Page 12 - Respond 2018 Magazine

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How many?
Prime minister Hasina’s forecast of 30 million
climate migrants is widely disputed, inside
and outside Bangladesh.

Analysis by Climate Central, a US-based science outreach
organisation, paints a less dramatic picture. It finds fewer
than a million Bangladeshis living within one metre above sea
level. Under five metres, the number is still less than 30m.

“It is a troublingly large difference,” says Ben Strauss, a Some inhabited parts of Bangladesh are already below sea level, with
biologist by background who leads Climate Central’s sea embankments to keep the water out
level work.

The government estimate has been in currency for at least
seven years, its source apparently lost along the way. An
official in the environment department could not say exactly
where it came from, suggesting it was a rough assumption
based on the population of 19 coastal districts.

Climate Central’s “Surging Seas” model is more transparent
and there are identifiable reasons why it might err on the
conservative side.

Firstly, Strauss explains, they use land elevation data from Up to one metre of sea level rise globally could happen this century
NASA’s Shuttle Radar Topography Mission (SRTM). It is the
best publicly available dataset for Bangladesh, but it has
limitations. The satellites cannot tell the difference between
the tops of buildings or trees and the soil. In places where
there is more precise light detection data to compare with,
SRTM has been found to overstate the height of the land on
average by more than 2 metres.

Secondly, it represents a narrow definition of those affected
by sea level rise. Surging Seas maps out homes that will fall
below the high tide mark or be exposed to annual flooding.
But a household does not have to be under water for its
members to feel the impacts of the creeping tide. Land subsidence means that some areas could experience faster sea
level rise than the global average. The western Ganges delta is thought
to be particularly vulnerable, although data is limited
All along the coast, saltwater intrusion is hitting crop yields,
contaminating drinking water and eroding infrastructure.
Other things being equal – and the amount of freshwater
India draws from upriver plays a major role – sea level rise
will push salinity further inland.

(It is worth mentioning that rising seas are not the only
climate change impact Bangladesh faces, just the most
predictable. Earlier this year, abnormally heavy pre-
monsoon rainfall wiped out 2m tonnes worth of rice crops in
the northeast. Flooding, drought and ocean acidification are
rising threats.)
In the far future, 2C of global warming is expected to unleash 4.7m
The flipside is that Surging Seas does not account for the of sea level rise, swamping much of Bangladesh. This could take
thousands of kilometres of embankments that surround between 200 and 2,000 years. (illustrations based on Surging Seas
data visualisation)
coastal settlements. Indeed, the ability and willingness