This chapter is a quantitative description and analysis of three factors that are crucial to understanding the relation between resource use and economic development in PR. These are: energy, land use, and waste generation. I describe these factors as indices of the sustainability potential of economic activity and development strategies. The objective is to describe each factor and its role on the extension of the natural carrying capacity of the island. Data presented includes mostly the period from 1960s to 1988. Where available I have used data since 1950.

    The analysis focuses on the period when the promotion of semi-heavy and heavy manufacturing activities was the main objective of the development programs during the 1970s and 1980s. During this time the promotion of intensive energy, capital, and non-intensive labor manufacturing activities was identified as the major objective in economic development on the island (Dietz 1986, Weisskoff 1985). I characterize the dynamics of land use, and agricultural productivity lost, and the rates of toxic waste generation, as indicators of environmental impact.

    On the first section of this chapter I describe the relationship between energy use and economic development. The description of energy dynamics is important in two ways: as a physical indicator of the intensity of economic activity1 , and as an indicator of the vulnerability of the system to changes in the fossil fuel market.

    In the second part of this chapter I describe and analyze the observed patterns of land use change during the last forty years. One of the objectives of this sections is to quantify primary productivity potential lost with changes in land use. Assessing this lost is important for describing the system's ability to satisfy basic population needs.

    The last part of this chapter is a description of patterns of waste generation and disposition. I describe solid waste generation as an impact and indication of a changing society. This section focuses on the description of toxic waste generation as an index of the environmental impact of the semi heavy and heavy sectors on the manufacturing sector composition, as illustrated in Chapter 3.

    The general goal of this chapter is to assess, through the description of these three factors, the potential of the natural system to assimilate the demands of the economic sectors. Through this analysis I purport to show the significance of these three factors as indicators of sustainable development tendencies of the island development pattern.

    The analysis of these three factors continues that of the system began in Chapter 3 with the presentation of the diagrams. Chapter Three also presented a description of two of the components of the system that have been classified as stocks or state variables: population and the manufacturing sector. The description of energy, land use and waste generated is a representation of other state variables and flows.


    Energy use is one index of a production system's dependence on biophysical factors, and in the case of fossil fuels derived energy, non-renewable resources. It serves as a macroindicator in the description of the aggregated environmental impact of an economic growth (Morales-Cardona 1989).

    Sánchez-Cardona et al. (1975) and Morales-Cardona (1989) describe energy density as an aggregated index of economic activity's impact on the environment. Energy density is also a measure of energy use per square kilometer of "active" land (urban plus arable). They estimated that by 1975, energy density in PR had increased 25-fold in the last 25 years. This increase resulted in a consumption of energy that was 4 times higher than the energy consumed per square mile of active land2  in the United States. As an describer of work done per unit area, energy density is an aggregated indicator of pollution generated per area. In a similar mode a direct relationship has been described between fuel energy use and impact on health (Morales-Cardona 1989).

    Energy use in Puerto Rico has increased significantly in the last 40 years. Available data show a 150 percent increase in total energy use from 1968 to 1988. Most of this energy comes from oil. In 1988, the island imported oil to satisfy 95 percent of its energy consumption (PRPB 1988). Hydroelectricity and biomass provides the remainder 5 percent. The dependence on oil imports makes the island's economy highly vulnerable to changes in the international oil market. Signs of that dependency were clear after 1973 because of the high rates of inflation that resulted from the increases in fossil fuel costs. Net fossil fuel imports significantly decreased after 1973 due to reductions in refining activity related to higher oil costs. The oil-refining industry established on the island in the 1960s and 1970s was mostly dependent on oil from OPEC countries.

    Although, there was a noticeable reduction in fossil energy use by the industrial sector (due to the reduction in petrochemical refining activity) in the 1970s, the manufacturing sector increase its demand for energy (Santiago 1987). Energy consumption grew at faster rates than economic or population growth indicators (Figure 4.1). The greater part of this increase was due to the semiheavy and heavy manufacturing sectors' growth in the 1970s and 1980s.

    In this section I examine the use and distribution of oil-derived energy and its relation to economic and environmental aspects in Puerto Rico. I use oil derived energy consumption as a macroindicator of economic activity and environmental impact.


Sources: PRPB 1988b; Office of Energy 1984
GNP on real dollars (1954)

Energy and the Economy

    Energy plays an important role in a region's economic development. It is an economic growth inducing factor. A correlation has been described in some cases between energy inputs and economic growth (Cleveland et al. 1984, Paruelo et al. 1987). However, empirical evidence shows that this relation has not been as clear in the case of PR as that described for other countries, for example the US economy (Cleveland et al. 1984), or the Argentinean economy (Paruelo et al. 1987).

    My analysis of the relation between economic output and energy inputs uses data from the 1960s to 1988, the period in which there was a shift to heavy and semi-heavy industry in PR. The objective of this analysis is to describe and review the relation between energy use and economic growth in PR, its beneficiaries and its impacts. Since energy can be considered a macro indicator of environmental impact, we can assume there is a relation between increasing energy use and pollution generation. Most common development models of this century assume that there is an automatic benefit in the growth of aggregated economic indicators. My analysis questions the validity of that assumption by expressing the need to describe the distribution of the benefits of the energy consuming activities and to internalize as costs the impacts of those activities.

    Petrochemical refining activities played an important role in PR's manufacturing sector development in the 1960s and 1970s. Reduction in refining activities that resulted from the change in energy markets during the 1970s is one of the reasons for the lower correlation between fuel energy use and economic output. The development of a petrochemical industry in the 1960s was a growth pole in the industrialization plan designed in part by Isard's regional planning group (1975). The oil-refining industry's development was intended to spark a spillover effect for the development of other energy-intensive manufacturing activities. These would provide employment opportunities and use by-products of the refining processes. The development of the oil refining sector served the Economic Development Administration's objective of reorienting the island's development plan toward more capital- and energy-intensive industries. The oil industry was intended to attract other manufacturing activities that had a large demand for, at that time, inexpensive energy.

    In addition the industrialization plan developed in PR in the 1950s required the availability of vast amounts of cheap energy. The development of an oil-refining industry would allow the island's economy to capture at least a portion of the value added in the process. It would contribute to job and income generation (Dietz 1986). However, the effect of the industry on the economy was much weaker than expected. Due to changes in the oil market during the 1970s, the petrochemical refining sector  reduced its operations significantly.  3In 1982, the Commonwealth Oil Refining Company (CORCO), the major refinery of the island, closed its  operations after several years of reductions. In 1988, another refinery, the Caribbean Petroleum Corporation closed indefinitely. There are now two other refineries, Sun Oil in Yabucoa and Phillips PR Core in Guayama. These satisfy around 80 percent of the island's demand for refined oil products, which amounts to about 168,000 barrels per day.

