Reproduced, with permission, from:
Turner, B. L., R. H. Moss, and D. L. Skole, eds. 1993. Relating land use and global land-cover change: A proposal for an IGBP-HDP core project. Report from the IGBP-HDP Working Group on Land-Use/Land-Cover Change. Joint publication of the International Geosphere-Biosphere Programme (Report No. 24) and the Human Dimensions of Global Environmental Change Programme (Report No. 5).Stockholm: International Geosphere-Biosphere Programme (IGBP) Secretariat, Royal Swedish Academy of Sciences.
IGBP Report No. 24
Published in Stockholm, February 1993, by the International Geosphere-Biosphere Programme: A Study of Global Change and the Human Dimensions of Global Environmental Change Programme
Contents Preface 1. Introduction and Definitions 2. Land Cover and the Global Environment Land-cover changes and impacts on biogeochemistry, climate, and ecological complexity The need for data on the distribution and patterns of change 3. Land Use and Global Change Changes in land-use patterns 4. Human Causes of Land-Use Change Candidate driving forces of land-use change Knowns and unknowns A schema for relating land use and changes in land cover 5. An Illustrative Case: Deforestation in Amazonia The underlying human driving forces Linking human driving forces to land-cover change 6. Research Plan Focus 1: The Situational Assessment Focus 2: Modelling and Projecting Global Land-Use and Land-Cover Change Focus 3: Conceptual Scaling Data Development Activities Bibliography Acronyms and Abbreviations Terms of Reference List of IGBP Reports List of HDP Reports
Understanding the significance of land-cover changes for climate, biogeochemistry, or ecological complexity is not possible, however, without additional information on land use. This is because most land-cover change is now driven by human use and because land-use practices themselves also have major direct effects on environmental processes and systems.
Land-use is obviously determined by environmental factors such as soil characteristics, climate, topography, and vegetation, but it also reflects land's importance as a fundamental factor of production. Thus understanding past changes in land use and projecting future land-use trajectories requires understanding the interactions of the basic human forces that motivate production and consumption. High population growth or increasing consumer demand combine with varied land-tenure arrangements, degrees of access to financial capital, shifts in international trading patterns, and local inheritance laws and customs to produce unique land uses in different places and times. Research on how such human factors interact in driving land use will improve projections of land use and our comprehension of human responses to environmental changes. For the economic, social, and behavioral sciences, it will also provide an opportunity for basic research into the factors that shape individual and group behaviour.
Evaluating the causes and the consequences of changes in land use and land cover is becoming an urgent need for more than the academic research community. At the 1992 UN Conference on Environment and Development, a framework convention on climate change and a convention on biodiversity were signed, as was a declaration of principles on forests; while no formal action was taken on desertification, a broad agreement was reached to work toward a conference and a convention in the near future. Changes in land use and land cover are significant components of all the problems addressed by these agreements, yet we do not have enough knowledge about such phenomena to decide how these conventions should best be structured and which of their proposed elements are likely to be effective. At present, we are unable to answer even the most basic questions. For example: are the world's deserts really spreading, and if so, why? Are population pressures extending land uses, such as agriculture or settlement, to areas that cannot sustain these uses? How are deforested areas of land used, and what are the implications of these different uses for the net emission of greenhouse gases?
Recognizing the importance of studies of changes in land use and land cover in developing our understanding of global environmental change, the International Geosphere-Biosphere Programme (IGBP) and the Human Dimensions of Global Environmental Change Programme (HDP) formed an ad hoc working group in early 1991 to investigate the possibilities of a joint effort by natural and social scientists to study the issue. The members of the working group were:
The working group recommended that a joint IGBP-HDP Core Project Planning Committee be established to develop an interdisciplinary research programme involving social and natural scientists to project future states of land cover. This recommendation was based on the following conclusions of the working group:
This report presents the main findings of the working group. It describes the research questions defined by the working group and identifies the next steps needed to address the human causes of global land-cover change and to understand its overall importance. The plan outlined by the working group calls for the development of a system to classify land-cover changes according to their socio-economic driving forces. Selected case studies will be carried out according to a common protocol and will provide detailed settings in which to refine the classification of socio-economic situations and land-cover changes. In the final step of the plan, the knowledge gained regarding the human determinants of land use and the driving forces of land-cover change will be used to develop a global land use and land-cover change model. The model will be designed to link to other global environmental models. In all of it activities, the CPPC will pay special attention to defining the data needed to support research on human forcing of land-cover change.
Drafts of this report were reviewed by the Scientific Committee of the IGBP in Rosenheim, Germany (March 1992) and Durham, New Hampshire (September 1992), and by the Standing Committee of the HDP in Madrid (October 1992).
For further information about this project, please contact: Land-Use/Cover Change Project Planning Office, Graduate School of Geography, Clark University, 950 Main Street, Worcester, MA 01610-1477, USA; Tel: +1 508 793 7336, Fax: +1 508 793 8881, E-mail: BTURNER@VAX.CLARKU.EDU (Internet), B.TURNER (Omnet).
While most land-cover changes are undertaken at the spatial scale of a field or a homestead, these discrete changes have attained global significance because they are repeated frequently. In this sense, local changes in land cover reach a global dimension by patchwork addition, in a process identified as globally cumulative (Turner et al. 1990b). Another example of such a cumulative change is the current magnitude and rate of loss in biodiversity.
