Carrying capacity using emergy and a new calculation of the ecological footprint

Capacidade de suporte usando emergia e um novo cálculo da pegada ecológica

ABSTRACT

Carrying capacity was evaluated using emergy assessment to improve the diagnosis of problems and tomake understanding sustainability easier, thereby supporting the formulation of public policies. IbiúnaCounty has an area of 105,800 hectare (ha) and it is located 72 km west of São Paulo, the largest Braziliancity. It has 72,029 inhabitants or 0.68 people per ha, but 2.16 people per ha of forest area. The city isonly 157 years old and about 67% of its population lives in the rural area and the other 33% in the urbanspace. In our assessment, the percent renewability of this municipality was high (47.20%). To determinethe renewable support area, the carrying capacity methodology suggested by Brown and Ulgiati (2001)was applied and the support area calculated was 306,679 ha or 0.23 people per ha. This result revealsa value for the equivalent natural area needed to absorb the impacts of the fossil fuel consumed in theproduction of industrial inputs used in the region. A recently proposed ecological footprint methodologywas used, where the calculus of support area is based on the consumption profile of the population.This methodology was adapted to obtain an alternate carrying capacity for the county. The result was249,650 ha or 0.29 individuals per ha.This study showed the importance of preserving natural areas and it introduced the need for changesin the configuration of the county economy and in its population’s lifestyle, which are needed to turnIbiúna County into a truly sustainable region.

Keywords: Carrying capacity, Emergy, Ecological footprint, Support area, Regional assessment

Introduction

In recent years, the concept of sustainability has been used not only as an idea for theoretical discussion, but also to help decision makers elaborate environmental policies for regional development that will promote well-being for human beings and their ecosystems. A literature review revealed several studies assessing the sustainability of cities and regions. Some of them used the emergy approach to evaluate sustainability.

Emergy evaluation is a form of environmental accounting, where the energies of material resources and services coming from the economy, and also all energy flows from nature are considered.

Hossaini and Hewage (2013) applied emergy accounting to Canada and its provinces, generating emergy maps that showed resource consumption as emergy per person, and emergy density under two parameters: (1) the quantities of resources consumed and (2) the location of consumption. These characterizations of the regions can be used for future planning for sustainable development and management of the land, both at the federal and provincial levels. In a case study in the Loess Hilly Region of China, emergy assessment was applied to evaluate the sustainability of an ecological restoration program (Dang and Liu, 2012). The results of this research indicated that the program was not successful and also that not enough was being done in terms of environmental preservation and optimizing resource usage. To enhance sustainability, they indicate that further actions are necessary to conserve environmental resources, to improve the emergy input structure for agricultural production and to change lifestyles of the local people living in that region. Vassallo et al. (2009) used emergy assessment to compare the sustainable development of six districts in the coastal Italian resort region called Riviera Del Beigua. In this region, tourism is the main economic activity and the traditional production capabilities of agriculture and fishing have been neglected. In these comparisons, it was verified that a large amount of emergy is expended to support tourists. This analysis supports the idea that coastal tourism is an expensive and resource intensive endeavor. Brown and Ulgiati (2001) determined carrying capacity for economic investments based on an emergy evaluation of the environmental resources of a region in Mexico and Papua New Guinea. Using data from tourism development, the concept of carrying capacity is related to intensity of development. The result is the area of the surrounding region that would be required, if the economic activity were using solely renewable emergy inputs. Macao is also a tourist city and in this case Lei and Wang (2008) applied emergy evaluation to investigate and characterize urban evolution and city development. They found that the region absorbs large amounts of emergy to support not only its survival, but also its booming development (Lei and Wang, 2008). In another study about Macao, the life support systems outside the city, tourism, and waste treatment were assessed and a comparison was made with other regions. In this study, Lei et al. (2008) found that the city with its large population and scarce natural resources showed a very high environmental loading. In an assessment of sustainability around the world, Lei and Zhou (2012) used the National Environmental Accounting Database data for 102 nations (2008 data) to evaluate the resource consumption in 17 mainstream countries. Emergy evaluation was applied to measure sustainability and these results revealed that most countries, have consumed too many resources, thereby, decreasing the overall global sustainability of the natural resources that sustain human society. Also, emergy evaluations can be used to assess the effects of waste compounds. Campbell et al. (2014a) performed emergy evaluations of the global biogeochemical cycles of the biologically active elements and compounds needed to accurately evaluate the near and far field effects of anthropogenic wastes. The authors concluded that the emergy evaluation results are compared to other means of ranking Greenhouse gases and other wastes; they recommended that more research and management attention should be focused on high transformity waste compounds like N₂O and SO₂, while continuing present efforts to better understand and manage CO₂ and reactive nitrogen.

