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Delhi lost over 300 trees in three weeks. Experts explain what needs to be done

Officials and experts HT spoke to pointed at a range of factors, from the rampaging winds to poor canopy management and weakened roots that brought down so many trees
UPDATED ON JUN 09, 2021 07:48 AM IST
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Amaltas trees in full bloom in Dwarka, New Delhi, on May 26. (Shivam Saxena/HT photo)

The spell of rain and squalls triggered by cyclonic storm Tauktae and multiple episodes of western disturbance over the last month made the Delhi summer less harsh this year. But the good weather extracted its price.

Since May 19, when Delhi witnessed the season’s first big storm, data from the three municipal corporations shows that at least 215 trees fell in the capital. Additionally, according to the New Delhi Municipal Council (NDMC) that looks after the British-era avenue trees, another 95 were uprooted in the last two squalls alone.

Officials and experts HT spoke to pointed at a range of factors, from the rampaging winds to poor canopy management and weakened roots that brought down so many trees.

Ashish Priyadarshi, director, horticulture at North Delhi Municipal Corporation blamed the unusually strong winds. “The fallen trees couldn’t withstand the cyclonic wind, which had higher intensity and was circular in motion. Also, because of higher buildings and existing roadside trees, there was also this tunnelling effect in the streets, which increased the speed of the wind,” he said.

Others were unanimous that a large number of trees in Delhi have been decaying from concretisation, disease and termite attacks, even as they underlined the urgency to save the surviving ones, which remain the city’s best health insurance against atmospheric and noise pollution, water-logging, groundwater depletion, and heat islanding.

Specialised care

To ensure better survival of trees in Delhi, experts emphasised engaging services of specialists in urban tree management.

“The forest department will do forestry, the horticulture will look after parks. For urban trees, we need good managers who are trained arboriculturists,” said CR Babu, professor emeritus at the Centre for Environment Management of Degraded Ecosystems at Delhi University.

Agreed Suhas Borker of Green Circle of Delhi, a voluntary group that has been collaborating with NDMC in restoring uprooted trees. There is so much injury inflicted on trees because agencies in charge lack the knowledge of tree architecture and tree conservation, he added.

S Chellaiah, director (horticulture) at NDMC, underlined the importance of a focussed approach. “All agencies that manage trees are multi-tasking. If we have trained arboriculturists for tree care management, they can take charge of the tree’s health — from pruning canopies to treating disease and decay,” he explained.

Canopy management

A large number of trees that got uprooted this season were lacking in balance. Their stability was compromised by a combination of the heavy canopy and shallow, narrow root base.

“This happens when trees are not pruned regularly. The weight of the canopy increases disproportionately to the size of the root zone, which is anyway shallow due to heavy concretisation around the base. Such trees lack balance and get uprooted easily,” explained Babu.

Pruning is an important part of canopy management and needs to be done scientifically. Maintained regularly, trees can grow in a sustainable manner. “But we often see lopping of large branches, which happens because trees are not pruned for years on end,” said Babu.

Root anchorage

A large number of urban trees are encased in cement or buried under construction waste, which starves them of water, air and essential nutrients. In 2013, the National Green Tribunal (NGT) made it mandatory to leave one-metre space around the trunk of a tree unpaved, but violations are rampant in Delhi.

For structural stability and cushioning, tree roots do not just need to go deep, they also need to spread horizontally. “But when we have an asphalted road with layers of tar running deep into the ground on one side and shops and buildings on the other, and pavements that have been fully concretised, the roots have nowhere to go,” said Babu.

The result is altered root patterns. “The deeper roots don’t get water and dry out. The shallow roots survive but are not strong enough to provide anchorage. Rain and strong winds just uproot them,” explained Chelliah.

Roots are also damaged by frequent digging of pavements by various agencies providing utilities. Also, wheel traffic and overflowing wastewater have a compacting effect on the topsoil that prevents nutrients and water from reaching the roots.

“Recently, we put back six Neem trees that had fallen in Lodhi Garden. They seem to be doing fine. We have also restored a mango tree near Pandara Road but we are not sure of its survival since its roots were not breathing because of concretisation,” said Borker.

Diseased trunks

Termites make root systems and stems hollow, making trees topple easily.

