The Dictionary of Human Geography

access to knowledge-rich workers will seek to
invest in clusters, such as Silicon Valley
(Saxenian, 1994), rather than rustbelt districts
of a country. Those seeking access to markets
will seek outagglomerationswhere demand
is high, such as advertising and law producer
service firms that congregate in theworld
cities of London and New York (Sassen,
2006). This means, however, that those
regionsthat fail to attract investment can
become backwaters of the global economy, as
has been experienced to a certain extent in
the North East of England since the closure
of the coal mines in the 1970s and 1980s
(Hudson, 2005) and the American Rust
Belts, around Detroit in particular (Glasmeier,
2005). jf

Suggested reading
Shatz and Venables (2000).

irredentism The claim by the government,
or by political groups, of one country that a
minority living in a neighbouring country
belongs instead to it because of historical and
cultural connections. Though at times the
minority may live in peace within the neigh-
bouring country, in other contexts irredentist
movements may mount a campaign to ‘unite’
the minority, leading to border disputes,
active guerilla-like conflict (as in Northern

Ireland), and even war. The term originated

from a disputed part of Austria in 1871, which

Italian nationalists calledItalia irredenta,or

unredeemed Italy. The 1990s war in the for-

mer Yugoslavia was driven by a combination

of irredentist claims. cf

Suggested reading

Ambrosio (2001).

isolines Lines on amapdescribing the inter-

section of a real or hypotheticalsurfacewith

one or more horizontal planes. On atopo-

graphic map, typically compiled from aerial

photographs by stereocompilation (Lyon,

Falkner and Bergen, 1995), each isoline, or

contour, represents a constant elevation, and

because the vertical interval is constant, their

relative spacing is a readily visualized indicator

of slope. On a statistical map, isolines may be

threaded manually through a network of data

points or plotted automatically by an interpol-

ation algorithm, which provides comparative

consistency and gives the map author some

control over the appearance and reliability of

the map (Schneider, 2001). Spot heights are

occasionally added to emphasize local minima

and maxima. mm

Suggested reading

Yang and Hodler (2000).

Gregory / The Dictionary of Human Geography 9781405132879_4_I Final Proof page 396 31.3.2009 7:05pm

IRREDENTISM