Swimming against the rising tide: the use of cetaceans for evaluating the ecological impacts of declining freshwater supplies and global climate change in Bangladesh. Unpublished Report. Bangladesh.

Project Details

Volunteer Name : Smith et al.
Category : ,

Project Description

Abstract: The effects of climate change are extremely difficult to predict and monitor because they are complex and operate on broad ecological scales. In biological monitoring, the assessment of complex processes is commonly approached through the use of indicator case-populations or species. These are assumed to integrate changes over time and space, thus reducing random variance of physical measurements, and to be sensitive enough to warn about changes earlier than the usual “spot” measurements. Cetaceans are normally considered to be poor indicators species due to their generalist capacity for adapting to environmental changes. However, the manner by which these large, mobile predators respond to environmental changes (e.g., by altering their movement patterns and foraging behaviour) may be particularly informative for identifying biologically significant environmental attributes, and for monitoring alterations in the spatial and temporal availability of these attributes. These responses may then be used to generate targeted and testable hypotheses, prioritize investigative efforts and identify local aggregations of biological productivity for site-based protection. The community of cetaceans inhabiting the inshore waterways of the Sundarbans mangrove forest and adjacent coastal waters in Bangladesh is composed of species that distribute themselves according to the physical characteristics in their environment (e.g. salinity, turbidity, depth, and channel configuration). Cetaceans farther offshore in the Swatch-of-No Ground, a 900m+ deep submarine canyon, may also show distinct distributional responses to a decline in the availability of nutrients associated with reduced freshwater discharge and alterations of current patterns that could suppress upwelling. Given that these waters support a diverse and relatively abundant cetacean community that will be dramatically affected by declining freshwater flows and climate change, it is concluded that the animals may be an efficient model for gauging the effects of these anthropogenic threats on the same species elsewhere in their range, and possibly other cetaceans subject to similar environmental pressures. In addition, studies of this cetacean community may provide fundamental insights on the nature and magnitude of more general ecological effects (e.g. changes in the abundance and species composition of lower-level trophic communities) and a basis for developing appropriate management responses. Baseline information and trained local expertise is available, thus offering a solid ground for long-term studies and monitoring.