Glimpse of Hoskote lake
Wetland, as the name says the land that is wet.
So every land that is wet is a wetland ? You may ask.
Well! not exactly, the land should have soil on it.
"I see, then can we consider the water that settles over a part of the soil on the side of the road that we see especially after a heavy downpour is a wetland?"
Umm... no, that does not count either because there is no vegetation in or around it.
You see, here is a way you can define a wetland. If the soil is covered with water either permanently or seasonally along with a vegetation and animal life in or around it.
"So clearly, it means that Antarctica is the only continent that does not have any wetland, right?"
Correct :) And while technically those are the key factors that determine the wetland, if you observe closely towards its vegetation you can determine the type of wetland. One more thing, along with vegetation the source of water also varies with each type of wetland.
"Ohh nice! By the way, can lakes be considered as wetlands?"
Oh I am not 100% sure on this although many definitions overlap and incline towards telling you that a lake is a wetland. Personally, however, I do not think so. Because lakes do not have hydric soils beneath them or have vegetation through them. But, the areas surrounding lakes definitely qualify as wetlands because either marsh or swamps are usually seen on their shores. We can go on...
"Wait, what is a Hydric soil?"
Hydric, the name that originates from Hydro, indicates an environment which has abundant of water. When the water is ample, there is a lack of oxygen within the soil and this is called as a hydric soil. As a result of this phenomenon, soil supports plants that are adapted to the type of wetland(marsh, swamps etc), fosters many animals and most importantly microbial life.
Allow me to survey and shine on few key aspects of wetlands by taking one such lake as an example which has marsh around its shore, Hosakote Lake, located in Hosakote Taluk, Bengaluru Rural district.
This 808 acres lake is a significant water body is ringed with a variety of habitats such as marsh, grassland and shrubs. From the highway, as you turn left (if coming from Bengaluru) towards the lake you will be greeted with songs from abundant avian friends. As you continue to walk on the right you will look a large lake witness flocks of different species, some are flying while many are wading. If you dwell at this lake daily, then you may recognise around 266 distinct species of birds (according to the data from eBird) had considered this lake and its surroundings as their home either permanently or for a shorter period of time when they migrate from long distances. Two-sixty-six, with that number on her heart, the lake smiles and tells you about the diversity of birds found here.
Some of the gorgeous guests that visit in and around this wetland include - Northern Shoveler (Spatula clypeata), Northern Pintail (Anas acuta), Black-tailed gotwit (Limosa limosa), Bluethroat(Luscinia svecica), Western Marsh Harrier (Circus aeruginosus) etc.
In this essay I explore different components attached to survival of the lake. This is one of the few places I used to visit often for photographing birds. First time I had visited Hoskote lake was in 2016 and for the next three years my visit was mainly during winters. When I first visited this lake the view of the construction work was distant but concrete had crawled its way towards the lake eventually. Then there was a familiar sight everywhere, plastics and other garbage. I feel there is an urgent need to not only clear the garbage but also find a way to protect the boundaries of the lake.
An Openbill Stork (Anastomus oscitans) against the backdrop of a marsh followed by a small forest patch. The marsh is home to many wetland birds, a little cormorant sitting below right of the stork.
Northern Shoveler (Spatula clypeata), one of the migratory birds that often visits in the lake during winters.
Another visitor, Little Ringed Plover (Charadrius dubius), which migrates within India and few come from outside to winter in the sub continent.
On my first glance it gives me joy as lines of majority of the birds are upwards but when I pay attention on the numbers at both ends (x and y axis), it had only increased from previous year. Understandably the one of the reasons for the dip from 2020-22 is due to records of these birds might not have taken due covid-19 pandemic. Hence I compared the data of 2024 with the year, 2019. On a positive side I see the numbers of every bird in the list are higher than the one from 2019, except Osprey(Pandion haliaetus).
Image taken from Google Earth Pro represents the scenario of Hoskote lake and its surroundings in December 31st, 1985.
Image taken from Google Earth Pro represents the scenario of Hoskote lake and its surroundings in December 31st, 2014.
Image taken from Google Earth Pro represents the scenario of Hoskote lake and its surroundings in December 31st, 2024.
White wagtail (Motacilla alba) which specialists in wetland habitat migrates within India during winter.
White-cheeked Barbet (Psilopogon viridis), an endemic to the Western Ghats is also seen around the Hosakote lake.
Data source and Acknowledgements:
The dataset (1990 to December, 2024) of birds was downloaded from eBird.
