The effects of air pollution on urban ecosystems and agriculture

Abstract

Over half the global population live in cities, with this proportion rising rapidly. Yet relatively little attention has been paid to the health of urban ecosystems, which are subject to more severe stresses in many cases than their rural counterparts. In this paper, the importance of urban ecosystems, including agriculture, is emphasised, with particular consideration given to the impacts of air pollution. Techniques for studying these impacts are fumigations, filtrations, transect studies and the use of chemical protectants, examples of which are considered for both the developed and developing world. Sulphur dioxide (SO2) and coal smoke formerly dominated the developed world and remain a growing problem in the developing countries. In both regions, the ‘modern’ pollutants, in the form of nitrogen oxides (NO x ), ozone (O3) and fine particulate matter (PM10), are also major problems for urban vegetation. Despite generally lower pollutant levels in the developed world, there is evidence that both crops and wild species are adversely impacted. However, urban crops in the developing countries have been shown to be of paramount importance for nutrition of the urban poor, yet studies in India indicate that their yield and quality are seriously impaired. Both fungal pathogens and insect pests of plants are also impacted, and examples are given in this paper. The most sensitive organisms are lichens, and research is described in which changes in air quality in London over the last 40 years have resulted in major shifts in the lichen flora.