[William Terrell]

I think of the coast as being below 250 feet elevation, for the purposes of all the land based ice in the world melting.

[curiosity]

I would venture to say that perhaps not a majority, but a very large fraction of the world's population lives below 250 feet in elevation and near the coast.

Think about some of the world's largest cities: New York, Tokyo, Singapore, Shanghi, Hong Kong, etc, etc, etc.

[curiosity]

FYI:

"44% of the world's population (more people than inhabited the entire globe in 1950) live within 150 kilometres of the coast. In 2001 over half the world's population lived within 200km of a coastline... The United States has clearly mapped its population expansion. In the United States, around 53% of the population lives near the coast and since 1970 there have been 2000 homes per day erected in coastal areas."

Source:

http://www.oceansatlas.org/servlet/CDSServlet?status=ND0xODc3JmN0bl9pbmZvX3ZpZXdfc2l6ZT1jdG5faW5mb192aWV3X2Z1bGwmNj1lbiY1NT0yMSYzMz0qJjM3PWtvcw~~

Anyway, my point is, even if melting land ice only reduces the livable land mass by a small amount, it will still cause a huge displacement since such a large fraction of the population lives near the coast.