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Energy flow analysis as a tool for developing a sustainable society—a case study of a Swedish island
Resources, Conservation and Recycling 25 (1999) 289–299
Energy flow analysis as a tool for developing a sustainable society—a case study of a Swedish island ˚ sa Sundkvist a,*, AnnMari Jansson a, A ˚ sa Enefalk b, Pia Larsson c A a
Natural Resources Management, Department of Systems Ecology, Stockholm Uni6ersity, S-106 91 Stockholm, Sweden b Oxhags6. 5, Kalmar, Sweden c ˚ rsta, Sweden Sla¨tbaks6a¨gen 4. A Received 29 September 1998; accepted 12 October 1998
Abstract In order to develop a sustainable society, tools are needed to analyze the relationships between human activities and ecosystems and to estimate the carrying capacity of the natural resource base. In this paper, energy analysis is applied in a study of the small island society Na¨mdo¨ in the Stockholm archipelago, Sweden. Na¨mdo¨ has a permanent population of 41 persons and ca. 1000 summer residents. We estimated the energy and material flows on the island, including the primary and secondary production in natural and cultivated ecosystems, human production and consumption of food, and production of waste. Our results show that the island society’s consumption exceeds the natural carrying capacity of the island. A great deal of food and energy is imported while only a minor amount of local resources are utilized. The island society is, at present, not constrained by the local resource base, but instead depends heavily on functioning transport communications with the mainland. Based on our findings we make recommendations for greater self-sufficiency, including use of locally available renewable resources and increased recycling. © 1999 Elsevier Science B.V. All rights reserved.
* Corresponding author. Tel.: + 46-8-164252; fax: +46-8-158417; e-mail: [email protected]. 0921-3449/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 8 ) 0 0 0 7 0 - 6
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Keywords: Energy flow analysis; Sustainable development; Resource management; Self-sufficiency; Island
1. Introduction Since the Earth Summit in Rio in 1992 and the UN adoption of Agenda 21 [1] work towards the transformation of society into one built on more sustainable grounds has slowly begun. In order to achieve this goal, we have to explore how natural, human-made and cultural capital interact and influence each other [2]. Because natural capital is becoming a limiting factor for human expansion in the world it is essential for every region to analyze its dependence on external resources and how it can become more self-sufficient. Self-sufficiency on a local or regional level means better food security and living within the region’s carrying capacity. A self-sufficient nation or region consumes fewer external resources and puts local ones to better use. If a society strives to be self-sufficient and can meet its own basic needs it is less vulnerable to external fluctuations, e.g. variations in climate and changes in national and global economies [3]. This is of utmost concern in a world of increasing population growth and decreasing food supply. Increasing self-sufficiency has not been considered an issue in rich countries because international trade can compensate for regional shortages of food and other resources [4]. Thus, regional carrying capacity can be exceeded through the import of food, but many of the environmental problems of the modern food industry could be solved with a higher degree of self-sufficiency at the local level. For example less imported food would mean less transport. Developed countries have less than 24% of the world population but our share in global consumption ranges from 50%–90% [5]. Changes in lifestyles and consumption patterns in developed countries is a key to supplying the world’s growing population with food, and at the same time securing future food production by maintaining the health of the world’s ecosystems. In this paper, we study the potential for self-sufficiency of a small island society in Sweden. Based on the results of our analysis we discuss possible measures for social development in an ecologically sustainable direction, mainly relating to food and energy supply.
2. Study area The study area is Na¨mdo¨, a Baltic Sea island situated in the Stockholm Archipelago, approximately 40 km east of the city of Stockholm. The size of the island is 10 km2. It can only be reached by sea, and a ferry runs to and from the mainland all year round. The island has several characteristics which are typical of the ‘middle archipelago region’. The bedrock consists mostly of gneiss with a thin layer of moraine on top. The landscape is varied with large areas of coniferous forest and bare flat rocks as well as dispersed small patches of deciduous forests,
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arable land, pasture, meadows and small lakes. The coastline is a mixture of rocky shores and muddy beaches. In 1995, there were only 41 persons (18 households) living permanently on the island. In addition, 950 summer residents (218 households) spend on average 90 days per year on the island. Na¨mdo¨, like the archipelago as a whole, has suffered from the increased urbanization of the Swedish mainland. At the end of the 19th century, the size of the permanent population in Na¨mdo¨ partridge (including several small islands) was ca. 300 persons compared with about 90 today. There are no large industries on the island and the islanders support themselves by working in several sectors, such as agriculture, tourism, service, business and handicrafts. The existence of a local school, a store, a post office and a church has been important for keeping the society alive.
