S18.Summary: Avian conservation and current pesticide use

1 National Wildlife Research Centre, Canadian Wildlife Service, Canada, 100 Gamelin Boulevard, Hull, Québec, K1A 0H3, Canada, e-mail Pierre.Mineau@ec.gc.ca; ²Unit for Pesticide Impact, Plant Protection Research Institute, Agricultural Research Council, Private Bag X134, Pretoria 0001, South Africa, e-mail nipbhb@plant1.agric.za

There is a well-established link between the decline of some bird populations -- notably birds of prey and fish-eating birds - and organochlorine insecticides (OCs). OCs are still a concern in many parts of the world because of their continuing use or because of heavy contamination from their prior use. However, in most pest-control practices today, the bio-accumulative OCs have been replaced by shorter-lived, although not necessarily less toxic, products. Complicating matters, both OC and newer-generation pesticides are often used side by side in developing countries. Many ornithologists believe that pesticide problems disappear when we restrict the use of OCs. This symposium will show that problems take on a different appearance but seldom disappear. Despite tremendous advances in pest-control technology, many of today’s new pesticides are as broad spectrum as ever. This is simply an economic reality: producing a pest-specific product does not pay. Manufacturers strive to develop pesticides that can control many of the world’s leading pests in several of the most important crops. By definition, the direct and indirect impacts of these products remain broad. Also, many of the older, more acutely toxic insecticides such as organophosphorus and carbamate compounds continue to be used, despite the availability of alternatives that would lessen bird mortality and debilitation. It is sobering to think that Rachel Carson, in her 1962 book Silent Spring, had already discussed several of these problems.

This symposium brings together key aspects of the current concerns about pesticides and bird conservation. Chuck Henny and colleagues will address the issue of direct kills, largely a result of unintended exposure during insect-control programs. Gerhard Verdoorn will continue the discussion of direct impacts but concentrate on pesticide misuse in Southern Africa. Christine Bishop and colleagues will describe a long-term study of hole-nesting birds in Canadian orchards which examined the effects of pesticide mixtures on reproductive success. Niels Elmegaard and colleagues will review the Skylark project, an ambitious multi-year study that delves into the indirect impacts of pesticides via their effect on the food supply. Finally, Andy Hart and colleagues will provide an example of the type of innovative research needed to better understand pesticide impacts before they occur so that they can be mitigated.

Except for primary habitat destruction, agricultural practices probably represent the most serious human impact on birds. These practices not only include crop management practices and protection with chemicals, but also problem animal control and off-site management of migratory pest species such as quelea and locusts. Other sources of pesticides that could affect birds include public health campaigns (e.g. malaria and tsetse fly control), as well as invader plant control, and domestic and industrial use.

Over time the profile of pesticide use has changed, and is still changing, due to new discoveries and approaches to pest control, as well as pressure from users, conservationists, regulators, and other concerned parties. Especially in developed countries, these changes, as well as conservation efforts have improved the lot of birds significantly. The introduction of new types of pesticides, application methods, biotechnology, integrated pest management and other practices can and have in many cases (Evans, D.A. 1998. 9 Int. Congr., Pesticide Chemistry, Vol. 1: PL1.), contributed to the improvement. In developed countries, although still experiencing serious poisonings (Henny, C.J. et al. 1998. Ostrich 69: 57.), efforts to investigate and understand the impact of sub-lethal effects have also gained prominence (Bishop, C.A. et al. 1998. Ostrich 69: 58; Elmegaard, N. et al. 1998. Ostrich 69: 59; Hart, A.D.M. et al. 1998. Ostrich 69: 59.).

