The Dictionary of Human Geography

the brink of exceeding the Earth’scarrying
capacityand precipitating widespread social
and ecologicalcrisis. Although the report
looked at resources in addition to those dir-
ectly related to agricultural production, its
argument was essentially a Malthusian one
(seemalthusian model). It was an important
milestoneinthedevelopmentofneo-Malthusian
trends in modern environmentalism, such as a
concern with the ‘population bomb’, as well as
an impetus towards calls for a ‘steady-state
economy’ and the development of the field of
environmental economics.
Belief in absolute limits to economic growth
based on material scarcity, and the politics
that follow from such a position, constituted
a direct challenge to the Promethean views of
human activity arguably shared by neo-clas-
sical economics and classical Marxism, both
of which denied the necessity of such absolute
material limits to human productivity. In
geography, David Harvey (1974a) and others
strongly criticized resurgent neo-Malthusian
models for overlooking issues of distribution,
justice, scale, changes in technology and prod-
uctivity, and other factors that would compli-
cate or undermine their predictions. A
significant amount of geographical work over
the subsequent several decades has essentially
reproduced and elaborated this debate in vari-
ous arenas. Perhaps the most notable example
is the rapid growth of scholarship centred on
the concept ofenvironmental security. This
literature is constituted largely by debates be-
tween dominant neo-Malthusian views, which
continue to articulate theories of how demo-
graphically fuelled conflicts over increasingly
scarce natural resources will produce escalat-
ing violence and geopolitical instability (see
resource wars), and more critical voices,
which continue to insist on attention to the
social causes, contexts, and complexities of
such scenarios (see Dalby, 2004).
Other work in geography, though, has revis-
ited the question of natural limits with increas-
ing theoretical nuance, moving beyond the
simple rejection of it in much of the Marxist
tradition. Theorists of natural resource indus-
tries in particular have begun to take nature’s
materiality seriously by attempting to under-
stand not only the constraints, but also the
affordances and surprises, that biophysical sys-
tems present to human activities in specific
circumstances, developing concepts such as
appropriationism, substitutionism, eco-regu-
lation, hybridity, and the formal versus the
real subsumption of nature to capital (see
Boyd, Prudham and Schurman, 2001). Nat-

ural ‘limits’ are thus increasingly understood

and investigated as differentially malleable

conditions of possibility for particular forms

of human activity, rather than as absolute

and universal barriers. Such a perspective has

proved compatible with recognition of the ne-

cessarily political and social character of any

claims about natural limits, as emphasized in

the literature on social constructionism. jm

Suggested reading

Benton (1989); Boyd, Prudham and Schurman

(2001).

linear programming Atypeofoptimization

modelused to find the optimal solution to a

wide variety of economic, business and geo-

graphical problems, such as the minimum total

transport cost of shipping goods through a geo-

graphicalnetwork.Optimizationmodelshavean

objective function(thequantitytobeminimized

ormaximized)andasetofconstraintsthatdefine

thepossibilitiesandrequirements(limitsonsup-

ply, demand requirements, route character-

istics). In linear programming both the

objective function and the constraints are linear

functions and this makes solution fast and easy,

even for very large problems. Thetransporta-

tion problemis a special form that has many

geographical applications. lwh

Suggested reading

Greenberg (1978); Killen (1979, 1983).

linkages The contacts and flows of informa-

tion and/or materials between two or more

individuals. The term is widely used in both

industrial geographyand the geography of

servicesto indicate inter-firm interdepend-

ence and its effects on location choice (see

agglomeration). A firm’s linkages can be

divided into: (1) backward, which provide

goods and services for its production activities;

(2)forward, links with customers purchasing

its products; and (3)sideways, interactions

with other firms involved in the same pro-

cesses. Membership of such networks in

increasingly seen as crucial to success and

survival for a firm, especially a small firm.

(See alsointegration). rj

literature Although the meanings of this

term have varied widely, two have been of

special interest to geographers: (a) imaginative

writing, especially that deemed to be of espe-

cially high quality or status by a critical estab-

lishment; and (b) published scholarly work on

a particular topic.

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LITERATURE