The opportunity of agriculture to use, during the last three to five decades, abundant and cheap sources of fossil-fuel energy, has enabled farmers to enjoy an extraordinary growth of output in developed countries and in some sectors of the Third World. Unfortunately this technical revolution has not had wholly beneficial effects: pushed to its extreme it is detrimental to the environment, creates little new employment, and can even increase unemployment. Moreover, it is by no means always adapted to the needs of the hundreds of millions of poor farmers and landless labourers in the Third World, and henceforth the emerging energycrisis will surely question the wisdom of pursuing this agricultural technology.

Tropical moist forests (TMFs) of ‘primary’ status, whether rain-forests or ‘seasonal’ biomes, are currently undergoing widespread conversion—including disruption, degradation, impoverishment, depletion, and outright destruction. These are forms of conversion that range in degree from marginal modification to fundamental transformation—at rates that are anticipated to leave large parts of the biomes involved in grossly altered states, if not eliminated altogether, by the end of the present century. The remaining portions could well undergo similar patterns of conversion within the first two or three decades of the next century.

This would mean the virtual end of the biomes that are ecologically more complex, biotically far richer, and scientifically less known, than any others on Earth. It would precipitate some ultimate shifts in the course of evolution. It would also entail the irreversible loss of many unique natural resources that offer multiple utilitarian benefits—inter alia through modern agriculture, medicine, and industry—to human society now and for ever.

Since 1977 the Sepik River backwaters between Pagwi and Angoram in Papua New Guinea have become increasingly covered by the exotic water-fern Salvinia molesta. By May 1979, Salvinia covered about 80 km2. Water chemical analyses for dissolved substances give no evidence that nutrients in the Sepik River and ‘lagoons’ might become limiting enough to affect the Salvinia population. The physical impact of the plant is reflected especially in the decline of the fisheries for Saltfish Tilapia (Sarotherodon mossambicus), crocodile hunting, collection of sago-palm, and in the slowing down or complete elimination of water transport. As a consequence, people in a number of villages are unable to reach markets and children cannot go to schools.

A programme of management has been formulated which will involve the United Nations, central and provincial governments, and local inhabitants. However, it should be understood that there is little chance of complete elimination of the weed from Sepik River backwaters.

Part 2 of this paper reviews the situation in the Central and Eastern regions of the Pacific Realm as well as in the Pacific mainland coasts of Australia, North America, and South America. Table I lists the ‘Pacific Faunal Balance’ as far as vertebrates are concerned, and gives the number and distribution of existing national parks or nature reserves in each subregion. It shows that the Hawaiian Islands have been subjected to a high number of extinctions. In addition an even larger number of Hawaiian vertebrates are at present on the verge of extinction. Hawaii tops the lists of both extinct (24) and endangered (37) vertebrates. It is also evident from Table I that Pacific islands are much more vulnerable to vertebrate extinctions than are the Pacific coasts of Australia, North America, and South America. Not less than six subregions of Pacific islands show a higher number of extinctions than the east coast of Australia, and 16 subregions are affected by extinctions, while the western coasts of North and South America are not.

Apparent effects of 2,4-D (2,4 dichlorophenoxyacetic acid, amine form) on some flora and fauna were observed following aerial application, under adverse meteorological conditions, of the chemical for control of Perennial Ragweed (Ambrosia psilostachya) in pasture, on the Author's farm in Oklahoma. Ragweed was greatly reduced, but there was widespread damage to a whole range of garden crops and trees, a few of which were killed. Damage to some tree species began to be reversed a few weeks after the spraying, but with others, sitespecific infestations of Spring Cankerworm and Fungi greatly extended the period of damaging conditions.

Environmental problems of agriculture constitute some of the most complex and significant problems of modern times. They are found in all countries, but are most prominent—and tend to be most serious—in Third World countries located in ecologically vulnerable areas. Their roots commonly lie in the culture of the population, the farmers' behaviour, or the economy of the area.

In order to assess patterns of agricultural development in general, or to assess the implications of development projects, we must include the environmental, behavioural, and policy, dimensions of the agricultural production system into a single framework, so that we can understand both the problems as narrowly defined and the measures which must be taken in order to solve them.

One way of doing this is through a comprehensive, out qualitative, overview of the system. This provides a general framework for any analysis, and it can be so simplified that a particular problem can be treated in a meaningful and adequate fashion.