GIS images were created from Google Earth Pro.
Soil Health information was captured from Perennial Earth. The satellite images represent the current health of the soil (June, 2025).
Vegetation index was calculated using Google Earth Engine. The duration considered was from 2025-06-01 to 2025-06-30. Sensor used: Harmonized Sentinel-2 MSI: MultiSpectral Instrument, Level-1C (TOA)
A big thanks to Canopy collective for providing the toolkit for conservation. It made connecting all components a bit easier for me.
Let us talk more about birds, shall we? As we know many species frequent this place, what we must also understand is that the population of these birds does not remain constant every year. Some may increase and some may remain constant or decrease. While reasons for this constant change could be many, it is worth taking a look at their trend starting with raptors to understand what is happening.
Above graph describes trend of raptors found in the lake from various periods. On the x-axis, you can see the years and on the y-axis, the number represents the count of the birds during this period.
I then find similar patterns in the graphs of migrant birds such as the numbers of Brown Shrike (Lanius cristatus), Gray Wagtail (Motacilla cinerea), Black-tailed Gotwit (Limosa limosa) and Green Sandpiper (Tringa ochropus) have gone beyond what it was in 2019. Only BlueThroat's (Luscinia svecica) and Garganey's (Spatula querquedula) records did not go beyond the one from 2019.
While I am not sure why the count of Bluethroat and Garganey did not go up even though they are insectivorous as others in the list. I can only imagine of the reasons which may not come close to the truth such as these birds could be more shy than others and prefer not to be disturbed. As a result, rather than foraging in the open they might have move to a secluded place and we could not make a record of theirs. Perhaps there isn't much place left for them over here to eat alone and could have been migrated else where. If that is the case, then it would be interesting to see where else they had decided to make their home.
Above graph describes trend of some of the migratory birds found on the lake from various periods. On the x-axis, you can see the years and on the y-axis, the number represents the count of the birds during this period.
Above graph describes trend of some of the birds that reside on and around the lake from various periods. On the x-axis, you can see the years and on the y-axis, the number represents the count of the birds during this period.
While that was the story of migrants, species who live around the lake permanently also tell a similar trend (as shown above). So collectively all three categories - raptors, migrants and resident birds - tell the same story, that we are increasing in number. We love this place. These may be a small list at display, however I observe similar trends in few other species as well, both resident and migrant.
"But why do birds migrate in first place?"
Of course for better conditions that will suite them for feeding, breeding and raising young ones. They mainly feed on fish, insects, other invertebrates, fruits, grains, seeds and in case of raptors they feed on small birds, small mammals, rodents etc. Hosakote lake is large enough to contain good quantity of fish for these birds to forage on, good soil quality which not only to produce enough vegetation for these birds to perch on but also to feed on insects who come out after a downpour.
"Looks like there are a lot of benefits that birds, small mammals, insects and needless to say humans who will get from this lake. But I am sure this was not the case a decade ago, isn't it?"
True, this may not be the case decade ago or even more than that since vegetation had changed. So as soil and dimensions of the lake. Lets peek at how the land around the lake was a decade ago, two decades and beyond. Observe maps below closely.
It is very much evident from these images that a good amount of vegetation has been lost in the past four decades. I had drawn various points along the boundaries of the vegetation surrounding of the lake for the map of December 31st, 1985 . I then referenced same location in the maps of 2014 and 2024. It may look like the quantity of water has increased from 2014 to 2024, however I do not have any data on hydrology aspects of this region to justify. I can only assume that there were rains that might have lasted beyond the typical monsoon period in 2024. The clarity and contrast of these images was also visibly increased without any modification done from my side.
This lake should be protected at any cost before it experiences the weight of a bus stand, a theme park or another gated community on her heart. Karnataka government recognises this lake under the category of Natural/Scenic beauty. We have seen various disasters in the past in various parts of the city when the lakes have been replaced by construction works, Bellandur and Varthur lake are prime examples and with latest one in 2025 at Manyata tech park. These concrete structures may bring economy to the city and wetlands are the primary habitats which gets affected when any city expands. The stakes are higher when these areas get effected during heavy rains . The lake is already filling with debris waste while the authorities say they will clear the garbage. Saving lakes like these not only helps biodiversity but also to humans as well. Think of this, from where do you get the oxygen you breathe?
The above narrative is based mostly on the colour coded regions that are favourable for birds, bees, microbes and soil in general. But we had also seen certain patches do not have colour coded, they are either covered with water or concrete.