    The monetary value of fossil fuels imported into Puerto Rico represents a significant portion of gross product. It illustrates the significance of oil imports in the PR economy. The 54.5 million barrels of oil imported in 1984 to the island cost $1,561 millions at the average price of $28.66 per barrel of oil. This represented 11.2 percent of that year's gross domestic product (GDP) and 13 percent of net income (Table 4.1). This is also equivalent to 1,909 dollars per family or 1,636 dollars per employee.  4This data shows the vulnerability of Puerto Rico's economy to potential future oil price increases.

    Of the 76.3 million barrels of oil imported in 1988, 61.3 (80.3 percent) was for local consumption.  5The rest was exported, mainly to the United States as derivatives. Around 40 percent of the local consumption was for the production of electricity, and 32.5 percent for terrestrial transportation.


Total Energy Consumed a
Real GDP dollars b
GDP/Energy ($d/Barrel)
Energy Cost as percent of GNP c

 Sources: PRPB, 1988a
Puerto Rico Energy Office 1984
a In million barrels of oil equivalents
b In million dollars of 1954.
c Based in nominal dollars.
d In 1954 dollars

    Industrial and commercial activities consumed the remaining 22.2 percent directly. The 5 percent of industrial energy not derived from fossil fuel comes from coal, solar energy, and sugarcane biomass. Of the electricity used, the industrial sector consumed 25 percent, the residential sector used 34 percent, and the commercial and other sectors, 41 percent. Fuel-derived energy consumption by the manufacturing sector in 1988 added up to 32.2 percent (108 trillion British Thermal Units) of the island's total consumption.

    Data on energy use show that 40 percent of the total fossil fuel consumed on the island is for electricity generation. Morales-Cardona (1989) estimates that the Electric Energy Authority of PR has an overall efficiency conversion rate of 30 percent, somewhat lower than the average for many stateside utilities of about 35 percent. Another major consumer of fossil fuel energy, terrestrial transportation, uses about 32.5 percent of the total fuel consumed. In this case the conversion occurs at an estimated 25 percent efficiency (Bonnet et al. 1982).

    GDP (real 1954 dollars) per barrel of oil used on the island decreased notably between the years 1974 and 1982 (Table 4.1), reflecting the impact on the local economy of the change in price related to the 1970s changes in markets. The ratio was, by the end of the 1980s, closer to its pre-1973 values due to reductions in oil price. Yet, it illustrates the vulnerability of the economy to changes in oil prices. The cost of fossil fuels used as a percentage of GNP also illustrates this dependence and vulnerability. This ratio, the total cost of oil divided by the total production of goods and services on the island, reached a maximum level of 13.21 percent in 1982. Although reductions in fossil fuel prices reduced this percent to 5.52 percent in 1988, the vulnerability of the system to future changes in oil prices is high, especially because of the dependence on oil as the only source. The impact of the dependence of the economy on oil imports resulted in the high unemployment rates recorded around 1983.

    Puerto Rico's total annual energy consumption increased rapidly after the second half of the 1960s (Figure 4.2). This significant increase coincided with the development of the refining industry. Reductions in total consumption at the beginning of the 1980s can be explained by the closing of parts of the industry, low rates of economic growth and high rates of inflation. The tendency toward a reduction in use reversed when the petrochemical refining activities were replaced by other energy-, and capital-, intensive industries, which kept the local demand high.


Sources: Oficina de Energía 1984, 1988

Economic Output and Fuel Energy Use

    Puerto Rico changed in a short span of time from a low to a high fuel energy-dependent system. From 1966 to 1980, there was a 250 percent increase in energy use, 101 percent between 1966 and 1972. Real GDP increased 101 percent from 1968 to 1980. The increase in energy consumption is explained by changes in the structure of the economy that were partly responsible for  economic growth (Bonnet 1982). These changes arose from the shift in priorities of the Economic Development Administration strategies of development (described in more detail in Chapter Two). The most significant of these changes was the shift to high capital and energy manufacturing sectors.

    To offer a biophysical perspective on the assessment of historical and current economic events and indicators, Cleveland et al. (1984) analyzed the relationship between fuel energy use and economic output in the US economy. Through this approach they purported to show the relation of dependency of economic production on resources and other physical factors.

    This biophysical perspective is based on models that describe energy use dynamics. It assumes that, because the laws of energy and matter determine the availability, use rate, and efficiency of economic processes, it is essential to include these elements in the analysis of economic production and structure.

    Following a similar framework I describe and assess the relation between energy use and economic production in Puerto Rico. Through this description I intend to clarify the relation between the manufacturing sector, as the major economic sector of the last decades, and demand for energy imports. This description also shows a relation between the pattern of substitution of labor by energy and capital and the shifts in industrialization strategies.

    Data for many modernized, industrialized countries show an almost linear relation between energy use (quality corrected for countries with significant changes in sources), and productivity (Hall et al. 1986). Cleveland et al. (1984) and Paruelo et al. (1987), described this relation and found high correlations between energy use and economic output in the US and Argentinean economies, respectively. Paruelo et al.'s analysis extended the concept to described the energy used in serving interest paid for regions with a high external debt.

    I extended this concept in the case of Puerto Rico, where there is high external capital investments, to account for the amount of energy that is used for serving profits on those investments. This analysis can also be used to clarify some aspects of the relationship between energy use and the beneficiaries of economic production in the region.

    The close link observed between economic output, measured as GNP and GDP, and energy use in industrialized economies is not as strong in Puerto Rico during the period between 1966-88 (Figure 4.3). Different from the results reported at Cleveland et al. (1984) and Paruelo et al. (1987), there is not a high correlation between energy use and those aggregate indices of economic production. 6The coefficient of determination for the regression between GDP and fuel use for years 1966-88 is 0.66, compared with a coefficient of 0.96 for Argentina (real GDP), and 0.98 for the United States.  The coefficient of determination for the regression between fuel energy use and GNP for the same period is slightly smaller, 0.65 (Figure 4.4).

    Correlation between these parameters decreases after the mid-1970s. There was a 22 percent reduction in total fuel energy use from 1979 to 1983. During this period there was a reduction in real GDP of 1.1 percent (GDP increased 32 percent in current prices during that period).

    The data show a higher correlation between energy use and economic output during the first 8 years of the 1966 to 1988 period than during the last 15 years, 1974-88. During the second period fuel energy consumption increased to over 300 trillion BTUs. The regression during this period has a coefficient of determination of .013 for GDP and energy use (Figure 4.4). This is significantly lower than the coefficient for 1968-88 (0.66). The coefficient of determination with GNP for this period was 0.005, also lower than the coefficient with GDP and the coefficient for the overall period.

