Why are so many trees falling in Mumbai?

On June 30, as heavy rains battered Mumbai, a 60-year-old peepul tree came crashing down on a school bus that had briefly stopped on Lane 11 near Chembur’s Diamond Garden.

As it collapsed on the bus roof, its trunk fell directly on Vihaan Srivastava, a Class 6 student of Universal School, who lived in the same lane and was about to alight at the next stop. Of the 13 students in the bus, four other students sustained injuries. But 11-year-old Vihaan died.

Six days later, 18-year-old Hasan Alam Syed died after a tree branch snapped and fell on his head in Aarey colony while he was on his motorcycle.

The next day, 63-year-old Yusuf Kundawala died after a large branch of Saptaparni tree collapsed over him in Kurla’s Naupada area. He was about to join the inauguration ceremony of his family’s new shop.

The three deaths occurred in a week when Mumbai received more than 300 mm of rain – almost an entire month’s rainfall.

The heavy rain came with an unprecedented number of tree falls.

On July 5, according to Brihanmumbai Municipal Corporation, the city saw 523 cases of tree or branch falls – 50% higher than the figure it usually records for an entire year.

The next day, 428 trees fell, taking the total number of tree fall episodes since June 30 to 1,516.

Experts say three factors have led to such a high number of tree collapses – intense rain, high wind speed, and unscientific tree handling.

Mahesh Palawat, vice president of Meteorology and Climate Change at Skymet Weather, attributed the four spells of triple-digit rainfall in Mumbai in the first week of July to changed monsoon dynamics linked to climate change.

“Weather systems forming in the Bay of Bengal have been travelling in the west direction, instead of northwest,” he said. “Additionally, there has been a rise in the moisture loading from the Arabian Sea due to the record-setting ocean warming.”

He explained: “This leads to continuous regeneration of clouds over the region in the presence of a weather system.”

In addition to the heavy rain, municipal commissioner Ashwini Bhide blamed high-wind speeds, ranging between 50 kmph to 70 kmph, for the exceptionally high number of tree falls.

But according to arborist Vaibhav Raje, while extreme weather events can contribute significantly to tree falls, it is usually concretisation around trees that accelerates root decay that eventually leads to collapses.

Arun Sawant, president of National Society of the Friends of the Trees, an organisation that works to preserve trees in cities, said Mumbai is undergoing rapid urban development. “The more concrete, the more tree falls we will see,” Sawant said. “Add to that unscientific pruning.”

A tree audit in Chembur

The Mumbai municipal corporation responded to the death of 11-year-old Vihaan by going into an overdrive. The civic body pruned, trimmed and chopped off tree branches along the entire leafy lane, even though many trees, including the peepul tree that had collapsed, had been trimmed just before monsoons.

The lane has over 27 trees, hugging the road and the footpath. Scroll, along with a horticulturist with National Society of the Friends of Trees, inspected 10 trees around the accident site.

Only two trees had a buffer zone of one metre by one metre at their base, as mandated by the National Green Tribunal in 2015 in response to a public interest litigation by Mumbai-based NGO Vanashakti seeking the removal of concrete around trees. Called a tree basin, the buffer creates breathing space for the roots and allows water to percolate into the soil.

Of the remaining eight trees that failed to follow the one metre rule, three had concrete choking their base while five had a basin of less than a metre. This was also the case with the peepul tree that had collapsed.

After its collapse, the municipal corporation suspended its assistant garden superintendent as well as a sub-engineer from the road department, indicating that it realised that negligence in road construction work had possibly led to the tree fall. In fact, the municipal corporation’s garden department had written two letters to the contractor responsible for the road construction work, flagging the damage that the digging had done to the tree’s roots.

“Footpath concretisation also happened around four months ago,” said Vikas Patharkar, a resident of Lane 11. He added that several residents had complained to the municipal cororation that the peepul tree appeared to be in a dangerous condition.

However, the municipal corporation maintained that it received no formal complaints and a visual assessment in May marked the tree as healthy and safe.

Scroll found a similar pattern in Bandra where we inspected 17 trees with an arborist and found that 11 did not have a one-metre tree basin. Ten trees had a localised decay. One tree was severely decayed and faced a high risk of collapse.

Jeetendra Pardeshi, garden superintendent, did not respond to Scroll’s queries about violation of National Green Tribunal’s directions.

How concrete kills the tree

For over a decade, citizen groups and ecologists in Mumbai have been expressing concerns about the concretisation of tree bases.

“When we lay cement or concrete at the tree’s base, we suffocate the roots from getting air or from spreading wide to get nutrients,” said Jagdish Mhatre, member of the National Society of the Friends of the Trees.

In 2014, Mumbai-based NGO, Vanashakti surveyed 1,965 trees and found that “water and nutrient stress resulting from concretised tree bases” were among the leading causes of dying tropical rain trees in the city.

