Edited by Jeroen C.J.M. van den Bergh
James S. Shortle and David G Abler 1. Agriculture and the environment Environmental externalities from agricultural activities, both past and present, are pervasive. Since neolithic times humans have been converting forests, wetlands and prairies into crop and grazing lands. These activities have shaped the rural landscape and the hydrology and ecology of agriculturally developed regions. Air quality, water quality and climate also influence agriculture as a bio-economic activity. Thus agriculture is both a source and receptor of environmental externalities. Contemporary evaluations of the environmental impacts of agriculture are both positive and negative. The loss of biodiversity that occurred with the expansion of the agricultural frontier and human settlement in developed regions is now recognized as an irreversible loss of natural capital. Yet, land drainage has been an important factor in eliminating malaria in Europe and North America, and agricultural land is an important habitat for many remaining wildlife species. Moreover, rural and urban populations often value agricultural landscapes as open space. In many developing countries, traditional extensive agricultural systems cause the kinds of environmental change that agricultural development has created since ancient times, as forests and grasslands are converted to crop production and grazing. In developed countries, techniques introduced during the last century have greatly increased what can be produced from the land, removing, at least for the present, the Ricardian imperative of expansion at the extensive margin to meet the needs of growing populations. However, the pesticides, fertilizers, irrigation, mechanization, specialization and structural change that have made these (and...
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