Relationships Between Land Use/Cover and Macro-Forces of Change -- Background Information

Introduction

Instead, we begin at the beginning, so to speak, and search for simple, direct links between certain candidate forces of change and certain land use changes at a global scale. Specifically, we ask how important are population, technology, and economic development in transforming certain land use/covers: cultivation, forest conversion, and livestock. To answer this question, we take each of the land use/covers separately and see how change in the area under, for example, cultivation is related to change in population, annual energy consumption, and Gross Domestic Product.

The data used in this analysis are those drawn from the sources described under each LULC section in Unit 2. The human driving forces or independent variables are the change in population size (population force), total annual energy consumption (a surrogate for technological capacity), and gross domestic product (GDP) -- a surrogate for the level of economic development. The land use changes or the dependent variables are area in cultivation (permanent crops only), forest (total area in forest), and livestock numbers and pasture land. These data were taken from FAO Production Yearbooks (land use and population) and the UN Statistical Yearbook (GDP and energy). The data were examined both spatially and temporally (1961-65 to 1985).

Our global-scale temporal analyses consisted of simple regressions of the dependent variables of land use/covers against the independent variables of the driving-force indicators for the time period of 1961-65 (average) to 1985. The intent was to determine if global relationships can be detected, e.g., whether population growth is associated with a loss of forest cover, and then see if we find similar relationships at the regional scale. Our spatial analyses involved regression of the same set of variables but through the optic of their percent change over time (% change of land-use divided by % change in driving forces indicators) by regional aggregates and for 36 countries. We aimed at representing all continents, a range of environments, forms of government, population densities, and levels of economic development. The percent changes were from the time period 1980-1985. The goal was to determine if relationships between the forces of change and the types of LULC change are related at the global scale.

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Results

To explore this regional diversity in more detail, 36 countries (representing an array of political, economic, and environmental conditions) were selected for analysis of these relationships at the scale of nations. We found no strong or significant correlations between the percent change in the driving forces variables and the percent change in land uses from 1980-1985 on a regional comparative basis.15 The same was true when the regions were grouped into three categories, representing the so-called First, Second, and Third Worlds. Between 1980 and 1985, population density and energy consumption increased in all regions, but a corresponding decrease in forest cover was not found everywhere. In the Americas, Africa, and both the developed and developing worlds, forest cover decreased. In Europe, Asia, and the centrally planned economies (Second World), forest cover increased!

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Preliminary Interpretations

This mismatch between spatial measurement units also afflicts studies that do show statistical correlations for macro-driving forces and land use change. For example, Rudel's (1989) recent demonstration of such a relationship between population increase and deforestation in the tropical forest realm of the world weighs country-wide population increases against more localized deforestation data. We must remember, however, that population increases can take place anywhere, especially in urban areas, while deforestation takes place only where there are forests, so who is to say that nation-wide population increase caused deforestation in a few regions of a country? When we do find correlations between driving forces and land use/cover changes, it is tempting to forget all the data problems and let our beliefs in certain macro-driving forces color our view of the processes that give rise to land use and cover change. These changes are, however, largely cumulative in nature, i.e., they are the sum of many interacting processes (Turner et al. 1990).

Our results, therefore, should be viewed cautiously. The global aggregate correlations may well be on target, but their importance for understanding global change must be weighed in light of the forces of change that were not tested here. In other words, to claim that population growth or economic growth drives a particular land use/cover change is only tenable if we can say with certainty that other forces were not involved (or at least negligible). The three driving forces examined here more-or-less capture the kinds of forces that drive consumption and production. It is largely a truism to demonstrate that land use change follows from increases in them, given sufficient time. More important to our understanding would be to demonstrate that these kinds of forces were correlated, but others, such as political culture, were not. Such a finding would signify that the production-consumption forces are more fundamental to land use change than the social organizations in which they operate. Unfortunately, land use/cover change research cannot make any assessment of this proposition at this time.

The regional comparative correlations may also be on target, and do not necessarily contradict the global aggregate patterns. The latter are, after all, averages, created by a range of relationships that differ across space. This variation is more important than seems to be recognized, because it indicates that a proposed macro-force changes its relationships with land use changes as the conditions in question vary. Until these differing relationships are thoroughly assessed and worked out for individual regions, we cannot claim that the social, political, and cultural conditions (i.e., the context in which macro-driving forces act) matter, and how exactly they influence any macro-force or the interactions among them. It should be pointed out here that pan-regional or -national demonstrations of relationships between proposed macro-forces and certain kinds of land use/cover change have almost invariably focused on regions that were similar with respect to either environmental or economic conditions (e.g., humid tropical, Third World countries; see Rudel 1989).

