Bengaluru in grey, green and blue colors

Jagadish Krishnaswamy remembers the barn owls that started nesting in his apartment complex after a long gap during the pandemic. “Some people complained about him. They can be scary and make a lot of noise,” he agrees. However, others in the same complex came to the rescue of these birds, including a nature-loving resident who told people that the owl was the vehicle of Goddess Lakshmi, recalls Krishnaswami, dean of the Indian Institute for Human Settlements School of Environment. . And stability. “They said we were exposed to a lot of noise from residents and children anyway and asked why we couldn’t block out a little noise from the owls,” he recalls.

When it comes to biodiversity, we are more likely to promote plants and animals that we are familiar with, so introducing people to the flora and fauna around them plays an important role in biodiversity conservation. “If citizens learn about a spectacular tree, a bird that keeps coming to nest at a particular spot in your neighborhood or a place where bats roost, it can help foster a natural history-based conservation approach in the city.” will help in promoting green infrastructure,” he says in an interview after his recent talk, “Bengaluru in Blue, Green and Grey: The Ecological and Environmental Dimensions of Blue-Green Infrastructure”.

In this illustrated talk held at the Science Gallery in Bengaluru, Krishnaswamy, who is working on building a long-term urban ecological observatory in Bengaluru, also mentioned that in India, which has committed to the global biodiversity framework, 30% The land is expected to come under some form of conservation and restoration regime by 2030. “In a few decades, 50% of Indians will be living in some form of urbanization,” he says. “To meet the 30% target, urbanized areas must play a role in biodiversity conservation.”

sustaining urban biodiversity

Krishnaswamy also provides an overview of Bengaluru’s blue, green and brown infrastructure and how all three can be integrated to maintain urban biodiversity and improve the quality of life of its citizens. Green infrastructure includes urban green spaces, including public parks, private gardens, and wooded university campuses, while blue infrastructure refers to all water bodies that are part of the urban environment. Human-engineered parts of a city, such as roads, pipes, waste water treatment plants and sewers, fall under gray infrastructure.

Over the last century of urbanization, our cities, including Bengaluru, have changed hydrologically and topographically, making the need for gray infrastructure more important than ever. “We have completely changed the hydrology of the city, and we can no longer aspire to the original hydrology of 150 to 200 years ago.”

This means that green and blue infrastructure will now have to rely on gray infrastructure such as drains, pipelines and sewage treatment plants, with constructed wetlands also playing a role. In a city that faces both severe water shortages and flood threats, Krishnaswamy explains, “Our water resource management has to face water shortages in some years and excess water in some parts of the city due to runoff from impermeable built-up areas. Both will have to be faced.” “You need gray infrastructure to take this water out of harm’s way and to a place where it can be stored or to help recharge groundwater and rejuvenate water bodies or tanks. Isolated green and blue infrastructure cannot help on their own.

Heavy rains on 22 October led to flooding in Bhadrappa Layout. Firefighters escort residents in and out of their homes to purchase daily supplies. , Photo courtesy: Murali Kumar

Challenges in water management

Krishnaswamy elaborates on the various water-related global crises, which have undoubtedly been exacerbated by climate change, making the need for effective water resources management all the more important. For starters, the Indian monsoon has seen a moderate decline since the 1950s. “Some of our climate scientists attribute the decline in the Indian monsoon to the weakening of the thermal gradient between land and sea,” he says.

Additionally, a warmer atmosphere can hold more moisture, and higher temperatures increase evaporation rates, thereby accelerating the hydrological cycle. “You can get more rainfall in more intense events on days with less rainfall,” he says, adding that since the 1950s, we have often seen daily rainfall totals in excess of 150-200 mm. However, the latter process may outweigh the former at some point, and we may end up with higher annual totals in some parts of the country, but in more intense rain events, he also says. “We need to plan and help our cities and citizens adapt to these changes.”

This means there will be more days without rain, and fewer but more intense days with rain. “This is going to be a huge challenge for us,” he says, pointing out that most Indian cities in their current state receive such unprecedented amounts of rainfall due to the nature of built infrastructure and the loss of their capacity to absorb rainfall. Can’t handle. In green spaces that have lost moisture and have accumulated moisture in groundwater or surface water bodies. Due to the rapid change of surfaces permeable to rainfall and large-scale changes in water bodies, “urban floods are becoming increasingly frequent and severe due to the intensive and inappropriate modification of natural topography and drainage patterns,” they say in Varthur Lake. It is said while depicting the water area. and its sub-watersheds, which were severely affected by the 2022 floods to illustrate the point.