Cumulative land-use and land-cover changes not only have considerable local and regional environmental significance in themselves, but they also have links to globally systemic environmental changes (e.g., climate change). For example, the increased use of irrigation and nitrogen fertilizers are both associated with increases of methane release. The relationship between deforestation and afforestation processes, and the role of the terrestrial biosphere as a source and sink of atmospheric CO}{\f22\dn4 2}{\f22 , are not well understood - yet are of critical importance in modelling future changes in atmospheric composition. (Bouwman 1990a, 1990b; Houghton et al. 1987; Melillo et al. 1990)
A better understanding of the physical, biological, and chemical processes involved in changes in land use and land cover is therefore crucial to developing a predictive understanding of globally systemic changes. Changes in land cover cannot be understood, however, without a better knowledge of the land-use changes that drive them, and their links to human causes (Ojima et al. 1991).
Relating the human driving forces of land use to changes in land cover is difficult because of the complexity of the interactions between human and environmental factors, and the different ways that these interactions unfold in particular areas of the world. The complexity of these situations (here used to mean the interactions of causes in their spatial and temporal settings) makes it difficult to identify simple relationships between human driving forces and global environmental change, or between environmental changes and their impacts on society. Linking the human and the environmental, even within the restricted field of land-use and land-cover change, requires a careful assessment of the variations of these situations as the key to understanding the general patterns of global change.
This report proposes a programme of research that will develop projections of land use and future states of land cover by linking the physical and human dimensions of this issue. The objective of this project is to improve our understanding of the human driving forces of land-use change, and hence changes in land cover.
In concentrating on the human causes of land-use and land-cover change, the project selects one subset of an integrated system of land-use/cover problems for detailed study (Fig. 1). Human driving forces operate together with natural forces to shape land uses and the associated land covers. The environmental consequences of changes in land use and cover include direct feedback effects on land cover as well as contributions to other global environmental changes. Any change in global conditions, such as projected climate warming, will in turn have impacts on the land uses and covers in question as well as on the driving forces. The "human dimensions" of the problem consist of two linked subsets: human driving forces that can cause change, and human responses to change.
The proposed project concentrates on human driving forces for several reasons. The amount of research effort devoted to response, largely in the form of environmental or climate impact assessment, has to date been much larger than that focused on human cause. Impact assessments analyze the likely interactions of environmental change with existing social structures and processes. Because these structures and processes include the very driving forces that initially brought about the environmental change in question, a better understanding of driving forces would also improve the reliability of impact assessments.
Before presenting the rationale and structure for the proposed project in greater detail, a few definitions are needed to establish a common terminology.
The magnitude, spatial scale, and pace of land-cover change have escalated, particularly over the last 300 years (Table 1). While estimates of human-induced changes in land cover vary according to the system of classification that is employed (e.g., whether a particular parcel of land is classified as "forest" or "shrub"), several examples illustrate the general scale of these changes. Over the past three centuries, human activities have resulted in:
While the direct effects of land-cover changes on biogeochemical flows and global budgets are not adequately understood, it is generally accepted that:
Attempts to develop global budgets of such radiatively important trace gases have suffered from the lack of spatial data. Regional extrapolation of trace gas fluxes has frequently been based on a very limited number of "representative" measurements. Matson et al. (1989) have argued that global budgets could be greatly improved by giving more attention to spatial and temporal variability. They argue for analyses based on spatial gradients, where functional relationships between fluxes and land cover, soils, climate, and disturbance could be derived.
The potential impacts of land-cover changes on climate can be only crudely assessed at present. Attention to date has focused on the effects of deforestation of large areas of tropical forest, with regional climate models predicting significant continental-scale consequences for surface air temperature, precipitation, and run-off. The spatial arrangement of land-cover change, particularly deforestation, influences the results of such model simulations: deforestation distributed as a few large blocks has a much greater influence on water and energy budgets than the same area distributed as many widely scattered small patches (Henderson-Sellers 1987; Henderson-Sellers and Gornitz 1984). Linkages between global climate conditions and land-cover changes are more speculative, since the grid size for the general circulation models (GCMs) is very large (mostly more than 10,000 km}{\f22\up6 2}{\f22 ) and biospheric feedback effects have not yet been included in their formation.
Finally, land-cover changes in both tropical and temperate regions have important implications for species diversity and community composition, and have caused a dramatic increase in the rate of species extinction (Ehrlich and Wilson 1991). Effects on biodiversity depend on the severity of the habitat disturbance, among other factors. In the case of tropical deforestation, such additional factors include the biogeographical history of the locality, its previous exploitation, the total area of forest conversion, the amount of forest fragmentation, the conversion process, and the rate of conversion. Quantifying fragmentation requires an understanding of the spatial arrangement of cleared areas (Soule 1991; Wilson and Peter 1988).
Additional data on land cover and land-cover change are therefore required. One of the highest priorities of the land-use and land-cover change communities is to acquire improved data and develop better means of monitoring on-going changes in land use and cover. Townshend (1992) outlines some of the characteristics of a land-cover data set that would meet a number of global change research requirements.
