322 E.F. Lambin et al. Agriculture, Ecosystems and Environment 82 2000 321–331
1. Introduction
Land-use and land-cover change, as one of the main driving forces of global environmental change, is
central to the sustainable development debate. Land- use and land-cover changes have impacts on a wide
range of environmental and landscape attributes in- cluding the quality of water, land and air resources,
ecosystem processes and function, and the climate system itself through greenhouse gas fluxes and sur-
face albedo effects. Whilst, a few years ago, most land-use and land-cover change research was fo-
cused on land-cover conversions e.g., deforestation, urbanisation, researchers have increasingly realised
that more subtle processes leading to a modification of land cover deserves greater attention. Land-cover
modification is frequently caused by changes in the management of agricultural land use including, e.g.,
changes in levels of inputs and the effect of this on profitability or the periodicity of complex land-use
trajectories, e.g., fallow cycles, rotation systems or secondary forest regrowth.
Agricultural land intensification has been one of the most significant forms of land-cover modifica-
tion, with dramatic increases in yields being the main feature during the previous 30 years. Yields of food
crops per area of land have outpaced global human population growth Matson et al., 1997, but if current
trends are extrapolated linearly into the future, inten- sification of agriculture will have major detrimental
impacts on non-agricultural terrestrial and aquatic ecosystems Tilman, 1999; Socolow, 1999. Intensifi-
cation levels can also be an indicator of the ability of land-use systems to adapt to changing circumstances,
e.g., because of policy or climate change. For exam- ple, many extensive land-use systems are marginal in
productivity terms e.g., uplands, semi-arid regions, high latitude areas, etc. and these types of land uses
often have little capacity to adapt. This does not fol- low, however, where extensive land use is a result
of deliberate policy constraints on land that is not marginal in productivity terms. In this paper, it is con-
tended, therefore, that land-use change research would benefit from a better understanding of the complex
relationships between people and their management of land resources, and that land-use intensification is
a vital consideration in these processes. This implies that, to fully understand and predict human impacts
on terrestrial ecosystems, there is a need for more comprehensive theories of land-use change Lambin,
1997, p. 389; Lambin et al., 1999, pp. 37–46, 89. Much land-useland-cover change research has been
based on the use of models. Modelling, especially if done in a spatially-explicit, integrated and multi-scale
manner, is an important technique for the exploration of alternative pathways into the future, for conduct-
ing experiments that test our understanding of key processes, and for describing the latter in quantitative
terms. Many different modelling approaches have been adopted in the study of land-useland-cover change,
although most have been concerned with issues of land use conversion Lambin, 1997; Kaimowitz and
Angelsen, 1998. Few modelling studies have explic- itly sought to evaluate potential changes in land-use
intensification resulting from changes in management. Note, however, that economists have a long tradition
in studying agricultural intensification in relation to management practices and conditions e.g., prices of
inputs, production functions. However, most studies have not revealed the driving factors, apart from eco-
nomic incentives, that cause management to change. In this paper, the different modelling approaches that
have been used in land-useland-cover change research were examined from the perspective of their utility for
the study and prediction of changes in land-use inten- sification. After clarifying the main concepts used, the
different modelling approaches that have been used to study land-use changes are examined, case study evi-
dence on processes and drivers of land-use intensifica- tion are discussed, and a conclusion is provided on the
present ability to predict changes in land-use intensity.
2. Definitions
It is important to clarify terminology and definitions used in land-useland-cover change research. Such ter-
minology can be esoteric and, thus, affect the under- standing of land-useland-cover change research by a
broad readership. The term land cover refers to the attributes of a part of the Earth’s land surface and im-
mediate subsurface, including biota, soil, topography, surface and groundwater, and human structures. Land
use refers to the purposes for which humans exploit the land cover. Forest, e.g., is a type of land cover that
is dominated by woody species and may be exploited
E.F. Lambin et al. Agriculture, Ecosystems and Environment 82 2000 321–331 323
for land uses as varied as recreation, timber production or wildlife conservation. Furthermore, one may dis-
tinguish between land-cover conversion, i.e., the com- plete replacement of one cover type by another, and
land-cover modification, i.e., more subtle changes that affect the character of the land cover without changing
its overall classification Turner et al., 1993.
The concept of intensification in land use often, although not exclusively, refers to agriculture. Agri-
cultural intensification has been defined by Brookfield 1972 as the substitution of inputs of capital, labour
and skills for land, so as to gain more production from a given area, use it more frequently, and hence make
possible a greater concentration of production. Inten- sity is usually measured in terms of output per unit
of land or, as a surrogate, input variables against con- stant land Turner and Doolittle, 1978. Thus, one can
distinguish between input intensification, which mea- sures the increases in input variables, e.g., chemical
fertiliser, pesticides, etc., and output intensification, which measures the increases in production against
constant units of land area and time, e.g., food-tonnes or number of calorieshectarenumber of years Turner
and Doolittle, 1978, p. 298. Because of data prob- lems, surrogate measures are often employed Kates
et al., 1993, p. 12. Regardless of the measures and variables applied, any finding will vary from what
is typically thought of as intensification since meth- ods used in data gathering and analysis will strongly
influence the relationship between variables. Conven- tional methods of measurement are, e.g., frequency of
cultivation or number of harvests per plot over a stan- dard time frame after Boserup, 1965 as compared
to, e.g., farm produce-generated income per hectare as a reflection of yields per hectare Dorsey, 1999,
p. 187.
Beginning at least with von Thünen in 1842, agri- cultural intensity viewed in terms of production or
yield per unit area and time has long been regarded as a key concept in numerous explanations of agricul-
tural growth and change Turner et al., 1977; Turner and Doolittle, 1978. It had been pointed out by Kates
et al. 1993, p. 21 that long-term population growth and economic development usually do not take place
without intensification and agricultural growth, al- though intensification and agricultural growth do
not inevitably follow population growth and are not necessarily beneficial or sustainable see Mortimore
1993 for a review and a discussion of the theories of Boserup and neo-Malthusians.
3. Categories of land-use models
