Herbicides

It began in the mid-’90s, when Monsanto developed genetically modified (GM) crops such as soybeans, alfalfa, sugar beets, and wheat. These Franken-crops were immune to its leading weed killer, Roundup. That meant that farmers no longer had to till the land to kill weeds, as they’d done for hundreds of years. They could simply blast their entire fields with chemicals, leaving GM crops the only thing standing. Problem solved. The so-called no-till revolution promised greater yields, better profits for the family farm, and a heightened ability to feed a growing world. But there was one small problem: Agriculture had placed a belligerent strongman in charge of the buffet line.

The role of common milkweed (Asclepias syriaca) in the lifecycle of the monarch butterfly has increased interest in the presence of this weed in the north central United States. An initial survey conducted in 1999 found that low densities of common milkweed occurred in approximately 50% of Iowa corn and soybean fields. In 2009, common milkweed was present in only 8% of surveyed fields, and the area within infested fields occupied by common milkweed was reduced by approximately 90% compared to 1999. The widespread adoption of glyphosate resistant corn and soybean cultivars and the reliance on post-emergence applications of glyphosate for weed control in crop fields likely has contributed to the decline in common milkweed in agricultural fields.

Unless regulators take action, one of gifts in the lyrics to “Twelve Days of Christmas,” the turtle dove, may become extinct. The dove has experienced major population decline in England over the past 20 years, due in significant part to the destruction of turtle dove habitat and food sources from increasing herbicide use in English agriculture. Other species, such as Monarch butterflies and other pollinators around the world, are also experiencing similar loses of habitat and food sources through an increase in herbicide use. These increasing rates of population decline in wild species underscore the problem that chemical-intensive agriculture plays in the degradation of natural habitats.

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.

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.