mumbai

Updated: Nov 24, 2017 16:58 IST

A city-based environment group, Centre For Environmental Research and Education (CERE), has calculated that it has cleared 3,420 tonnes of carbon dioxide (CO2) in the past two-and-a-half years by planting 16,213 trees at 24 locations in the city. The gas, which is responsible for trapping heat and raising global temperatures, is stored in biomass as carbon.

CERE identified 10 fast-growing native species that are efficient at capturing CO2 (see box). “The uniqueness of our project is that we focus only on urban areas because it is high time we start greening our concrete jungles,” said Dr Rashneh N Pardiwala, founder and director, CERE, and an ecologist from University of Edinburgh. “We plant native species because we want to regenerate local flora and fauna as well.”

Among the 56 native species that have been planted are Peepal (sacred fig), Arjun, Bakul, Palash, Teak and Rudraksh. CERE calculates the amount of carbon captured at each plantation site and takes into consideration species type, age of tree and projected growth rates to assess carbon sequestration in the trees. Plants use photosynthesis to convert carbon dioxide (CO2) into sugar, cellulose and other carbon-containing carbohydrates that they use for food and growth.

Plantation site near Malabar Hill. ( Kunal Patil/HT )

Pardiwala said that the carbon sequestration potential of each tree is measured using a model that calculates the above-ground and below-ground bio-mass of the tree. “We measure the height and diameter of the tree and then multiply its volume by its species specific density. This helps us calculate the mass and the dry weight of the tree in carbon units. This can then be converted into carbon dioxide (using its molecular weight), telling us just how much CO2 a tree of a specific species and age can sequester,” said Pardiwala, adding that while international papers take an average value, we know the exact amount being sequestered to the second decimal point considering growth rate, wood density and other specific details.

HT had reported earlier this month that India is the third-highest CO2 emitter in the world after China and USA, according to the International Energy Agency, a Paris-based energy policy advisor. The study found that CO2 levels from fuel combustion increased in India from 181 million tonnes (MT) in 1971 to 2,066 MT in 2015, a 1,041% increase.

Some of the areas where maximum plantations were carried out include – 5,858 trees across villages near Bhiwandi, 3,747 trees at Ambawadi in Malabar Hill, 1,000 trees each at the Mulund forest headquarters and both at the Borivli and Thane ends of the Sanjay Gandhi National Park.

“We plant large well rooted trees that are three to four years old and at least five feet tall. We do this to ensure high survival rate in the hostile environment in a city like Mumbai where pollution levels are high and there is poor soil quality and limited watering facilities,” said Pardiwala. “Once these trees are planted, we geotag them to know that exact latitude and longitude of saplings planted. It is updated on a real-time database on our website so that there is complete transparency.”

She added that even though CERE is aware about species that capture maximum CO2, they focus on having mixed plantations. “We are looking create natural eco-systems and biodiversity islands. The plantation is chosen keeping in mind nurturing the biodiversity of birds, butterflies and reptiles at every location,” she said.