Past and future freshwater availability scenarios and their impact on the Indian Sundarbans ecosystem and fisheries

Abstract

The Indian Sundarbans are considered one of the zones of highest vulnerability in the world in terms of climate change. About 4.43 million people living in the Indian Sundarbans face a lack of freshwater availability due to the erratic behaviour of monsoon rains, frequent cyclonic storms, intrusion of saline water, and other factors, all of which affect the fisheries and agriculture activities of this area. In this study, estimates of freshwater availability through past and predicted future rainfall and evapotranspiration change scenarios in the Sundarbans are presented. Due to the lack of high-quality in situ data, various sources of gridded rainfall and evapotranspiration data were used. Between 1948 and 2010, half of the 19 administrative blocks showed a decreasing trend of monsoonal rainfall while the rest showed an increasing trend. Freshwater availability showed a decreasing trend during the monsoon season over different blocks of the Sundarbans, which is a matter of great concern for fisheries and agricultural activities. Statistical downscaling was used to generate future rainfall and evapotranspiration scenarios, using coarse resolution Global Climate Models from the Coupled Model Inter-comparison Project, Phase Five for a smaller area like the Sundarbans. Downscaled global climate models project an increasing trend in future monsoon rainfall in both RCP 4.5 and RCP 8.5 emission scenarios. The increasing rainfall can trigger excessive run-off and flooding, which would in turn affect aquaculture infrastructure and damage lentic aquaculture productions across the Sundarbans. However, increased rainfall may expand the flood plain area and extend the feeding grounds of fish. Hence, the impact of rainfall change is quite unpredictable. Proper adaptation techniques may be required to harness the positive impacts while preventing negative effects.

Modelling to inform the conservation and management of aquatic ecosystems: A synthesis of five case studies

“…This special issue provided five case studies (Table 1) of the application of modelling to management issues in aquatic ecosystems, including fisheries (Weyl et al, 2023), aquaculture (Muralidhar et al, 2023), freshwater availability (Das et al, 2023), water quality (Zhang et al, 2023), and foodweb responses (Giacomini et al, 2023; Zhang et al, 2023). These papers do not rely on a single modelling approach but provide examples of the application of models that are tailored to the needs of the management issues of concern with the available data.…”

“…These papers do not rely on a single modelling approach but provide examples of the application of models that are tailored to the needs of the management issues of concern with the available data. These case studies range from data limited to data rich applications, making use of surplus production and statistical catch-at-age models (Weyl et al, 2023), system dynamics modelling (Muralidhar et al, 2023), downscaled global climate modelling (Das et al, 2023), size spectra (Giacomini et al, 2023), and Ecopath with Ecosim (Zhang et al, 2023).…”

“…Das et al, (2023) aimed to estimate freshwater availability in the Sundarbans region (India) under climate change scenarios to inform fisheries and aquaculture management. Their analysis of long-term trends (1948-2010) showed decreasing freshwater availability (rainfall minus evapotranspiration) during the monsoon season, with only one of 19 blocks examined showing an increase.…”