Physiological indicators of exposure, such as cholinesterase determinations, are already well established (Mineau, P. (ed) 1991. Chemicals in Agriculture, Vol.2; Elsevier, Amsterdam.), but the use of that specific bio-marker should be extended to cover most cases of suspected poisonings, and even cases which are not so obvious, such as car strikes and collisions with wires and fences. The increased use of newer generation pesticides means that the analysis of traditional organochlorines as well as cholinesterase determinations, though still relevant, will provide increasingly less information regarding pesticide exposure. The trend to reduce the amount of active ingredient applied per area, does not only indicate the increased toxicity of newer products, but also complicates residue analysis in biological matrices after incidents.

In developing countries, both older and newer generation pesticides are used (Verdoorn, G. 1998. Ostrich 69: 58.), complicating the determination of exposure through chemical analysis, and presenting a broad range of exposures. In many areas, concomitant use of pesticides for non-agricultural purposes also adds to exposure. National priorities in many developing countries do not consider off-target effects, when these have to compete with food security, health and other aspects for available funding. However, when we transpose the concerns and experiences of developed countries as represented by the speakers at this symposium (Canada, USA, Denmark and UK) to the Southern African situation, then the combined release of pesticides by agricultural and non-agricultural sectors in developing countries amounts to a sizeable impact on our avifauna. Some of those impacts have been confirmed by Verdoorn (1998).

Another important aspect to developing countries, should be the relevance of the ecotoxicological and environmental data of the active ingredients, generated mainly for temperate climates and conditions, to more tropical and arid regions. We do know that linear extrapolations in many cases do not predict toxicity due to invalid assumptions (eg. soil types) or unknown local conditions (Henney 1998). Improved registration requirements, for those countries that have registration authorities, although seemingly the answer, will not always be practical due to high costs and reduced income for the distributors, as well as the capacity of these authorities to evaluate the results, and to regulate accordingly.

Emergent farming (small-scale farming), supported by governments and development agencies, often not only put chemicals into the hands of untrained farmers, but also introduces these chemicals into new areas. Most of the areas now being developed for farming are located close to rivers and conservation areas, adding to environmental risks. Poisonings and other effects are poorly reported, due probably to a lack of awareness or concern.

In our view, the current and future challenges of bird ecotoxicology in Southern Africa are the following:

(1) To better understand current use impacts, to predict possible outcomes, and to actively monitor environmental performance of new compounds following their introduction. This understanding should not only include lethal aspects, but also sub-lethal effects and other environmental parameters, such as breakdown rates and transport.

(2) Ideally a partnership comprising the chemical industry (producers and suppliers), users, researchers and Non- Government Organisations should be established to promote cost effective and attainable / realistic outcomes regarding food production (as well as other intended uses such as malaria control), and environmental effects.

(3) The challenges faced by developing countries remain almost intractable, when one considers the needs and expectations, as well as the development lag. Awareness improvement as well as education will go a long way to reduce negative effects (Verdoorn 1998), but a better knowledge of environmental characteristics of active ingredients, related compounds and formulation types under tropical or arid conditions is also needed. In many cases there are also special circumstances under which chemicals are applied, which does not reflect normal use patterns for which environmental data has been generated.

(4) The effects of combinations of different pesticides on bird populations also needs further investigations, especially longer terms studies, as has been demonstrated by the studies of Henny et al. (1998), Elmegaard et al. (1998) and Bishop et al. (1998).

(5) We should also not forget that chemicals not only affect birds directly (mortality, behaviour and reproductive effects) and indirectly (food supply), but also affects other components of the ecosystem in which they are applied. These include humans, insects, mammals and plants as well. It therefore stands to reason that this relationship should be accentuated in bird ecotoxicological studies. In developing countries, the human relationship needs to be documented, before recommendations, based on research results, will be accepted and implemented.

(6) The costs to analyse low levels of active ingredients in biological matrices, remains prohibitive in cases of exposure determinations. There is therefore a need to develop a physiological indicator, or suite of indicators, that can indicate stress due to exposures. Cholinesterase determination is a very useful tool, but is relevant only to certain classes of pesticides. The development of other physiological stress indicators would therefore be of great assistance in toxicological studies, especially the more difficult aspects of sub-lethal effects.