    For a clearer description of these parameter changes in time, I compared their annual rates of change. The analysis covers the years between 1966 through 19887.  This represents most of the second and third economic periods of the post-1940s industrialization programs described in Chapter Two, that is, the shift to an emphasis on petrochemical refining activities and later to chemical, pharmaceutical and electronics manufacturing (Figure 4.5).

    Annual GDP and energy use rates of change also exhibit the erratic behavior and low correlation observed for fuel energy use and GDP. The coefficient of determination for the regression for 1966-88 is 0.084. This is low compared with the 0.43 value for the Argentinean economy during the 1950-84 period (Paruelo et al. 1987).


Sources: PRPB 1988a; Oficina de Energía 1984


Sources: PRPB 1988a; Oficina de Energía 1984


Sources: PRPB 1988a; Oficina de Energía 1984

    Changes in the island's economic structure and attributes of the manufacturing sector such as: increase in export oriented production, energy and capital substitution patterns, and the lack of linkages between local production and consumption, are partly responsible for the difference in the coefficient of determination between the two periods8.

    The rapid change in economic structure resulting from the shift in public policies in the sixties was a response to decreasing economic growth rates and increasing unemployment. This shift in priorities which promoted the establishment of high energy- and capital- dependent activities continue through the 1970s when economic conditions worsened and unemployment rates increased due to the oil-related economic crises. Ironically, during part of this period fuel energy use increased from 9 percent to more than 20 percent annually in conformity with pre-established petrochemical refining industry development plans and programs. After a decade of development of the petrochemical and heavy industries since the 1960s, a high dependency on foreign fossil fuel, goods, and raw materials had developed.

    In the 1970s the Commonwealth Development Administration intensified its efforts to attract investments in the capital- and energy- intensive industries (chemical and electronics) to substitute for the fleeing petrochemical industry. These were also energy- and capital-intensive operations. Therefore, although there was a period of negative annual growth rates in fuel energy use, total use remained high.

    Because of the high level of external capital investments and the export-production and import-consumption orientation of the economy, a high percentage of fuel energy use serves profits, dividends, and interests to external investors. These payments in the Puerto Rican economy are analogous to payments of interest in countries with significant capital debts. In these, as is the case of Argentina (Paruelo et al. 1987), significant portions of economic output served interest payments.

    In PR we observe a growing divergence between GNP and GDP. The difference between GNP and GDP was 348 millions dollars in 1970 and 6,936 millions in 1988 (Table 4.2). In 1988 this was 22.7 percent of total domestic product (Figure 4.3). Therefore, I conclude that a large and increasing part of the continuous growth in energy consumption is related to the outflow of capital investment profits. These figures understate the exportation of profits since they are balanced in part by the inflow of federal wages paid on the island (Dietz 1986).

    I calculated energy yield as a ratio of fuel energy use per GDP in real 1954 dollars. Energy yield estimates describe a pattern of reduction in energy used per unit of economic output between 1979 and 1985. For similar time periods in other economies this has been interpreted as meaning that factor substitution and conservation measures can decreased the quantity of fuel used per unit of economic output (Stobaugh et al. 1979) (Figure 4.9). Cleveland et al. (1984) explained the increase in energy use yield over long periods of time in the US as mainly caused by a change to more efficient energy sources rather than to actual improvements in end use efficiency9.  In  PR I relate this change in energy use yield to changes in the manufacturing sector composition with an increase and then reduction of the refining industry. There is a noticeable increase in this ratio in the 1970s. However, it decrease after 1976 to 52 percent of the 1968 ratio, a reduction of 59 percent between 1976 and 1988.


Sources: Oficina de Energía 1984; PRPB 1988a

    The change in composition in the manufacturing sector resulted in a substitution of capital for energy in PR's economy. There has been substitution of labor by energy and capital during the 1970 and 1980 decades. The increased in economic output per unit of energy input is partly caused by the substitution of energy with capital. In other economies increase in energy yields have been related to changes in energy sources. PR however did not have significant changes in energy sources during this period10.

Energy and Employment

    The substitution of labor with energy and capital in the manufacturing sector is partially responsible for keeping Puerto Rico's rates of energy imports high. The tendency toward substitution intensified during the 1970s in the manufacturing sector, with the substitution of capital for labor. In 1982, electronic and pharmaceutical activities, accounted for 56.4 percent of the total value added and 32 percent employment (Census of Manufacturers 1987). These are capital-intensive, high value-adding industries, but non-labor intensive (Alameda et al. 1984). The chemical and electronics sectors also consumed 6.7 percent of the total energy used on the island in 198211.

    Alameda and Mann (1984) did a study to determine  substitutability of energy and capital in the manufacturing sector in Puerto Rico. They concluded that capital and labor display a high degree of substitutability. They found that energy and capital are complementary factors. Labor is readily  substitutable for energy and capital. However capital is more readily a substitute for labor than energy (Alameda and Mann 1984).

    The pattern of industrialization of the last 50 years resulted in capital- and energy-intensive production activities. Tax exemptions to manufacturing industry reduced the price of capital services (Alameda et al. 1984). It had the impact of serving as an incentive for the continued high demand for energy. The increase in energy consumption increased the vulnerability of the system to unpredictable changes in prices of fossil fuel markets, and has a direct impact on the form of residues disposed of in the environment.

    The suggestion of developing an exemption plan to attract labor-intensive industries to the island is simplistic according to Alameda and Mann (1984). Their opinion is based on the existence of competition presented by lower-wage countries. However, diversification toward labor-intensive manufacturing and local market oriented production systems must be explored if long-term sustainability is to be an objective.12


    Energy use increased rapidly in PR after the second half of the sixties. Although energy demand increase resulted initially from oil refining activity, energy use remains comparatively high. This is the result of the shift to energy- and capital-intensive high technology and export oriented manufacturing activities, the change in structure of the economy, and  composition, and change in lifestyles.

    Increase in fossil fuel energy use resulted in an increase in rates of economic production, however I did not observe a high correlation between these variables for the years in which data were available. This shows that there are other factors that need to be examine, together with energy use, when describing the functioning of an economic system and its dependency in physical factors such as the political economy and mechanisms by which this exchange takes place. An important factor is the growth and decline of the very energy-intensive petroleum refining industry.

    Another major point of this section is that the evaluation of fossil fuel-derived energy use should take in consideration the receptors of the economic benefit of the activities in which that energy is used. Because of the high rate of external investment, a considerable part of the energy used on the island goes to pay profits on capital investments to foreign investors. Assuming there is a direct relation between energy consumption by manufacturing industry and GNP and given that there is a 31.5 percent divergence between GDP and GNP, I estimate that at least 10.1 percent of the energy use on the island serve profits on external investment.


