Environmental monitoring with indicator plants for air pollutants in Asia

Abstract

Air pollution is a regional issue in Asia. To assess air pollution levels and their actual impacts on plants, environmental monitoring using indicator plants has been conducted since the 1970s. In particular, in Japan, during the 1970s/1980s when air pollution levels were relatively high, various kinds of indicator plants were used for monitoring air pollution. Some vascular plants, such as morning glory and petunia, were used as indicator plants for monitoring the pollution of photochemical oxidants (Ox), including O3 and peroxyacetyl nitrate (PAN). In the middle of the 1970s, nationwide surveys using morning glory revealed Ox pollution in 37 of the 47 prefectures in Japan. Epiphytes, such as bryophytes and lichens, were used as bio-indicators for SO2 pollution. The "epiphyte desert" observed in urban and industrial areas showed severe SO2 pollution in large cities in Japan during the 1970s. An improvement in the distribution of epiphytes resulted in reduced SO2 pollution in Japan during the 1980s. Similar environmental monitoring using bryophytes and lichens as bio-indicators was conducted in other Asian countries. Common tree species, such as cedar, can also be used as indicator plants for environmental monitoring. Further application of such monitoring in Asian countries should be promoted.