5-Jul-2021: Excess irrigation over northern India shifting monsoons towards northwest risking agriculture

Climate researchers have discovered that excess irrigation over northern India shifts the September monsoon rainfall towards the north-western part of the subcontinent increases widespread weather extremes over Central India. These meteorological hazards expose the vulnerable farmers and their crops to risks of failure.

The study which establishes that monsoon precipitation is sensitive to the choice of irrigation practices in South Asia can help plan agricultural practices in this region.

South Asia is one of the most heavily irrigated regions of the world, largely using groundwater, and its major summer crop is paddy which is cultivated in water flooded fields. Hence it was pertinent to study how such practices can influence the monsoons which form the fulcrum of this agro-based economy.

Subimal Ghosh, Professor in Department of Civil Engineering and Convener at Interdisciplinary Programme in Climate Studies (IDPCS), a Centre of Excellence at IIT Bombay supported by the Department of Science and Technology and his climate group, investigated the impact of agricultural water use on the Indian Summer Monsoon using a climate model.

The research published in the journal ‘Geophysical Research Letters’ recently showed that monsoon precipitation is sensitive to the choice of irrigation practices in South Asia. In another study, Prof. Subhankar Karmakar from IDPCS, IIT Bombay, and his research group identified for the first time that risks for rice and wheat have increased in the recent decade, with wheat at a two-fold higher magnitude than rice. The study followed the Assessment Report 5 of IPCC definition to quantify ‘Risk’ and has been published in ‘Environmental Research Letters.’

Increasing crop risk is predominantly driven by the decreasing number of farmers, and the wheat risk is also attributed to increasing minimum temperatures during the crop growing season. This study provided compelling evidence indicating that the hydro-climatic hazards related to precipitation extremes and drought are specifically alarmingly increasing the crops risk as compared to temperature extremes.

Another finding obtained from this study was extreme rainfall in recent decades in Central India has been increasing, and this is also caused by an increase in irrigation and consequent increase in evapotranspiration (the sum of evaporation from the land surface plus transpiration from plants).

2-Jul-2021: Study on social behaviour of Male Asian elephants

As human-elephant conflicts increase with time and expanding human range, understanding social behaviour becomes crucial to the conservation and management of the highly social and endangered Asian elephant.

The Asian elephant is a charismatic species with a long history of co-existence with humans. Yet works on male societies of wild elephants based on long-term observations are rare. To fill this gap, researchers from Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), an autonomous Institute of the Department of Science and Technology, Government of India, studied associations of male Asian elephants by collecting and analysing data on behaviour of identified nonmusth wild Asian elephants of Nagarhole and Bandipur National Parks.

They found that the time spent by male Asian elephants in all-male and mixed-sex groups depended on the age of the male. Adult Asian male elephants preferred to spend their time alone than in mixed-sex or in all-male groups. Besides, old males were found mostly in the company of their age peers and less frequently with young males (15 to 30 years of age). Also, young males did not disproportionately initiate associations with old males.

Adult male Asian elephants are less social than females. They enter musth -- a mate-searching strategy for old (above 30 years of age) males, annually. The researchers hypothesized that when the adult males enter musth, dominance relationships may affect the number of mating opportunities they procure. Hence, it might be more crucial for old males than for young males to test strength with each other and settle dominance relationships during their nonmusth time.

On the other hand, since young males associated less with females during musth than non-musth time, they might also be using their non-musth time to search for mating opportunities.

The team observed male elephants and identified them using features of their ears, tails, and tusks and recorded whether males associated with each other in the presence or absence of females. They used six years of field data on 83 identified males for this study, which was published in the open-access journal ‘Frontiers in Ecology and Evolution’. They considered two possible reasons for male associations --non-musth males may use their time to fight with males of the same age class, who would be of similar sizes, to decide their dominance relationships, and young males might also use their associations to learn from older males about food resources and/or reproductive behaviour.

Their results showed that all-male groups (in the absence of females) were rare and small. According to the team, social learning from older males did not seem to play a big role in male associations. In contrast, African savannah elephants have been found to spend more time in all-male groups and to form larger groups, and young males preferred to associate with older males.

The researchers said that this could be due to the difference in the dispersion of food resources in the habitats occupied by the two species.

This study is one of the few that examines male associations in species in which males rove between social groups. It provides an example of how ecological differences could possibly drive differences in male societies in related species with similar male reproductive strategies.