The levels of four sets of pollutants (heavy-metals, artificial radionuclides, petroleum components, and halogenated hydrocarbons), have been measured in U.S. coastal waters, using bivalves as sentinel organisms. The strategies of carrying out this programme are outlined and the results from the first year's work are given. Varying degrees of pollution in U.S. coastal waters have been indicated by elevated levels of pollutants in the bivalves, which comprised certain species of mussels and oysters and were collected at over one hundred localities.

An oil-spill by the ocean cruise liner Statendam, in Hamilton Harbour, Bermuda, on 2 August 1976, was pursued in the courts, the Captain of the ship being prosecuted successfully because of strong circumstantial evidence—including chemical analysis by gas chromatography which matched the ship's fuel-oil with a sample taken from the harbour immediately after the spill.

The conviction was upheld on appeal. The Chief Justice's decision set a strong precedent for absolute liability when oil is discharged in contaminated ballast.

A similar case of a spill off the Florida Keys, by the M. V. Garbis in 1975, was identified by gas chromatography and other chemical methods, but did not result in conviction because of lack of jurisdiction over the waters in which the spill occurred. The Statendam case appears to be the first in which chemical analysis played an important role in establishing a conviction for oil pollution.

There are numerous instances where, through injudicious use, Man has contributed to desertification of the agricultural environment by increasing the aridity and decreasing the ability of the soil to support vegetation. This may come through erosion, even in areas with very high rainfall (e.g. Amazonia). But in many arid regions dedesertification has occurred under the influence of Man (e.g. Imperial Valley in California, Hungry Desert in Uzbekistan, 90-Miles Desert in Australia).

However, under certain conditions, such as those of fog-drip, an irreversible desertification can be caused by removal of the original vegetation (e.g. Central Chile).

Dew may be an important source of water for plants even in deserts, where there is a shortage cf liquid water for plant growth.

This paper makes a series of broad recommendations concerning the understanding of damage and recovery of tundra vegetation. It deals primarily with arctic vegetation and with principles rather than specific recommendations or instructions for restoration. Actual procedures for restoration or revegetation, although practised, are still in their experimental stages.

Despite this lack of established methods in tundra vegetation restoration, much can be done to help offset some of the worst effects of the present surge of economic development that is occurring in certain sectors of the Arctic. First, a rational assessment of types and extent of damage that is likely to accrue from different kinds and degrees of impact should be attempted, based on existing experience and theory. This should be accompanied by similar assessments of degrees and rates of recovery.

Europeans began introducing plants into southeastern Florida during the 16th century, and by the middle of the 18th century several of these were already naturalized. Few of these events have been recorded, but we know that the Guava, Papaya, and oranges, were among the early immigrants. American settlement in the middle 1800s began another phase of plant movement which continues to the present. H. M. Flagler, Henry Nehrling, John C. Gifford, and others, brought plants in for landscaping or other uses. Among those brought in by the United States Department of Agriculture were the Sisal, introduced by Henry Perrine, and the many food and ornamental plants sent by David Fairchild to the Miami Introduction Station. Many of the plants brought to Florida have become important as ornamentals or foods; however, some of the exotics have escaped and now present problems to the native ecosystems and to Man.

Over 170 species of ferns and flowering plants are naturalized in southeastern Florida. Hundreds of other exotic plants have been introduced into the region and the potential exists for others to escape. Species such as Melaleuca quinquenervia are invading wet habitats and decreasing diversity; the Australian Pine (Casuarina equisetifolia) has become so abundant on some beaches that it interferes with nesting seaturtles and American Crocodiles, as well as contributing to dune erosion. Water-hyacinth (Eichhornia crassipes) and Florida Elodea (Hydrilla verticillata) clog natural and artificial lakes, ponds, and canals, blocking boat traffic and slowing water movement. Several grasses that were introduced as pasture plants are now considered pests. Even human health is being threatened by exotic plants such as the Melaleuca and Pepper-tree (Schinus terebinthifolius), which cause respiratory allergies and contact dermatitis.

