Although we may speak of environmental change as if it were something new, the earth is constantly changing, driven by human and natural forces.  The crash of ocean tides reshapes coast lines, winds push sand dunes across desert landscapes, rivers meander and scour new channels, and the construction of new shopping centers alters urban landscapes.  These changes are most pronounced in the small envelope of the environment that sustains life called the biosphere.   The biosphere can be defined in at least two ways:  (1) the zonal space extending from the immediate subsurface of the earth to the upper atmosphere; (2) the parts of the earth’s atmosphere (air), hydrosphere (water), lithosphere (rock), pedosphere (soil), and cryosphere (ice) in which all livings things exist and interact. Changes to components of the biosphere occur at different times, at different spatial scales, and at different rates; such changes are usually interacting and interdependent.  Thus, the earth can be visualized as a complex system of changing and interacting environmental domains.
 
 

Humans As Driving Forces of Global Change

 
    This unit focuses on the changes to the earth system that are the product of human activity.  Humans alter their environment in many ways; their activities bring about changes in land cover and landscapes, changes in the composition of atmospheric gases with resulting climatic effects, and changes in plant and animal species diversity.

 Figure 1 shows trends in human transformation of some components of the biosphere over time.  The graph depicts the percentage change in human population, terrestrial vertebrate diversity, deforestation, water withdrawals, and some chemical releases since 1650.  This graph, with time on the x-axis and percentage change on the y-axis, shows that through time, the amount of change to components of the biosphere has increased.
 

Source:  Adapted from Turner et al. 1990.  The earth as transformed by human action.  
©1990 Reproduced with the permission of Cambridge University Press. Any reproduction or copying of this material in any format, beyond single copying by an authorized individual for personal use, must first receive the written consent of Cambridge University Press. 

Deforested area  Terrestrial vertebrate diversity  Carbon releases  Population size  Water withdrawals  Nitrogen releases

Source:  Adapted from Turner et al. 1990.  The earth as transformed by human action. ©1990 Cambridge University Press.  Reproduced with the permission of Cambridge University Press. Any reproduction or copying of this material in any format, beyond single copying by an authorized individual for personal use, must first receive the written consent of Cambridge University Press. 

    Finally, our ways of organizing as human beings are profoundly tied to environmental transformations.  Although they are difficult to measure, economic systems, political systems, cultures, and traditions all affect the ways in which human beings relate to, utilize, and affect their environment.
 
 

Putting the Driving Forces Together

 
    The configuration and operation of population change, technological change, and socio-economic/cultural organization structure the patterns of production, consumption, and impacts throughout the globe.  Although China has a population of over 1 billion, other countries with fewer people consume more resources.  North America, for example, accounts for a relatively small portion of the world’s population, but because of its level of technology and its social and economic organization, it consumes a much greater share of resources and contributes a much larger portion of environmental changes.  In other words, the ways in which population, technology, and society are arranged in different places produces a factor of affluence, or a measure of material goods, wealth, or quality of life, (among others) found in a society, country, or region.
 
    Figure 3 is a map of Gross National Product (GNP) of various regions in the world.  GNP is the value of the total output of goods and services produced in a country in a given time period and is used here as an indicator of affluence.  It should be noted that GNP is not a perfect measure of a region’s level of economic development.  It does not account for unused resources or for the informal economy (economic activities not recorded by a government, such as domestic labor, street vending).  Despite its limitations, Figure 3 is still a useful illustration of areas of mass consumption and development vs. areas of underdevelopment at a global level.

High Income Countries in black (GNP per capita > $9,386), Middle Income Countries in gray (GNP per capita between $765 and $9835), and Low Income Countries in white (GNP per capita < $765).  Categories are based on World Bank data, 1995.  Some designations have been estimated by the World Bank.  
Source:  Data taken from the World Bank Economic Development Institute, Development Education Program. http://www.worldbank.org/depweb/activ/bigdata.htm (July 21, 1998).  Map created by J. Holman, Web Author.

The IPAT Identity

 
    In 1972, Paul Ehrlich and John Holdren introduced a concept known as the IPAT (pronounced “eye-pat”) equation as a way of describing the variables that interact to produce environmental change.  The equation states that Impact = Population x Affluence x Technology or I = P * A * T.  In other words, the magnitude (amount or size) of environmental change in an area (I) depends on the magnitude of demand created by the size of population (P) and its level of per capita consumption (A), both of which are influenced by the efficiency of production/consumption methods (T).  All three of the factors influencing environmental impact and change are interrelated.

    IPAT is often taken to mean that the telling factors in global environmental change are overpopulation, excessive affluence (or its opposite) and consumption, and inappropriate technology operating together.  But most global environmental change is driven by local actions taken in our daily activities which are influenced by such factors as policies, rules, and regulations concerning the allocation of resources.  For this reason, it may be more appropriate to expand the rather limited idea of the IPAT equation so that we understand human actions as outcomes of human agents within social structures. This viewpoint seems particularly relevant at the local and regional scale.  Thus, while the earth as a closed system may function in terms of the IPAT equation, local or regional places may not.  Environmental change at the local level may be driven by complex interactions among ideologies, beliefs, institutions, and markets, for example (Kasperson et al. 1995).
 
 
 

Proximate vs. Non-Proximate Sources of Change

 
    So far we have looked at the human driving forces of global change.  We can further refine our understanding of these driving forces by placing them into two groups -- proximate and non-proximate forces of global environmental change.  Proximate forces are immediate human actions that directly alter the physical environment.  We can group proximate forces into industrial metabolism (or ecology) and land-use/cover change.  Industrial metabolism refers to processes involved with industrial production and consumption (e.g., large factories, energy production and consumption, transportation).  Land-use/cover change includes human activities that alter either land and its vegetative cover or the human use of the land (e.g., deforestation, cropland intensification).  Land-use/cover change will be addressed in more detail in Unit 2.

    Of the two types of proximate forces, those dealing with industrial production and consumption produce about 70% of the radiative gases leading to climate change.  Human activities that produce changes in the land account for the remaining 30% of the radiative gases; such activities can also affect biodiversity, ecosystem fragmentation, and basic sustainability.  To the human sciences, the critical need is to better understand the societal forces that drive industrial metabolism and land-use/cover change.  This requires that we look beyond proximate forces to the factors that actually drive proximate forces, known as non-proximate forces.

    Non-proximate forces are forces of change that underlie, at various levels, the proximate forces.  For example, deforestation can be explained as a result of the proximate force of slash and burn activities.  But what causes farmers to slash and burn?  To answer this, we need to consider the non-proximate or distal forces of deforestation, which may include factors such as migration into the area, political decisions encouraging migration, the political-economic context of the area, or global market forces.  Each of these non-proximate sources of change underlie the proximate action of slash and burn activities.

    How do we conceptualize these forces?  At the global or “macro” scale, proximate forces change according to the demand for natural resources and the ways in which resources are produced and consumed.  At the local scale, other factors may be more important in explaining driving forces.  The important point is that driving forces have different characteristics at different geographical scales.

 

Conclusion

 
     So far, we have seen that a variety of factors related to human activity interact to produce global environmental changes, and we’ve seen that these factors may vary from place to place and at different geographic scales.  In the remainder of this module, we will look specifically at two types of global environmental change -- land-use/cover change and climate change -- and will consider the ways that human activity has led to these changes and how we can respond to them.