    Puerto Rico's most valuable natural resource is its land. Because of PR's high population density, land is a relatively scarce resource. The last 50 years of economic growth and social development resulted in rapid change in the landscape's character and use. Extensive-low density residential development have proliferated in the best low elevation agricultural lands. Since the 1940s, when industrialization programs and modernization of production and society intensified, manufacturing replaced agriculture as the major element of the economy. Agricultural production decreased significantly. This process increased the dependency on imports for the satisfaction of food demand (Table 4.2). The pattern of substitution of local agricultural products with imports continues.

    During the first decades of industrialization, migration from the countryside to the metropolitan zones increased. Land increased in value. Agriculture was perceived as an obstacle to progress and was replaced by export-oriented manufacturing following the prevailing models of development.




Sources: Weisskoff 1985

    The reduction of agricultural activity caused an increased dependence on imports to satisfy food demand. The shift in land use patterns toward non-agricultural uses observed after the 1950s can be linked to the general restructure of the economy and its opening to international markets, especially the US. In this section, I describe this change in land use and its impact on the primary productivity potential of the island. This loss occurs as a function of the natural energy assimilation capacity lost in agriculture and forestry when land is shifted to more permanent and irreversible uses such as urban or industrial development.

    I observe two main tendencies in PR's pattern of land use change during the last 40 years. First, there is a tendency toward substitution of agricultural uses by more permanent uses, such as, urban, residential, industrial, and commercial development (especially on the coastal plains). The scarcity and inconsistencies of data available make it hard to describe this change accurately. However, we know that farmland decreased significantly: from around 747,000 hectares in 1950 to around 359,000 in 1987 (Table 4.3). Part of this change is due to the second identifiable pattern, that is the increase in secondary forest that replaced land previously under agricultural use (Table 4.4).


Farmland a
% of Total Land
% of Total Employment

Sources: USDC 1974, 1978, 1987
a Includes cropland, pastures, fallow agricultural land, woodland in farms, and water bodies in farms.


                                          Forestland a           % of Total                                      Neither-Forest         % of Total
                                                                                                                            nor Farmlanda ha.


Source: USDA Soil Conservation Service 1982; Table 4.3
a Estimated from difference of total land from forestland and farmland.

Land Use and Agricultural Production

    The last 50 years of institutional development planning and management did not prevent rapid change in land use toward non-agricultural uses.13  According to the US Department of Agriculture (USDA) Soil Conservation Service data of land use in the Caribbean, there has been an increase in forestland from 18.3 percent of total land in 1967 to 23.1 percent in 1982. The increase in forestland was 43,275 hectares over the 15 years. Farmland decreased approximately 181,000 hectares during the same period.

    Increase in forestland has been interpreted as a positive trend and a sign of success in conservation policies.14  Puerto Rico is one of the few tropical-subtropical zones where there  has been an increase in forestland during the last 50 years. However, the pattern of change in land use in Puerto Rico has to be analyzed in the context of the activities that replaced agriculture, their impact, and the shift to permanent uses.

    After the 1950s, the highest rates of reduction in farmland area occurred in the 1964-69 census period when 24,786 hectares of land turned annually to non-farmland uses. By 1969 around 60 percent of the total land on the island was still farmland. By 1978, there was a reduction of 10 percent, and by 1982 farmland area was only 43.2 percent of the total land. The 1974-78 and 1978-82 census periods also had two of the highest rates of change since the 1950s.


    Using data available on farmland and forest area since 1950s, I determined patterns of change in farmland and forestland and projected change in farmland to the future. The projection uses three land use change estimates based on three different scenario-assumptions. In the first scenario, I assumed a continuation of the pattern of reduction in agricultural area observed from 1950 to 1987, that is an average 9,699 ha/year. In this scenario farmland area was estimated from the regression equation of farmland vs. time. In the second scenario I assume that the reduction in farmland area will be equal to the average annual rate observed during the last census period (1982-87), that is 6,119 ha/year. In the third scenario I assume the farmland reduction estimate to be the lowest average rate of change for a census period since 1950. The lowest average rate of change is 3,360 ha/year, the rate of reduction in farmland area for a census period 1959-64.

    The last Census of Agriculture in 1987 presents a figure of 358,894 ha for farmland, a reduction from the previous figure, for 1982, of 7.9 percent. Estimates for 1990, 2000, and 2015 based on this rate of change will result in further reductions of 11.8, 43.7 and 91.5 percent of the 1987 farmland, reducing it to 30,325 hectares by 2015. This would represent a worst case scenario in terms of agricultural land conservation. Farmland would become 35.1, 22.4, and 3.4 percent respectively of total land (Table 4.5).


Farmland Area (ha)
 Percentage of Total Land b
                                                                                    Scenario 1


Scenario 2

1987 358,893a 43.2
1990 340,534 37.8
2000 279,337 31.0
2015 187,541 20.8

                                                                                     Scenario 3

1987 358,894a 43.2
1990 348,814 38.69
2000 315,214 34.96
2015 264,813 29.37

Sources: USDC Bureau of the Census, 1987
a Actual census figure from Census of Agriculture 1987.
b Percentage of land based on estimate remaining farmland.

    The pattern of reduction in actual farmland occurs as a function of many factors not explained by the regression model used to estimate these figures. The estimates, however, deserve attention as a scenario given that the reduction of farmland and its transformation to other uses has increased significantly over the last 37 years (Figure 4.7). These estimates forecast an average annual rate of change from farmland to other uses of 10,884 hectares.

    Land use changes from agricultural use to either forestland or other nonagricultural uses. Although not necessarily developed as permanent uses, nonagricultural non-forestland is land in residential, industrial, commercial, water, wetlands, public, and the other use categories. In this study I am assuming that land within these other categories cannot be returned to agricultural use. Farmland transformed to forest maintains its agricultural potential because it is not a permanent kind of development.


Sources: USDC Bureau of the Census 1987

    Excluding forest in reserves or special planning units, mangroves and areas that cannot be developed, forestland in the coastal plains has almost disappeared in PR. Therefore, it is highly probable that most of the land changed from farmland to forest occurs in the highlands. Long-term agricultural production in these areas is constrained by their slope and the erosion potential. On the other hand, most of the land transformed to nonagricultural or forest use is in the coastal plains, where most of the arable and highly productive land lies and where stronger pressure for development exists.

    The second scenario assumes that the annual rate of change in the last census period (1982-87) will continue. In this case farmland would be reduced for the forecasted years (1990, 2000, and 2015) by 5.1, 22.2, and 47.7 percent respectively, from farmland in 1987. With this rate of change farmland decreases to an area of 187,541 hectares in 2015, 20.8 percent of the total land of the island.

