Editor's Note: New Zealand, isolated 80 million years ago by the vagaries of continental drift, blessed with a high degree of endemism as a result of the isolation, and protected from human depredations until about 1,000 years ago, offers a window on the effects of rampant mismanagement of an especially vulnerable flora and fauna. The most conspicuous transition was the destruction of the lowland forests by Polynesian settlers and the replacement of the forests with fernlands, shrublands, and tussock grasslands. But the introduction of exotic mammals, apart from humans, has been an almost equivalently destructive force, changing plant and animal communities throughout the islands. The changes have been the more profound in that the indigenous plants and animals were of the large-bodied, slowly reproducing forms that are most vulnerable to disruptions.

The principal solution advanced by Mark and McSweeney is a more elaborate system of reserves. The lessons from New Zealand are many and rich. The danger is that they will be seen as peculiar to that entrancing place and not the window on the world that they are.

Introduction

The continuous isolation of New Zealand since its separation from the Gondwanaland supercontinent during the upper Cretaceous era has allowed preservation of unique archaic elements among its limited indigenous biota.

Three periods in the recent past have had important influences on the current biota. Some of the ancient biota became extinct during the Pleistocene glaciations.

Editor's Note: Is it possible to restore an impoverished landscape? What if the landscape is insular, the vegetation has been the victim of goats and other insults compounded with introductions of exotics, including disease, to the point where species have been lost? Is there a possibility of rebuilding a stable community that will have the resilience and vigor of the original? The answer has implications for a globe now wracked regionally by waves of impoverishment without obvious end.

David B. Wingate is one of the few ecologists who has addressed this challenge. He has been successful because he is an extraordinary naturalist with the knowledge, energy, interest, will, and the opportunity to divine the details of the structure, function, and successional relationships of the original vegetation of Bermuda. He tells here the story of how he has reconstructed it on Nonsuch Island. To the extent possible, he has also reestablished the animal community as well, although extinctions and introductions make the reconstruction partial.

The story is unique and delightful. Told here in flowing prose, it is as rich in lessons in ecology as any lifetime could be. And yet, the history of Bermuda is short. It was inundated during the interglacial periods and its biota prior to human settlement in the seventeenth century was limited, even for an oceanic island.

Editor's Note: Bromus tectorum is a desert annual, an exotic to North America. It offers us a classical case of biotic impoverishment: it is one of those small-bodied, rapidly reproducing, hardy plants that finds a variety of open niches around the world and changes the world. In this case, in the Great Basin of North America, its chance introduction is displacing an indigenous forest and a native shrubby ecosystem.

W. D. Billings has been a lifelong student of the vegetation of the earth, extending his insatiable curiosity and capacity for new knowledge with a continuing flow of equally intense and able students. Billings has been an especially avid student of deserts and tundra, both Arctic and montane. It is his lifelong interest in deserts that we have tapped here to draw out one of the best-documented and most important case histories of how one exotic has changed a landscape, reducing its potential for support of plants and animals, including people, for all of time.

Introduction

From the tropics to the boreal forest, the destruction of vegetation by clear-cutting or fire is a common occurrence. The resultant loss of floristic and faunistic diversity is, in the main, due to direct human interference and impact. Subtle invasions by pathogens or by most exotic animal and plant species more likely result in selective loss, one species at a time, as was the case with the loss of the American chestnut, Castanea dentata (Marsh.) Borkh., from the eastern deciduous forest due to attack by the Asiatic fungus Endothia parasitica

My assignment has been to listen, reflect on what I have heard, and offer some final comments from the perspective of someone who, for good or ill, has been in our nation's capital working on environmental policy, both domestic and international, for almost twenty years.

The research represented in this volume certainly shows the limitations of the “one-pollutant/one-effect” approach to environmental regulation. That's not the way natural systems work. It is not consistent with the goal “design with nature.” When we look at natural systems, we see multiple stresses – chemical and physical, natural and humanly generated. The benefit of these critiques of one-pollutant/one-effect is that they force us to focus beyond individual pollutants to the underlying processes that generate pollution.

