“Bangladesh, the Poster Child“. B.Quartero guest posts for Anthony Watts that Bangladesh’s ‘climate risk’ is simply about living on a massive river delta. The delta will magically stay balanced with changes in sea-level because of sediment deposition, “almost by definition”. So don’t worry about them!
This is classic past equals present don’t-worryism. Natural conditions have not been maintained. Reduced sediment volumes in the Ganges-Brahmaputra delta owing to climate change means that we have no clear idea if sediment deposition will keep pace with sea-level rise. But they’re all poor and brown, so it doesn’t really matter anyway. “Learn to swim!”
Geologically speaking, deltas “sink” if sediment intake doesn’t balance compaction + sea-level rise and “grow” laterally if sediment intake exceeds that balance. So can the 1 mm/year of flood deposition continue? Will it keep pace with sea-level rise and sediment compaction? B.Quartero is optimistic, but offers no evidence in support of this (even a single reference would be start).
Here’s something brought to my attention, from Nicholls & Goodbred (2004), Towards Integrated Assessment of the Ganges-Brahmaputra Delta:
This early-Holocene mangrove facies has been recognized across the entire delta front indicating that the coastal ecosystem was widespread, and radiocarbon dates and deposit thickness indicate the environment’s long-term stability (GOODBRED and KUEHL, 2000b). In terms of delta response, that the Ganges-Brahmaputra system was able to maintain coastal stability under 30 meters of sea-level rise at rates exceeding 1 cm/yr is not a result recognized by traditional deltaic models.
Let’s keep our fingers crossed that the future situation be stable enough to allow millions of people to live there and grow a crop a year.