For instance, when their team dug the vicinity of the trees, they found up to 5 feet of concrete, tar and other construction material that constituted the trees’ base. There was no soil, which should ideally be present for three feet.

“In natural conditions, trees anchor and grow in the soil,” the report stated, explaining that the top soil and subsequent layers provide food and water. But, “urban trees lack this basic necessity, which consequently weakens the trees,” the report said.

Raje, from arboricultural consultancy firm TreeCoTech, also voiced these concerns. “In a forest, trees form a community,” he said. “The roots create a network that supports each other. In urban areas, even if they are near each other, trees are alone due to concretisation.”

Moreover, Mumbai’s water logging also weakens the trees. With concretisation, there is no porous soil left to allow rainwater to absorb, said Prakriti Srivastava, a former principal chief conservator of forest of Kerala.

“When this water is retained in the live tissues of the tree, it ultimately causes it to rot away,” she explained. “Fungus and termites find a good breeding ground, ultimately hollowing out the tree and weakening it.”

Srivastava added: “Ultimately, a hollow and weak tree is only the symptom of the problem. The real cause is the water logging due to poorly planned urban infrastructure and the subsequent decay that is happening because of that.”

This held true in case of another tree collapse in Chembur’s Postal Colony. A Bridelia Retusa tree uprooted and collapsed on the night of July 4 after being submerged in knee deep water for four days. A car escaped the crash seconds before the fall. The tree’s base was also covered by concrete.

Unscientific pruning can disbalance trees

Experts also blamed unscientific pruning for the weakening of trees.

“Trees take a crown shape when they grow, they know that they have to balance themselves to withstand wind and water, they have a mechanism to grow in such self-sustaining structures,” said Govind Singh, Director of Delhi-based NGO, Delhi Greens. “These aspects have to be kept in mind when pruning is done to ensure that the existing structure that you leave behind is also self-balancing.”

This, however, is often not taken into account, said Srivastava, Kerala’s former chief conservator.

Often, authorities trim the side of the tree towards the road, to keep the road free of obstacles, she said, while the rest is allowed to grow. “This tilts the tree towards one side”, making it susceptible to fall.

Raje said contractors commonly prune lower branches which “shifts the center of gravity to upper branches and disrupts the tree’s balance”.

In Mumbai, at least four experts told Scroll that pruning exercise is undertaken “unscientifically” by the municipal corporation. The civic body has no permanent arborist to assess trees. It relies on horticulturists for that.

“A horticulturist is an expert in plants and its propagation,” an arborist said on the condition of anonymity. “They cannot really assess if a tree has issues.”

Dr Nilesh Baxi, a former tree committee member of municipal corporation, said he has “not seen a single arborist inspect trees before they are pruned” in Mumbai.

Even in cases where horticulturists assess trees, they do not accompany the contractor during pruning exercise. Nor do other officials from the municipal corporation’s garden department.

Scroll accessed copy of work orders issued by municipal corporation’s garden department to contractors for pruning trees. These orders specify the tree, the number of branches to be cut and the length and width to be cut, but do not specify which branch to cut. “Contractors are not experts,” Baxi said. “They just prune any branch.”

Baxi said that a branch which is more than four inches at the point where it joins the main trunk must not be cut unless specifically required. “Often we see these big branches being hacked,” he said, attributing this to the fact that several contractors were in the wood supply business. “They chop big woody branches for commercial profits.”

Mhatre, a resident of Chembur, said he had witnessed big tree branches chopped in his locality by “contractors who are in the wood business”.

Previous directions ignored

Despite the January 2015 National Green Tribunal order that recommended removing concrete to leave a one-metre buffer around trees within three months, only 273 tree bases were de-concretised by April that year.

In the meanwhile, more tree fall-related deaths continued. “In 2018, a young lawyer died after a tree fell on him, and in 2022, another such accident happened,” Thane resident Rohit Manohar Joshi told Scroll.

In both cases, he explained, the residents had alerted the municipal corporation that the trees were dangerous and should be removed, but there was no action.

Frustrated at the deaths, Joshi filed a public interest litigation in the Bombay High Court in 2023. He asked for a uniform compensation plan for victims of tree falling and deconcretising trees in Thane district.

While hearing the matter, the court directed the Thane Municipal Corporation to de-concretise 7,400 trees within 45 days. It also suggested the petitioners to make Brihanmumbai Municipal Corporation a party respondent since the 2015 green tribunal order dealt with the same subject in Mumbai city.

“Now, years have passed and this work has still not been done,” said Joshi, adding that the court directed an inspection by Thane and Mumbai civic commissioners.

A joint inspection with commissioners, representatives of the garden department, and citizens was conducted in Mumbai in June this year. They found that 61% of around 1,100 trees “still need to be de-concretised”, said Joshi. “Fifty of these are dead and are dangerous to the public.”