The fundamental goal of conservation planning is biodiversity persistence, yet most reserve selection methods prioritize sites using occurrence data. Numerous empirical studies support the notion that defining and measuring objectives in terms of species richness (where the value of a site is equal to the number of species it contains, or contributes to an existing reserve network) can be inadequate for maintaining biodiversity in the long-term. An existing site-assessment framework that implicitly maximized the persistence probability of multiple species was integrated with a dynamic optimization model. The problem of sequential reserve selection as a Markov decision process was combined with stochastic dynamic programming to find the optimal solution. The approach represents a compromise between representation-based approaches (maximizing occurrences) and more complex tools, like spatially-explicit population models. The method, the inherent problems and interesting conclusions are illustrated with a land acquisition case study on the central Platte River.

At the 12th General Assembly of the International Union for Conservation of Nature and Natural Resources, held at Kinshasa, Zaire, in September 1975 (see the report in press for our next issue), a new programme was agreed upon for the Union.

Increasing public awareness of the need to protect Environmentally Sensitive Areas (ESAs), as well as the establishment of regional municipalities, provided the impetus for local governments to initiate ESA planning in Ontario. As of 1981, twenty municipalities—primarily regional municipalities and counties—had adopted ESA programmes.

This paper examines the current status of ESA-protection planning in Ontario and the problems encountered by municipalities in adopting and implementing ESA programmes. Using a questionnaire survey, data were collected concerning 66 municipalities, and a review was carried out of the ESA policies in 36 Official Plans. The results show that an additional 11 municipalities have adopted ESA programmes since 1981, and that most of these have been designated cities. The primary problems encountered by municipalities in implementing ESA-protection programmes have been a lack of landowner support, weakness of any provincial policy-directive, and shortness of funding. These problems are also faced by uninvolved municipalities, and play an important role in preventing them from adopting ESA programmes.

If a wider municipal adoption of ESA programmes is to be achieved, a stronger commitment will be needed from the Provincial Government in the form of guiding policies, financial assistance, and incentives to landowners who wish to protect their sensitive lands. A greater emphasis on landowner contact and public education programmes will also be required. Municipalities should cooperate with other conservation agencies and organizations in working towards this end.

Trade in tropical timber, while a minor cause of deforestation in the tropics, can be a substantial factor in promoting forest degradation and deforestation. International organizations and conferences increasingly recognize that adverse environmental effects of international trade can be reduced through regulations and economic incentives. Three international agreements, the GATT, the CITES, and the ITTA, now affect the tropical timber trade and are here reviewed. Adopted at different times, they illustrate different philosophies, pursue different objectives, and develop contradictory trade policy perspectives. Legal conflicts among these agreements reduce their effectiveness, and mitigate a global objective of making international trade in tropical timber more responsive to environmental issues. Harmonization among the GATT, the CITES, and the ITTA, and collaboration among organizations in charge of managing these agreements, should be reinforced in order to establish a coherent and uniform policy for tropical timber trade.

This article examines, through a molecular perspective, the ‘ozone-friendly’ refrigerants R-134a and R-123 vis-à-vis R-12 and R-11, which are targeted to be phased out under the Montreal Protocol on Substances that Deplete the Ozone Layer, Final Act (1987). It appears that the molecular weight, size parameter, and dipole moment, of R-134a and R-123, may induce a pronounced effect on the chemical equilibrium of ice particles in the polar stratospheric clouds and subsequently influence the photochemical reactions therein.

Non-polar, high-molecular-weight perfluoropropane (R-218), could be a better substitute for R-12, while R-134, which is a non-polar HFC of the ethane family, could also be a candidate although its molecular weight is lower than that of R-12. The search for a good substitute for R-11, however, must continue.