A recent report on the impact of planting invasives on lakes in Bengaluru Urban has revealed that 49% of lake areas are covered with trees and shrubs.
According to a report by Paani.Earth on “Assessing the scale and impacts of planting invasives on lakes in Bengaluru Urban and its surrounding districts”, the Forest Department has actively planted exotic and invasive tree species across lake beds since the 1990s. As a result of this, there has been an increase in forest cover.
The report states that, according to data from the European Space Agency (ESA) World Cover 2021, 49% of lake beds are covered with trees and shrubs, with specific areas like Anekal Taluk experiencing even higher coverage at 57%.
“In some instances, entire lakes have transitioned into forest-type woodlands or tree parks,” the report states.
The Paani.Earth team comprising Nirmala Gowda, Madhuri Mandava and Khushbu Birawat said in the report that trees are typically planted around the peripheries of lakes where they serve as riparian buffer zones.
“In these zones, trees play crucial roles in maintaining lake ecosystem health by filtering pollutants, stabilizing shoreline soils, providing habitat for diverse wildlife, regulating water temperature through shading, maintaining stream channel structures by reducing runoff velocity, and absorbing excess water during heavy rainfall to mitigate flood risks,” the report said.
Invasive and exotic species
However, the report said when trees, especially invasive and exotic species, are extensively planted directly on lake beds, they pose significant problems. The team utilised the ESA Copernicus Sentinel 2 imagery to assess the mature tree coverage across the lakes in the Hesaraghatta Lake catchment of the Arkavathi River Basin.
“Using supervised classification techniques, we estimated that approximately 2,917 acres out of the total 11,961 acres of lake area were covered with vegetation, representing 24% of the lake area as of 2023,” it said. It added that their spatial analysis revealed that nearly half (47%) of the lake area in the Hesaraghatta Lake catchment is covered by trees and shrubs.
The ESA dataset revealed that in Bengaluru Rural and Chikkaballapura, around 40% and 35% of lake areas consist of tree and shrub cover, respectively. In Kolar district, 38% of lake areas feature tree and shrub coverage, and in Tumakuru district, tree and shrub cover accounts for 38% of lake areas in the district.
The report concluded that while trees are often beneficial to many environments, their placement in lakes needs careful consideration.
“Trees should be restricted to the catchment areas and peripheries, not the lakebeds themselves. Collaborative efforts among stakeholders, including the Minor Irrigation Department, local panchayats, and citizens, are crucial to rectify the consequences of past inappropriate planting practices by the forest department,” it said.