    The third scenario estimates farmland reduction using the lowest annual rate of change for any census period since 1950, that is, 3,360 ha/yr. This rate is almost equal to the annual rate of increase in forestland from 1967 to 1982, 3,604 ha. At this rate of change, farmland would decrease to 264,813 ha. by 2015, 29.37 percent of the island's total land. This represents a reduction of 26.2 percent of farmland existent in 1987.

    To estimate the preserved agricultural potential based on land use, I calculated the percentage of farmland reduction due to conversion into forest through a regression of the change in forestland area in time. For this estimate I assumed that total annual increase in forestland comes from reforested farmland.  Therefore, I assume that this land can return to agricultural use since its potential for agricultural production remains.

    Data available from the Soil Conservation Service (SCS) show that forestland increased between 1967 and 1982 at a rate of 3,604 ha/yr between 1967 and 1982. If that pattern of change continued there should have been an increase in forestland of 10,047 ha between 1987 and 1990. There would be an increase of 33,489 ha of forest between 1990 and 2000, and 50,234 ha between 2000 and 2015. The total increment in forestland for 1987-2015 is equivalent to 29.26, 54.72, and 99.67 percent of the total change in farmland for each of the three previously-mentioned scenarios. I estimate, based on these figures, that around 70 percent of the projected change of farmland to other uses will be to the permanent ones. If changed, this land would lose its agricultural production potential. That would happen to 50 percent of the farmland shifted to other uses under the second scenario assumptions, and to around only 1 percent in the third scenario (Table 4.6).


                                                                   Forestland                    Percentage                  Percentage
                                                                  Estimates (ha)                of Land b                    of Change


Sources: USDA SCS 1982
a Figure from SCS Inventory for 1982.
b Percent of total land of Puerto Rico (901,571.59 ha.).

    Using projected estimates of existing farmland and forestland, the average primary productivity and respiration rates for tropical zones, I calculated the primary productivity lost by the transformation of farmland into forestland and other uses. I assume that farmland transformed to nonagricultural uses, except to forest, loses its primary productive capacity. Estimates include the primary productivity rates for tropical forest and mangrove in the calculus of forestland productivity (Table 4.7) (Lugo et al. 1982). To calculate the primary productivity potential of agricultural land, I used rates for sugarcane productivity (Lugo 1982). The objective is to calculate the primary product foregone by the transformation to other uses. I will use these estimates in Chapter Five to calculate the significance of the change in terms of its impact on the biological carrying capacity (food production) of the island resources.


Farmland Converted to Developed Uses
Farmland Converted to Forestland b
Net Primary Production Potential Lost c
                                                                                        Scenario 1

1987-1990 32,397 10,047 9.38 x 1012
1990-2000 80,961 33,489 2.51 x 1013
2000-2015 121,442 50,234 3.46 x 1013

Total 234,800 93,769 7.20 x 1013

                                                                                      Scenario 2

1987-1990 8,313 10,047 1.09 x 1012
1990-2000 27,708 33,489 1.28 x  1013
2000-2015 41,563 50,234 1.92 x 1013

Total 77,584 93,769 3.59 x 1013

                                                                                    Scenario 3

1987-1990 33 10,047 1.95 x 1012
1990-2000 111 33,489 6.51 x 1012
2000-2015 167 50,234 9.76 x 1012

Total 211 93,769 1.82 x 1013

a Based on the following rates of primary production, 2.70 x 108 kcal/ha/yr, 7.34 x 108 kcal/ha/yr; and respiration for agricultural and natural systems in the tropics, 4.05 x 107 kcal/ha/yr, 7.34 x 108.
b in hectares
c in kcal/yr

    These estimates and projections have not consider the variability in land productivity throughout the island. The USDA SCS National Resource Inventory (1982), classifies land in US Caribbean territories according to their limitations for agricultural use. The Inventory divides land by capability classes from I to VIII. The higher the capability class (I), the higher is its potential use under "ordinary farm practices." The lower capability class VIII is land not suitable for cultivation or grazing, although it has some potential for wildlife and recreation.

    Of the total rural land in the Caribbean, 55.35 percent lies in the VII and VIII capability classes. Therefore, most of it is not suitable for cultivation or grazing based on the SCS classification. Twenty seven percent of total land is in the I to IV categories, which means it is suitable for cultivation at different limitation levels. Of that, 8.4 are soils with few or no limitations. The remaining 17 percent is land with severe limitations for cultivation but suitable for pasture.

    If we apply these categories to the estimates projected in this section and in the geographical context of an island where most of the urban development occurs in the low coastal plains, we can conclude that the pattern of land use change in Puerto Rico has replaced most of the more productive and accessible agricultural land by permanent uses. The island has lost significant primary productivity by its urbanization of the coastal plains.


    The pattern of land use change observed in Puerto Rico in the last 50 years has important implications for the long-term sustainability of the system. The lost capacity for agricultural production implies an ever-increasing vulnerability to changes in international markets. It also creates a dependency on external capital, technology, and energy inputs necessary to maintain the system's high economic production level.

    Land use and agricultural production patterns in PR differ from other developing countries that followed an export production model. The main difference is the composition and structure of productive sectors. Most developing countries developed natural resource and agricultural product exporting economies while others developed the manufacturing sectors. However in both cases most developing economies maintained a significant local-oriented agricultural sector. In few cases has such a rapid change in land toward developed uses and increase food import dependency occurred as that observed in Puerto Rico.

    The island's general pattern of land use change has been more intensive on the coastal plains, where most of the urban and industrial development occurred in the last 20 to 30 years. Examples are the municipios (towns) of Barceloneta and Manatí, located on the North Coastal Plain Karstic Zone, to the northwest of the metropolitan area of San Juan. The area, particularly Barceloneta, has had in the last 20 years a significant increase in the development of manufacturing industry, mostly in the chemical, pharmaceutical, and food processing sectors. The easy access to major communication routes and port facilities, particularly the San Juan bay, and the availability of abundant, cheap underground water as well as abundant skilled labor, were major reasons for choosing that location. In Barceloneta, farmland decreased by half from 1987 to 1974, 3,359 ha to 1,514 ha (a reduction from 51.6 to 23.3 percent of total land). In Manatí there was a reduction from 52.7 to 37.5 percent of total land in agriculture. The high rate of reduction of farmland in these coastal zone towns is especially important since it is there where stronger pressure for development exists and where most of the arable land is. In general, land in these areas has higher agricultural productivity, and its conversion is most likely to be to permanent uses.


    Land use change is probably the most important factor related to the conservation of the sustainable carrying capacity in PR. Fifty years of development policies and planning have not been effective in protecting agricultural lands from shifting to other permanent uses. This has resulted in a shift of about 43 percent of the farmland (387,705 ha) to other uses. An increase of around 22,000 ha in forestland from 1958-82 explains only part that shift. However, most of the land shifted from agricultural production has turned to permanent uses such as residential, commercial, industrial and transportation. This shift is a significant food production capacity lost and reduces the natural capacity of the system to sustain its population.