The problem is particularly acute among the older trees in Lutyens’ Delhi, said Chellaiah. The majority of the trees that have fallen in the last few years in the NDMC areas are Neem, susceptible to both termite and Ganoderma fungal intrusions, and the growth of gall or tumour-like growth caused by insects laying eggs are also weakening a lot of trees in Delhi.

“Many silver oak trees in Nehru Park have also been infested with the Ganoderma fungus. If it is in the advanced stages of infestation, it is difficult to save these trees,” said Chelliah.

Therefore, periodical inspection, early detection and timely treatment is the only strategy to control termite and fungal attacks, said experts. To do that, Delhi needs to monitor its trees.

Tracking trees

The Delhi Preservation of Trees Act, notified in 1994, mandated a tree count but the first city-wide census is yet to be conducted. In 2007, the NDMC along with Forest Research Institute-Dehradun did survey the health of trees in the VIP zone. It also got itself a tree ambulance, the only such facility in Delhi. Another census with geo-tagging of trees in the NDMC area has been completed and the data is awaited, said Chellaiah.

Having long waited for the government, residents of Sarvodaya Enclave conducted their own tree census in 2012. They followed it up with another census between 2018 and 2019 and recorded a loss of at least 77 trees. A few other South Delhi neighbourhoods including Gulmohar Park and Vasant Vihar also initiated their own tree health surveys.

Padmavati Dwivedi, an environmental activist who spearheaded the census in Sarvodaya Enclave, said any long term strategy for tree care management has to start with a census and it was time the government conducted one covering the entire city.

“In the absence of a city-wide tree census, there’s only firefighting happening in the name of tree care. Only when we have the data, we know which trees are infested with termites, which ones have gone hollow, which ones have been impaled with nails or wires, which ones have been concretised etc. It is then we can follow up with the agencies and seek remedial action,” said Dwivedi, urging the residents to get proactive and begin their own tree count.

While native trees have far better survival rates, most of the species planted in Delhi’s neighbourhoods are monoculture, some of which are not suited for Delhi’s micro-habitat, she added.

“As the way forward, we need to plant more indigenous species. Also, instead of saplings, we are now planting young trees — six feet in height — because they establish easily, and we don’t need tree guards to save them from trampling,” said Priyadarshi.

The spell of rain and squalls triggered by cyclonic storm Tauktae and multiple episodes of western disturbance over the last month made the Delhi summer less harsh this year. But the good weather extracted its price.

Since May 19, when Delhi witnessed the season’s first big storm, data from the three municipal corporations shows that at least 215 trees fell in the capital. Additionally, according to the New Delhi Municipal Council (NDMC) that looks after the British-era avenue trees, another 95 were uprooted in the last two squalls alone.

Officials and experts HT spoke to pointed at a range of factors, from the rampaging winds to poor canopy management and weakened roots that brought down so many trees.

Ashish Priyadarshi, director, horticulture at North Delhi Municipal Corporation blamed the unusually strong winds. “The fallen trees couldn’t withstand the cyclonic wind, which had higher intensity and was circular in motion. Also, because of higher buildings and existing roadside trees, there was also this tunnelling effect in the streets, which increased the speed of the wind,” he said.

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Others were unanimous that a large number of trees in Delhi have been decaying from concretisation, disease and termite attacks, even as they underlined the urgency to save the surviving ones, which remain the city’s best health insurance against atmospheric and noise pollution, water-logging, groundwater depletion, and heat islanding.

Specialised care

To ensure better survival of trees in Delhi, experts emphasised engaging services of specialists in urban tree management.

“The forest department will do forestry, the horticulture will look after parks. For urban trees, we need good managers who are trained arboriculturists,” said CR Babu, professor emeritus at the Centre for Environment Management of Degraded Ecosystems at Delhi University.

Agreed Suhas Borker of Green Circle of Delhi, a voluntary group that has been collaborating with NDMC in restoring uprooted trees. There is so much injury inflicted on trees because agencies in charge lack the knowledge of tree architecture and tree conservation, he added.

S Chellaiah, director (horticulture) at NDMC, underlined the importance of a focussed approach. “All agencies that manage trees are multi-tasking. If we have trained arboriculturists for tree care management, they can take charge of the tree’s health — from pruning canopies to treating disease and decay,” he explained.

