By Anusha Sanjeev Mehta and Robert Wilby, Loughborough University
The monsoons are the most important climate feature of India. They dictate the seasons and ultimately shape human well-being and livelihoods. But these dramatic transitions between hot/dry and cooler/wet conditions affect not just people but also the region’s flora and fauna.
Recently there has been a surge in nature-related recreational activities in India, particularly bird watching. Home to more than 1,000 species (of which about 45 are endemic), India is the ideal place for ornithologists. However, bird counts can vary a great deal between years, dropping markedly for example in 2015. Could there be a connection between climate conditions and birds in India?
Our new study, published in the journal Area, found that ocean-atmosphere patterns, such as the El Nino-Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) in the Pacific and Indian Oceans, could be affecting the number of bird species and counts of selected bird types in the states of Goa and Tamil Nadu. This is because ENSO and IOD patterns are linked to regional precipitation and temperature anomalies over large parts of the world, including India.
We pooled bird data for the years 1990 to 2015 by prevailing ENSO and/or IOD phases. They discovered that greater numbers of bird species occurred under El Niño and/or negative IOD events compared with La Niña and/or positive IOD events. In particular, bird diversity is higher when both Goa and Tamil Nadu experience locally wet conditions (under El Niño) compared to locally dry conditions experienced during La Niña. It was also found that temperature has a strong effect on the number of birds. Overall, bird communities were more abundant under warmer/wetter conditions.
The Brahminy Kite, Indian Pond Heron, and Lesser Whistling Duck were used as marker species to further detect the influence of ENSO and IOD. All three species were much more abundant in Goa during El Niño than La Niña events, while more Kites were found in Tamil Nadu during negative IOD than positive IOD events. Some seasonal and lagged impacts on bird communities were also observed. The picture could be further complicated by ENSO and IOD events operating in tandem, but datasets are generally too short to be sure.
The changes in bird species and individual bird numbers may be due to the indirect effect of ENSO on prey, habitats, nests, and migration. Wetter conditions during the winter and pre-monsoon period are favorable for birds due to the increase in food and water availability and reduced negative impacts on eggs and young birds caused by high temperatures. However, very wet weather and flooding can destroy breeding grounds, negatively affecting bird communities.
The study contributes to scientific knowledge by showing how ENSO and IOD signatures may be detected in the bird communities of India. The approach could be extended to other indicator species. This could deepen our understanding of the future climate vulnerability of one of the most ecologically vibrant areas of the planet.
About the authors: Anusha Sanjeev Mehta is Loughborough University graduate and Rob Wilby is Professor of Hydroclimatic Modelling at Loughborough University.
Kotteswaran, C. S., (2015) Vedanthangal bird sanctuary closes early. Deccan Chronical, 31st May 2015. Available at: http://www.deccanchronicle.com/150531/nation-current-affairs/article/vedanthangal-bird-sanctury-closes-early [Access date 7 November 2017]