It was noted above that those promoting the concept of sustainable development in the 1980s had a rather "environmentalist" approach to the issue. In fact, development agencies had used the concept of sustainability in the past in the narrow sense of the sustainability of their own efforts: many projects brought into existence with the support of development agencies had collapsed once the agency support was removed. So, in this context, "sustainable development" meant that the initiatives started within a development project would continue after the supporting agency had left. This meaning remains in currency in parallel and occasionally confused with the more recent interpretations.

What IUCN and the Brundtland Commission meant by "sustainable development" was motivated by the worry that non - renewable resources - such as fossil fuels and minerals - which are being used to support the development process, will at some stage in the foreseeable future no longer be available. Worse yet, many renewable resources such as forests and fisheries are being overexploited to such an extent that they, too, may be exhausted in the foreseeable future. Furthermore many fragile ecosystems are being destroyed by developments that, although they may be productive in some way for human needs, are nevertheless depleting the overall capacity of nature to regenerate itself if needs and conditions change. In the extreme, the conservationist interpretation of sustainable development tends to attempt to preserve existing ecosystems against almost any kind of development, thereby denying local resources to local people.

While the environmentalist dimension of sustainable development must clearly remain important, during the 1990s, as the term broadened out from the environment and into the discourse on economic, social and political development, the emphasis shifted. Sustainable development, as a term, was adopted by agencies and organizations concerned with issues other than the Earth's atmosphere, seas, forests and ecosystems. In the case of sustainable urban development, the term "brown agenda" was coined to emphasize the need to deal not only with the global and rural environment (the "green agenda"), but also to improve the environmental conditions in which the urban population - and particularly the urban poor - were living.

This resulted in a common assumption that good urban environmental management - perhaps coupled with measures to improve equity and the quality of governance - will automatically culminate in sustainable development. This is not, however, the case. There are many choices with regard to improving the immediate living environment, some of which promise to lead to sustainable development and some of which do not. For instance catalytic converters on cars improve local air pollution but result in increases in energy use. Conventional waste management without regard for improving recycling and reducing the production of waste may result in a cleaner environment that does nothing, however, for sustainability.

Discourse came to focus attention on the meaning of sustainable development in the context of severe social and economic problems and more specifically the problem of urban poverty. McGranahan et al. (1996) point out that in fact poorer cities, although most in need of immediate environmental improvements, are considerably more sustainable than rich cities where major investments have been made to remove immediate environmental problems, but where the citizenry consumes resources at a much higher level. This does not, however, exempt poorer cities from considering the question of longer term sustainability even if the most pressing problems to be addressed in LA21 processes in such cities turn out to be those of the "brown agenda" - environmental problems narrowly defined.

In fact the great emphasis of virtually all the bilateral and multilateral development assistance agencies involved in urban development projects and programmes has been heavily on brown agenda problems with a rhetoric of "sustainable development" that is never carried through to any substantive analysis of what this might mean in the context of poverty alleviation. The multilateral banks focus attention particularly on "getting the financing policies right", assuming that this will solve all other problems (McGranahan et al., 1996:128). So neither the green agenda nor complex issues such as local organization, accountability, allocation of responsibility - coupled with the generation of a sense of ownership - are paid adequate attention.

In this context, Allen (1999) refers to the "natural resources approach" to understanding sustainability as "primary sustainability" and the capacity of urban authorities and communities to manage resources (and the environment) effectively as "secondary sustainability" - the point being that without radical changes in attitudes, management methods and much else besides, "primary sustainability" will not be achieved and even local environmental problems will fester on. As becomes evident later in this paper, the move seems slow and painful from a narrow functionalist approach (making money available for urban infrastructure) to solving what seem to be local problems to one that recognizes the complexity of local intervention. One is looking eventually for a situation where local populations are willing and have the capacity to create better living environments that can also be demonstrated to be sustainable into the reasonably distant future.

It might be said by way of summary that "sustainable development" is concerned with the longer term - the durability - of development in a situation were all too many development decisions are taken in a crisis atmosphere for short - term gain. In this sense, sustainable development aims to introduce a little more wisdom into the development process. But it cannot afford to disregard the very real and urgent needs of the present, or imagine that it can bypass the severe impediments it finds in the inadequate management structures and the difficult political conditions encountered in the cities of the South.