How Chennai is growing its own Forests?

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Context: Chennai made news internationally this year, but it was not a proud moment for its residents. Chennai's water crisis made headlined across various newspapers- which reflected what we already know-  that we are playing fast and loose with our natural resources. But in the past few years- various NGOs with the help of volunteers, and few individuals are regrowing Chennai's Forests to avoid droughts and floods. 

Prelims: General issues on Environmental Ecology, Bio-diversity, and Climate Change.

  • GS II- Development processes and the development industry- the role of NGOs, SHGs, various groups and associations, donors, charities, institutional and other stakeholders.
  • GS III-
    • Conservation, environmental pollution and degradation, environmental impact assessment.
    • Disaster and disaster management.

Over the last few years, Chennai has witnessed several climate extremities:

  1. Floods in 2015,
  2. Cyclone Vardah in 2016 (which brought down over a lakh of trees),
  3. Diminishing rains in 2017 and 2018,
  4. Drought in 2019.

The World Health Organisation recommends a minimum availability of 9 square metres of tree cover per individual.

Chennai has just 0.46 sq m of open space and one tree for every 33 people, according to a report submitted by Care Earth Trust to the Greater Chennai Corporation.


  • This year, however, local conversations on what we can do to offset such disasters have finally moved beyond a few select groups.
  • One of the points of focus is planting saplings- not just to regain what we lost in 2016 but for the role that trees play in our environment.
  • Apart from many individuals who are regrowing their own forests, consisting of various rare as well as native species, there are many NGOs who are regrowing forests in order to ower the impact of floods and drought on the city.
  • Meanwhile, the Corporation of Chennai has announced a ₹228-crore project to up the city’s green cover, from 14.9% to 20.2%, by 2023.
    • Starting in 2018, they’ve planted around a lakh sapling- of 103 different species of native trees that are ideal for Chennai's hot, humid weather, monsoon rains, and water and wind conditions.
    • The target is to plant about a million more (two lakh a year) in the next five years, as avenue trees, traffic islands, and green, open spaces.
  • Healthy forests and wetland systems provide a host of watershed services, including water purification, groundwater and surface flow regulation, erosion control, and streambank stabilization.

Various NGOs working in towards making different areas of Chennai green are: 

  1. Nizhal, Kotturpuram Tree Park: 
    • Plans for 2020: To set up a Tree Resource Centre for Chennai.
    • This NGO is behind the tree parks in Kotturpuram, Madhavaram and Chitlapakkam, and the building of green corridors around water bodies to serve as a bio-shield and to prevent breaching during floods.
    • The idea is to link with citizens to transform open spaces.
    • Working at a grassroots level can be more productive if people let go of the sense of entitlement over such lung spaces, and instead, help create and nurture them.
  2. CRRT, Adyar Creek:
    • Plans for 2020: To create 9 sq m of green cover per person.
    • The Chennai Rivers Restoration Trust has been consistently working to green the 358-acre Adyar Creek.
    • It has developed a green belt along the water bodies, planting indigenous saplings such as neem, Jamun and Pongamia pinnata (pongam), besides creating mangroves.
    • More than 1.7 lakh saplings of 170 native species have been planted between 2010 and 2016.
    • Restoration has also been initiated on the Adyar and Cooum river banks with riverine vegetation.
  3. Thuvakkam, across Chennai:
    • Plans for 2020: To plant 4,000 saplings, in Thuraipakkam or Moulivakkam, on land allotted by CoC.
    • The Miyawaki method is a technique of growing dense plantations in a short period of time.
    • Thuvakkam is working to establish about 112 of these ‘forests’ in government schools in Chennai and the Thiruvallur district. 
  4. Tree Bank, across Chennai:
    • Thi NGO has planted over 1.47 crore saplings across Tamil Nadu.
    • A few years ago, it launched the Brown Tree Project, which encourages people to identify sick trees in the city.
    • As part of the year 2019 drive, 176 trees were identified and tended to across the 15 zones.
    • The numbers of sick trees have come down. In 2016, the city had over 500 such trees.
    • Starting January 2020, Tree Bank will team up with the Chennai Corporation to launch an awareness drive.
      • It will plant a sapling in a place of a felled tree and put up paintings to indicate why the tree died.

These are some good examples of the impacts of community involvement in environmental protection. As we enter another decade, we look at a few individual and community initiatives that, if supported and sustained, will help recharge our green lungs and water tables.

How Trees Reduce Flood & Droughts?

  • Trees help rain seep into the soil because living and decaying roots make the soil porous by creating a network of well-connected, minuscule channels in the soil.
  • Rainwater seeps into the soil with such channels several hundred times faster than it seeps through the soil without channels.
  • Additionally, when plant debris falls on the soil and starts to organically degrade, it helps the soil maintain the integrity and form small aggregated clumps.
    • These clumps also ensure that soil is porous.
  • Thus, land under tree cover is more capable of absorbing rainwater.
  • This reduces the volume of water flowing over the surface after a rain event, and thus reduces the volume of water entering rivers and streams.
  • Computational models show that if reforesting is done in 20-35% of the river’s catchment, a 10-15% reduction is seen in flood peak heights after 25 years of forest growth.
  • When trees are taken off, floods often increase because most of the rainwater enters streams and rivers in a very short timeframe.
  • Such high-intensity flow is often not usable by human beings and usually flows into the ocean, while also causing soil erosion which leads to a loss in soil nutrients.
  • This is why large areas of formerly productive land, where annual rainfall is relatively high, have become desertified once tree cover is removed.
  • A study by IIT Roorkee compared the peak flood levels before and after vegetation has been removed due to urbanization.
    • Conversion of woodland to low-density residential uses gives an 11-30% reduction in groundwater recharge.
    • Conversion of woodland to high-density residential uses gives 52-100% reduction in groundwater recharge.
    • Conversion of woodland to commercial uses gives a 94-100% reduction in groundwater recharge.
  • However, tree-planting reduces these high-intensity events and creates a more sustainable flow that is available even after rain ceases. It also limits soil erosion.
  • The mechanism through which trees prevent floods is the same mechanism through which they mitigate droughts.
    • When trees are planted water is absorbed by the soil, and just as rainwater percolated downward into the soil, water can percolate horizontally in the soil as well.
    • This kind of underground water flow can feed water into streams and rivers wherever the water table intersects the streambed.
    • This underground or base flow is what keeps most of India’s rivers flowing even in the dry season. 

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