In part, this is because most land-cover modification and conversion is now driven by human use, rather than natural change. In this sense, land-cover change is an immediate response to land-use changes, as all studies and modelling efforts demonstrate (e.g., Grainger 1990). The diversion of net primary production to meet human wants usually requires alterations of nature (e.g., Vitousek et al. 1986). The scale of land use for such appropriation is so great that nearly all land cover is likely to be intensively managed by the middle of the next century, other than in mountainous, polar, and desert regions. To understand human-induced change in land cover, therefore, requires an understanding of its underlying social causes (Houghton, Lefkowitz and Skole 1991; Lugo et al. 1987).
But land use practices also have major direct effects on other global environmental changes. Variations in agricultural practices, for example, have very large impacts on biogeochemistry. Adding organic matter to rice-paddy soils has been reported to result in an 22-fold increase in methane emission (Cicerone et al. 1992). Variation in the timing and frequency of flooding and drainage of rice paddies during the growing season has been demonstrated to increase methane emission 12 times (Sass et al. 1992). Thus variation in agricultural practices is a likely explanation for differences in the measurement of trace gas flux in different stands of the same crops. Accounting for the biogeochemical impacts of variations in land use will be important in establishing accurate global budgets for greenhouse gases.
This is especially true considering that most of the Earth's land is already managed, if only peripherally or haphazardly. Of the Earth's total land surface (around 130 million km}{\f22\up6 2}{\f22), roughly 40 percent of the land cover has been extensively modified or converted for production or habitation, while only 25 per cent remains in a near-natural condition.
Certain land uses have significant impacts out of proportion to their spatial extent. Settlements, for example, emit a large variety of chemical pollutants, which can locally exceed threshold levels for safe human habitation. They also exert enormous influence on their hinterlands, exacerbating or lessening rural land-use changes. The human management of wetlands also has far-reaching impacts on water regimes, biodiversity, and biogeochemistry.
Cropland has increased in area by about 12 million km}{\f22\up6 2 }{\f22 over the last 300 years, at expense mostly of forest, but also of some grasslands and wetlands (Myers 1991; Richards 1990). This change has been accompanied by other impacts, such as the depletion and pollution of groundwater. Despite recent deforestation in parts of the tropics for livestock production, the area of rangeland and pasture has remained virtually the same over the last 300 years. The intensity of livestock production has increased significantly, however, creating substantial modifications of grassland ecosystems (including both enrichment through fertilizers and degradation through overgrazing).
Cropland expansion will undoubtedly continue in the near future, but land-cover modification, through increasing intensification of agriculture, is likely to be of greater importance than further land-cover conversion (Ruttan 1993). Most of the prime agricultural lands of the world, with the exception of some areas in the tropics, are already cultivated, and major increases in food production are likely to come from yield improvements on these lands through the application of fertilizers, pesticides and herbicides, and irrigation. Irrigation of cropland has expanded some 24-fold over the past 300 years, with most of that increase taking place in this century. This practice has increased methane emissions, while the increasing frequency of land tillage world-wide has affected soil carbon (e.g., Cole et al. 1989; Rozanov et al. 1990) We know very little about the overall land-cover and environmental impacts of the intensification of cultivation, although its significance through greenhouse gas emissions to global environmental change is apparent (Vitousek and Matson 1992; IGBP 1990).
General global trends in land-use changes are characterized by considerable temporal and spatial variations. Although the total area of rangeland and pasture is at present relatively stable, these uses are expanding in tropical Africa and Latin America while shrinking in Europe, North America, and Southeast Asia (Richards 1990). The great expansion in croplands over the last 300 years began with the European settlement of North America and Australia, continued with expansion in the former USSR, and more recently has been concentrated in the tropical world (Wolman and Fournier 1987). Croplands currently appear to be decreasing in the developed world (Europe and North America) and increasing in the former socialist bloc and the less-developed world. This spatial pattern is important because it affects different kinds of land cover (e.g., midlatitude versus tropical forest).
Documentation of land-use patterns for several regions of the world exists for the past 80-100 years, but very little of this information has been used to investigate the regional and local dynamics of major land uses (cropland, livestock raising, settlement), regionally important sub-classes of these uses (such as paddy cultivation), or the modifications in land cover brought on by the intensification of agricultural processes.
Human activities that make use of, and hence change or maintain, attributes of land cover are considered to be the proximate sources of change. They range from the initial conversion of natural forest into cropland to on-going grassland management (e.g., determining the intensity of grazing and fire frequency) (Schimel et al. 1991; Hobbs et al. 1991; Turner 1989).
Such actions arise as a consequence of a very wide range of social objectives, including the need for food, fibre, living space, and recreation; they therefore cannot be understood independent of the underlying driving forces that motivate and constrain production and consumption. Some of these, such as property rights and the structures of power from the local to the international level, influence access to or control over land resources. Others, such as population density and the level of economic and social development, affect the demands that will be placed on the land, while technology influences the intensity of exploitation that is possible. Still others, such as agricultural pricing policies, shape land-use decisions by creating the incentives that motivate individual decision makers.
Interpretations of how these factors interact to produce different uses of the land in different environmental, historical, and social contexts are controversial in both policy-making and scholarly settings. Furthermore, there are many theories regarding which factors are the most important determinants. Particular controversy arises in assessing the relative importance of the different forces underlying land-use decisions in specific cases (e.g., Kummer 1992). For example, apparent dryland degradation could be the result of: overgrazing by increasingly numerous groups of nomadic cattle herders; an unintended consequence of a "development" intervention such as the drilling of bore holes which increases stress on land close to the wells; or the political clout of groups that, through governmental connections, are able to over-exploit land belonging to the state or local communities (Pearce 1992; NERC 1992). Identifying a particular cause may have implications for the rights of competing user groups or the formulation of policy responses.