Krishnaswamy also expands on the three types of water – green, blue and brown – into which the rainfall we receive globally is divided. Green water is precipitation that infiltrates the soil and reaches plants, including rain-fed crops, while blue water is water that flows and is in groundwater, aquifers, or rivers. “This is the water we depend on for drinking, washing clothes, everything else… even building buildings.”

He says human appropriation has already exceeded the blue water limit in many areas, causing damage to the aquatic ecosystem, which has had an irreparable impact on our rivers and wetlands. “If we can change some of the water requirements for agriculture through changes in cropping patterns and other measures and treat the waste water of our cities so that it changes from black to blue or blue, we will save We may be able to convert some of the lost water into our blue infrastructure, rivers, lakes and wetlands,” he says.

Additionally, he believes that in cities, we take a lot of blue water and turn it into gray (waste water from sinks, washing machines, showers) and black water (waste water from toilets) , if recycled, is a valuable potential water source. “Bangalore has made some progress in doing this (recycling). This can be a part of urban transformation, the sustainable change we are all interested in,” he says.

Hesarghatta Grassland, lake and man-made reservoir built on the Arkavathy River at Hesarghatta, 18 km from Bengaluru. , Photo courtesy: Murali Kumar

Biodiversity and cities

Earlier this month, Hesaraghatta, a grassland ecosystem on the north-western edge of Bengaluru, was declared a conservation reserve by the Bengaluru State Wildlife Board, something Krishnaswamy is happy about. “The grasslands of Hesarghatta fortunately have now got some protection.”

While cities do not have the scope for large reserve forests except on the periphery – like Bannerghatta National Park – urban green spaces, whether a campus, a garden, or even a small neighborhood park, if best practices are adopted , then native biodiversity can be maintained. “As cities face the double burden of the heat island effect from their built infrastructure as well as climate change-induced warming, we will need a good network of green and blue spaces across the city so that citizens can benefit from it. Cooling capacity and shade during hot weather,” he says.

He brings up the concept of other effective area-based conservation measures, or OECMS, which is a new category of conservation that recognizes “any type of land and water that is being used for some other purpose but where biological Diversity can co-benefit.” He says that Aravali Biodiversity Park (ABP) in Gurgaon is the first such OECM in the country. “There is potential to have multiple OECMs in Bengaluru, if with integration between blue, green and brown, we can work together and find and manage as many of these spaces as possible.”

alien species

Krishnaswamy offers insights on how to better manage our urban biodiversity. For example, a serious issue in the urban environment is how we deal with alien species of plants and animals found in many cities today, including Bengaluru.

Not all alien species are invasive or harmful, and of course, “if they don’t spread too much at the expense of native biodiversity, they’re fine, and some provide habitat and resources for native species of birds or bats.” . But there are also other alien species – both plants and animals – that become invasive and damage or displace native biodiversity,” he says. He believes that we should not put all foreign goods under one umbrella. Of course, not all alien species are dangerous, “if they don’t spread too much at the expense of native biodiversity, they’re fine. But there are also other alien species, both plants and animals, that have become invasive,” he says.

Krishnaswamy also highlighted other aspects of urban ecology and its management: the high species diversity of bees in the city, how urban and peri-urban farming can have a positive impact on both people and creatures, how green spaces reduce heat stress. Although some cities are more at risk due to their built-up infrastructure, we need to be cautious in our approach towards lake rejuvenation, and adopt a scientific approach while creating sustainable urban ecosystems.

little help

“Green spaces come in all shapes, sizes and functionalities, but those that really contribute to native biodiversity conservation in the city are those that support key ecosystems such as plant-animal interactions, including pollination, predation and nutrient cycling, and the whole of life. Should be allowed. The cycle of diverse sets of organisms has to be completed,” he believes. “If you provide housing, as well as a little help, nature can flourish in the city. ,

published – October 23, 2024 09:00 AM IST