AS DELHI braces for the upcoming monsoon, a recent study found that the Aravalli Biodiversity Park helps retain nearly three million litres of rainwater annually, reducing surface runoff that can contribute to waterlogging and urban flooding. According to the study, the 692-acre restored forest is doing more than providing a patch of green amid the urban sprawl. It said urban forests with roughly 2.02 lakh trees help prevent nearly three million litres of surface runoff annually, replenishing groundwater reserves and helping slow the movement of rainwater across the ground, allowing more water to infiltrate the soil instead of rapidly flowing over paved surfaces. The researchers added that the Aravalli Biodiversity Park is located in an important groundwater aquifer recharge zone and plays a key role in replenishing underground water reserves.

 

The study, titled “Structure, ecosystem services and economic evaluation of native tree diversity: a case study of the restored Aravalli Biodiversity Park, Delhi, India”, was conducted by researchers from the Centre for Environmental Management of Degraded Ecosystems (CEMDE), Biodiversity Parks Programme, Department of Finance and Business Economics and Satyawati College, all affiliated with the University of Delhi. “Delhi has a dry-winter humid subtropical climate bordering on a hot semi-arid climate and receives an average annual rainfall of 774.4 mm, most of it during the monsoon months between July and September,” the study said. Besides regulating water, the park also plays a significant role in improving air quality.

 

The study estimated that its trees remove around 126.89 tonnes of air pollutants every year, generating environmental benefits valued at nearly Rs 1.89 crore. Researchers said the trees help remove particulate matter and other harmful pollutants from the atmosphere. The study noted that structurally diverse urban forests are particularly effective in trapping airborne pollutants and improving environmental quality. The biodiversity park was also found to function as a growing carbon sink. Researchers estimated that its trees currently store around 8,360 tonnes of carbon, valued at nearly Rs 11.34 crore, while absorbing another 1,236 tonnes of carbon every year as they continue to grow. The study explained that carbon storage refers to the amount of carbon locked in tree biomass at a given time, while carbon sequestration refers to the annual accumulation of carbon by growing trees.

 

For economic valuation, carbon estimates were converted into carbon dioxide equivalents using a standard molecular conversion factor. Researchers said such ecosystem services are increasingly important in rapidly urbanising cities where shrinking green spaces and expanding built-up areas often worsen flooding and waterlogging during heavy rainfall. Researchers found that bigger trees generally store and absorb more carbon. According to the study, trees with thicker trunks, greater height and wider canopies were more effective at capturing carbon from the atmosphere. Researchers said the significance of these findings becomes clearer when viewed against the park’s past. Located on Delhi’s southern ridge, the area was once a heavily degraded mining site.