The first three have been linked to environmental change in the I = PAT relationship that considers environmental impact (I) to be a function of population (P), affluence (A), and technology (T) (Commoner 1972). The relationships of these three categories of driving forces with environmental change have been statistically analyzed. Some of this work specifically addresses land-use and land-cover change (Ambio 1992; Meyer and Turner 1992) and suggests measures for each category: respectively, population density, GNP or GDP per capita, and energy consumption per capita.
Of these three categories of driving forces, population produces the most controversy. It is, however, one of the few variables for which worldwide data of reasonable accuracy are available, providing a basis for statistical assessments of its role in various kinds of environmental change (e.g., Ambio 1992). At the global level of aggregation, the neo-Malthusian and "cornucopian" positions use the same data to reach opposite conclusions: that population growth is or is not a cause of environmental damage (Boserup 1965, 1981; Ehrlich and Ehrlich 1990; Ehrlich and Holdren 1988; Simon 1981). At the regional scale, several studies relate population growth and deforestation in developing countries in the tropics (e.g., Allen and Barnes 1985; Palo 1990; Rudel 1989), although their findings and methods have been questioned (Kummer 1992).
Comparative assessments of population and land use suggest that: (i) population growth is positively correlated with the expansion of agricultural land, land intensification, and deforestation, but (ii) these relationships are weak and dependent on the inclusion or exclusion of statistical outliers (Bilsborrow and Geores 1991; Bilsborrow and Okoth-Ogendo 1992). Sub-continental comparisons for Africa have led Zaba (1991) to conclude that population density and growth ranked below environmental endowment and economy as factors in environmental degradation. Population density was found to be related to agricultural expansion and intensification everywhere, but only in some regions to deforestation. Detailed studies of specific regions for example, modelling exercises with Amazonian data likewise indicate subtle and varying relationships (Jones and O'Neill 1992; Skole 1992).
The interactions of population, affluence, and technology as causes of environmental change have been explored extensively (for implications appropriate for land-use, see Lee 1986), but research on the direct association of affluence or technology with landuse change is not as common. This is because of the paucity of globally comparative data for statistical assessments and because of the common assumption that level of affluence or technology do not by themselves govern human-environment relationships but must be considered within a larger set of contextual variables.
Nonetheless, some historical assessments associate high levels of affluence and industrial development (and thus the ability to draw resources from elsewhere) with the return of forest cover (Williams, 1989; Hagerstrand and Lohm 1990; Pfister and Messerli 1990). Global comparisons indicate that afforestation is largely a phenomenon of advanced industrial societies, which are both affluent and have high technological capacity (Young et al. 1990). Wealth, however, also increases per capita consumption, bringing about environmental change through higher resource demands, although these higher demands can be reduced by advanced technologies available to wealthy societies. Poverty is often associated with environmental degradation (IDRC and SAREC, 1992), although recent research shows that this relationship is strongly influenced by other factors as well (Kates and Haarman 1992). These mixed conclusions indicate the importance of further studies of the relationship between level of affluence and environmental change.
The role of technology as a potential cause of past and prospective changes in land use and land cover also requires further study. It is obvious that technological development alters the usefulness and demand for different natural resources. The extension of basic transport infrastructure such as roads, railways, and airports, can open up previously inaccessible resources and lead to their exploitation and degradation. Technological developments and their application (such as improvements in methods of converting biomass into energy; use of information-processing technologies in crop and pest management; and the development of new plant and animal strains through research in biotechnology) may lead to major shifts in land use in both developed and developing countries during the coming decades (Brouwer and Chadwick, 1991).
To these three sets of candidate forces, three others have been added: political economy, which includes the systems of exchange, ownership, and control; political structure, involving the institutions and organization of governance; and attitudes and values of individuals and groups. The candidate driving forces grouped within these categories have received much less attention than population growth. They do not yet encompass clearly defined variables and causal relationships, but comprise similar explanations of relationships of societal and environmental change (Blaikie and Brookfield 1987). Changes in land tenure (an institution in socio-economic terms) have direct impacts on land use, as does the move from non-market to market exchange of resources (political economy). Changes in attitudes and values may add a dimension to environmental change that cannot be explained otherwise, such as impact on land use of the "green" movement. Identifying the key variables within each set of potential driving forces and developing proxy measures for them will be one of the objectives of the IGBP-HDP project on land-use and land-cover change.
Detailed examinations link all of these candidate forces (e.g., Scott et al. 1990). For example, the model of socio-economic and environmental interactions with land use developed at Oak Ridge National Laboratory explores the interrelated effects of changes in technology, political economy, and political structure in Amazonia (Jones and O'Neill 1992). Improved transport facilities are expected to exacerbate land degradation if the region in question is small, but its impact on larger regions will vary by circumstance. Additional comparative studies are needed to address the interactions of different driving forces with their environmental context.
Finally, environmental transformations - whether potential climate change or localized impacts such as soil depletion - themselves affect land use. Assessments of the impacts of climate change on land use and land cover (e.g., Glantz 1989; Parry, Carter and Konjin 1988; Riebsame 1991) rely on assumptions about land-use change that can only be improved through studies of the dynamics of land use. For example, a study in Oaxaca, Mexico, indicates that local deforestation has caused a drop in the local water table and/or a reduction in local rainfall, and that the local population has responded by expanding the area under cultivation to maintain production (Liverman 1990). Crosson (1990) calls for a better understanding of the interactions of soil depletion, land-use systems, and environmental changes.
