In the last few decades, rapid urbanisation and unplanned construction have caused the loss of several trees in the city. Residents of Bengaluru from the 1980s and 1990s would have noticed the changing green cover across the city. A recent study on land cover change in Bengaluru by researchers from Gubbi Labs shows that the vegetation cover in the city has gone down by 43.57% in 17 years, from 2000 to 2017. The debate of development vs conservation still rages on, while the tree numbers have continued to diminish. Consider the role of a tree in an ecosystem – it not only provides food, but also provides oxygen, regulates temperature and controls soil erosion. The absence of trees then has diverse effects, many of which are yet to be understood.
One of the important roles of trees is in maintaining the biodiversity of a city. They harbour several city-dwelling fauna such as birds, butterflies, insects, and small mammals such as the Slender Loris. Loss of trees, leading to a loss of habitat, is one of the main reasons for the decline in urban biodiversity. Usually, communities take measures to conserve a particular species only when they see a decline in numbers. The House Sparrow, for instance, did not disappear suddenly from Bengaluru. People failed to notice the gradual decline; more often than not, it is too late by the time this change is noticed. Continuous monitoring of biodiversity is essential to keep tabs on the status of flora and fauna, and more so in cities with an unsustainable rate of development. Having data gathered in advance could prove to be a powerful conservation tool. Scientists can use this to predict the areas and organisms that need attention. At the same time, it provides an opportunity for scientists and concerned citizens to collaborate and take necessary actions.
Another ill-effect of the missing vegetation is the rapid rise of the temperature of the city. In the early 2000s, one would often wake up to chilly, foggy mornings in winters, while summers were warm enough to have a pleasant time outdoors. Today, this is not always the case. Last year, the city faced its hottest summer in the last 85 years, with a maximum temperature record of 39.2°C in April. In the last 20 years, the average annual maximum and minimum temperatures have increased by about 1°C. Although this does not implicate a decrease in the number of trees directly, it certainly is one of the main reasons. Other factors contributing to the increase in temperature include heat island effect, rapid urbanisation and greenhouse gas emission due to the burning of fossil fuels. However, trees play a significant role in keeping the city cool. Dr.Harini Nagendra, a Professor of Sustainability at Azim Premji University, in her book ‘Nature in the City’, reports that at 3 pm, the temperature of the road surface on Bellary Road went up to 51.5 degrees Celsius as compared to 32.5 degrees Celsius under the shade of trees. This huge temperature difference clearly shows what kind of impact trees have in keeping the streets cool.
An inventory of tree data with information of their location, species name, and other useful attributes could be one of the first steps towards a wider conservation effort. Several cities around the world have already started mapping trees in an effort to monitor them regularly. Different methods are being used, based on feasibility and resources available. In the US, cities like Philadelphia, Tampa and San Diego have begun mapping trees using open-source software applications such as OpenTreeMaps, while aerial imagery has been deployed in England and Wales. In cases where the area being monitored is small, like in the case of Ohio State University, aerial paper maps have been used in the field, followed by updating the digital map.
Some organisations such as Vruksha, Open Street Maps and India Biodiversity Portal have also initiated tree-mapping activities in India. India Biodiversity Portal launched the ‘Neighbourhood Tree Campaign’ in an attempt to document tree species and their distribution. More recently, interested citizens and organisations have come forward to map the trees of Bengaluru. People from all walks of life, including business owners, naturalists, academicians, students and concerned citizens have collaborated with researchers in an effort to document the trees around them. All the information is open-source and made freely available to the public, allowing them to maintain a real-time database.
Gubbi Labs, as part of its larger project of monitoring biodiversity across Karnataka, initiated a field-testing of some of the different tools available to map trees. The different methods used were: a mapping application built on Github, aerial paper maps such as Fieldpapers, and satellite imagery. After looking at the pros and cons of each method, the mapping application seemed to be the most suitable tool for mapping trees in Bengaluru based on ease of use and accuracy. This platform allows users to map trees on their phone or laptop using the link: https://gubbilabs.github.io/tree-map/
Tree attributes such as height, girth measurements and canopy width can be added by the users, while counting trees. The map gets updated in real-time and the changes can be viewed by anyone using the application.
Using this application, volunteers documented and mapped trees in Bengaluru, while also building on the data mapped on Open Street Map. Indiranagar, Cooke Town and Basavangudi were the main areas of interest for the initial phase. However, citizens contributed to the project and initiated tree mapping in several areas across Bengaluru including Electronic City, Domlur, IISc and Lalbagh.
So far, volunteers have mapped nearly 5000 trees in Bengaluru. Citizens across the city have started using the application to help monitor trees in their neighbourhood. This data will not only tell us the number of trees Bengaluru has, but can also be used by researchers and citizens alike to assess different issues such as to compare the tree density in different localities, identify immediate threats, and arrive at solutions. From the preliminary analysis of the data, it has been deduced that within the area where mapping was carried out, Indiranagar had 12.3 trees per hectare whereas Cooke Town had 9.5 trees per hectare.
With the tree data in place, a scientific approach can be used to solve issues concerning biodiversity. For instance, the Slender Loris is found in Bengaluru only in pockets of areas in IISc and Malleshwaram. Using this data, the canopy cover can be connected to extend its habitat to urban parks such as Lalbagh and Cubbon Park. Or, consider the Rs.1800 crore steel flyover project that was proposed in Bengaluru in 2016, which threatened to cut down around 800 trees. The project was eventually called off after protests by over 10,000 citizens. If the data were available, researchers could have objectively shown the negative effects of cutting the trees for the flyover.
A number of such activities can be planned once the data is available to everyone. From the example of the steel flyover, it is apparent that a large number of citizens are concerned about the environment and are enthusiastic to contribute to conservation. Activities like tree mapping provides a platform for such nature enthusiasts to contribute towards improving the city by simply monitoring their woody neighbours. Perhaps activities like these could help conserve the greenery of our city, enough to live up to its name of ‘The Garden City’.
Nagendra, H. (2016). Nature in the City: Bengaluru in the Past, Present, and Future.
H. S. Sudhira, Shashikala V. & Priyadarshini J. Shetty, 2017. Bengaluru – Land Cover Changes from 2000 to 2017. Poster by Gubbi Labs.