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GEOGRAPHYDelta Danger
Newly calculated elevation means
millions of residents may need
to leave Vietnam’s Mekong DeltaA stunning 12 million people could be
forced to retreat from rising seas in Viet-
nam’s Mekong Delta within half a century.
Geographer Philip Minderhoud and his
colleagues at Utrecht University in the
Netherlands arrived at this conclusion after
analyzing ground-based topography mea-
surements to which outside scientists’
access was limited for years. The new
analysis, published in August in Nature
Communications, shows that the Mekong’s
elevation above sea level averages just
0.8 meter—almost two meters lower than
commonly cited estimates.
The locally measured figures more than
double the number of Vietnamese people
living in low-lying areas that will be inun-
dated as the earth’s climate warms, with
some places likely to be underwater in only
a few decades.
For elevation readings in many develop-
ing countries, international researchers
rely on freely available global satellite data
be cause there are few on-the-ground
records—and because some governments
closely guard their own data. But satellite
elevation readings can be notoriously unre-
liable in low-lying areas. Torbjörn E. Törn-
qvist, a geologist at Tulane University, says
this is a concern not just for the Mekong but
also for other mega deltas inhabited by tens
of millions of people (such as the Ganges in
Bangladesh and India and the Irra waddy in
Myanmar). “My hope is that these findings
will wake people up to the fact that we’re
BRUNO DE HOGUES dealing with terrible data sets that aren’tGetty Images© 2019 Scientific American