Relatively few global aggregate or regional comparative studies have explicitly investigated the role of these proposed driving forces, either independently or as a group. Still fewer have investigated statistical relationships among them. In contrast, many regional or smaller-scale case studies have been undertaken that offer detailed insights into specific cases that cannot necessarily be generalized. Thus the literature is rich in insights and "stories", but weak in comparative assessments that illuminate the causes and courses of land cover change. As a result, research is driven by subjective interpretations and assumptions rather than by attempts to test different hypotheses.
In this schema, a land cover (physical system) exists in a systemic relationship with human uses (land use) and the causes of those uses. Driving forces interact among themselves and lead to different land uses depending on the social context in which they operate. At time t}{\f22\dn4 1}{\f22 , the underlying human driving forces lead to actions precipitating demand for land use #l (# corresponds to Figure 2), which requires the manipulation of the land cover by means of technology employed in human activities such as clearing, harvesting, or adding nutrients (proximate sources of change). This manipulation is directed either to changing the existing land cover (#1 to #2 or #3) or to maintaining a particular cover (#1). In the former, the existing cover is changed to a new state that must be maintained in the face of natural processes that would alter it (physical maintenance loop).
Changes to a new state of land cover are of at least two kinds: modification as in land cover #2 (e.g., fertilization of cropland or planting exotic grasses in pastures) and conversion as in land cover #3 (e.g., forest to cropland or dryland to paddy agriculture). Maintenance processes sustain the land-cover conversion (#3) or modification (#2). Therefore, proximate sources can be seen as those of conversion, modification, or maintenance.
The environmental consequences of uses of land cover (changes in the state of cover) affect the original driving forces through the environmental impacts feedback loop. Likewise these land-cover changes (#2 and #3) can be repeated elsewhere such that they reach a global magnitude that triggers climate change, which, in turn, feeds back on the local physical system, affecting land cover and, ultimately, the driving forces through the environmental impact loop. Regardless of the stimuli - local or global environmental impacts or the interaction of the driving forces in their social context - changes in driving forces at time t}{\f22\dn4 2}{\f22 may trigger a new land use (#2), with new consequences for the land-use/cover system.
This perspective indicates that understanding of global environmental change must consider the conditions and changes in land cover engendered by changes in land use; the rates of change in the conversion-modification-maintenance processes of use; and the human forces and societal conditions that influence the kinds and rates of the processes.
Much of the land in Amazonia currently being deforested is not primary forest but is actually in some stage of secondary succession. This is indicated by high-resolution satellite data, which show that human activities comprise a dynamic pattern of clearing, abandonment, and reclearing. Figure 3 shows the rates of forest clearing and land abandonment measured at a test site in the Brazilian Amazon between 1986 and 1988, and again between 1988 and 1989. These data provide a basis for interpreting the coupling between land in active agriculture and land abandoned to secondary growth in the same area; they indicate that the land cover subsequent to deforestation is not uniform but linked to the specific management strategies in place. The fact that secondary, not primary, forest is being converted calls into question conclusions regarding the precise magnitude of contributions of deforestation in the Amazon to anthropogenic carbon flux.
Large-scale deforestation in the Amazon had its beginning in the mid-1970s through an effort to develop this tropical frontier. The most important agent of deforestation at this time was agricultural expansion, through both increasing numbers of smallholder farmers and large-scale, commercial activities, the latter including the conversion of forest to pasture for livestock production (largely for a regional market). This expansion followed two geographical fronts: along (i) a north-south corridor adjacent to the Belem to Brasilia highway, and (ii) a northwesterly corridor into the state of Rondonia. Although the southern sections of Brazil continued to have the highest density of agriculture during the period, the Amazon region showed the most dramatic increases in deforestation rates. This was particularly true in Rondonia, which had the highest density of frontier deforestation in Brazil from 1970 to 1980, and where 13 per cent of the forests was cleared by 1987 for colonization and settlement programmes.
Resettlement and agricultural expansion/modernization programmes were established as national policy by Brazil in the 1970s as a way to encourage migration from "overpopulated" regions in the south and northeast of the country. Rondonia and other colonization "poles" in the state of Para were earmarked for "people without land in a land without people" (Moran 1981). The vast Amazon was seen by many as an empty frontier, which could be consolidated under Brazilian national sovereignty and provide immense opportunities for the exploitation of mineral and biotic resources, for the benefit of millions of poor and landless (e.g., Bunker 1984, 1984b).
How did "over-population", the existence of the frontier, and other human forces interact to "drive" the policy of frontier development and make it economically feasible and desirable? One study reports a good correlation (r}{\f22\up6 2}{\f22 = 0.8) of deforestation with several anthropogenic variables, including the density of population, and supports the conclusion that population growth and density are related to " deforestation density" or the fraction of an administrative district deforested (Reis and Margulis 1990). This study, however, assumes that the areas in question were completely forested at the beginning of the study. It also overlooks environmental factors such as soil type and fertility, topography, temperature. and precipitation (which define the spatial concentration of deforestation), as well as the spatial congruence between population and forest change.
