Air quality enhancement zones in Taiwan: A carbon reduction benefit assessment

Abstract

Air pollution control is an important aspect of environmental protection in Taiwan. In 1995, Taiwan's government began, via afforestation, to establish air quality enhancement zones (AQEZs) in order to promote multiple environmental benefits, including improved air quality, increased carbon sequestration, and enhanced environmental quality of life. In 2010, there were over 504 such zones. In addition to providing urban forests and green spaces, tree growth in AQEZs can sequester atmospheric carbon dioxide and, by shading and evapotranspiration, reduce energy demand and increase soil storage of organic carbon. In addition, afforestation can offset the carbon footprint of the world's population and is one of the best approaches to implementing carbon neutrality. The purpose of this study was to analyze the carbon reduction benefits of afforested AQEZs. Investigations of 48 AQEZs showed (1) a high diversity of trees planted (168 species), (2) an average density of trees of 1142/ha, (3) a forest timber volume of 23.92m3/ha, lower than in standard plantations, (4) a carbon storage capacity of 9.25tons/ha, and (5) average annual carbon sequestration of 1.34ton-C/ha/yr. Carbon sequestration by AQEZs in Taiwan, although not remarkably high, is nevertheless, along with other ecosystem services provided by AQEZs, a significant and direct benefit to the urban public. This study provides a reliable basis of measureable results with which decision makers can evaluate benefits of urban forest carbon sequestration.