3. Methods The carrying capacity of ecosystems to provide human societies with products and services on a long-term sustainable basis can be evaluated by several methods [6]. One method is to calculate and compare the energy values of different products, services and transactions [7]. Energy flow analysis can be a useful tool in regional planning and decision making [8]. The approach used in this study was to map the flows of energy and materials on the island and its surrounding coastal waters down to a depth of 20 meters. Areas of the different ecosystems were established from maps (1:10 000), sea charts (1:25 000), aerial photos and field studies. Energy and material flows in society were established through a questionnaire and interviews made with the islanders, visitors, local authorities and various experts. All flows were expressed in terms of energy (kJ/year) using transformation numbers from the literature. Many ecological processes (like nutrient recycling, gas regulation and degradation of waste) were not included in this study. Collected data were compiled in an energy systems diagram, sensu Odum [7]. Detailed compilation of data and calculations can be found in Enefalk et al. [9]. The following estimates were made: inflows of natural energy such as, solar, wind and wave energy. primary and secondary production of natural ecosystems human food production energy use in households and other human activities consumption of food and water production of latrine and other waste. import and export of goods and services The collected data represent annual averages for consumption (although consumption by summer residents accounts for the time they spend on the island). Statistics on annual consumption of food products by Swedish consumers was obtained from the Swedish statistics [10].
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4. Results The model in Fig. 1 shows the major natural and cultural energy flows for Na¨mdo¨. To the left in the figure are the imports, in the middle the net primary production, and food and goods both produced and consumed locally. To the right are the exports, mostly to the mainland or to other archipelago islands.
4.1. Production of local resources The total net primary production (NPP) on Na¨mdo¨ amounts to 101·109 kJ annually (Table 1). According to our estimates, ca. 0.2% of the annual solar insolation (45.6× 1012 kJ) is accumulated in plant biomass in forests and other local ecosystems (Table 1). Shallow coastal areas around the island are the most productive, contributing 45% of the total net primary production, while productive forest accounts for 37% and arable lands for 7% (Table 1). Lakes, wetlands, gardens, bare rock, roads, etc. make up for the remaining 11%. Residents pick mushrooms and berries and gather firewood in the island forest, while most of the timber is transported to the mainland.
Fig. 1. Internal and external energy flows (106 kJ) in the island of Na¨mdo¨, 1995. To the left, natural inflows and imports; in the middle goods both produced and consumed on the island; and to the right natural outflows and exports. Food consists of both vegetable and animal products.
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Table 1 Net primary production of the photosynthetic systems on Na¨mdo¨a Ecosystem
Area (km2)
Net primary production kJ/m2
Coastal waters Lakes Arable land Wetlands Timber forests Other Total
3.08 0.13 0.54 0.11 3.84 5.38
14 700 1350 13 000 10 900 9610 1910
13.08
106 kJ/year 45 200 175 7020 1200 36 900 10 300 100 795
a Coastal waters includes the coastal area down to a depth of 20 m. Timber forests is defined as producing more than 1 m3/timber year. The category ‘other’ includes bare rocks, non-commercial forest, gardens, roads and built up areas.
Primary production supports a secondary production which provides the inhabitants with animal products such as fish and game. There is no professional fishing on the island and the store does not sell fresh fish, but according to our inquiry, many households fish regularly to cover personal needs. Agriculture on Na¨mdo¨ consists of one organically managed farm and a small-scale vegetable garden. The farm mainly produces meat (beef and lamb) and eggs. Today, most farm products are exported to the mainland.
4.2. Imported consumption goods and energy The electricity, energy and water use on Na¨mdo¨ is summarized in Table 2, in total and per household. Most houses are electrically heated and a few use oil. Liquefied petroleum gas, LPG, is used for cooking. Electricity is brought to Na¨mdo¨ by cable from the mainland (Fig. 1). Gasoline and diesel are used mainly for driving mopeds, lawnmowers and small private motorboats, which the islanders use to get to the mainland. Some of the imported gasoline and diesel is sold to visiting leisure boats via the local petrol station. Summer guest households and permanent households use approximately the same amount of LPG, electricity and firewood in proportion to the time they spend on the island (Table 2). Summer guests have a high water consumption and permanent residents use more petrol and diesel than the summer guests do (Table 2). Local energy sources, such as sun and wind energy, are little used, with the exception of the above mentioned firewood use.
4.3. Natural energy inflows The natural energy inflows to Na¨mdo¨ are extensive and contribute indirectly to the island society through various ecosystem services. The inflows to Na¨mdo¨ are very large compared to the outflows (Fig. 1). A major part of the difference
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between these amounts is the outflow of degraded energy—in the form of heat. The natural energy inflows represent potential energy sources that could be used to generate electricity and heat the households.
4.4. Local production/consumption In Fig. 2, food consumption on Na¨mdo¨ is compared to potential local supply. The islanders have a variety of locally produced foods to choose from: agricultural products (meat, eggs, vegetables), home-grown vegetables as well as what the natural ecosystems provide, such as berries, mushrooms, game and sea fish. More than 50% of households cultivate vegetables in private garden plots and fish for household needs. The diagram (Fig. 2) shows the potential self-sufficiency for some of the foodstuffs, assuming that the households of Na¨mdo¨ would choose locally produced food as much as possible. Responses to the questionnaire reveal differences in consumption patterns between the permanent residents and the summer guests. The locals eat more locally produced food than the summer guests do; they fish more, grow more vegetables and pick more berries and mushrooms locally.