    There is a need for a more accurate description of land use in Puerto Rico to quantify more accurately the pattern of change of agricultural lands to residential and other uses. This description would serve as basis for specific policies designed to protect remaining agricultural lands of high productivity to preserve the island's capacity to satisfy part of its population food needs.


    An objective of this study is to described and evaluate the degradation and conditions of instability created by the development model and the restructuring of the economy. Energy use and land use change has been describe as indicators of the environmental-economic balance of the system. Waste generation is also consider a determining factor in the assessment of that  balance. The generation of waste is one of the main factors affecting the system's ecological stability and quality of life because of the island's limited assimilative and regenerative capacity. Geographically small islands have a limited assimilative capacity for external materials.

    In Puerto Rico, with a high population density, its economic structure, and consumptive patterns, conflicts exist between land uses and waste disposal. These include the impact of the latter on vital resources such as aquifers or land quality, and the conflicts between disposal sites and residential or agricultural land uses.

Solid Waste

    Currently Puerto Rico has 62 landfills for the disposal of solid waste from domestic (population of 3.293 million), industrial, and commercial uses, and two industrial landfills (PRPB 1988c). These range in size from 0.4 to 51 ha and together occupy a total area of 523 ha. The landfills own by local governments, at the municipio (township) level, are sometimes administered by private companies. Two of these landfills, Ponce and Peñuelas, were designed for the disposal of industrial waste.15  Yet, according a Solid Waste Management Authority report (1989), 13 (21 percent) of these receive industrial waste. Already 2 of the landfills operating, Barceloneta and Cidra, have been included in the National Priority List under CERCLA (Comprehensive Environmental Response, Compensation, and Liability Act). Twelve landfills receive sludge from municipal waste water treatment plants.

    In 1989, the Solid Waste Management Authority reported that 48 of the 62 municipal landfills were "deficient operations." The deficient operation of landfills is an important cause of the serious water pollution problems on the island. A report by the Environmental Quality Board (JCA 1988), The Final Disposition of Solid Waste Problem in Puerto Rico, informs as that, by 1988, 8 landfills had been closed. Of 62 that remained functioning 48 (77 percent) were deficient. Twelve landfills  (19 percent of the total), although still operating, had exhausted their useful life based on land capacity. Another 33 (53 percent) had from one to five years left of useful life.

    Solid waste generation and final disposition have an impact on the island's sustainable carrying capacity. This impact has two dimensions. First, land used for solid waste disposal loses its agricultural potential. Land is already a scarce resource, and that used for the final disposal of solid waste has limited uses. Land used as landfills lose their agricultural potential and might be suitable only for certain types of permanent development. A second and more significant impact is the leaching of chemicals from landfills to water bodies, surface and aquifers. The fact that many municipal landfills receive industrial waste increases the potential impact caused by deficiencies in landfill site selection and design.

    Another source of water contamination from landfills derives from the disposition of sludge from municipal sewage treatment plants. Recently, USPIRG (United States Public Interest Group 1990) reported that the PR's public waste water treatment system receives 2.8 million kilograms (6.1 million pounds) of toxic industrial waste.16  The sewage treatment plants sludge which is deposited on landfills, is a source of toxic substances. The number of landfill sites in the Superfund National Priority candidate list illustrates the gravity of this situation. The 1990 List includes 191 sites in Puerto Rico, of which 68 are or have been  municipal landfills.

    Estimates by the Solid Waste Authority of Puerto Rico shows that the average person generates 2.05 kilograms of solid waste per day (4.5 pounds). With an approximate population of 3.294 million in 1987, this is equivalent to 2,459.3 million kilograms per year (2.7 million tons). Assuming an average depth of compacted solid waste in a landfill of 10 feet and an average density of 800 lbs/yd3, this required 167.7 hectares for land disposal.17  If PR's population grows as projected (Table 3.2) and solid waste generation remains the same, total generation between 1990 and 2015 will be 8.389 x 1010 kilograms (92.3 English million tons). At the average rates mentioned above, this volume will require approximately 5,700 ha of land for accumulative disposal.

Toxic and Hazardous Waste

    Toxic and hazardous waste generation and release has increase in Puerto Rico in the last 50 years as a result of the change in manufacturing sector composition and the modernization of the economy. The main manufacturing activities on the island  are the chemical, pharmaceutical, electronic and machinery sectors. These are all characterized by their use and generation as by-product of toxic and hazardous substances.

    Although the main manufacturing activities maintain few linkages with other local economic activities these depend on natural resources in two ways: to satisfy their water demand with vast and cheap underground water resources and for waste disposal. Although it is not conventionally described as a natural resource, waste assimilation capacity is a factor of production that needs to be internalize to account for the real cost of manufacturing and other economic activities.

    The main manufacturing sectors in Puerto Rico, based on value added, are: the Chemicals and Allied Products sector (SIC 28) (including pharmaceuticals), Food and Kindred Products sector (SIC 20), and Electronic and Other Electrical Equipment and Components sector (SIC 36). Other major sectors are the Non-electrical Machinery sector (SIC 35), Apparel and Other Textiles sector (SIC 23), and Instruments and Related Products (SIC 38). The first three were responsible for 58.5 percent of the total value added by manufacturing in 1987.

    The Chemical and Allied Products sector alone, was responsible for 43 percent of total value added. This sector is by far, the major manufacturing activity in PR. That sector is also the major toxic waste releaser on the island. In 1988, the Chemical and Allied Products sector reported releasing into the environment 54.2 percent of the total toxic waste reported on the island by industry (EPA 1991).18

    Total toxic waste released reported under Title III of the Superfund Amendment and Reauthorization Act (SARA) was 14,177,054 kilograms (31,189,519 pounds) in 1988 (Table 4.8).19  The Chemical and Allied Products sector reported the larger volume of toxic substances released. The Petroleum Refining and Related Industries (SIC 29) follow it together with the Food and Kindred Products (SIC 20), and the Rubber and Miscellaneous Plastics Products (SIC 30).

    The two categories that account for most of the released toxic waste in 1988 were fugitive emissions, and discharges to publicly owned treatment works (POTW). Of the total reported, 30.2 percent, or 4,281,818 kg, were fugitive or non-point air emissions. These include equipment leaks, evaporative losses from impoundments or spills, releases from building ventilation systems and any other on-site non-point air emissions (EPA 1990). Thirty-three percent, or 4,635,735 kg, were discharges to the POTW. These two release categories account for 62.9 percent of the total releases reported.


