The proposed felling of 1,128 trees for Bengaluru’s Hebbal Short Tunnel Project is not only a question of losing roadside greenery. A Rapid Environmental Impact Assessment by researchers from Azim Premji University indicates that 950 of these trees currently hold 77.54 metric tonnes of stored carbon, while the wider stretch supports wildlife, moderates heat and helps connect the city’s remaining green spaces.
That makes the project a test of how Bengaluru values mature urban trees when transport infrastructure expands through an already congested corridor. The assessment does not establish that every tree will be felled: most are marked for transplantation. But it raises a more consequential question about whether transplantation and compensatory plantations can replace the ecological functions of mature trees, particularly in a city facing rising temperatures, air pollution and continuing biodiversity loss.
The distinction matters because an urban tree is more than a physical obstruction or a unit that can be counted and replaced elsewhere. Mature trees store carbon over time, provide shade, intercept dust, support insects and birds, and contribute to connected ecological networks. The assessment identifies all of these functions along the Bellary Road-Hebbal stretch, which already experiences heavy traffic and construction.
The carbon estimate is based on the 950 trees for which data were available. Researchers calculate that these trees store nearly 78 metric tonnes of carbon, with the assessment putting the figure at 77.54 metric tonnes. If the trees are removed, that stored carbon would be lost from the urban system. The assessment also warns that the loss could worsen air pollution and rising temperatures, although it does not quantify the resulting increase in pollution or local heat.
This is an important limitation as well as an important finding. The available evidence establishes the ecological value of the trees and the carbon they currently store. It does not provide a full projection of the project’s future emissions, the exact change in local temperatures or the net carbon outcome after transplantation and replacement planting. Those unanswered questions should be part of the project’s environmental accounting rather than treated as secondary concerns.
The species composition described in the assessment shows why a simple tree count is inadequate. The 1,128 trees comprise 92 species, including 17 fig trees. Figs provide food for birds, bats, squirrels and insects, making them part of a wider food web rather than isolated landscaping elements. The stretch also contains 30 rain trees, which researchers identify as important for regulating temperatures, and 173 paper mulberries that help trap dust and reduce air pollution.
The assessment records 199 bird species in the vicinity between 2016 and 2026, drawing on data from eBird and iNaturalist. The list includes the Vulnerable greater spotted eagle and the Near Threatened spot-billed pelican, along with the Indian peafowl and Indian roller. The presence of these species does not by itself prove that the project will eliminate their habitat. It does, however, establish that the corridor has ecological value that extends beyond its immediate roadside appearance.
The researchers describe the trees as part of ecological corridors connecting green spaces and water bodies. In a city where green areas are fragmented, this connecting function can be as significant as the area covered by any one park. A line of mature trees can provide movement, shelter and feeding opportunities for urban wildlife while also creating shade for people using the road and surrounding public spaces.
Seema Mundoli, one of the researchers, said the concern was that “every remaining patch of green space and every avenue tree in the city is being lost, with little or no meaningful replacement”. She also pointed to a mismatch between development expanding towards Bengaluru’s peripheries and the lack of corresponding expansion in green spaces. Her observation frames the Hebbal project within a broader pattern of urban growth: infrastructure is added to address mobility pressures, while the ecological systems that make the city liveable are treated as replaceable.
The project’s proposed transplantation strategy is therefore central to the environmental question. More than 800 trees are proposed for transplantation, according to the assessment. But researchers warn that severe lopping can reduce mature trees to a fraction of their original size and sharply diminish their ecological value. They also question the survival rate of transplanted trees and the effectiveness of compensatory plantations.
Transplantation is often presented as a way to reconcile construction with tree protection. In practice, its success depends on the size and species of the tree, the condition of its root system, the time and method of removal, the receiving site, post-transplant care and long-term monitoring. The supplied assessment does not provide a survival-rate figure for this project or a detailed monitoring framework. That absence makes it difficult to judge whether the proposed mitigation can reproduce the benefits of the existing trees.
The same problem applies to compensatory planting. A replacement plantation may satisfy a numerical requirement while failing to replicate the ecological function of a mature avenue. Newly planted trees need time to develop canopy, store substantial carbon, provide nesting and roosting sites, trap dust and create shade. A plantation located far from the affected corridor may also be unable to maintain the ecological connections identified in the assessment.
The institutional issue is not whether infrastructure should ever be built in a city with limited road capacity. The issue is how project approvals account for the full value of existing natural assets before construction begins, and how authorities measure whether mitigation actually works after the project is completed. The assessment brings that question into focus without providing the project’s complete approval documents, detailed design alternatives, transplantation protocol or post-project monitoring commitments.
That missing information is significant because the environmental trade-off cannot be assessed from the number of trees alone. Readers would need to know how many trees are expected to be transplanted successfully, where they will be moved, how severe lopping will be controlled, who will maintain them and for how long, and how compensatory plantations will be audited. They would also need clarity on whether the project design considered alternatives that could reduce the number of affected trees.
The available data also show why biodiversity should be treated as a planning consideration rather than a separate conservation issue. The trees support birds and other wildlife along a transport corridor, while their dust-trapping and cooling functions directly relate to the human environment. In this setting, ecological protection and urban public health overlap. The same canopy that provides habitat can also reduce exposure to heat and airborne dust for people moving through the area.
Bengaluru’s challenge is intensified by the condition described by the researchers: heavy traffic and construction along the Bellary Road-Hebbal stretch, combined with concerns over rising temperatures, pollution and biodiversity loss. The assessment does not claim that the proposed project alone caused these pressures. It shows instead that the project would operate within an already stressed urban landscape, where the removal of mature trees could reduce one of the few existing buffers against those pressures.
The most useful next step is therefore not a general argument for or against development, but a transparent accounting of what will be lost and what mitigation can realistically deliver. The project authorities would need to publish the final tree list, transplantation plan, expected survival benchmarks, compensatory-plantation locations and monitoring arrangements for the public to evaluate the claims made on either side.
The assessment confirms that the Hebbal trees hold measurable carbon and ecological value, and that the corridor supports a notable range of bird species. It also identifies serious uncertainty around transplantation and replacement planting. Until those uncertainties are resolved with project documents and measurable commitments, the debate over Hebbal’s trees remains a larger question about whether Bengaluru’s infrastructure planning counts mature urban nature as essential city infrastructure or as an asset that can be replaced on paper.