4.5. Outflows The outflows from the island society consist of food and forest products, but the largest outflow is waste. 50 tons of household waste is produced each year on Na¨mdo¨, half of which is transported to waste dumps on the mainland (Fig. 1). However, local recycling of nutrients from animal manure and household toilets is important. Dry toilets are common on the island. Urine and faeces are composted on the island and sewage water from the households is purified through soil infiltration.
5. Discussion The study of islands has been, and still is, important within biology to formulate general ecological and evolutionary principles and to identify relationships between natural and human made systems [8,11–15]. Islands have often been used in pilot Table 2 Per household consumption and total consumption of energy (106 kJ) and water (m3) on Na¨mdo¨ in 1995
Gasoline and diesel Oil LPG Electricity Firewood Water
Permanent households
Summer guest households
Total consumption
41.3 ? 0.3 52.2 58.2 50.5
1.2 ? 0.1 11.1 19.1 27.1
1011 1100 18 5111 3500 6824
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Fig. 2. Comparison of the supply of locally produced foods to food requirements on Na¨mdo¨, in tons per year.
projects in order to try out different methods or management strategies [8,16]. However, island and mainland conditions are not entirely comparable because small islands (like Na¨mdo¨) have space-related limitations of natural resources, and they are generally more vulnerable to environmental change than mainland regions [17]. On an island, an expanded use of local resources means less need for import of energy and goods from the mainland, and combined with increased local recycling of materials this enables the island to be more self-supporting, as long as resources are managed sustainably. One limitation of the study is that the distribution of resource consumption over the year is not reflected. In reality it is during the summer that the main part of the total consumption takes place and it is important not to overlook the heavy pulse of environmental load that is caused by summer guests and boat tourists during a few summer months. The large number of summer guests cause an increased consumption of fresh water, fuel and electricity as well as release of waste and sewage water. Boat tourists, who berth at the shores of Na¨mdo¨, have not been included in the study. They also impact on the island ecosystems through emission of pollutants to air and water and by sport fishing and other leisure activities. The summer guest households use more than half of the amount of fresh water that the permanent residents do (Table 2), even though they only spend on average a quarter of the year on the island. The supply of fresh water is at a minimum in the summer when the tourist season is at its peak and there is a potential risk of salt-water intrusion in local wells. A large problem is that the islanders have not been able to benefit economically to any large extent from the summer tourism. Most summer residents own their
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summerhouses and pay taxes to their home municipalities. Because the demand for houses in the archipelago is very high, their taxation value has increased several 100%. The result has been that many islanders can not afford to live there any longer, and people who want to move permanently to Na¨mdo¨ or other islands in the archipelago can not afford to buy a house. There are of course also many positive effects of tourism. It creates conditions for survival of a local store and creates a potential market for locally produced goods and services [18]. Summer tourism is also the main reason for improved ferry-communication between the islands and the mainland, and for providing public services to the island such as health care and postal service [19]. There are many reasons for trying to facilitate an increase in the number of people living year around in the archipelago, e.g. to counteract the increasing concentration of people in urban areas. But, one has to be aware that such an increase would probably require a decreased number of summer guests, otherwise the carrying capacity of the island could easily be exceeded. The results from the study indicate that there is a great potential to develop a more self-sufficient and sustainable supply of food and energy. Today the inhabitants on Na¨mdo¨, including the summer guests, are far from living within the carrying capacity of the island. They rely heavily on imports of food and energy from the mainland while at the same time only a minor fraction of local resources are being utilized. This situation is very different from what it was 100 years ago. People living in the archipelago were then able to support themselves with local resources — even though this way of living was often hard. The island community was an integrated part of the natural ecosystem, exploiting locally available resources in a diverse and sustainable way. Now, industrialization has brought about an island society that is not constrained by the local resource base, but depends heavily on functioning transport communications with the mainland. Energy, food and other goods are transported from the mainland and some islanders travel in the opposite direction to work. Our analysis of Na¨mdo¨ gives an example of an unsustainable island system typical of the present archipelago, highly influenced by the urban way of living. The situation could be significantly improved by decreasing the level of dependence on imported energy, and, instead, making better use of the local resources. One obvious measure towards increasing self-sufficiency would be to generate electricity from local sources. Preconditions for utilizing wind and solar power are good, but to provide electricity for all the households on Na¨mdo¨ would require four windmills (220 kW) producing about 400 000 kWh each per year or 1.5 ha of solar cells (with a solar insulation of 969.5 kWh/m2 and an efficiency of 12%) producing 99 kWh/m2 a year. If the houses and water were heated by means of solar panels, firewood and burning of combustible waste or biofuels instead of electricity—only one windmill or 0.4 ha of solar cells would be sufficient. However, neither electricity and heating requirements nor availability of electricity from wind and solar power are evenly distributed over the year and so a supplement of other electricity sources has to be provided.
