Flexible Strategies for Coping with Rainfall Variability: Seasonal Adjustments in Cropped Area in the Ganges Basin

Christian Siderius,Petra J. G. J. Hellegers,Ekko C. van Ierland,Hester Biemans,Pavel Kabat,Paul E. V. van Walsum,Ulrich Melcher

doi:10.1371/journal.pone.0149397

Christian Siderius, Petra J. G. J. Hellegers + Show 5 more

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https://doi.org/10.1371/journal.pone.0149397

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Abstract

One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for coping with rainfall variability. Such adjustments are not incorporated in hydro-meteorological crop models commonly used for food security analyses. Our paper contributes to the literature by making a comprehensive model assessment of inter-annual variability in crop production, including both variations in crop yield and cropped area. The Ganges basin is used as a case study. First, we assessed the contribution of cropped area variability to overall variability in rice and wheat production by applying hierarchical partitioning on time-series of agricultural statistics. We then introduced cropped area as an endogenous decision variable in a hydro-economic optimization model (WaterWise), coupled to a hydrology-vegetation model (LPJmL), and analyzed to what extent its performance in the estimation of inter-annual variability in crop production improved. From the statistics, we found that in the period 1999–2009 seasonal adjustment in cropped area can explain almost 50% of variability in wheat production and 40% of variability in rice production in the Indian part of the Ganges basin. Our improved model was well capable of mimicking existing variability at different spatial aggregation levels, especially for wheat. The value of flexibility, i.e. the foregone costs of choosing not to crop in years when water is scarce, was quantified at 4% of gross margin of wheat in the Indian part of the Ganges basin and as high as 34% of gross margin of wheat in the drought-prone state of Rajasthan. We argue that flexibility in land use is an important coping strategy to rainfall variability in water stressed regions.

Highlights

South Asia’s climate is strongly influenced by land, ocean and atmosphere interconnections resulting in strong intra-seasonal [1,2,3], inter-annual [4,5] and decadal variability in rainfall [6,7]
In this paper we explore the impact of flexible land use strategies for coping with rainfall variability
In our model we find that in the drought year of 2002 the area cropped in Rajasthan was reduced by 34% compared to the maximum over the modelled period (2000–2009)–a percentage very similar to the reduction found in the statistics for the whole state of Rajasthan

Summary

Introduction

South Asia’s climate is strongly influenced by land, ocean and atmosphere interconnections resulting in strong intra-seasonal [1,2,3], inter-annual [4,5] and decadal variability in rainfall [6,7]. Climate change seems to reinforce this decadal drying: recent research linked cooling of the Tibetan anticyclone region and warming over the equatorial Indian Ocean during the recent decades to a weaker monsoon circulation [6]. Predictions for periods towards the end of the 21st century are as yet inconclusive [9,10], with models generally suggesting an upward trend in regional rainfall and an increase in inter-annual variability [11,12]. Whatever the long term trend, South Asia is facing a period with uncertainty in monsoon rainfall

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