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This essay sheds new light on the meaning and measurement of compactness—one of the most intriguing and least‐understood properties of geographic shapes. We articulate a unified theoretical foundation for the study of shape compactness that rests on two simple observations: First, that the circle is the most compact of shapes. And second, that there are 10—and possibly more—distinct geometrical properties of the circle that make it the most compact of shapes. We introduce these 10 properties, illustrate them with real‐world examples and define indices associated with these properties that can be calculated using a geographic information system.  相似文献   
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The paper gives a comparative and historical assessment of climatic and economic hazards in the five main fruit‐growing areas of Canada, and how the industry has responded. The northern location of fruit growing in Canada poses a number of climatic hazards. The most serious hazard is winter low‐temperature injury to trees and vines, which results in a capital loss and crop loss for up to five years. The industry has responded to this hazard by abandoning fruit growing in areas with unfavourable climatic conditions and concentrating in areas with the most favourable climatic conditions. Other responses include changing to hardier varieties, improving management practices, and government subsidies. The fruit‐growing industry has also had to face many economic hazards, including changes in technology and consumer preferences, changes in international trade rules, increased foreign competition, a cost‐price squeeze, and urbanization of the industry's land base. These economic hazards area a greater threat to the industry than the natural hazards because, in most cases, there are limited coping mechanisms available to growers, and economic globalization is preventing the federal and provincial governments from providing an adequate safety net. L'article nous présente une évaluation comparative et historique des risques climatiques et économiques des cinq principales régions agricoles du Canada, ainsi que les réactions de cet industrie face à ceux‐ci. La situation géographique nordique des champs de fruits au Canada amène un certain nombre de risques climatiques. Les basses températures de la saison hivernale causent le plus de dommages aux arbres et aux vignes, ce qui se traduit en une perte de capitaux et une perte de récoltes allant jusqu'à cinq ans. La réaction de l'industrie de l'agriculture face à ces risques fût d'abandonner les endroits dont les conditions climatiques ne favorisaient pas la récolte de fruits. II a aussi été question d'utiliser des variétés plus résistantes au froid, d'améliorer les pratiques de management, et les subventions gouvernementales. L'industrie de la culture de fruits a aussi fait face à des risques économiques, incluant les changements technologiques et les préférences alimentaires des consommateurs, les changements au niveau des règles d'échanges internationaux, la compétition croissante au niveau international, une réduction du prix‐coûtant, et l'urbanisation des terres agricoles. Ces risques économiques représentent un plus grand danger pour l'industrie que les risques naturels puisque, dans la plupart des cas, les agriculteurs se retrouvent avec des moyens de rechange limités et la mondialisation économique empêche les gouvernements fédéral et provincial de fournir des mesures de sécurité adéquates.  相似文献   
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Urban pattern and land cover variation in the greater Toronto area   总被引:1,自引:0,他引:1  
Recent epistemological shifts in environmental geography have created a space to consider the interactions between ecological and urban systems more seriously. While openness to thinking about urban ecosystems has increased in recent years, there remain fundamental gaps in our knowledge. For example, recent research has examined the impact of urban–rural gradients on ecological conditions, but major voids exist regarding the relationship between urban development patterns and land cover heterogeneity, particularly for new forms of urbanization. This article attempts to address some of these gaps by examining the relationship between urban pattern and land cover in the greater Toronto area (GTA). In particular, measures of urban pattern that reflect aspects of development density, grain and function, as well as socio-economic characteristics, are systematically analyzed in relation to land cover heterogeneity. The regression analysis shows that multiple components of urban development pattern and socio-economic conditions are correlated with vegetated land covers, while urban density variables are not related. These results indicate more detailed representations of urban pattern should be incorporated into future human–environmental interaction studies in cities.  相似文献   
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