Some studies indicate that population growth should be seen as part of a multiple feedback system, where it is as much a consequence of poverty and land degradation as it is a cause of deforestation. Using data compiled on Brazilian deforestation from both statistical land-use surveys and satellite data which provide the location of deforestation, a low correlation between population density and rates of deforestation is obtained (see Figure 6).
In a study of cattle ranching in the Amazon, Hecht (1983) and Hecht and Cockburn (1989), found that government policies, fiscal incentives, and the fact that cattle are a good way of storing wealth in an inflationary economy were more significant determinants of deforestation than were demographic considerations alone. These results and those of other studies (e.g., on deforestation in the Philippines, Kummer 1992; on declining wood stocks in sub-Saharan Africa, Anderson 1986) suggest that in isolation, demographic factors may not be a good basis for projecting future land-use and land-cover change.
Large-scale investment in agriculture, including an extensive programme of crop credits, followed during the 1970s. The export crops of wheat, soybeans, and coffee consumed almost half of all crop credits, with the largest portion of the credits invested in soybean production (Figure 7).
As a result, the area under soybean production increased 6-fold in the 1970s, ten times more than most other crops, and yields increased five-fold. The combination of land, fertilizers, improved seeds, and government-sponsored credits and incentives made soybeans one of Brazil's major internationally competitive export crops. Most soybean production was concentrated in two states: Rio Grande do Sul and Parana Figure 8 shows that soybean production (and wheat) replaced coffee as the major crop in Parana. This development was encouraged by government programmes (World Bank 1982) because the international market for coffee was highly variable and undependable. Consequently, a labour-intensive crop (coffee) was replaced with a capital and energy intensive component of the national export economy, particularly in Parana. Land prices rose significantly, as land was consolidated into larger holdings. This transformation of land use changed the average size of land holdings from small farms to very large, presumably commercial, farms, as illustrated for the State of Parana in Figure 9.
Another consequence was that from 1970-1980, migration from rural to urban areas increased. Part of this migration was in response to "pull" factors as industrial development increased wages in urban areas. But commercialization of agriculture in Parana shifted the means of production from labour to machinery, creating a "push" factor. Large numbers of people left the state of Parana during this period; out migration was higher than from any other state. Undoubtedly many, if not most, of the migrants left for urban areas, but a large number also went to new opportunities in the Rondonia frontier (Hecht 1989).
The deforestation of Amazonia illustrates the challenges encountered in trying to link human driving forces to changes in land cover through land use. It demonstrates that:
To participate effectively in the proposed multi- and interdisciplinary research activities the social science community needs to:
The CPPC will need to develop links with other IGBP and HDP projects. It is expected that the CPPC will call on the resources of IGBP-DIS, HDP-DIS, and START in formulating the detailed science plan. The key projects and relationships are identified in the research plan and potential links to those within IGBP are summarized in Table 2.
Focus 1 will establish the basis for the incorporation of sub-global complexities in the relationships among human driving forces, changes in land use, and consequent impacts on land cover by creating a typology of socio-economic-environmental driving forces (situations), associated conversion and modification processes, and end-states of land cover. It involves two sets of activities, one aimed at identifying and delineating the situations (or groups of regions) with common patterns of human causes of land use and associated changes in land cover, the other at validating and elaborating this framework through case studies carried out according to a common protocol.
Activity 1.1: Typology and Demarcation of Situations
This activity will create a classification scheme that abstracts the essential human and physical characteristics from episodes of land-cover change with similar human causes, even though these episodes may be located in different geographic regions or have taken place in different historical periods. It will do so by identifying and defining a conceptual unit of analysis that not only captures more of the details of and variability in the dynamics of land-use and land-cover change than can the global aggregate scale, but which is also analytically more streamlined and efficient for global modelling. This approach is based on the recognition that it is impractical to address the global situation through separate studies conducted in many small areas, because of the enormous effort required and the problems in \ldblquote scaling up\rdblquote (moving from the micro level to the global). At the aggregate level of the globe or even continents, key processes and important variations in use and cover are obscured. The problem, then, is to find a basis for grouping like areas together and keeping different ones separate, avoiding the gloss of macro-scale aggregation without sacrificing too many of the practical advantages of a relatively small number of study units. We define the building blocks of these middle-level units of study as regions and seek to classify them in groups of situations that have common human driving forces, land uses, and land covers (cause-to-cover situations).
Specifying the characteristics of these cause-to-cover situations is more difficult than might be imagined, particularly if the diversity of cover types and processes of change within the study units is high. The divisions must be made on the basis of broad but critical attributes of the human and physical realms involved, and the dynamics of their relationships. Few attempts of this kind have been made, let alone tested for their value in providing an understanding of specific cases or for making generalizations across cases.
The 1991 Global Change Institute (GCI) held in Snowmass, Colorado, USA, developed trial framework to be used for creating a typology of regional cause-to-cover situations (McNeill et al. 1993). This approach recognizes that both the physical setting (land cover) and the social setting (e.g., population density, level of economic development, type of economic and political system) differentiate situations of change from one another. The framework can be seen as a cubic matrix (Figure 11) whose three dimensions are proximate sources of change, possible driving forces, and predominant types of land cover. Nineteen proximate sources are identified, grouped as activities of harvesting, replacement or conversion, and transfer (importation of resources to sustain the change involved). The driving forces of change include both human factors (e.g., population growth, degree of political centralization) and natural processes (e.g., climate variability on desert margins). Appropriate surrogate variables for the human forces are suggested.
