There has been a systematic increase in the length of the freeze-free season in several Canadian cities since 1940. This increase is believed to be due mainly to urbanization. Although the rate of urbanization during the period 1940–70 was not significantly higher than the rates in the preceding decades, urban growth during those thirty years was accompanied by higher levels of fossil-fuel conversion, which produced higher temperatures in towns and cities than in surrounding rural areas, and a generally reinforced ‘greenhouse effect’. The higher temperatures in turn combined with other urban factors to enhance the length of the freeze-free season.

In a northern climate where the growing-season is already precariously short, a longer freeze-free season should have beneficial effects on agriculture and affect other aspects of the environment. There is general agreement among research workers that the energetics of solar variability are too small to affect tropospheric or stratospheric processes directly to any significant degree. This study reinforces belief in the importance of local factors; such influences tend to override any subtle connection between solar variability and the weather.

The Republic of Niger is establishing a vast national nature reserve in the Aïr Massif and Ténéré Desert. With its 77,360 km2, the reserve will cover a wide variety of arid-land habitats. Both rainfall and vegetation are sparse, but the area harbours a varied fauna that includes a number of threatened species. The Twareg inhabitants of the reserve subsist by raising livestock, by irrigating small gardens, and by caravanning. Their day-to-day existence relies heavily on natural resources, and their continued existence will depend on the conservation of those resources. Drought, desertification, and abusive use, are all responsible for the deterioration of those resources.

Although highly necessary, the rational management of the area's natural resources will conflict with current landuse practices. Examples of where this happens are presented, and some proposals are put forward for their solution. Ideally, a flexible management system needs to be elaborated that will satisfy both the aspirations of the zone's managers and the immediate needs of its residents. The Authors hope that work in Niger will find its application elsewhere in the Sahel, and meanwhile emphasize the need to reconcile conservation with development.

A comprehensive approach to the problem of examining impacts on tundra landscapes is presented, using the Prudhoe Bay oilfield as a model. Development of the oilfield is documented, utilizing a series of ‘historical’ disturbance maps for the period 1949–83. Cumulative development of the entire field was mapped at a scale of 1:24,000, and an intensely developed portion of the field was mapped at 1:6,000, using an integrated geobotanical and historical disturbance map (IGHDM). The IGHDM data were automated, and a series of maps was made which depict a variety of information—including geobotany of the area as of 1949, and the historical sequence of development from 1968 to 1983.

Environmental law is an important tool for environmental management. A review of the environmental legislation existing in developing countries presents a very diverse picture. Generally speaking, the Asian countries have for the most part well-established and often highly-developed legal systems, which, when necessary, can assimilate new legal mechanisms and legislation for environmental management without undue turbulence. In contrast, the African countries have not on the whole made environmental protection a part of the fundamental laws that exist at present.

Poor effectiveness of environmental legislation in developing countries should be a matter of very serious concern. Such poor effectiveness is primarily due to two major problems: a piecemeal, unsystematic legal approach to environmental management, and the lack of effective implementation of existing environmental legislation—irrespective of how good it may be to deal with the overall problem.