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Another way of decreasing dependence on outside resources would be to increase the recycling of material and nutrients, for example, by making use of the waste from household toilets as fertilizer in the local farm. This would be an efficient way to avoid lack of phosphorus in the soil, which otherwise is often a limiting factor in organic agricultural production. If all the nitrogen from the household toilet waste on Na¨mdo¨ was recirculated to the local farm, 920 kg nitrogen/year could be added to the farms nutrient budget and the agricultural land presently used for growing nitrogen-fixing crops could be reduced by 40%. Instead more grain could be grown and local food production could increase. To further increase the internal cycling of materials it is essential that households on the island be induced to buy more food from the local store and producers, which is not the case at present. Today farmers sell 50% of their products to customers on the mainland, even though there is a potential market for them on the island. This is partly due to the unfortunate mismatch of demand and availability of local products, the tourist season does not coincide with the harvest season, but also because of lower prices in stores on the mainland. If people on Na¨mdo¨ bought locally produced food, in the local store, this would also reduce the need for transportation and thereby the dependence on fossil fuel. Our study has revealed that there is a great potential for increased self-sufficiency on Na¨mdo¨. This would, however, require some major changes and investments. The farm would have to start diversifying, by adding milk and food-grains to its production. Our calculations indicate that the farm would have the capacity to supply 46 permanent households with their basic food needs. There is also a great potential for households to grow more vegetables and fruit in their own gardens and to make better use of available fish resources. On a more sustainable Na¨mdo¨ the energy balance would look quite different from the present one. The internal flows would dominate the picture and the inflows would mainly consist of renewable energy resources. The outflows would be diminished and mainly consist of wastes that cannot be taken care of on the island. However, in order for this vision to become true, at least in part, a substantial change in inhabitants’ consumption patterns is necessary. 6. Conclusions In summary, our analysis leads to the following recommendations or measures that could be taken for increasing sustainability on Na¨mdo¨ and other archipelago islands: (1) Increase local food production. (2) Prioritize the purchase of locally produced groceries. (3) Recirculate nutrients from the households by using compost and human waste in agriculture. (4) Produce electricity locally by means of wind-power stations and solar-cells. (5) Supply the energy needed for house heating through the burning of combustible waste, firewood and biofuels and by means of solar-panels. (6) Consider the limited supply of fresh water. (7) Introduce alternative techniques for purification of sewage water. (8) Inform the inhabitants about how their own actions can stimulate sustainable development on the island. (9) Enhance the preconditions for living permanently in the archipelago.
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The recommendations are of a general character and correspond well to other action plans for sustainable development on a local level, e.g. Agenda 21. These recommendations may also be valid for other rural areas where tourism and permanent living compete for resources in a similar way as on Na¨mdo¨. These kind of changes will demand support from the islanders as well as from tourists and local authorities, and may be difficult to realize in the short term and from an economic pint of view. We believe, however, that an increased awareness of the problems and their possible solutions, in the spirit of Agenda 21, will encourage people to accept and contribute to the suggested changes, many of which require an active participation from all parties involved.
References [1] Anonymous. Earth Summit, Agenda 21, the United Nations Programme of Action from Rio. New York: United Nations Publication, United Nations Department of Public Information, 1992. [2] Folke C, Hammer M, Costanza R, Jansson A-M. Investing in natural capital — why, what and how? In: Jansson A-M, Hammer M, Folke C, Costanza R Jr., editors. ‘Investing in Natural Capital: The Ecological Economics Approach to Sustainability. Washington DC and Colevo: International Society for Ecological Economics Island Press, 1994:1 – 20. [3] Daly HE Jr., Cobb JB. For the Common Good: Redirecting the Economy Toward Community, the Environment, and a Sustainable Future. Boston: Beacon Press, 1989:270. [4] Pimentel D, Huang X, Cordova A, Pimentel M. Impact of population growth on food supplies and environment. Popul Environ 1997;19:9 – 14. [5] Parikh J, Parikh K, Gokarn S, Painuly JP, Saha B, Shukla V. ‘Consumption Patterns: the Driving Force of Environmental Stress. Goregaon (East), Bombay-400 065, India: Indira Gandhi Institute of Development Research, Gen Vaidya Marg, 1991. [6] De Groot RS. ‘Functions of Nature: Evaluation of Nature in Environment Planning, Management and Decision Making. Groningen: Wolters-Noordhoff, 1992:2-5. [7] Odum HT. ‘Environment, Power, and Society. New York: Wiley, 1971. [8] Zucchetto J, Jansson AM. Resources and Society, A Systems Ecology Study of the Island of Gotland, Sweden. Ecol. Stud. Springer-Verlag, New York 1985;56. ˚ , Larsson P, Sundkvist A ˚ . En systemekologisk studie av naturresurshusha˚llning pa˚ [9] Enefalk A Na¨mdo¨. Department of Systems Ecology, Stockholm University. Exam work, 1996 (in Swedish). [10] Statens livsmedelsverk. Livsmedelstabeller, energi och na¨ringsamnen, 1988 (in Swedish). [11] Darwin C. ‘On the Origin of Species. London, Murray, 1860. [12] McArthur RH, Wilson EO. An equilibrium theory of insular zoogeography. Evolution 1963;17:373378. [13] McArthur RH, Wilson EO. ‘The Theory of Island Biogeography. Princeton: Princeton University Press, 1967. [14] Rappaport R. Aspects of man’s influence upon island ecosystems. Alteration and control. In: Fosberg FR, editor. ‘Man’s Place in Island Ecosystems. Honolulu: Honolulu Bishop Museum Press, 1963. [15] UNESCO. Island agenda: an overview of UNESCO’s work on island environments, territories and societies. UNESCO, Paris, 1994. [16] UNESCO, UNFPA. Population, resources and development in the eastern islands of Fiji: information for decision making. Man and the Biosphere (MAB) programme. Project 7: Ecology and Rational Use of Island Ecosystems, 1997. [17] Brookfield HC. An approach to islands. In: Beller W, d’Alaya P, Hein P, editors. ‘Sustainable Development and Environmental Management of Small Islands. Man and the Biosphere Series, vol. 5. Paris: UNESCO, 1990.
