immigrated to the United States in the past four centuries, with the majority arriv-
ing in the past 150 years. This trend continues, as in 2009 more than 38 million
American citizens, or well over 10 percent of the total, were foreign born. Of
course, other countries also are “nations of immigrants” as well, most notably
Australia, Canada, and some Latin American countries like Brazil and Argentina.
Rural to urban migration in Great Britain as a result of theagricultural revolu-
tionsin the early 19th century provided labor that fueled the industrial revolution,
a process that was repeated to some extent in every other economically advanced
country, and that continues to occur to a significant degree in the developing world.
This migration provided the labor resources to build the modern global economy,
and labor migratory flows continue to be vital to the economic progress of many
nations.
On the other hand forced migration, or population shifts brought about by war
or decolonization, resulted in millions of deaths in the 20th century alone. At the
conclusion of World War II, millions of ethnic Germans living in theshatterbelt
of Eastern Europe were forced to migrate back to Germany, even though their
ancestors had lived in the region for generations. The partition of British India in
1947 set in motion one of the largest migrations in modern times with some 12 mil-
lion people shifting between India and Pakistan, along with an estimated one mil-
lion deaths. Human beings migrate because of both hope and fear; and indeed, the
mass movement of people is a recurrent theme in the history of humanity, bringing
advancement and development along with calamity and cruelty.Monsoon
Somewhat less than half ofEarth’spopulation lives in monsoon zones and is
highly dependent on monsoonprecipitationfor agricultural production. Religious
festivals are timed to the onset of the wet and dry monsoons. Failure of monsoon
rains or flooding from monsoon rains raise the specter of famine.
Monsoon is a commonly used but misunderstood term. One might hear an
acquaintance talk about “today’s monsoon” out of a Great Plains thunderstorm,
but the term was not originally used to convey the sense of prodigious wetness.
The word is derived from the Arabicmausammeaning “season” and referring to
the seasonal reversal of wind directions in the arid Arabian Sea and western Indian
Ocean. Sailors were able to reliably time their trading trips by this expected fea-
ture of the atmosphere. Pronounced seasonal wind reversals are present in much
of the world, but the term monsoon now most properly refers to a climatic regime
of reversal of seasonal winds bringing alternating seasons of wetness and dryness.230Monsoon