Are all green landscapes really sustainable?
By Sakshi Saxena and Arjun S
Ahead of World Day to Combat Desertification and Drought on 17 June 2021, we start this blog series on water consumption in cities.
During the COVID 19 lockdowns I, like many others, have sought respite from being locked in, by enjoying the greenery surrounding my home. Interestingly, rather than being captivated by the birds and butterflies that frequent the garden, what I was most struck by was the amount of time and resources that the landscape consumes! Our resident mali (gardener) routinely watered the lawn for almost 3 hours every other day. With news of water shortages looming all around us, this got me thinking .
Just because a landscape is green, is it really sustainable?
I started to investigate the key elements of this landscape, starting with its most abundant element — lawns! A few recent studies reveal that:
- Lawns produce more CO2 than they absorb.
- Lawns can be more harmful than permeable paved areas.
- In countries like the USA, where lawns are abundant, it’s estimated that 30 to 60% of domestic freshwater is consumed by lawns.
A lot of the landscapes around me are moving towards global trends rather than being designed to respond to the natural environment in which they are located. This is why we find a large array of landscapes in our cities, ranging from palm trees and lawns to Japanese style gardens. Our cities are now a melting pot for global landscapes. This not only has negative environmental consequences but is also a huge missed opportunity, as sustainable landscapes can go a long way in building healthier cities.
Instead of providing benefits such as improved rainwater capture and micro-climate regulation these landscapes often guzzle water, contaminate the soil with pollutants, and actually consume more than they give back.
So what does it take to make a man-made landscape sustainable?
I enlisted the help of my colleague, Arjun, to determine what makes a landscape sustainable. During the latest lockdown, we conducted a comparative analysis of the two landscapes adjacent to our buildings. Our goal was to illustrate the differences between sustainable and unsustainable man-made landscapes.
My colleague’s landscape, which was modelled on the surrounding natural forests, will be called Landscape A. My landscape with palm trees and lawns will be called Landscape B. We assessed both landscapes across 5 different parameters: plant species, water consumption, maintenance and micro-climate regulation. Although the comparison was done specifically for the two landscapes located in Delhi, the same principles could apply to any urban landscape.
Some of the key highlights from the study:
Plant selection
The sustainable landscape (Landscape A) had mostly native plant species whereas the unsustainable landscape (Landscape B) had plants from all over the world.
Water consumption
Choosing plant species intelligently can have a significant impact on water savings. Even though lawns are famously high maintenance, their water consumption can differ significantly based on the species selected. We were able to see this first hand through the landscape comparison. However, we would like to add that there is a need for better water use data for different landscapes.
Temperature differential
We conducted an experiment where we both went outside at noon (the hottest time of the day) to measure the impact of each landscape on air temperature. We first measured the temperatures standing in an uncovered paved area. The second reading was taken from the middle of the landscape.
The air temperature reading taken from the paved areas adjacent to Landscape A, read at 40°C. When standing in the middle of the landscape the air temperature readings were 38°C. For Landscape B the temperatures were 2°C higher. The paved area readings were at 42°C and the temperature in the middle of the landscape was at 41°C.
Interconnected green spaces and microclimate
It’s clear that dense vegetation with multiple layers of native plant species can reduce air temperatures. What also became clear was that when small landscapes are strung together they can actually have an effect on the microclimate.
In the case of Landscape A, the landscape is situated next to a series of other small landscapes that collectively form a patchwork of interconnected green spaces. This seems to help with the microclimate as the air temperature in the paved area was 2°C lower. Whereas, the areas surrounding Landscape B, are largely agricultural and industrial areas which seem to have a negative impact on the microclimate, leading to higher temperatures. This, of course, is based on our anecdotal data and there is a need for empirical data to support our findings.
There are multiple benefits to interweaving landscapes into our cities. This has propelled major Indian cities to integrate boosting green cover into their vision. While this is a step in the right direction, it will be crucial that this newly installed green cover is sustainable. That is the only way to ensure that these landscapes give back more than they will consume.
