are planted, to eventually fall.
Tamarind, though an exotic being native to Africa, is widely used in Indian cuisine. Many mature trees (about 50 years old or more), with a girth of about 5-7m have been uprooted in many places. Until now, it was considered a hardy tree, resistant to squalls, and a highly recommended species for social forestry and livelihood programmes.
Rain Tree, another common tree in avenues, parks, and large compounds is also an exotic species. It is native to Southern American countries like Venezuela, Colombia, Costa Rica, Nicaragua, and Panama. Though an alien species, its wide-spreading canopy offers excellent shade and great reprieve from sweltering heat.
Since these trees are quite sturdy, entire trees did not fall during the cyclone, but their heavy branches snapped. Their numerous, small leaflets were swept away to distant terraces and clogged storm water pipes and other outlets. Diwi-diwi, often used in the tanning industry for its rich tannins is native to tropical America and is not common in Chennai. Few of these trees were lost due to Vardah, proving that their otherwise knotted and twirled trunks cannot withstand cyclones.
While exotic species are good study materials and curio specimens to understand tree diversity, they need to be planted in small numbers in a few protected areas where they will be monitored constantly. Most Baobabs in the city are intact, though they are from Africa, and most rare exotics in Chennai have survived the cyclone.
Native species
Vardah brought down quite a few native trees in the city, but in very few numbers as compared to Gulmohrs and Copper Pods. Mango, Neem, Java Plum (naval), Anjan (a very rare native tree), Peepul (arasamaram), Crepe Myrtle, Portia tree (poovarasam), Madras Thorn (kodukaapuli), and even the majestic banyan, are a few such affected native species. Though the mother trunk of the Adyar Banyan fell victim to one such cyclone in the 80s, this is the first time many have witnessed a Banyan tree collapse.
Maintenance
Healthy trees are ecological indicators of a sustainable and providential ecosystem. When the right trees are planted at the right places, they offer irreplaceable, irreversible, and invaluable services such as wind breakers, flood channelizers, carbon sinks, buffer zones, disaster barriers, dust, and noise filters.
It is not about numbers but about the species. Chennai needs trees suited to coastal zones, as these trees will face tidal fluxes, salt sprays, fierce winds, inundation, storm surges, high temperatures, and low humidity. Typical coastal trees such as coconut and palmyra palms did not show any distress during the storm. Not every open space should be cluttered with trees under the pretext of greening, because Open Space Reserves (OSRs) are necessary for refuge during certain calamities and as urban breathing-spaces.
Just the way buildings and waterways need maintenance, trees too need post-planting care and maintenance. Branches have to be constantly pruned, and pest control has to be administered if there are any symptoms of infestation. Dead wood can be put to discreet use as tree monuments and in carpentry.
Loss assessment
Assessment has to be done in gated compounds and public spaces for the type and reason of loss. Replanting or transplanting will cost money, involve labour, and require skill.
While chances of survival cannot be ascertained, loss estimates can be calculated based on already existing data, post-loss data, species, and number index. Gulmohrs and Copper Pods are usually not included in the estimation as they prone to damages. Loss can be calculated and interpreted based on the following statistics:
1-20% - normal loss
21-40% - considerable loss
41-60% - quite serious
61-80% - severe loss
81-100% - total loss
The loss of green cover in Chennai can be considered in the 21-40 per cent category, where the chances of restoration and enhancement of green cover are very high. This needs to be done with proper guidance from tree experts. Trees showing signs of distress can be axed so that they do not cause any fatalities in the future.
Before every monsoon, a survey has to be done to identify such trees for further action and follow-up. If trees like the Red Sander or Sandalwood have fallen even in private lands, it has to be reported and surrendered to the forest department, since these species are classified as ‘royal trees’.
Vardah taught us hard lessons that will be etched in our memory for a long time. It is easy to be wise after the event. But why wait for an event to regret folly and then turn rational, when nothing much can be done to undo the past?
The writer is Associate Professor, Department of Plant Biology, Womens’ Christian College