Kgs Toxic Waste Released % of Total a Value Added b Waste/Value Added e Employment c Toxic Waste /Employment
Chemical & Allied 28d 7,724,214 54.4 43.0 .0013 14.6 352
Petroleum & Refining 29  1,743,777 12.3 1.8 .0071 1.0 1203
Food & Kindred Products 20 1,475,748 10.4 14.1 .0007 15.3 64
Rubber Miscellaneous Plastics 30 1,417,705 10.0 2.4 .0043 4.0 238
Instruments & Related Products 38  496,197 3.5 4.4 .0008 4.2 79
Electronic &  Electric Equipment 36  426,199 3.0 12.9 .0002 12.3 24

Total 13,283,84c 93.6 57.8b 14.8c

Sources: Environmental Protection Agency 1991; USDC 1987
a Percentage of total by manufacturing sector in 1987.
b Value added by sector as percentage of total GNP
c Percentage of total employment
d Standard Industrial Code
e kgs toxic waste emitted per dollar of value added
f kgs of toxic waste emitted per employee

    Stack or point air emissions, another on-site emission, accounted for 19.7 percent of the total reported, that is, 2,787,254 kg. This includes releases to the air through stacks, vents, duct pipes, or other confined air streams. Also included are storage tank emissions. Another category was non-POTW off-site releases. Sixteen percent of the total waste reported for 1988 went to other off-site locations. The remaining 1 percent of toxic waste released went to streams, surface water bodies and land. Water bodies and streams received around 0.5 percent, or 68,402 kg of the waste releases reported. Landfills and land applications as surface impoundment accounted for 64,075 kg of the disposals reported.

    The relationship of toxic waste release with value-added and  employment gives us an idea of the significance of the manufacturing sector in PR. Value added by the manufacturing sector accounts for approximately 58 percent of GNP, although it provided only 14.8 of total employment in 1987. When we examine individual data for sectors the disproportionate labor demand and toxic waste release of some sectors become evident. The Chemical and Allied Products, Petroleum and Refining, and Rubber and Miscellaneous Plastics are the sectors where the ratio waste to employment is higher.

    The toxic chemical category in which releases had the largest volumes is the organic waste from the Chemical and Allied Products sector (Table 4.9). Dichloromethane, a carcinogen, was the chemical substance reported released in greatest quantities in PR and the United States. It is used as a solvent by the chemical and other industries.

    The limitations inherent in the way that the Toxic Release Inventory is prepared gives us an indication of the uncertainty of this information. Industries report releases based on their estimates. For calendar year 1988, only facilities that exceeded 50,000 pounds of a listed chemical were required to report releases. Toxic or "priority pollutants", as classified by EPA under the Clean Water Act constitute only around 20 percent of the hazardous substances emitted by industry. In Puerto Rico, the greater volumes reported released in 1988 were fugitive emissions, a non-point category, and emissions to POTW. The Toxic Release Inventory is the only substantial source of information for this data.


Sources: Environmental Protection Agency 1989
a In kilograms per year
b 1,1,2-TriChloro-1,2,2-TriFluorethane
c Hazard rating given by Sax and Lewis (1985). The hazard rating varies from 3, the highest hazard potential, to 1.
d SIC 28- Chemical and Allied
e SIC 20- Food and Kindred Products
f SIC 29- Petroleum and Refining

    The Chemical and Allied Products sector was responsible for almost all (87 to 99 percent), of the total emissions for four of the ten substances reported as released in greater quantity. The volume of these four organic compounds amounted to 39.1 percent of toxic releases reported. Five of the ten substances are high hazard potential chemicals according to Sax's classification (Sax et al. 1985).

    Metals emissions amount to 0.3 percent, or 40,909 kgs (90,000 pounds), of the total volume of toxic substances reported. The Petroleum and Refining sector released 52.4 percent of the total metal emissions. The Chemical and Allied Products sector released 31.9 percent of metal emissions, and the Electronics sector 8 percent.

    Forty-seven percent of total metal emissions were disposed of in an off-site, not a POTW. Other main receptors of metals were land (24 percent), air (10.7 percent), POTW (8 percent), the fugitive emissions accounted for 7.6 percent, and surface bodies and streams received 1.7 percent.

Estimates of Toxic Waste Generation

    Toxic waste generation and disposal have a direct influence on a system's natural capacity to sustain productive activities and population. A description of the specific impact of toxic substance release would need to consider individual ecosystems, their productive capacity, and their significance in life-sustaining systems. That is out of the scope and would need to be covered by a spatial specific locational examination.

    In the next chapter I will make a projection of toxic waste release. With the goal of establishing a relationship between generation and impact, as a macro indicator of impact, I will estimate the potential increase in toxic waste release under conditions of growth in the manufacturing sector.

    I use toxic waste release as an aggregated indicator that can be described based on patterns of change in production in the manufacturing sector. To describe production in this sector I use aggregated indexes. I suggest a pattern of change based on historical behaviors and then use it to estimate changes in waste volume released. This approach assumes that toxic waste generation is directly proportional to production in the manufacturing sector and does not take in consideration technological innovations that might reduce releases. The estimate of the rate of growth in toxic waste generation is calculated based on aggregated growth rates for the  manufacturing sector.


    In general, waste generation has to be assessed in relation to the socioeconomic and geographical context in which it occurs. Population density and consumption habits determine the volume of the solid waste stream, while toxic waste stream depends mostly on type and intensity of manufacturing activities. In Puerto Rico the composition of the manufacturing sector is a major factor to consider in relation to the volume and type of toxic waste generated and released to the environment. This analysis of toxic waste release is made in the context of the socioeconomic relations in which these occur. This approach has the objective of relating toxic waste generation to non-technological policy based development strategies.

    A description of major generators and releasers shows that toxic waste generation and release reductions have not been a major objective of development strategies on the island. This is illustrated by increase in the economic significance to the island of the major contributors to toxic waste release in the last 20 years. Description and assessment of these patterns can be used to justify the need for alternative policies and strategies due to the social cost of pollution.


    In this chapter I described three factors considered adequate indicators of the pattern of environmental disruption in Puerto Rico. These factors have been related to the socioeconomic context in an attempt to assess how these have been influenced by development policies and strategies of the last 40 years.

    In the case of energy, I show that, although there is a relation between energy use and the aggregated indicators of production, this relation has not been as tight as described for other economies. In part this has been explained in terms of the type of industries established at various periods on the island. The pattern of increase in energy use suggests that the environment of the island might has been exposed to a greater pressure due to the intensity of industrial manufacturing activity than the benefits that could have been derived from development focussed on other economic activities or a more locally oriented economic structure. This conclusion is based on the description of the difference between Gross National Product and Gross Domestic Product and on the assumption that the export orientation of the economy has been the major cause for the high dependency on imports to satisfy local demand for goods.

