Beleid en debat

Rising levels of cancers and fertility problems have attracted scientists’ attention to endocrine disrupting chemicals, with some calling for strict regulation of the substances, in line with the precautionary principle. Others meanwhile, stress the worthiness of those chemicals in everyday products such as plastics and warn that the foundations of science risk being turned upside down if precautionary measures are taken. Endocrine disruptors are suspected of triggering diseases such as cancer or diabetes and contributing to people becoming overweight or infertile. The controversy has gone beyond the traditional confrontation between the chemicals industry and environmental and health activists. Among scientists, too, opinions vary on whether a link exists between these chemicals and diseases. But all parties agree on one point – that the protection of consumers and the environment must be ensured. Henk Tennekes comments that a new risk assessment is needed to evaluate the effects that chemicals have on humans and the environment and that endocrine disruptors may be a case in point.

Most literature on birds and rice (Oryza sativa) focuses on the non-growing period and little is known about the influence of management practices during cultivation. A review found that the main factors affecting species composition and abundance in rice fields during the growing season were water level, flooding period, rice plant structure and size, and pesticide use. Highest bird density and diversity occurred at intermediate water levels (10–20 cm). Early flooding and late drying favored waterbird density and diversity, and the stopover of migrating species. Taller plants, at higher densities, reduced prey availability to most waterbirds but favored smaller species. Pesticides and herbicides have been shown to be toxic to birds and reduce food resources.

Invertebrates are an essential food source for most farmland birds yet their relative abundance and biomass in the most commonly grown arable crops are poorly understood. Dvac suction sampling was used to determine the abundance, biomass and community composition of those invertebrate groups considered important in the diet of farmland birds for the commonest arable crops. Approximately 40 fields were sampled at the edge and mid-field over 2 years in three different locations in England. In cereals, the fauna was primarily comprised of Araneae (10%), Coleoptera (30%) and Hemiptera (58%), whereas the oilseed rape fauna was dominated by Coleoptera (65%) and peas and potatoes by Hemiptera (89%). Beans contained a high proportion of Coleoptera (39%) and Hemiptera (49%). Aphididae were the most abundant family (20–86% of total), although in oilseed rape and beans, Chrysomelidae, Curculionidae and Nitidulidae formed ca 20% of the fauna. Aphids only formed a small proportion (7%) of the total biomass, except in peas (32%).

During the past 50 years, the human population has more than doubled and global Agricultural production has similarly risen. However, the productive arable area has increased by just 10%; thus the increased use of pesticides has been a consequence of the demands of human population growth, and its impact has reached global significance. Although we often know a pesticide´s mode of action in the target species, we still largely do not understand the full impact of unintended side effects on wildlife, particularly at higher levels of biological organization: populations,
communities, and ecosystems. In these times of regional and global species declines, we are challenged with the task of causally linking knowledge about the molecular actions of pesticides to their possible interference with biological processes, in order to develop reliable predictions about the consequences of pesticide use, and misuse, in a rapidly changing world.