Emergy-based sustainability assessment of a loblolly pine (Pinus taeda) production system in southern Brazil

Abstract

The world’s wood demand from planted forests is expected to drastically increase in the following decades. Brazil displays very high levels of forest productivity for Pinus and Eucalyptus planted forests. Loblolly pine (Pinus taeda) is the most important species in terms of planted forest area in southern Brazil. There, it is mainly used for paper and pulpwood production, but also allows for multi-purpose and high quality wood production. Of particular interest is whether loblolly pine management in southern Brazil comprises a sustainable alternative to world’s wood demand. A promising tool to assess forest sustainability is named emergy synthesis (or emergy accounting). It is a top-down environmental accounting approach set out to assess holistically nature and society’s contributions toward a production process. It converts all forms of energy, materials, and human services into equivalents of one form of energy: Emergy, expressed in solar emjoules (seJ). This study aimed to assess the emergy-based sustainability of a loblolly pine wood production system practiced by a private forest company in southern Brazil (municipality of Rio Negrinho, Santa Catarina State). Data on society’s input (materials, fuels and labor) were provided by the company itself and subsequently checked through field measurements and personal communication with the forestry staff. Nature’s input was segregated into renewable and non-renewable resources, with their estimates being derived from literature information. Renewable natural resources in the form of rainfall comprised 82.4% of total emergy. The organic fraction of soil loss represented the emergy flow of non-renewable natural resources and accounted for 0.85% of total emergy. The remaining 16.75% of total emergy comprised society’s contribution. The loblolly pine system outperformed large-scale, intensively managed agriculture and eucalyptus production systems in Brazil as regards the emergy index of renewability. In relation to planted forests worldwide, this loblolly pine system displayed the lowest transformity, indicating that it was the most efficient system at producing a joule of wood per emergy investment. From the perspective of emergy synthesis, this loblolly pine production system is a feasible alternative to world’s wood demand and to sustainable land use in southern Brazil. While we perceived emergy synthesis to be an important tool to assess forest sustainability, we strongly argue that it should be complemented by other assessment approaches in order to consider, inter alia, short-term adverse impacts on soils and the socioeconomic benefits of providing job opportunities and ecosystem services.