The widespread global effects of pollutants on natural biological systems are demonstrated clearly. In regulatory circles there has been a tendency to think of pollution principally in terms of health effects. That has certainly been the dominant thrust of EPA initiatives in recent years. As a useful corrective, this work calls attention forcefully to the long-term, cumulative effects of pollutants on the biota.

Similarly, this work focuses attention on the chronic, insidious changes caused by multiple stresses on biological systems. We tend to think more of dramatic “physical” changes – deforestation, desertification, extinction, and so on. Now we must be aware of more subtle biological erosion and impoverishment. An analogy to human health may be useful. We have concerns with both sickness and death.

Editor's Note: The Everglades of southern Florida are a subtropical wetland, unique in North America but taken here as an example of wetlands globally. They are as unusual and rich as the Anavilhanas of the Rio Negro, the Pantanal of the southwestern Amazon Basin, and the moist prairies of North America. They have suffered a succession of disruptions, including hunting, logging, fire, abrupt and fundamental changes in the water regime, and the encroachment of farms with their toxins aimed at “pests.” William Niering, an indefatigable student of ecology and a fountain of knowledge, points to the richness of the region by observing that it supports more than 1,000 species of higher plants, 300 species of birds, 60 species of reptiles and amphibians, and 25 species of mammals. Its role in maintaining fisheries of the southern coasts is certain, yet poorly known.

The Everglades are vulnerable and are being encroached upon rapidly. The patterns of change are familiar; the causes, textbook cases. But the effects are diffuse, erratic, difficult to codify, open to interpretation and argument. They become clear when species are threatened, habitats lost, water flows disrupted, whole populations eliminated. At that point they appear to be isolated disasters, such as a fish kill, caused by some quirk of environment and of no general significance. Niering has summarized these changes on the basis of years of experience. He treats the scholarly and the political as inseparable, which they are.

INTRODUCTION

In comparing the reactions of different aquatic organisms to toxic chemicals (whether they are inorganic in the form of heavy metals, ammonia, cyanides etc. or more complex organic pesticides), it has long been the aim of the toxicologists involved to attain some standardisation or uniformity in the experimental techniques they devise. This approach to unification of methods has been particularly marked in the case of freshwater fish, for which group there are now standard methods acceptable in most countries.

These standard methods lay down guidelines on the exact conditions of the tests vis-à-vis water quality, temperature, number and size of test organisms, duration of exposure to the chemical dilution and, finally, the criteria to be adopted when measuring the effect in terms of immobility or mortality.

The need for the same degree of uniformity in testing other forms of freshwater life, invertebrates in particular, though slow to develop has gained increasing momentum in the last 10 years or so. Much of this incentive has come from the US Environmental Protection Agency (EPA) which now plays an international role in the screening and clearance of all pesticides and other toxic chemicals likely to have a harmful effect on the environment. One of the first fruits of this increased interest in aquatic invertebrates appeared in 1972 in the form of an exhaustive summary – compiled by the EPA – of all published information on their reactions in the laboratory to a wide range of pesticides, mainly insecticides, and herbicides (NTIS, 1972).

INTRODUCTION

The use of herbicides to control undesirable plant growth first developed on a large scale shortly after World War II and has been extending rapidly ever since that time. With their increasing use in agriculture, forestry and water-way clearance particularly in developing countries these chemicals now rank alongside insecticides as major environmental contaminants (Balk & Koeman, 1984). The continuous monitoring programme of streams flowing into the Great Lakes over the last 10 years for example, has shown that herbicide use in agricultural land has now increased to such an extent that they now constitute more than half the total volume of pesticides used in agriculture (Frank et al., 1982). Even in the UK where there are unusually stringent regulations controlling pesticides in the environment – particularly with regard to natural water bodies – many of the long-established herbicides such as 2, 4-D, dalapon, dichlobenil and diquat have been cleared under the Pesticides Safety Precautions Scheme, 1973, for use as aquatic herbicides for control of submerged and emergent aquatic weeds, and for the control of vegetation along the banks of rivers and drainage channels (Ministry of Agriculture, Fisheries & Food, 1985).