Conclusions

• What forces drive land use/land cover change?
• What impacts -- direct and indirect, now and in the future -- do these changes have on the environment and on human society?
• Does society need to respond to these changes, and if so, how, and how well is it able to do so?

The data, however, are just part of the story. Similarly fundamental is the lack of a theoretical foundation that adequately captures the dynamics between land use change and human driving forces at different scales and between scales. This shortcoming is clearly evident from the correlation analyses and the discussion of the results here. Leaving the data problems aside for the moment, these analyses show that whether or not we find a relationship between two variables also depends on scale and the specific regional contexts of the land uses and driving forces in question. There is no single answer to "what driving forces cause what land use/cover change and how much of it?".

Clearly, the fundamental issues in answering just the first of the three questions stated above severely limits our ability even to begin to answer the other two. Yet those are the questions to which most of us -- the John and Sally Smiths of the world, and policy makers in particular -- want answers. What will happen to us? And what can we do about it? "Good" answers to these questions need to include good data and a good understanding of the fundamental causal linkages, yet, in a different sense, "good" answers might be those given soon, simply because we might have to act soon in order to mitigate or even prevent some of the impacts that are likely to occur.

The dilemma that results is a dilemma for everyone: it is a dilemma for scientists who do not want to compromise on the quality of research, yet who are in a position to recognize and examine potential dangers; for policy makers, who are under political pressure to act on what is perceived as a threat to health, well-being or even survival by some, and to economic welfare and profit by others; and for every lay person who must choose between believing either the "alarmist, red-flag wavers" or the "wait-and-see, thumbs-up optimists" camp, and then draw their own conclusions on whether or not to change their behavior. After all, some of these changes are supposed to occur only in the distant future and in far-away places. For each one of them it would be easier to turn a blind eye to the issues of environmental change than to confront these global, enormously complex, often hidden, and politically charged problems that -- depending on the pace of global change vs. that of our scientific progress -- might challenge us beyond our capacity to fully comprehend and adequately respond to them.

What stops us from turning that blind eye, however, is that we have high stakes in the issue of global change: we have face and political clout to lose, we have our investments to lose, we have human health and environmental assets to lose, in fact, we have people to lose ... or rather, I have the cropland to lose on which I depend for food, I risk losing the water that I need for survival, I risk losing my favorite beach to sea-level rise and coastal erosion, my farm can go bankrupt, I can lose my job, the forest I like to go for walks in might be clear-cut.

And while I -- here in the rich First World -- have many things to lose that I value, there are other people on this earth who will suffer less, maybe even gain, from global environmental change, and many, many more in the Third World who will suffer a great deal more than I. We all need to think of our personal share in causing global environmental change (or, more specific to this module, land use/cover change), and our personal responsibility in responding to it. It appears as if our ability to affect the environment on a global scale has skyrocketed while the evolution of a similarly far-reaching global ethic continues to lag behind.

Our immense scientific concern with global change and the heated debates from international forums to parliamentary floors to backyard parties over whether or not there are dangers involved, and for whom, are but the most audible indication of the fact that global change -- ultimately -- is a personal matter: it is about the ethical decisions each one of us does or doesn't make, the behaviors of consumption and reproduction each one of us does or doesn't reconsider and maybe change, and the benefits and burdens each one of us will experience in an ecological and human environment that tomorrow might not look anything like what we see outside our window today.

Key Terms / Phrases

Untested claims about the causes of global environmental change

Complex relationships

Analysis

Independent variables:

• Change in population
• Annual energy consumption
• Gross domestic product

• Area in cultivation
• Forest cover
• Livestock numbers
• Pasture land

Global findings

Global vs. regional relationships

Regional diversity

Interpretation of results

Mismatch of spatial units

LULCs result from many interacting forces

Conclusions

Focus of this module

Data are just part of the story

Scale dependence Context matters!

There is no single answer to what causes land use/land cover change

What are "good" answers to these questions?

A dilemma for everyone

High stakes

Global change is a personal matter

Endnotes

15. For the percent change in population compared to the percent change in the land uses for the 36 countries, correlation coefficients (r^2's) between 0.000 0.085 were generated.