southern city of Cordoba, located on the river Baetis, was also
accessible by water.
To the south of Italy, directly across the Mediterra-
nean, lay North Africa. Its proximity to Sicily and Italy
made for easy travel from one place to the other. North Af-
rican peoples had occupied Sicily before Rome took it, and
Carthage, in what is now Tunisia, was geographically close
enough—barely 100 miles by sea from Sicily—to present a
military threat. All of North Africa, including Egypt, was
also close enough to be an ideal location for Roman farms
and military installations. During the Roman Republic and
the Roman Empire much of Rome’s food came from North
Africa and Egypt. Th e climate was warm and sunny most of
the year; during the 500-year period between 200 b.c.e. and
300 c.e. the weather was especially warm, making the re-
gion extremely productive, even despite its perpetual water
shortages. Roman troops were oft en sent to North Africa to
subdue local people and consolidate Roman control of the
area. Roman generals also based troops there during Roman
civil wars, such as those involving Julius Caesar in the mid-
fi rst century b.c.e.
By the time of the empire, the warm weather zone had
reached northern France. During the fi rst two centuries
b.c.e. Roman landlords created large-scale farms in northern
Gaul, producing cereals for cities and military installations.
Th e well-being of Roman civilization depended on the gov-
ernment’s ability to grow food in its northern territories; this
made it possible to feed the armies and citizens who main-
tained order in the more far-fl ung provinces.
Rome’s more northerly territories, Germany and Britain,
never received the attention or the level of Roman control
that the more southern possessions did. Th is neglect was due
to a combination of geographic distance from Rome and a
colder climate. Germany lay north of the Alps and east of the
Rhine. It was densely forested and had a colder climate than
Italy, making it unsuitable for Mediterranean agriculture.
Britain was separated from Europe by the English Channel,
so Romans could only reach it by sailing. Th e sea voyage was
diffi cult and dangerous and proved a substantial disincentive
to settlement. Th e sheer distance of Britain from Rome also
made it diffi cult to govern the province. Britain’s climate was
much colder and wetter than that of the Mediterranean, and
Mediterranean crops did not thrive there.
Th e warm period persisted until about 400 c.e., when
conditions suddenly grew cooler and wetter. Th e Mediterra-
nean zone moved back south into Italy, and southern Europe
ceased to be suitable for Roman agriculture. At this point it
became clear how much the Roman Empire had relied on the
climate to sustain its control of Europe. Britain and Germany
were the fi rst regions to be abandoned. Gauls and Germans
began encroaching from the north again as the warm climate
band crept south. By the late 400s the Mediterranean climate
zone had moved entirely south of the European continent;
Mediterranean crops continued to thrive in North Africa,
but Italy itself now had a colder continental climate. Romans
could no longer withstand the attacks of Gauls and Germans,
and the Western Roman Empire fell apart, at least in part the
victim of climate change.THE AMERICAS
BY AMY HACKNEY BLACKWELL
In the Americas diffi culty of travel and isolation from other
cultures kept people from developing large civilizations until
well aft er the ancient period. Humans came to Alaska from
Siberia during an ice age between 18,000 and 13,000 b.c.e.
By 10,000 b.c.e. they had reached the southern tip of South
America and inhabited all parts of both American conti-
nents. By 8000 b.c.e. the climate had warmed considerably all
around the world, the passage between Asia and the Americas
was blocked, and Americans lived separately from humans
on other continents until Europeans crossed the Atlantic in
ships in the 1400s.ALASKA
Humans moved into the Americas sometime between 18,000
and 13,000 b.c.e. Th ey appear to have traveled from Siberia
across the Bering Strait to what is now Alaska, though wheth-
er they walked across a land bridge, paddled in boats, or com-
bined the two methods is a matter of debate among scholars.
In any case, the fi rst place humans inhabited in the Americas
was western Alaska. Western Alaska has a long coastline on
the Bering Sea. Many inlets and bays lie along the coast. Th e
Yukon River empties into the sea in southwestern Alaska,
creating a wide delta. To the east the Aleutian Islands stretch
in an arc westward across the northern Pacifi c Ocean. Early
settlers probably stayed in these areas, fi shing and hunting as
they had done in Siberia.
Northern Alaska is very cold. Th e Brooks Range of
mountains runs from east to west, south of the northern tun-
dra. North of Alaska is the Arctic Ocean. People living in this
region had to adapt to long winters during which the sun al-
most never appeared. Th e ground is permafrost, never thaw-
ing even in summer, and agriculture is impossible. Central
Alaska is heavily forested and is home to many wild animals.
Th e Alaska Range runs along Alaska’s southern coast, which
is pocked with glaciers and fj ords. Th is coastal area has rich
fi sheries that attracted human settlers who already had the
skills needed to live there.
Th e weather in Alaska can be very bad. Th e winters are
long and cold, even in the southern areas. Many of Alaska’s
rivers stop fl owing entirely in the winter. Th e western and
southern coasts have cool summers and cold winters. Fog
and storms on the ocean are common, especially in winter;
these weather phenomena killed many ancient sailors and
kept others from going to sea in the winter.NORTHERN NORTH AMERICA
From Alaska humans walked into what is now Canada’s Yu-
kon region. Th is area is cold, forested, and mountainous. Th e264 climate and geography: The Americas