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[18] Nordin U. Ska¨rga˚rdshandlarnas strategier, problem och mo¨jligheter. Meddelanden nr 100. Kulturgeografiska Institutionen, Stockholms Universitet, 1997 (in Swedish). [19] Nordin U. Fritidsbebyggelse for ska¨rga˚rdsbor? Studier av fritidsboendets betydelse fo¨r sysselsa¨ttningen i Blido¨ fo¨rsamling, Norrta¨lje kommun 1945 – 1987. Meddelanden serie B 86. Kulturgeografiska Institutionen, Stockholms Universitet, 1994 (in Swedish).
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Energy flow analysis as a tool for developing a sustainable society—a case study of a Swedish island ˚ sa Sundkvist a,*, AnnMari Jansson a, A ˚ sa Enefalk b, Pia Larsson c A a
Natural Resources Management, Department of Systems Ecology, Stockholm Uni6ersity, S-106 91 Stockholm, Sweden b Oxhags6. 5, Kalmar, Sweden c ˚ rsta, Sweden Sla¨tbaks6a¨gen 4. A Received 29 September 1998; accepted 12 October 1998
Abstract In order to develop a sustainable society, tools are needed to analyze the relationships between human activities and ecosystems and to estimate the carrying capacity of the natural resource base. In this paper, energy analysis is applied in a study of the small island society Na¨mdo¨ in the Stockholm archipelago, Sweden. Na¨mdo¨ has a permanent population of 41 persons and ca. 1000 summer residents. We estimated the energy and material flows on the island, including the primary and secondary production in natural and cultivated ecosystems, human production and consumption of food, and production of waste. Our results show that the island society’s consumption exceeds the natural carrying capacity of the island. A great deal of food and energy is imported while only a minor amount of local resources are utilized. The island society is, at present, not constrained by the local resource base, but instead depends heavily on functioning transport communications with the mainland. Based on our findings we make recommendations for greater self-sufficiency, including use of locally available renewable resources and increased recycling. © 1999 Elsevier Science B.V. All rights reserved.
* Corresponding author. Tel.: + 46-8-164252; fax: +46-8-158417; e-mail: [email protected]. 0921-3449/99/$ - see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 3 4 4 9 ( 9 8 ) 0 0 0 7 0 - 6
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Keywords: Energy flow analysis; Sustainable development; Resource management; Self-sufficiency; Island
1. Introduction Since the Earth Summit in Rio in 1992 and the UN adoption of Agenda 21 [1] work towards the transformation of society into one built on more sustainable grounds has slowly begun. In order to achieve this goal, we have to explore how natural, human-made and cultural capital interact and influence each other [2]. Because natural capital is becoming a limiting factor for human expansion in the world it is essential for every region to analyze its dependence on external resources and how it can become more self-sufficient. Self-sufficiency on a local or regional level means better food security and living within the region’s carrying capacity. A self-sufficient nation or region consumes fewer external resources and puts local ones to better use. If a society strives to be self-sufficient and can meet its own basic needs it is less vulnerable to external fluctuations, e.g. variations in climate and changes in national and global economies [3]. This is of utmost concern in a world of increasing population growth and decreasing food supply. Increasing self-sufficiency has not been considered an issue in rich countries because international trade can compensate for regional shortages of food and other resources [4]. Thus, regional carrying capacity can be exceeded through the import of food, but many of the environmental problems of the modern food industry could be solved with a higher degree of self-sufficiency at the local level. For example less imported food would mean less transport. Developed countries have less than 24% of the world population but our share in global consumption ranges from 50%–90% [5]. Changes in lifestyles and consumption patterns in developed countries is a key to supplying the world’s growing population with food, and at the same time securing future food production by maintaining the health of the world’s ecosystems. In this paper, we study the potential for self-sufficiency of a small island society in Sweden. Based on the results of our analysis we discuss possible measures for social development in an ecologically sustainable direction, mainly relating to food and energy supply.
