Many of the world’s cities are growing in biodiverse areas, which spells trouble for the native species displaced by them. Cities themselves can have patches of biodiversity in gardens and parks, but is it the right biodiversity? Kiran Choudaj and Varsha Wankhade have studied the interrelationship between woody plants and birds in Pune urban area, India. Their report that birds benefit from diversity of native plant species, but not exotic species, can be read in Tropical Ecology.
Choudaj and Wankhade studied the plants and bird life of the Pune Metropolitan Region. Pune is one of India’s fastest expanding cities, so urban green space is essential to bird life as the urban area expands. A lot of this green space will be parks or gardens. Choudaj and Wankhade comment that this leads to the arrival of exotic ornamental plants. “Smaller green spaces such as gardens, parks are created for recreational purposes, the desired surrounding for raising children, and space for exercise, but their role in biodiversity is neglected. Gardens that used to be comprised of stratified local plant species have now been changed into open landscapes with exotic plant species,” they write in their article.
The ecologists set up transects to sample the vegetation and bird life and then examined the data to see if they could find any correlations. “We observed that increase in the richness and diversity of woody species increased the richness and diversity of birds. In the same case, noted a decline in the richness of birds as an increase in the density of exotic woody plants. The diversity of plants keeps the continuous food supply to various animals such as insects, birds, and other vertebrates,” write Choudaj and Wankhade.
The problem with exotic species is that comparatively few arthropods feed on them. With fewer insects, there is less food to support the bird population, and so the effects are felt higher up the food chain. They also found birds avoided some exotic species for nest building.
The authors write that while this kind of study has been done in North America and Europe, it’s comparatively rare for the tropics, where many cities are growing explosively. They conclude with some advice for planners that’s relevant to cities around the world. “The urban green spaces dominated by turfgrass and exotic ornamental plants provide little opportunity for native plants to flourish and provide little to no habitat for wildlife.”
“There is a misconception that native plants give a poor appearance and creates a messy yard, which is not true. There are many benefits associated with the use of native plants for landscaping. The use of native plants for landscaping saves money and water, they are resistant to local weather, require low maintenance, restore natural habitat, and they are rarely invasive.”
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Choudaj, K. and Wankhade, V. (2022) “Study of the interrelationship between woody plants and birds in Pune urban area, insights on negative impacts of exotic plants,” Tropical Ecology, https://doi.org/10.1007/s42965-022-00269-3