Bengaluru's Riot of colours: A call for sustainable urban forestry

The transition from verdant lanes to brown, litter-strewn streets poses a significant and laborious challenge for residents and municipal authorities alike. The carpets of fallen leaves and flowers not only mar the aesthetic appeal of the city but also necessitate labour-intensive efforts to clear them away. Unfortunately, the prevailing practice of burning this organic debris not only exacerbates air pollution but also harms the very trees that contribute to Bengaluru's greenery.

The Bruhat Bengaluru Mahanagara Palike (BBMP) has regulations that discourage litter burning, despite which, the easy management of leaf litter through burning persists. The leftover leaf litter clogs stormwater drains following the summer rains, exacerbating flooding issues. Moreover, in addition to leaves, residents must contend with the chore of sweeping up fallen flowers and seeds from trees such as Tabebuia, Pongamia, Mayflower, and Copper pod.

Traditionally, our ancestors understood the importance of aligning household activities and cultural celebrations with the phases of trees.

Festivals such as Makar Sankranti, Pongal, and Bihu were observed in harmony with nature's cycles, emphasising the interdependence between humans and the environment, along with inculcating sustainable management efforts into cultural practices.

Given these challenges, it is crucial to reassess our approach to urban forestry and tree management. One potential solution lies in the promotion of evergreen tree species as part of avenue tree plantations. Unlike their deciduous counterparts, evergreens offer the dual benefits of year-round greenery and minimal litter production. By prioritising the planting of such species, Bengaluru can strive towards becoming a truly "garden and evergreen city," minimising the need for extensive litter management efforts and mitigating the associated environmental impacts.

Deciduous trees, like Tabebuias, shed their leaves and flowers in abundance as part of their natural nutrient cycling processes. This shedding serves multiple purposes, including preventing desiccation during the summer months by reducing transpiration through the leaves. The fallen leaves, flowers, and seeds become valuable food sources for a diverse array of insects, fungi, and bacteria, eventually contributing to the enrichment of the soil as organic matter. However, when this litter is burned, it disrupts this essential nutrient recycling process.

After every shedding cycle, deciduous trees invest resources in producing new foliage and flowers, drawing nutrients from the soil, while simultaneously drawing groundwater. Burning litter deprives the soil of the nutrients needed by these trees, leading to a gradual decline in soil fertility. Furthermore, burning releases stored carbon in the soil and disturbs soil microbial communities further exacerbating environmental degradation. Consequently, the soil in Bengaluru may become nutrient-depleted, and water tables may be diminished due to reduced water retention capacity.

The practice of burning tree litter not only disrupts vital ecological processes but also threatens the long-term health and sustainability of Bengaluru's urban environment and residents. Adopting alternative methods of waste management and promoting the preservation of organic matter can help mitigate these detrimental effects, ensuring the continued vitality of the city's systems.

The deteriorating living conditions experienced during winters in cities like New Delhi serve as a stark warning, emphasising the urgent need for Bengaluru to prioritise sustainable practices and the preservation of green spaces to combat air pollution. Through a commitment to environmental stewardship and the implementation of sustainable forestry practices, Bengaluru can maintain its status as the "garden city" while leading the way towards a more sustainable urban future.

This article is authored by Ganesan Rengaian, plant taxonomist and Namratha Murali, senior communications associate, ATREE, Bengaluru.