2. Study area The study area is Na¨mdo¨, a Baltic Sea island situated in the Stockholm Archipelago, approximately 40 km east of the city of Stockholm. The size of the island is 10 km2. It can only be reached by sea, and a ferry runs to and from the mainland all year round. The island has several characteristics which are typical of the ‘middle archipelago region’. The bedrock consists mostly of gneiss with a thin layer of moraine on top. The landscape is varied with large areas of coniferous forest and bare flat rocks as well as dispersed small patches of deciduous forests,
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arable land, pasture, meadows and small lakes. The coastline is a mixture of rocky shores and muddy beaches. In 1995, there were only 41 persons (18 households) living permanently on the island. In addition, 950 summer residents (218 households) spend on average 90 days per year on the island. Na¨mdo¨, like the archipelago as a whole, has suffered from the increased urbanization of the Swedish mainland. At the end of the 19th century, the size of the permanent population in Na¨mdo¨ partridge (including several small islands) was ca. 300 persons compared with about 90 today. There are no large industries on the island and the islanders support themselves by working in several sectors, such as agriculture, tourism, service, business and handicrafts. The existence of a local school, a store, a post office and a church has been important for keeping the society alive.
3. Methods The carrying capacity of ecosystems to provide human societies with products and services on a long-term sustainable basis can be evaluated by several methods [6]. One method is to calculate and compare the energy values of different products, services and transactions [7]. Energy flow analysis can be a useful tool in regional planning and decision making [8]. The approach used in this study was to map the flows of energy and materials on the island and its surrounding coastal waters down to a depth of 20 meters. Areas of the different ecosystems were established from maps (1:10 000), sea charts (1:25 000), aerial photos and field studies. Energy and material flows in society were established through a questionnaire and interviews made with the islanders, visitors, local authorities and various experts. All flows were expressed in terms of energy (kJ/year) using transformation numbers from the literature. Many ecological processes (like nutrient recycling, gas regulation and degradation of waste) were not included in this study. Collected data were compiled in an energy systems diagram, sensu Odum [7]. Detailed compilation of data and calculations can be found in Enefalk et al. [9]. The following estimates were made: inflows of natural energy such as, solar, wind and wave energy. primary and secondary production of natural ecosystems human food production energy use in households and other human activities consumption of food and water production of latrine and other waste. import and export of goods and services The collected data represent annual averages for consumption (although consumption by summer residents accounts for the time they spend on the island). Statistics on annual consumption of food products by Swedish consumers was obtained from the Swedish statistics [10].
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4. Results The model in Fig. 1 shows the major natural and cultural energy flows for Na¨mdo¨. To the left in the figure are the imports, in the middle the net primary production, and food and goods both produced and consumed locally. To the right are the exports, mostly to the mainland or to other archipelago islands.
4.1. Production of local resources The total net primary production (NPP) on Na¨mdo¨ amounts to 101·109 kJ annually (Table 1). According to our estimates, ca. 0.2% of the annual solar insolation (45.6× 1012 kJ) is accumulated in plant biomass in forests and other local ecosystems (Table 1). Shallow coastal areas around the island are the most productive, contributing 45% of the total net primary production, while productive forest accounts for 37% and arable lands for 7% (Table 1). Lakes, wetlands, gardens, bare rock, roads, etc. make up for the remaining 11%. Residents pick mushrooms and berries and gather firewood in the island forest, while most of the timber is transported to the mainland.
Fig. 1. Internal and external energy flows (106 kJ) in the island of Na¨mdo¨, 1995. To the left, natural inflows and imports; in the middle goods both produced and consumed on the island; and to the right natural outflows and exports. Food consists of both vegetable and animal products.
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Table 1 Net primary production of the photosynthetic systems on Na¨mdo¨a Ecosystem
Area (km2)
Net primary production kJ/m2
Coastal waters Lakes Arable land Wetlands Timber forests Other Total
3.08 0.13 0.54 0.11 3.84 5.38
14 700 1350 13 000 10 900 9610 1910
13.08
106 kJ/year 45 200 175 7020 1200 36 900 10 300 100 795
a Coastal waters includes the coastal area down to a depth of 20 m. Timber forests is defined as producing more than 1 m3/timber year. The category ‘other’ includes bare rocks, non-commercial forest, gardens, roads and built up areas.
Primary production supports a secondary production which provides the inhabitants with animal products such as fish and game. There is no professional fishing on the island and the store does not sell fresh fish, but according to our inquiry, many households fish regularly to cover personal needs. Agriculture on Na¨mdo¨ consists of one organically managed farm and a small-scale vegetable garden. The farm mainly produces meat (beef and lamb) and eggs. Today, most farm products are exported to the mainland.