With respect to cover types, the GCI working group sought initially to identify priority land-cover regions for study rather than to demarcate the entire land surface of the Earth. Using spatial extent and significance of different cover types for global change as the main criteria, it identified seven priority land-cover types, excluding such covers as desert, tundra, and urban settlement. There is no reason, however, that the excluded cover types could not be brought into the cubic matrix in order to complete the demarcation of the terrestrial surface.
Not every possible combination of variables within the cubic matrix will occur or be significant globally. It is expected that recurrent patterns will be identified that indicate common conditions of cause-to-cover relationships. The degree to which units of a particular size can be characterized by any of the three dimensions or by particular situations may vary and pose some challenges. Temporal dimensions may also require attention; for example, do rates of change matter in the typology?
The proposed schema of regional cause-to-cover situations offers a way of standardizing context in order to identify the circumstances under which particular driving forces are or are not significant. It also provides a framework within which areas of the world can be selected for in-depth case study examination as exemplifying globally significant trends. The matrix detailed here may be too detailed for practical application, but it provides a beginning from which regional situations could be established.
The typology and demarcation Activity is fundamental to all others proposed for the land-use and land-cover change project. It involves both a near-term product - an initial typology and demarcation - and longer-term research leading to refinements and changes in the typology and demarcations. The near-term product is proposed for development over the life of the CPPC, providing a base for the modelling and case study activities. The longer-term research activity awaits results from the case studies and modelling activities as they progress.
Short-term Objective
Implementation
Tasks 1.1.1 and 1.1.2 should be completed during the stage of Core Project planning (1993), serving as a catalyst for Activity 1.2 and Focus 2, and should be developed in close consultation with both. The long-term objective awaits the results of the research that is involved in Activity 1.2 and Focus 2.
Activity 1.2: Case Studies
As noted, different areas of the world with similar land covers display different courses and rates of land-cover change, and these differences are related to their socio-economic and physical context. Beyond this recognition, the impacts of socio-economic context on land-cover change is a source of considerable debate, little of which is well grounded empirically. It is true that numerous case studies (local and regional) have been conducted that contribute to our collective understanding of varying cause-to-cover dynamics. Almost all were individually undertaken, however, lacking a common protocol of study and standardized data sets, and thus are virtually impossible to compare in a rigorous way. One of the most important mechanisms of improving understanding and, ultimately, global models, is through systematic case studies designed to collect common data sets to answer standard questions about the impact of socio-economic context on land-cover change.
Short-term Objective
Task 1.2.2
Task 1.2.3
Long-term Objective
Implementation
All tasks should be completed during the Core Project planning stage, although they cannot be fully completed until the first stage of Activity 1 is completed. Task 1.2.1 can begin independently of Activity 1, but the other two tasks await the completion of the typology of regional situations. Activity 1.1 and 1.2 must be tightly integrated.
Activity 2.1: Framework for Models and Projections
Short-term Objective
The framework must also take account of the evolution of analytical tools for modelling and projections, and the varying scale of resolution among data on land cover (1 km x 1 km, IGBP-DIS), land use, and driving forces (typically collected by political boundaries). Current social data may be manipulated to complement land cover, but cannot be used to specify models over the past 300 or even 100 years.
Long-term Objective
Implementation
Development of the framework will take place throughout the core project planning process. It must, however, be coordinated with both activities of Focus 1.
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Activity 3.1: Linking Cause-cover Explanations and Scale
Generally, to the degree that land-use research is conducted at the macro-scale, it is assumed that the levels of analysis are continuous and that there is a relatively clear hierarchy beginning with the international or global system level and descending to the local land manager or plot. So, for example, world agricultural prices govern the decision-making of an individual farmer, hence the agricultural conversion rate within a region, and so on. This presumed nesting of relationships leads to a presumed nesting of explanations, each descending explanatory scale embedded in the previous one.
While such assumptions are familiar to a range of studies geared towards the international level, they have not been examined systematically in relation to landuse/cover change. Indeed, the general issues of scale and nesting are not adequately understood within the human sciences (e.g., Meyer et al. 1992), still less tied to considerations in the physical sciences (e.g., Clark 1987). Yet inferences and implications regarding scale and hierarchy abound in the emergent studies of global environmental change. The existence of continuity or discontinuity requires examination and should not be assumed.
Long-term Objective
Implementation
This activity will be implemented when the results of activities in Foci 1 and 2 become available.
An effort will need to be mounted to define the data sets required to support directly the research into land-use change, including those that would be used as primary forcing functions in the modelling or as parameters to define typologies. Data sets are also required for validation of models. This activity involves the land-use effort with the IGBP-DIS as well as with IGBP-GAIM (e.g., Townshend 1992; Moore 1993).
Many of the global-scale data efforts now under way or planned by IGBP-DIS lack adequate resolution for land-use/cover studies. For instance, the IGBP-DIS plan to obtain 1 km resolution AVHRR data for land-cover classification and mapping, which is a high resolution data set on a global scale, is inadequate for detailed analysis of landuse change. However, finer resolution information for specific areas is becoming available. For instance, the NASA Landsat Pathfinder project is mapping deforestation as a land-use change for selected regions of the humid tropics, and this will provide 1:1 000 000 scale or better digital data sets. Such fine resolution data will be essential for specifying models coming from a global land-use/cover effort and for validating results of models. The CPPC should specify the requirements for such fine resolution data sets in close coordination with IGBP-DIS and HDP-DIS.