Canopy management

A large number of trees that got uprooted this season were lacking in balance. Their stability was compromised by a combination of the heavy canopy and shallow, narrow root base.

“This happens when trees are not pruned regularly. The weight of the canopy increases disproportionately to the size of the root zone, which is anyway shallow due to heavy concretisation around the base. Such trees lack balance and get uprooted easily,” explained Babu.

Pruning is an important part of canopy management and needs to be done scientifically. Maintained regularly, trees can grow in a sustainable manner. “But we often see lopping of large branches, which happens because trees are not pruned for years on end,” said Babu.

Root anchorage

A large number of urban trees are encased in cement or buried under construction waste, which starves them of water, air and essential nutrients. In 2013, the National Green Tribunal (NGT) made it mandatory to leave one-metre space around the trunk of a tree unpaved, but violations are rampant in Delhi.

For structural stability and cushioning, tree roots do not just need to go deep, they also need to spread horizontally. “But when we have an asphalted road with layers of tar running deep into the ground on one side and shops and buildings on the other, and pavements that have been fully concretised, the roots have nowhere to go,” said Babu.

The result is altered root patterns. “The deeper roots don’t get water and dry out. The shallow roots survive but are not strong enough to provide anchorage. Rain and strong winds just uproot them,” explained Chelliah.

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Roots are also damaged by frequent digging of pavements by various agencies providing utilities. Also, wheel traffic and overflowing wastewater have a compacting effect on the topsoil that prevents nutrients and water from reaching the roots.

“Recently, we put back six Neem trees that had fallen in Lodhi Garden. They seem to be doing fine. We have also restored a mango tree near Pandara Road but we are not sure of its survival since its roots were not breathing because of concretisation,” said Borker.

Diseased trunks

Termites make root systems and stems hollow, making trees topple easily.

The problem is particularly acute among the older trees in Lutyens’ Delhi, said Chellaiah. The majority of the trees that have fallen in the last few years in the NDMC areas are Neem, susceptible to both termite and Ganoderma fungal intrusions, and the growth of gall or tumour-like growth caused by insects laying eggs are also weakening a lot of trees in Delhi.

“Many silver oak trees in Nehru Park have also been infested with the Ganoderma fungus. If it is in the advanced stages of infestation, it is difficult to save these trees,” said Chelliah.

Therefore, periodical inspection, early detection and timely treatment is the only strategy to control termite and fungal attacks, said experts. To do that, Delhi needs to monitor its trees.

Tracking trees

The Delhi Preservation of Trees Act, notified in 1994, mandated a tree count but the first city-wide census is yet to be conducted. In 2007, the NDMC along with Forest Research Institute-Dehradun did survey the health of trees in the VIP zone. It also got itself a tree ambulance, the only such facility in Delhi. Another census with geo-tagging of trees in the NDMC area has been completed and the data is awaited, said Chellaiah.

Having long waited for the government, residents of Sarvodaya Enclave conducted their own tree census in 2012. They followed it up with another census between 2018 and 2019 and recorded a loss of at least 77 trees. A few other South Delhi neighbourhoods including Gulmohar Park and Vasant Vihar also initiated their own tree health surveys.

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Padmavati Dwivedi, an environmental activist who spearheaded the census in Sarvodaya Enclave, said any long term strategy for tree care management has to start with a census and it was time the government conducted one covering the entire city.

“In the absence of a city-wide tree census, there’s only firefighting happening in the name of tree care. Only when we have the data, we know which trees are infested with termites, which ones have gone hollow, which ones have been impaled with nails or wires, which ones have been concretised etc. It is then we can follow up with the agencies and seek remedial action,” said Dwivedi, urging the residents to get proactive and begin their own tree count.

While native trees have far better survival rates, most of the species planted in Delhi’s neighbourhoods are monoculture, some of which are not suited for Delhi’s micro-habitat, she added.

“As the way forward, we need to plant more indigenous species. Also, instead of saplings, we are now planting young trees — six feet in height — because they establish easily, and we don’t need tree guards to save them from trampling,” said Priyadarshi.

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