4.2. Imported consumption goods and energy The electricity, energy and water use on Na¨mdo¨ is summarized in Table 2, in total and per household. Most houses are electrically heated and a few use oil. Liquefied petroleum gas, LPG, is used for cooking. Electricity is brought to Na¨mdo¨ by cable from the mainland (Fig. 1). Gasoline and diesel are used mainly for driving mopeds, lawnmowers and small private motorboats, which the islanders use to get to the mainland. Some of the imported gasoline and diesel is sold to visiting leisure boats via the local petrol station. Summer guest households and permanent households use approximately the same amount of LPG, electricity and firewood in proportion to the time they spend on the island (Table 2). Summer guests have a high water consumption and permanent residents use more petrol and diesel than the summer guests do (Table 2). Local energy sources, such as sun and wind energy, are little used, with the exception of the above mentioned firewood use.
4.3. Natural energy inflows The natural energy inflows to Na¨mdo¨ are extensive and contribute indirectly to the island society through various ecosystem services. The inflows to Na¨mdo¨ are very large compared to the outflows (Fig. 1). A major part of the difference
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between these amounts is the outflow of degraded energy—in the form of heat. The natural energy inflows represent potential energy sources that could be used to generate electricity and heat the households.
4.4. Local production/consumption In Fig. 2, food consumption on Na¨mdo¨ is compared to potential local supply. The islanders have a variety of locally produced foods to choose from: agricultural products (meat, eggs, vegetables), home-grown vegetables as well as what the natural ecosystems provide, such as berries, mushrooms, game and sea fish. More than 50% of households cultivate vegetables in private garden plots and fish for household needs. The diagram (Fig. 2) shows the potential self-sufficiency for some of the foodstuffs, assuming that the households of Na¨mdo¨ would choose locally produced food as much as possible. Responses to the questionnaire reveal differences in consumption patterns between the permanent residents and the summer guests. The locals eat more locally produced food than the summer guests do; they fish more, grow more vegetables and pick more berries and mushrooms locally.
4.5. Outflows The outflows from the island society consist of food and forest products, but the largest outflow is waste. 50 tons of household waste is produced each year on Na¨mdo¨, half of which is transported to waste dumps on the mainland (Fig. 1). However, local recycling of nutrients from animal manure and household toilets is important. Dry toilets are common on the island. Urine and faeces are composted on the island and sewage water from the households is purified through soil infiltration.
5. Discussion The study of islands has been, and still is, important within biology to formulate general ecological and evolutionary principles and to identify relationships between natural and human made systems [8,11–15]. Islands have often been used in pilot Table 2 Per household consumption and total consumption of energy (106 kJ) and water (m3) on Na¨mdo¨ in 1995
Gasoline and diesel Oil LPG Electricity Firewood Water
Permanent households
Summer guest households
Total consumption
41.3 ? 0.3 52.2 58.2 50.5
1.2 ? 0.1 11.1 19.1 27.1
1011 1100 18 5111 3500 6824
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Fig. 2. Comparison of the supply of locally produced foods to food requirements on Na¨mdo¨, in tons per year.
projects in order to try out different methods or management strategies [8,16]. However, island and mainland conditions are not entirely comparable because small islands (like Na¨mdo¨) have space-related limitations of natural resources, and they are generally more vulnerable to environmental change than mainland regions [17]. On an island, an expanded use of local resources means less need for import of energy and goods from the mainland, and combined with increased local recycling of materials this enables the island to be more self-supporting, as long as resources are managed sustainably. One limitation of the study is that the distribution of resource consumption over the year is not reflected. In reality it is during the summer that the main part of the total consumption takes place and it is important not to overlook the heavy pulse of environmental load that is caused by summer guests and boat tourists during a few summer months. The large number of summer guests cause an increased consumption of fresh water, fuel and electricity as well as release of waste and sewage water. Boat tourists, who berth at the shores of Na¨mdo¨, have not been included in the study. They also impact on the island ecosystems through emission of pollutants to air and water and by sport fishing and other leisure activities. The summer guest households use more than half of the amount of fresh water that the permanent residents do (Table 2), even though they only spend on average a quarter of the year on the island. The supply of fresh water is at a minimum in the summer when the tourist season is at its peak and there is a potential risk of salt-water intrusion in local wells. A large problem is that the islanders have not been able to benefit economically to any large extent from the summer tourism. Most summer residents own their
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summerhouses and pay taxes to their home municipalities. Because the demand for houses in the archipelago is very high, their taxation value has increased several 100%. The result has been that many islanders can not afford to live there any longer, and people who want to move permanently to Na¨mdo¨ or other islands in the archipelago can not afford to buy a house. There are of course also many positive effects of tourism. It creates conditions for survival of a local store and creates a potential market for locally produced goods and services [18]. Summer tourism is also the main reason for improved ferry-communication between the islands and the mainland, and for providing public services to the island such as health care and postal service [19]. There are many reasons for trying to facilitate an increase in the number of people living year around in the archipelago, e.g. to counteract the increasing concentration of people in urban areas. But, one has to be aware that such an increase would probably