Campbell (1998) in one of the earliest considerations about the carrying capacity in the emergy literature, concluded that human carrying capacity at a specified standard of living represents the anthropogenic load on a given regional environmental resource base. Such anthropogenic load varies in pulse cycles of change, the human populations and their living standards must constantly be adjusted to maintain the same load of resources. Carrying capacity is also a way to assess the sustainability of cities, regions or countries. The results are expressed in the amount of area required to support an individual, then carrying capacity becomes an easy way to help decision makers understand the complex idea of sustainability. Ecologists define carrying capacity as the maximum size of a species population that a given area can support without reducing its ability to maintain a given species for an undefined time period (Daily and Ehrlich, 1992). The support area is defined by Brown and Ulgiati (2001) as the minimum carrying capacity needed for a human-made system. Thus, the support area is an indicator of the load on the environment, as is the ecological footprint indicator. There are several research studies that combine several tools to measure the carrying capacity. In the last decade, two tools have been extensively used worldwide to measure the human impact on nature: The ecological footprint (EF) and emergy synthesis (ES). Galli et al. (2012) analyzed the ecological footprint in some countries, and verified that in the high income countries the ecological footprint has increased greatly, while in middle or low income countries it has remained the same or even decreased in some cases. Although the country of China is considered a middle income nation, its ecological footprint is high, and it is because of the dramatic increase in carbon footprint due to continuous industrial and population growth since 1982. Merkel (2007), concerned with a population’s intense consumption, suggests measuring it using a simplified ecological footprint, which is a fast and accurate tool for assessing the individual’s consumption; this calculus has been used in the United States and Europe. This method estimates the amount of area that is required to meet consumption and absorb the waste that consumption generates.

Zhao et al. (2005) modified the ecological footprint calculations through combining them with emergy synthesis calculations. This new methodology was applied in an analysis of Gansu province of China and they concluded that both methods have corresponding biological productivity units. Chen and Chen (2006) slightly modified this concept and compared the bioproductivity ecological footprint method to an emergy-based method in a time series (1981–2001) study of Chinese society. Liu et al. (2008) also use ES to calculate the carrying capacity and EF of cropland in a time series case study of Jiangsu province, China and they compared their results to conventional EF. Pereira and Ortega (2012) discussed the strong points and shortcomings of the ecological footprint, emergy synthesis and other approaches derived from both and how to use the positive aspects and potential improvements from both methodologies at a national level in a case study of Brazil. The method of emergy-ecological footprint was applied by Zhao et al. (2013) to evaluate the environmental sustainability of an offshore small fish farm in the East China Sea and they concluded that the emergy ecological footprint can serve as a practical and meaningful tool for comparing and monitoring the environmental impact of fish farming. Cuadra and Bjorklund (2007) evaluated the relationships and usefulness among three different analysis methods for assessing economic viability, ecological carrying capacity and sustainability in six tropical agricultural crop production systems in Nicaragua. The results found showed poor coherence between economic profitability and ecological sustainability. They argue that these evaluation methods may be used for quantitatively assessing different production systems, leading to new indices constructed by weighting both economic and environmental aspects of those systems that then may be used to make decisions. Siche et al. (2008) makes a comparison between the ecological footprint and “environmental sustainability index” using two emergy ratios (renewability and the emergy sustainability index) to measure the sustainability of nations. They suggest that the combination of EF and ES would result in an improved sustainability index expressed in emergy units that might serve as a basis for the calculation of EF equivalence factors. Agostinho and Pereira (2013) assess the support area index for Brazilian sugarcane and American corn crops through four different approaches: Embodied Energy Analysis, Ecological Footprint, Renewable Empower Density, and Emergy Net Primary Productivity.

Section snippets

Study area

Ibiúna is located 72 km west of the city of São Paulo, São Paulo state, Brazil (Fig. 1). Table 1 shows the characteristics of Ibiúna County.

The municipality is located in a mountainous region and possesses a large green area, almost 45% of its total area. The green area is composed of native forests, savannas and reforested area. There is a large water basin with three rivers that flow to the Itupararanga dam that provides water to 6 cities. The dam is located within the state preservation area

Methodology

Emergy evaluation was carried out in Ibiúna County and after obtaining the emergy indicators, the carrying capacity was evaluated using the support area methods developed by Brown and Ulgiati (2001). To compare the carrying capacity results, the simplified ecological footprint developed by Merkel (2007) was applied. In this ecological footprint methodology the biocapacity calculation was not made, therefore the results are given in real hectares.

Emergy evaluation

The ESL diagram representing the main flows of Ibiúna County is shown in Fig. 2. The diagram representing the ecosystem functions of the municipality are presented in Appendix A. The emergy table was built and is presented as Table 2; it is possible to see the calculations in the Appendix. Both Appendices are in supplementary data. The results of calculating the emergy indicators for Ibiúna County and its rural area are shown in Table 3.

Support area by emergy evaluation

The Brown and Ulgiati (2001) equation (1) was applied

Emergy indicators

The analysis of emergy indicators showed that the environmental load, ELR, in Ibiúna County is high pressure, and in the agricultural area it is even higher. Sustainability in terms of renewability percentage in Ibiúna County is high, while in agricultural area it is lower. This behavior can be explained because in the County calculations considered all the area, that include the city, agriculture, forest and pasture. While in the rural area, only the agricultural production area was

Conclusion

This study presents the importance of preserving natural areas and the environment and it introduced the need for changes in the configuration of the Ibiúna county economy and the lifestyle of its population in order to turn it into a more sustainable region.

Determining the carrying capacity using emergy and the recently proposed ecological footprint was presented as a useful tool to measure sustainability. Both methods used in this study to determine the support area, show that the area of

Acknowledgments

The authors are grateful to CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) and CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) for their financial support.

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