CHENNAI: To boost urban sustainability, Chief Minister MK Stalin on Monday released the City Biodiversity Index (CBI) for Chennai, making it the first city in the state to adopt this globally recognised framework. The index, also known as the Singapore Index, helps cities assess their biodiversity assets, set conservation priorities, and integrate ecosystem health into urban planning.
Developed in collaboration with ICLEI South Asia, the Greater Chennai Corporation (GCC), and state departments, the index uses 23 indicators to measure native biodiversity, ecosystem services, and governance. For its baseline year of 2024, Chennai scored 38 out of 72 points across 18 indicators. While the score highlights areas for improvement, the city also demonstrated strong ecological resilience.
Chennai earned its highest scores for the proportion of natural areas (20.12% of the city’s landscape comprises wetlands, forests, rivers, beaches, and marshes), connectivity of ecosystems (with wetlands and rivers still linked in a functioning network), and bird diversity in urban areas (90 species recorded in built-up spaces, thanks to the city’s location along the Central Asian Flyway).
Chennai’s unique ecological lungs - Guindy National Park, Pallikaranai Marsh (a Ramsar site), IIT-Madras’s dry evergreen forest patch, and the Theosophical Society campus - continue to act as irreplaceable green refuges amid rapid urbanisation. These areas not only shelter species such as blackbuck, spotted deer, and over 115 bird species, but also provide carbon sequestration, groundwater recharge, and urban cooling benefits that are vital for climate resilience.
The launch aligns with the state’s various green initiatives. Importantly, Stalin announced that five more cities in Tamil Nadu will soon prepare their own biodiversity indices, creating a model for other states to emulate.
Supriya Sahu, additional chief secretary for Environment, Forests and Climate Change Department, told TNIE the index would strengthen governance. “When we make some plan, we don’t look at the biodiversity component. What this will do is help us integrate biodiversity into the planning process. We will train officers on how to use this index in their decision making,” she observed.
Yet, the index also shines a spotlight on gaps that need urgent policy attention. Chennai scored poorly in areas like protected natural areas (just 5.02% of city area), invasive alien species management (72 invasives identified), water regulation (only 62.8% permeable area), and green cover (18.09% tree canopy). The city also lacks a Local Biodiversity Strategy and Action Plan (LBSAP), a key requirement under the Convention on Biological Diversity.
Pallikaranai Marsh remains under pressure from the Perungudi dump yard, with studies showing heavy metal contamination and alarming microplastic densities. Encroachments on lakes and wetlands have worsened flood risks.
Emani Kumar, executive director of ICLEI South Asia, said, “This is a five-year cycle, and many points are dependent on institutionalisation. Already, about 20 cities in India use this index, from Srinagar to Kochi. Chennai now joins an international network of biodiversity cities,” he told TNIE and added this will improve the cities case for securing climate finance from global funds.
Experts say the index provides a roadmap. Strengthening waste management, restoring wetlands, expanding urban forests with native species, and integrating nature-based solutions in city planning can help Chennai improve its scores while safeguarding its ecological heritage.