Water is good but with the increase in the concrete around the lake is one of the primary reason for many birds to not opt this place for breeding and raising their young ones over these years. An increase in cement, steel and paint not only indicates decrease in the vegetation but it also means the probability of an increase in the temperature of air in this area is high. There are potential side effects such as when the air temperature increases around wetland area, the water body will absorb more heat and will evaporate more than what it normally does. Which is not good.
With the rise in the heat, people may die due to heat related cardiovascular diseases. There is one more aspect which will cause problem with this phenomena, which is the possibility of Heat Shock Proteins (HSPs) getting affected because of this increase in the temperature. I could not find any study as such which directly links affecting HSPs due to the heat generated in the Urban Heat Island, a phenomenon where an area in the urban experiences warmer than its rural parts. Now, Hoskote lake is in the rural side of Bengaluru hence the affects may not be visible as of now but if the concrete continues to occupy more space especially towards the lake then there is definitely a reason to concern. Starting with an unsettling sight of decrease in the number of birds that migrate and the ones to who stay permanently will face shortage in the food, a severe shortage of a place to take shelter, breed and raise young ones, there will be shortage of fish in the lake which are also a bread winner for the local fishermen. I am assuming there could be other side effects that may arise. Do not forget the Heat shock proteins which play a critical role in promoting tumor progression.
Relative Sequestration Rate Potential. The potential rate at which a soil system can absorb and store additional carbon
Atlas SOC (Soil Organic Carbon) is the amount of carbon stored in the soil for a given area.
Carbon Efficiency Use. Indicates how efficiently microbes inside the soil convert the carbon they consume into their own biomass versus releasing it as CO₂
Microbial Soil pH Index. Indicates acidic/alkaline nature of the soil as experienced by microbes.
Microbial Moisture Response Index. Indicates how microbial activity and soil carbon sequestration are affected by soil moisture conditions
Microbial Soil Temperature Index. Indicates how the temperature of the soil affects microbes.
"This is extremely painful to witness loosing good amount of vegetation over years. What does this loss mean to birds and humans?"
Yes, indeed it is a very unpleasant view. This certainly will have an impact on birds and humans too. Before I tell you those, we first need to understand that replacing vegetation with concrete will have an impact on soil. Allow me to show to you a few images (they are a bit colourful though) of the lake and its surroundings which convey different aspects that measure the soil health. I will briefly explain what these represent followed by my understanding on how everything is interconnected. Most of them are self-explanatory. In all images lets take a close look at areas around the lake. By now you might have already noticed the presence of the scale at right bottom of every image. We shall discuss on that too.
Starting with the first image, Atlas SOC (Soil Organic Carbon). This represents the amount of carbon stored in the soil at a given area. The measurement as displayed in the scale is in SOC %. In the image the green colour that you see around the core part of the lake is the area which stores maximum amount of soil carbon, approximately around 2-2.5% as per the scale.
While Atlas SOC tells us the amount of carbon stored in a specific place, the speed at which this carbon is absorbed and stored over years is determined by Relative Sequestration Rate Potential . It is measured in tonnes of Carbon per hectare per year. By looking at the image we can see colours coded in gradients of green and purple. There are patches where there is no colour on the right and left, I assume based on what I am seeing is that there is only concrete and no soil that absorbs carbon. And the one in the center is perhaps covered with water.
Back to focussing on the green colours in the image, especially towards the north of the lake where the colour turns more lighter has the potential of storing carbon relatively faster than other regions. As per the scale it is measured up to 0.8 tonnes of Carbon per hectare per year. Although this region might not be in hectares but it gives us information that its storage rate is higher than its surroundings.
Remaining images tell the story more about the role of microorganisms. For instance, Carbon Use Efficiency (above image) tells how efficiently microbes transform the soil carbon into organic biomass. You see bluish-green colours right on the north of the lake (same patch as we had focussed in previous images) which falls from middle to few bars on the right of the scale.
For the microbes to function effectively which is to take the soil carbon they would need conditions favourable to them and one of them is the pH value. This is given by Microbial soil pH Index. The north of the lake as more lighter green shades, which as per the scale is more favourable for microbes.
Perhaps the most important image of all, Microbial Moisture Response Index indicates how well microbes are responding to the given moisture conditions in the region. In this case not only on the north of the lake but the pale blue colour is spread uniformly to further north.
The only index among others whose values that are favourable to microbes fall on the left side of the scale. The Microbial Soil Temperature Index tells how temperature affects microbial activity. In this case the image has purple shades on the north of the lake and extends further north which according to the scale is relatively lower temperature (compared to the right) and is suitable for microbes to their job.