Early recognition of possible effects on fish life of herbicides applied directly to water or contaminating water by run-off from agricultural land, led to very thorough laboratory investigations in the UK on fish toxicity, and established the relative lethal levels of about 20 common herbicides based on 24-h LC50 values (Alabaster, 1969).

At the time when I last carried out a review of the subject of pesticides and freshwater fauna (Muirhead-Thomson, 1971) it was still possible for a single author to do justice, within one book, to the information then available regarding all forms of freshwater animal life and all types of freshwater body. In the 15 years since that book was published, there has not only been an enormous proliferation of knowledge about this subject but also noteworthy changes in emphasis and priorities. There has been increasing specialisation within this general subject as well, making it increasingly difficult for a single author to encompass all aspects of this problem. For all these reasons, the scope of the present review is restricted to running waters, rivers and streams, and to the macroinvertebrate fauna of such water bodies. The restriction to macroinvertebrate fauna is dictated in part by the fact that a great deal of the voluminous literature in the last 15 years deals with studies on the reactions of freshwater fish, to such an extent that a competent review of that aspect, including all the physiological work on uptake and retention of pesticides by different organs, would require a separate volume. However, one aspect of those fish studies cannot be omitted from any review devoted to aquatic macroinvertebrates, that is the effect of pesticides and allied toxic chemicals on feeding habits of fish in so far as these are influenced by drastic changes in the availability of different invertebrate fish food organisms, as measured by changes in the composition of the stomach contents.

INTRODUCTION TO BLACKFLY CONTROL

Blackflies (Simuliidae) are biting flies which are widely distributed in both temperate and tropical regions. In some northern countries such as Canada their main economic importance is as biting and bloodsucking pests of humans and domestic stock. In other regions such as tropical Africa and Central America their main importance is in their role of vectors of human diseases such as onchocerciasis caused by a parasitic filarial worm. A feature common to all species of Simulium is their association with running waters which form the larval habitat. According to species and country, these habitats or breeding places may range from quite small trickling streams to very large rivers of Africa such as the Niger, the Zaire, the Volta and the Nile. In many of these rivers and larger streams the highest larval populations tend to be concentrated in the fast-flowing sections of turbulent water such as those associated with rapids and dam spillways.

Shortly after the discovery and rapid developments of DDT in the early 1940s, it was found that Simulium larvae are extremely sensitive to this insecticide and that, in some cases, effective larval control was still achieved many miles downstream from the point of application. This opened up entirely new possibilities for Simulium control on a large scale by effectively reducing or eradicating larval populations with insecticide. In one of these early and successful control operations DDT was applied at high dosages of 5–10 ppm, or even greater on occasions, which produced massive fish kills and drastic effects on other stream fauna.

THE SPRUCE BUDWORM IN CANADA AND THE US

Since the early 1950s the spruce budworm (Choristoneura fumiferana) has posed a serious threat in parts of eastern Canada, particularly New Brunswick, (Eidt, 1975, 1977; Symons, 1977a) and adjacent states of the US (Nash, Peterson & Chansler, 1971). In order to protect the valuable timber trees against defoliation, the method of control originally adopted was aerial spraying with DDT, which was practised from 1952 onwards. Since that time the intensity and extent of the infestation has increased. In New Brunswick for example, between 1952 and 1957 the sprayed area increased from 75 × 103 ha to 2.3 × 106 ha (8876 sq. miles). Many of the areas treated twice a year recorded a total application of 560 g/ha DDT per annum, and it was after such heavy treatment that Atlantic salmon, living in streams and rivers in the sprayed forest area, were found to be severely affected.

