Why Mumbai’s monsoon takes a toll on its trees
The heavy rains over the last three days has felled nearly 50 trees in Mumbai. One person was killed in Malad when a tree fell on his car. An ongoing study by environment watch group Vanashakti looks at the problem and possible solutions.mumbai Updated: Aug 01, 2016 16:52 IST
The heavy rains over the last three days has felled nearly 50 trees in Mumbai. One person was killed in Malad when a tree fell on his car.
The Brihanmumbai Municipal Corporation’s disaster control department recorded 276 complaints of tree fall and 107 instances of breaking tree branches in June.
An ongoing study by environment watch group Vanashakti looks at the problem and possible solutions. HT spoke to environmentalists, botanists and tree department members to understand the issue -
Why trees fall
Concretisation of tree base
When roads are covered with concrete, paver blocks or tar, no space is left around tree trunks. Cement and tar around the base does not allow the tree to get adequate anchorage on the ground and ultimately a tree falls down.
“If you take a vertical profile of the soil around the base of the tree, you will find layers of concrete, brick, cement, tar and gravel. There is hardly one feet of soil on either side of the trunk,” said Kavita Mallya, project officer, Vanashakti
Removal of soil when trenches are dug to plant trees
During excavation of trenches to lay utilities like cables, soil excavated from the base of trees is not replaced.
“It has been observed that contractors fill up the tree basin with gravel, stones in place of mud during excavation that does not allow water to get absorbed by roots,” said Stalin Dayanand, director, Vanashakti.
Planting non-native trees
Experts said there are a host of non-native trees that had been outsourced from nurseries from abroad or parts of the country where conditions are not similar to that of Mumbai. Examples such as the gulmohar, rain tree, spathodea, trumpet tree are some that are not suited to the city’s topography.
“Non-native trees are unable to sustain the city’s weather conditions. Owing to excess of water in the roots during monsoons, they are unable to distribute nutrients uniformly across the bark and leaves,” said Rene Vyas, naturalist who has conducted 74 tree walks in Mumbai.
Incorrect method of pruning trees
Contractors hired by the civic body’s garden department use unscientific techniques to prune tree branches, making the tree unstable.
“Improper trimming forces trees to become slanted. This alters their original form and balance, which leads to tree fall during bad weather conditions,” said Marselin Almeida, botanist.
Trees are used to support ads, banners
Nails hammered into barks to hold advertisement banners and cables can weaken the tree. An order by the National Green Tribunal (NGT) in April 2013 said that trees should not be used to support advertisements or banners.
“In spite of several judgments, BMC is not checking banners and advertisements being nailed to trees. This has been observed at Mumbai, Thane and Navi Mumbai,” said Ajay Marathe, Navi Mumbai based environmentalist.
• Removal of concrete around the tree base has to be done manually so that machines do not damage the trunk
• All junction boxes and joints for utilities must be installed at some distance from trees so that frequent excavation does not affect the roots
• A 2mX2m basin with soil needs to be created around the tree base to allow proper anchorage, percolation of water and nutrients
• Tree basin needs to have adequate soil so that roots can spread deep into the ground
• Porous concrete should be used during excavation on city roads to allow percolation of water
• Scientific methods should be used for tree trimming, experts should be roped in
• Native trees such as arjun, peepal, karanj, peltoforum, amaltas, mango, jamun should be planted as they can cope with excess water
“The garden department does not identify dead and dangerous trees before the arrival of monsoon season, which is the root cause of all problems faced in Mumbai with regard to fatal accidents during tree falls. This is a clear violation of rules as per the Tree Preservation Act,” said Abhijeet Chavan, municipal tree authority member.
Environmentalists ask where the tree cess is being used?
“Mumbaikars pay taxes for the upkeep of public trees and have a right to expect quality care of our valuable heritage trees,” said Sumaira Abdulali, convener, Awaaz Foundation, adding that 0.05% Tree Cess is added to taxes that runs into hundreds of crores of rupees over the last 10 years to the Tree Authority’s credit. “While funds for proper upkeep of trees are abundantly available, this funding does not appear to be used for maximum benefit towards safeguarding trees.”
What the garden department has to say?
“Owing to unpredictable and excessive rain in the city, there has been an increase in tree fall incidents. At the same time, telecom companies have dug up various areas across the city where cables have been laid that have resulted in trees being uprooted,” said an official from BMC’s garden department.
NGT order to protect trees
In January 2015, the NGT directed the civic body to remove concrete within a radius of one metre around tree trunks and ensure that no construction or repair work is done in that space after Mumbai-based NGO Vanashakti filed an application for removal of all concrete bases in the critical root zone of the trees in Mumbai.
The garden department had told HT that till December last year the base of 11,000 trees were freed from concrete. However, officials said that they had no such data for this year.