Let me explain the relations among these images with another image! The flow diagram below will help us to understand the connections better.
It all starts with Photosynthesis. Plants capture carbon from the atmosphere via Photosynthesis. Then via plant's leaf litter, dead organisms, any of its debris etc along with certain compounds of its such as sugars, amino acids, enzymes etc (known as root exudates) release into its surrounding soil, carries carbon with them.
Everything over here is Soil Organic Matter(SOM). When microbes such as Bacteria or Fungi decompose this organic matter, some of the carbon goes back to atmosphere as CO2 and some proportion is transformed into microbial biomass. So think microbes as gatekeepers which decide how much to transform into biomass and back to atmosphere. How effectively microbes do this job is measured by Carbon Use Efficiency.
How effectively this transformation happens is determined by various factors starting with having appropriate levels of pH level in the soil. It should neither be to acidic nor too alkaline. Bacteria prefers from neutral to alkaline while fungi may thrive in acidic soils. Next factor is the temperature of the soil, it should be neither too cold nor too hot. Microbes are active at a very moderate temperatures.
The most important of all factors is the moisture content in the soil. This has to be higher. Moisture in the soil plays a key role as it directly affects photosynthesis, soil respiration, microbial activity, and soil organic matter dynamics. If there isn't adequate moisture in the soil then it effects photosynthesis which in turn affects microbes since the input for them, root exudates and litter, gets effected. As a result, microbes function less efficient in decomposing these materials into organic biomass which means it alters the soil structure and availability of nutrients for the plants and this hinders the growth of plants. So its a cycle. Excessive moisture can create anaerobic conditions (lack of oxygen) in the soil which results in increased amount of Methane releasing into the atmosphere by microbes. Hence maintaining optimum levels is important the storage of carbon.
Soil moisture is a key regulator in balancing Carbon Sequestration and Co2 emissions. Good moisture content also influences microbial activity and controls emissions of Methane (CH4) and Nitrous oxide (N2O)
When all these factors such as appropriate levels of pH, moderate temperature and appropriate moisture content align, microbes function well in transforming organic matter into microbial biomass. And finally when microbes die, their remains becomes part of this place where carbon is stored (also known as carbon pool). When microbes function well they provide necessary ingredients (such as Phosphorous) to the plants. This about this, if birds are migrating from different continents to breed here, what do they eat and where do they get food from? The flowers, fruits, insects are main sources of food for them. When living beings like these increase, their fecal matter and dead birds/bees decaying matter are also a product of Soil Organic Matter. These living beings are found on the plants that thrive near the lake, on the soil that is kept healthy by these microbes. And because the soil and plants are healthy they in turn provide energy to these microorganisms. No matter how you see there is a positive feedback loop everywhere.
"If the soil health is good then we should see some good vegetation isn't it?"
Indeed it will. Surely, for me the quality of the soil looks good in this region. If you have a healthy soil then it becomes an imperative to produce a good vegetation. Lets have a look on that as well. The polygon below in the map shares almost similar boundaries with the ones shown in the Perennial above. The NDVI value is 0.11662704602928746 as you can see on the highlighted box below the polygon.
Image showing the NDVI value of the polygon, calculated in Google Earth Engine.
Black and white image showing the polygon which is used to measuring NDVI.
What is NDVI value?
Well it stands for Normalised Difference Vegetation Index. The difference in this context is the value between near infra-red (which the vegetation reflects) and red light(which the vegetation absorbs). It is calculated based on the below formula:
NDVI = (NIR-Red) / (NIR+Red) [NIR = near infra-red]
Healthy vegetation (chlorophyll) reflects more near-infrared (NIR) and green light compared to other wavelengths. But it absorbs more red and blue light. This is why our eyes see vegetation as the colour green. The index value ranges from -1 to +1 where negative values indicate that there is a high possibility of water in the area and positive values indicate presence of vegetation. Higher the values, denser the vegetation. And zero indicates the possibility of an urbanised area.
The value in the polygon selected is in between 0.1 and 0.2 which most likely could be anywhere from barren rocks to shrubs and grasslands. No wonder there are many ground birds in the area. I was a bit liberal in drawing boundaries of the polygon. The index would not have changed much if I was strict on my choice. Let the boundary start from where the concrete ends. Let the agricultural lands be included. They are the life for many birds as well. All these areas, not just the shores of the lakes, need to be protected as well.