One aspect of the study of land-use change is the feedback from anthropogenic perturbation in climate, biogeochemistry, and terrestrial ecosystem dynamics. These changes, in turn, influence human activities in positive or negative ways as indicated in Figure 1. For instance, biotic impoverishment from deforestation may affect the rate of future deforestation in the area, or it may influence a transition from extensive to intensive use of inputs such as land and fertilizers. There must be close linkages between the other Core Projects of the IGBP and HDP and the land-use/land-cover change project so that data produced can be easily exchanged and integrated.
The HDP data assessment series will provide sources and evaluations of existing socio-demographic data (HDGEC 1991). Published reports include assessments of survey research data (Worcester and Barnes l991), demographic data (Clarke and Rhind 1992), and economic data (Yohe and Segerson 1992). The following questions will need to be addressed:
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AVHRR Advanced Very High Resolution Radiometer BAHC Biospheric Aspects of the Hydrological Cycle (IGBP) CPPC Core Project Planning Committee DIS Data and Information System FAOUN Food and Agriculture Organization FRN Swedish Council for Planning and Coordination of Research GAIM Global Analysis, Interpretation and Modelling (IGBP) GCI Global Change Institute GCM General Circulation Model GCTE Global Change and Terrestrial Ecosystems (IGBP) GDP Gross Domestic Product GIS Geographic Information System GNP Gross National Product HDP Human Dimensions of Global Environmental Change Programme ICSU International Council of Scientific Unions IDRC International Development Research Center IGAC International Global Atmospheric Chemistry Project (IGBP) IGBP International Geosphere-Biosphere Programme: A Study of Global Change IIASA International Institute of Applied Systems Analysis ISSC International Social Science Council Landsat Land Remote-Sensing Satellite (USA) LOICZ Land-Ocean Interactions in the Coastal Zone (USA) MOIRA Model of International Relations in Agriculture NERC National Environmental Research Council (UK) OPEC Organization of Petroleum Exporting Countries SAREC Swedish Agency for Research Co-operation with Developing Countries SPOT Systeme pour l'Observation de la Terre (France) UNEP United Nations Environment Programme
The IGBP and the HDP will contribute to funding the work of the CPPC.
The CPPC will complete its work in approximately eighteen months. At the conclusion of the work of the CPPC, and assuming approval of the proposed plan by the SC-IGBP and the SC-HDP, a Joint Scientific Steering Committee for the project will be formed to carry out the scientific plan.
No. 12 The International Geosphere-Biosphere Programme: A Study of Global Change (IGBP). The Initial Core Projects. (1990) No. 13 Terrestrial Biosphere Perspective of the IGAC Project: Companion to the Dookie Report. Edited by P A Matson and D S Ojima. (1990) No. 14 Coastal Ocean Fluxes and Resources. Edited by P M Holligan. (1990) No. 15 Global Change System for Analysis, Research and Training (START). Report of the Bellagio Meeting. Edited by J A Eddy, T F Malone, J J McCarthy and T Rosswall. (1991) No. 16 Report of the IGBP Regional Workshop for South America. (1991) No. 17 Plant-Water Interactions in Large-Scale Hydrological Modelling. (1991) No. 18.1 Recommendations of the Asian Workshop. Edited by R R Daniel. (1991) No. 18.2 Proceedings of the Asian Workshop. Edited by R R Daniel and B Babuji. (1992) No. 19 The PAGES Project: Proposed Implementation Plans For Research Activities. Edited by J A Eddy. (1992) No. 20 Improved Global Data for Land Applications: A Proposal for a New High Resolution Data Set. Report of the Land Cover Working Group of IGBP-DIS. Edited by J R G Townshend. (1992) No. 21 Global Change and Terrestrial Ecosystems: The Operational Plan. Edited by W L Steffen, B H Walker, J S I Ingram and G W Koch. (1992) No. 22 Report from the START Regional Meeting for Southeast Asia. (1992) No. 23 Joint Global Ocean Flux Study: Implementation Plan. Published jointly with SCOR. (1992) No. 24 Relating Land Use and Global Land Cover Change. Published jointly with HDP. Edited by B L Turner II, R H Moss, and D L Skole. (1993) No. 25 Land-Ocean Interactions in the Coastal Zone. Science Plan. Edited by P M Holligan and H de Boois (1993)
No. 1 A Framework for Research on the Human Dimensions of Global Environmental Change. Edited by H K Jacobson and M F Price. ISSC/Unesco, Paris (1990) No. 2 Dynamics of Societal Learning about Global Environmental Change. Edited by R M Worcester and S H Barnes. ISSC/Unesco, Paris (1991) No. 3 Population Data and Global Environmental Change. Edited by J T Clarke and D W Rhind. ISSC/Unesco, Paris (1992) No. 4 Economic Data and the Human Dimensions of Global Environmental Change: Creating a Data Support Process for an Evolving Long Term Research Program. Edited by G Yohe and K Segerson. HDP, Barcelona (1992) No. 5 Relating Land Use and Global Land-Cover Change. Edited by B L Turner II, R H Moss, and D L Skole. IGBP/HDP, Stockholm (1993)