require a decreased number of summer guests, otherwise the carrying capacity of the island could easily be exceeded. The results from the study indicate that there is a great potential to develop a more self-sufficient and sustainable supply of food and energy. Today the inhabitants on Na¨mdo¨, including the summer guests, are far from living within the carrying capacity of the island. They rely heavily on imports of food and energy from the mainland while at the same time only a minor fraction of local resources are being utilized. This situation is very different from what it was 100 years ago. People living in the archipelago were then able to support themselves with local resources — even though this way of living was often hard. The island community was an integrated part of the natural ecosystem, exploiting locally available resources in a diverse and sustainable way. Now, industrialization has brought about an island society that is not constrained by the local resource base, but depends heavily on functioning transport communications with the mainland. Energy, food and other goods are transported from the mainland and some islanders travel in the opposite direction to work. Our analysis of Na¨mdo¨ gives an example of an unsustainable island system typical of the present archipelago, highly influenced by the urban way of living. The situation could be significantly improved by decreasing the level of dependence on imported energy, and, instead, making better use of the local resources. One obvious measure towards increasing self-sufficiency would be to generate electricity from local sources. Preconditions for utilizing wind and solar power are good, but to provide electricity for all the households on Na¨mdo¨ would require four windmills (220 kW) producing about 400 000 kWh each per year or 1.5 ha of solar cells (with a solar insulation of 969.5 kWh/m2 and an efficiency of 12%) producing 99 kWh/m2 a year. If the houses and water were heated by means of solar panels, firewood and burning of combustible waste or biofuels instead of electricity—only one windmill or 0.4 ha of solar cells would be sufficient. However, neither electricity and heating requirements nor availability of electricity from wind and solar power are evenly distributed over the year and so a supplement of other electricity sources has to be provided.
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Another way of decreasing dependence on outside resources would be to increase the recycling of material and nutrients, for example, by making use of the waste from household toilets as fertilizer in the local farm. This would be an efficient way to avoid lack of phosphorus in the soil, which otherwise is often a limiting factor in organic agricultural production. If all the nitrogen from the household toilet waste on Na¨mdo¨ was recirculated to the local farm, 920 kg nitrogen/year could be added to the farms nutrient budget and the agricultural land presently used for growing nitrogen-fixing crops could be reduced by 40%. Instead more grain could be grown and local food production could increase. To further increase the internal cycling of materials it is essential that households on the island be induced to buy more food from the local store and producers, which is not the case at present. Today farmers sell 50% of their products to customers on the mainland, even though there is a potential market for them on the island. This is partly due to the unfortunate mismatch of demand and availability of local products, the tourist season does not coincide with the harvest season, but also because of lower prices in stores on the mainland. If people on Na¨mdo¨ bought locally produced food, in the local store, this would also reduce the need for transportation and thereby the dependence on fossil fuel. Our study has revealed that there is a great potential for increased self-sufficiency on Na¨mdo¨. This would, however, require some major changes and investments. The farm would have to start diversifying, by adding milk and food-grains to its production. Our calculations indicate that the farm would have the capacity to supply 46 permanent households with their basic food needs. There is also a great potential for households to grow more vegetables and fruit in their own gardens and to make better use of available fish resources. On a more sustainable Na¨mdo¨ the energy balance would look quite different from the present one. The internal flows would dominate the picture and the inflows would mainly consist of renewable energy resources. The outflows would be diminished and mainly consist of wastes that cannot be taken care of on the island. However, in order for this vision to become true, at least in part, a substantial change in inhabitants’ consumption patterns is necessary. 6. Conclusions In summary, our analysis leads to the following recommendations or measures that could be taken for increasing sustainability on Na¨mdo¨ and other archipelago islands: (1) Increase local food production. (2) Prioritize the purchase of locally produced groceries. (3) Recirculate nutrients from the households by using compost and human waste in agriculture. (4) Produce electricity locally by means of wind-power stations and solar-cells. (5) Supply the energy needed for house heating through the burning of combustible waste, firewood and biofuels and by means of solar-panels. (6) Consider the limited supply of fresh water. (7) Introduce alternative techniques for purification of sewage water. (8) Inform the inhabitants about how their own actions can stimulate sustainable development on the island. (9) Enhance the preconditions for living permanently in the archipelago.
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The recommendations are of a general character and correspond well to other action plans for sustainable development on a local level, e.g. Agenda 21. These recommendations may also be valid for other rural areas where tourism and permanent living compete for resources in a similar way as on Na¨mdo¨. These kind of changes will demand support from the islanders as well as from tourists and local authorities, and may be difficult to realize in the short term and from an economic pint of view. We believe, however, that an increased awareness of the problems and their possible solutions, in the spirit of Agenda 21, will encourage people to accept and contribute to the suggested changes, many of which require an active participation from all parties involved.
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