1. Air pollution and agriculture.
Outlook on Agriculture, 20, 1991, 139-144
Air pollution has long been known to damage plants.
Up to the middle of this century, the problem was very largely restricted to urban and industrial regions of Europe and North America.
Over the past two decades, however, it has become evident that pollutants can be transported over long distances, and hence their impact may be felt widely over rural regions. The rapid pace of industrial development and urbanization in many developing countries means that adverse impacts on agriculture are beginning to be felt in many parts of the world.
The major pollutants of concern in relation to agriculture are summarized in this article and some important sensitive crop species and the approximate concentration at which adverse effects are observed. The pollutants may conveniently be divided into primary pollutants, such as sulphur dioxide and ammonia, which are emitted directly into the atmosphere, and secondary pollutants, such as ozone, which are formed by subsequent chemical reactions in the atmosphere.
Although particulates act primarily by reducing light interception, certain particulates (e.g.cement dust) have chemical properties which may lead to more specific injury. Other particulates may contain high concentration of heavy metals, such as lead and zinc, which may contaminate foliage directly, or contribute to an increased soil burden.
Other primary gaseous pollutants which may be of concern around industrial works include hydrogen chloride, chlorine and ammonia.
Apart from ozone, the most important secondary pollutants are acid mists and rain which contain high concentrations of nitrate and sulphate, produced from the oxidation and dissolution of nitrogen oxides and sulphur dioxide. Acid rain has been shown to cause soil and fresh-water acidification in areas with poorly buffered soils. Ozone is undoubtedly the most important gaseous secondary pollutant in terms of impact on agriculture, but other gases have local impacts on sensitive crops too.
These pollutants are photochemical and are produced in high concentrations under hot, sunny conditions.
National estimates indicate crop losses of about 5% in the USA and Netherlands, but these estimates do not take into account indirect effects, via altered pest and pathogen performance, which could substantially alter the economic loss assessment. The greatest concern in the coming decades should be the impact of air pollution on food production in the developing countries. There is a need, in particular, for an objective assessment to identify the regions and pollutants of greatest concern; improved rural monitoring of pollutant concentrations; evaluation of the pollutant sensitivity of local crops and cultivars; and field experiments to quantify impacts of air pollution. A great contribution could be made to these needs by the governments and scientists of developed countries where agricultural impacts of air pollution are of less immediate relevance for the welfare of the population.
1152 92 - 6/31
Review, book, Europe, primary production, agriculture, greenhouse effect, climatic change, crop distribution
GOUDRIANN, J. et al
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