Today, we live in an age of heightening environmental awareness.”Plant trees to Save the Environment is a common mantra in today’s urban ecology domain. However, this mantra may indeed be detrimental to the native plants and the birds, particularly in parks and grasslands, research shows. Urban aforestation movements have speeded up in India’s big cities-Delhi, Bengaluru and Pune. However, research from Pune shows that the plantation of exotic species reduces the bird diversity in the hilly grasslands they were planted on. To understand the effects of these plantations, first, we must understand the ecological context of Pune city.
Pune’s Ecological context
Pune is blessed with grassland savannas on the hilly ranges which run across the city. These ranges are an extension of the Western Ghats. These hills, locally known as tekdis harbour a huge variety of flora and fauna. The prominent tekdis of Pune include Vetal Hill complex and Pashan-Baner Hills.
The hotspot with the highest bird diversity in Pune city limits is the Vetal Hill Complex,a savanna grassland ecosystem. Pune’s hills also are home to endangered flora like J.nana. Today, Pune’s grasslands are also facing the issue of exotic plantations, particularly of Gliricidia sepium.
What does Research on plantations and bird diversity in urban regions indicate?
Dr.Kiran Choudaj and Dr.Wankhede conducted a study on bird diversity across the native and exotic plant patches in Pune’s savannas (Choudaj and Wankhede,2022). .The researchers concluded that there was higher bird biodiversity in natural savannas, while areas with exotic plantations had low diversity.
Moreover, resident grassland birds like Indian roller, zitting cisticola and long-tailed shrike do not frequent exotic patches and were found only in native savannas. Even migrant birds like Tree Pipits,red-breasted Flycatchers and Jacobin Cuckoos were observed only in the urban grassland regions.
On the other hand, only generalist birds, which do not mind living in a variety of habitats,(grassland/garden/plantation) were found in exotic plantations. These birds include Rufous Treepie, Black Drongo, Spot-breasted Fantail etc. This paints a picture of a diversity rich savannas and diversity-poor exotic plantations.
These observations are also corroborated by papers studying other Urban green spaces in India-like Dehradun and Delhi. Kaushik et al found that large green spaces with old, native trees and “unmanaged” natural vegetation harboured the highest bird diversity. (Kaushik,2022)
A study in Delhi also found a similar trend-there was a negative correlation between exotic woody species richness and bird diversity. The authors found that the density of the invasive plant per hectare was negatively correlated to bird diversity. One of the usual suspects amongst invasive species-Prosopis juliflora also negatively impacted bird diversity. (Khera et al, 2009)
How do invasive species affect bird diversity?
The rapidly growing invasive trees stop the growth of native bushes and shrubs which harbour a lot of grassland birds. As a result, these birds hardly use plantations for their daily activities like foraging and roosting.
However, not all plantations are bad for urban green spaces, particularly for avenues. Native trees like Ficus species and Jamun harbour a great deal of bird diversity. For example, Ficus trees are a favourite of woodland and forest-edge birds. Coppersmith barbets relish the fig fruits and Tickell’s blue flycatchers find lots of their insect diet there. Red silk cotton(locally Semal, Kaatesawar)trees are visited often by starlings, sunbirds and bulbuls. (personal observations).
Planting native trees in urban green species may not be the worst environmental action. Still, there needs to be a lot more thought and scientific basis to it. Moreover, this basis should be combined with consideration given to the “habitat history” of the region in which the plantation is planned. Specifically, it is the practice of planting ecologically harmful exotic trees which need to be stopped.
All of the above research points to one action that must be practised by environmentalists and NGOs from now on-Let the urban savannas/grasslands be.
Grasslands are not wastelands and need to be kept intact
Unfortunately, there is a misconception sometimes amongst pro-afforestation groups as well as Forest Dept. that the grasslands are some kind of barren wastelands which need to be” rescued” by planting trees. A recent write-up in Scientific American puts forth this flawed understanding in more detail. (We Must Stop Treating Grasslands as Wastelands – Scientific American). In fact, grasslands harbour their own unique species which deserve to be protected not rescued by plantations.
Grasslands in their original form have a very high density of grasses, with sparse tree vegetation. Moreover, these urban grassland regions are adequate ecosystems in their own right. They do not need ill-thought-out exotic tree plantations for “environment protection”.
This thought is echoed by Dr. Choudaj, whom I met to discuss the issue of exotic plants. He said” Grasslands are delicate ecosystems which need time to recover. Thus, even removing invasive plants may not yield results quickly. There is no need to plant more trees there. In this case, keeping the ecosystem intact is the best way forward.”
Conclusion
These results should ring an alarm bell for urban afforestation movements. Therefore, the entire activity needs to be well thought out and stopped in grasslands. Some regions simply do not need exotic plantations. Planting exotic trees then might be doing more disservice to the environment than helping it!
Going forward, the best way to spread grassland awareness might be to adopt some bird mascots as “grassland ambassadors”. A grassland inhabitant sporting a stunning aqua blue wing plumage, the insectivorous bird Indian Roller could be a great grassland mascot.
There are multiple ways to conserve natural urban green spaces like grasslands and parks. Planting exotic trees for the sake of “doing something for the environment” is not one of them!
Written by: Arjit Jere
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