Tropical New World cloud-forest may best be described as the area of persistent cloud contact with tropical mountain vegetation. Cloud-forest exists in at least five life-zones, being characterized, generally speaking, by having high precipitation and humidity, dripping moisture, continuous cloud or mist cover, absence of frost, and trees laden with mosses and epiphytes.

In April 1975, the Walking Catfish (Clarias batrachus) was known to be established in ten counties of Florida. The present range of this exotic species covers 18 counties or somewhat more than 25 % of the freshwater area of Florida, and this has happened in the ca ten years since the first specimens were found in the wild. Severely cold winters have failed to stem range expansion, and future northward migration in peninsular Florida can be expected.

Increasing evidence indicates that a major portion of the enormous amount of polymorphism present in natural populations is maintained by natural selection. This polymorphism is necessary for adaptation. In the absence of a suitable amount of genetic diversity, a species will tend to die out in a changing environment.

The genetic diversity of most species has been considerably reduced in historical times. Breeding for uniformity, and reduction in the number and size of wild populations, are largely responsible for this loss. Replacement of a natural forest ecosystem by modern agriculture reduces the genetic diversity by three orders of magnitude at the very least. A comparison of the estimated prehistoric and present amount of genetic diversity leads to the alarming conclusion that we may already have lost as much as 90% of the total genetic diversity of the biosphere. Further loss is expected because of the rapid growth of human population.

The isolation of nature reserves by encroaching civilization may provide significant changes in the structure and composition of protected animal communities. Recent models from applied island biogeographic theory provide a means of predicting the possible effects of isolation in the large-mammal community in the Mkomazi Game Reserve of northern Tanzania. A decrease in the number of large-mammal species inhabiting this preserve is predicted by all the models.

The dynamic interdependence of the large-mammal communities of East African reserves is vital to their survival and yet is especially vulnerable to disruption from surrounding human activities. Knowledge of the effects of increasing isolation on the complex community interactions among the component ecosystems in East African reserves, will enhance conservationists' ability to minimize extirpation pressures in this region.

The watershed of the River Euphrates lies within the boundaries of the present-day states of Turkey, Syria, Iraq, and Saudi Arabia. Almost 90% of the runoff from the basin is generated within the highlands of eastern Turkey as the result of snow-melt occurring during late spring and early summer. At this time, flood levels are usually reached along the whole length of the River.

The former inhabitants of the floodplain lands of Iraq utilized the waters of the River Euphrates for at least 6,000 years. By so doing, empires dependent upon irrigated agriculture flourished and then decayed, leaving behind spectacular ruins practically throughout Mesopotamia. Until the time of the Second World War, Iraq was the only country within the Euphrates basin that made large demands on the water resources of the River. Since that time, Iraq's demand has continued to increase, resulting in average water withdrawals of over 16,000 million m3/year during the 1960s. This figure represents about 45% of the average annual discharge of the Euphrates into Iraq.

Since the mid-1960s, both Syria and Turkey have planned major dam schemes to utilize the waters of the Euphrates. The Tabqa Dam in Syria, and the Keban Dam in Turkey, have already been constructed, and Turkey has planned other major hydraulic works along its section of the River. When the irrigation projects associated with these schemes are in full operation towards the end of the century, it seems that the likely demand for water will be in excess of the available flow of the River.

The country which is likely to suffer most as a result of this is Iraq, owing to its situation in the lowest part of the basin. Already, diplomatic relationships between Syria and Iraq have been severely strained as the result of disagreements about the allocation of the water resources of the River Euphrates. In future, it seems possible that such disputes will continue to occur, and perhaps also to become of increasing severity as both Turkey and Syria begin to use large proportions of the available riverflow for irrigation. The only permanent solution to the problem would seem to be the establishment of an international body to supervise the just allocation of the water resources of the Euphrates between Turkey, Syria, and Iraq. At present it seems unlikely that a lasting agreement will be reached between the three countries.