    The patterns of change in land use, the second factor described, illustrate the significance of the restructuring of the economy in the conservation of natural resources. The shift in economic development priorities to the industrialization of the manufacturing sector resulted in a substitution of agricultural by export oriented manufacturing activities. Parallel changes in social structure, spatial distribution and population growth reinforce the changing priorities and induced urban sprawl in the coastal plains substituting agricultural land uses with residential and other permanent development. The pattern of change in land use reduced total agricultural production potential significantly. This reduced the natural capacity of the island to sustain its population by decreasing  the primary productive capacity of the island, increasing its  dependency on imports of capital, energy, and goods.

    At the same time the major activities that substituted agriculture in the Puerto Rican economy introduced a burden in the natural resources in the high levels of toxic wastes release to the environment. Although toxic waste release implies a cost that has not been internalized completely in the description of the real costs and benefits of the changing economy, its characterization as an indicator of environmental impact serves to illustrate the burden imposed on resources by their generation and release.

    The current economic structure masks the significance of land use in the natural capacity of the island to sustain its population. It also masks the significance of increasing energy demand and toxic waste release as macroindicators of environmental impact that must be internalized in development alternatives analysis. New ideological frameworks are necessary to assess and develop policies and plans that can evolve to respond to the specific economic activity related impacts observed on the island.

    The next chapter continues this systematic analysis with a description of relations between the manufacturing sector activity, economic indicators, population and toxic waste release as an environmental macroindicator of environmental disruption.

1    Energy use is one aggregated indicator of environmental impact (Sánchez-Cardona 1975; Morales-Cardona 1989).
   Sánchez-Cardona et al. (1975) defined active land as land where most economic activity occurs, that is arable plus urban, commercial and industrial land.

3    In the beginning of the seventies the oil industry in Puerto Rico generated 7,800 direct jobs, and around 22,000 indirect jobs. During the last half of the 1970s this industry's participation in the economy significantly decreased. It provided in 1988 only 2,300 direct jobs and .7 percent of GNP and 1 percent of the net income.

4   Based on an estimate of the Office of Energy in the 1988 economic report to the Governor by the Planning Board(PRPB 1988:12.4).

5    The section on energy on the 1988 Informe Económico al Gobernador: 1988 from the Planning Board classifies as costly and dangerous PR's dependence on imported oil to satisfy 95 percent of the country's energy demands (PRPB 1988).

6    The coefficient for the US economy was estimated for years 1890-1980 (Cleveland et al. 1984). The coefficient for the Argentinean economy was estimated for 1950-84. When the GDP value was corrected to account for  interest paid on debt in the last nine years (1976-84) the coefficient of determination (1950-84) increased to .99. The coefficient of determination for this last period only (1976-84) increased when GDP was corrected for interest paid from .03 to .91 (Paruelo et al 1987).

      No data are available for total fuel energy use before 1966 according to a personal communication with personnel in the Office of Energy of Puerto Rico.

8    In 1978, 80 percent of the international firms located on the island were subsidiaries of a parent corporations with headquarters in the continental United States (Dietz 1986). The USDC in its Economic Study of Puerto Rico (1979, 1:21 and 2:7) observed that subsidiaries "have primarily used the island as a production point, bringing in raw materials and intermediate goods while shipping the output directly to their mainland parent companies for distribution.... Corporate investment and production decisions, materials supply, and product distribution  systems are almost entirely related to policies, practices, and financial, and tax considerations of mainland parent corporations with little influence from Puerto Rican economic forces." The lack of backward and forward linkages among these industries has resulted in manufacturing operations that are export enclaves unarticulated with other industrial activities.

9    This is not the case of Puerto Rico since energy use have been almost entirely oil during this period.

10    In this study, I did not make corrections for energy sources since there has been no major changes in these during the study period. In 1976 nonfossil fuel-derived energy accounted for 5.8 percent of the total. Biomass and hydroelectricity were the only non-oil sources used. In 1988, non-oil energy used accounted for 5.2 percent of total energy use; that year coal-derived energy was 2.4 percent, solar 0.8 percent, and biomass and hydroelectricity 1.9 and 0.4 respectively.

11    This estimate is based on the costs of electricity and fuels used by these sectors. Average costs of KWH for 1982 were taken from the "Informe para el año fiscal 1989-90 del Departamento de Proyecciones y Estudios Tarifarios", of the Autoridad de Energía Eléctrica (1990). Estimates of fuel used were based on average oil costs per barrel found in "La situación energética 1983-84," published by La Oficina de Energía de Puerto Rico (1984).

12    Zucchetto (1985) has suggested that an energy flow analysis helps to clarify the economic system stability potential. In ecological studies, stability refers to the system's capacity to recover its original behavior after it has been subject to perturbation. Many ecologists have hypothesized that higher diversity leads to greater stability. This idea is extended to economic systems by Zucchetto (1981). Diversification however, originates changes that must be described and accounted for. Zucchetto suggests the incorporation of diversification costs into an objective function to evaluate if the system is evolving toward the maximization of specific functions (Zucchetto 1985). The use of maximization functions could serve in this way to evaluate trends. To achieve more realism, Zucchetto recommends the formulation of simulation models.

13    The main governmental institution in charge of planning in Puerto Rico, the Planning Board, was founded in 1948. Other government bodies directly or indirectly involve in land use planning are: the Department of Natural Resources, the Economic Development Administration, and the Environmental Quality Board.

14    Communication by Ariel Lugo, Lecture given at the State University of New York College of Environmental Sciences and Forestry as part of the Graduate Student Association Seminar Series, 1990.

15    Personal communication with Ilvelisa González of the Solid Waste Authority in San Juan, Puerto Rico, October 1991.

16    This figure constitutes 22.8 percent of the total 12.195 million kilograms (26.83 million pounds) of toxic waste generated annually on the island according to the US Public Interest Research Group (USPIRG 1991).

17    Based on estimated average depth of compacted solid waste in landfill of 10 feet and estimated compacted density of solid wastes in landfill of 800 lbs/yd3. These values represent approximate averages in practice as presented by Tchobanoglous et al, 1977.

18    Based on description in Section 313 of the Emergency Planning and Community Right to Know Act, Title III of the Superfund Amendments, and Reauthorization Act of 1986. The Toxic Release Inventory includes any facility classified with Standard Industrial Codes 20-39 that manufactured, processed, or otherwise used any of the listed chemicals in quantities equal to or greater than the established threshold for that calendar year (EPA 1990).

19    This volume is smaller than the total volume released since manufacturers are only required to report if above the threshold established for the corresponding year. The threshold for 1988 calendar year was 25,000 pounds. There were 320 toxic chemicals included in the 1988 reporting requirements.

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