DDT began to be phased out in 1968, and by 19 70 was replaced completely by organophosphorus compounds, mainly fenitrothion. By 1976 the sprayed area in New Brunswick had increased to 4.0 × 106 ha (15000 sq. miles). By that year infestation had extended to other provinces, Quebec, Ontario and parts of Newfoundland and Nova Scotia up to a total area of 30 × 106 ha.

Fenitrothion continues to be the insecticide of choice, in Canada, and at the time of writing appears unlikely to be superseded by other insecticides (D. C. Eidt, personal communication).

The term ‘pesticide’ embraces a wide range of toxic chemicals used for controlling or eradicating undesirable forms of life. Compounds specifically designed for the control of insects and other arthropods, i.e. insecticides, make up the bulk of these; another range of pesticides is designed to deal with undesirable fish (both predatory and competitive) while still others were developed for use against the aquatic snails which harbour intermediate stages of human parasites. The term pesticide now conveniently includes herbicides, chemicals specifically designed for control of undesirable plant growth, and this inclusion recognises the fact that the greatly increased use of herbicides in recent years has, in many cases, placed these chemicals equal to or ahead of insecticides as major environmental contaminants (Balk & Koeman, 1984)

CONTAMINATION AS A DIRECT CONSEQUENCE OF PEST CONTROL OPERATIONS

DIRECT APPLICATION OF PESTICIDE TO WATERBODY

Pesticide contamination of running waters can occur in many different ways and from many different sources, and may be only of short duration or it may be prolonged. In view of the emphasis in this review on the problems of evaluation, it would be convenient to consider pesticide contamination under two main categories. In the first category would be listed all those cases where the presence of pesticide in running water is the direct consequence of control operations carried out against undesirable fauna or flora.

INTRODUCTION TO FISH TOXICANTS: DEVELOPMENT OF SELECTIVE PISCICIDES

Fish toxicants are widely used to eradicate some or all of the fish in a body of water in order that desirable fish may be stocked, free from predation, from competition or from other interference from undesirable fish. Fish poisons have a long history of use in many countries but it is only in the last 40 years that the subject has really been scientifically investigated, and only within the last 20 that the full environmental or ecological effect of such toxic chemicals has been examined critically, particularly in the US and in Canada. Fish toxicants have been used in all types of water body, both static and running. Earlier progress in their study has been exhaustively reviewed (Lennon et al., 1971), and information available at that time regarding the reactions of freshwater fauna in general, including fish, to those fish toxicants was also the subject of a separate review at that time (Muirhead-Thomson, 1971). In the present review, space limitations would now make it extremely difficult to do justice to the mass of new information covering all freshwater fauna and all types of water body. Accordingly, in keeping with the scope of the coverage, progress since that time will deal only with the use of fish toxicants in running water, and only with the macroinvertebrate fauna at risk.

INTRODUCTION

For many years, control of tsetse fly in Africa was carried out by a variety of methods based on environmental manipulation, such as bush clearing, game exclusion, habitat destruction by burning etc. The choice of methods was mainly determined by the nature of the habitats characteristic of different species of tsetse, and also by whether the objective of these operations was tsetse control or tsetse eradication.

With the advent of the synthetic insecticide DDT and its allies, increasing emphasis has been on the application of insecticide to the tsetse environment either by means of heavy residual dosages to tsetse-resting sites, or by repeated non-residual applications at lower dosage rates (Jordan, 1974). Initially the insecticides of choice were DDT and dieldrin, the latter being favoured because of its higher toxicity to tsetse. However, it was recognised early that such tsetse control measures had a serious immediate effect on wildlife, mammals, birds, reptiles and fish (Graham, 1964). Over the last 20 years therefore, the preferred insecticide for tsetse control has been the allied organochlorine chemical, endosulphan (Thiodan) (Goebel et al., 1982) selected because of its high lethal effect on tsetse combined with less inimical effect on wildlife (Hocking et al., 1966; Park et al., 1972). That period has also been marked by operational changes; insecticides originally applied by means of ground spraying or fogging equipment, are now applied almost entirely from the air, both by fixed-wing planes and by helicopter.