Acidification in developing countries: Ecosystem sensitivity and the critical load approach on a global scale

Acidification represents a growing threat to certain developing country eco systems in tropical and subtropical climates. A methodology investigating t he extent of acidification risks from sulfur emissions on a global scale is presented. Atmospheric transfer models have been used to calculate transfe r and deposition of sulfur (using emissions for 1990 and a projection for 2 050) and alkaline soil dust. A method to derive the relative sensitivity of terrestrial ecosystems is explained and preliminary critical load values a re assigned. A range of values for critical loads and base cation depositio n have been used to investigate uncertainty in maps depicting the excess of deposition above critical loads. These show an increasing risk:of acidific ation in 2050 in extended regions of southern and eastern Asia, as well as parts of southern Africa, in comparison to 1990. Certain areas, especially in Asia, are shown at risk even when high values of critical load and base cation deposition are used.