First, Corn & soy insecticides similar to nicotine found widespread in Midwest rivers — USGS news
Insecticides similar to nicotine, known as neonicotinoids, were found commonly in streams throughout the Midwest, according to a new USGS study. This is the first broad-scale investigation of neonicotinoid insecticides in the Midwestern United States and one of the first conducted within the United States.
Effective in killing a broad range of insect pests, use of neonicotinoid insecticides has dramatically increased over the last decade across the United States, particularly in the Midwest. The use of clothianidin, one of the chemicals studied, on corn in Iowa alone has almost doubled between 2011 and 2013.
“Neonicotinoid insecticides are receiving increased attention by scientists as we explore the possible links between pesticides, nutrition, infectious disease, and other stress factors in the environment possibly associated with honeybee dieoffs.” said USGS scientist Kathryn Kuivila, the research team leader.
Neonicotinoid insecticides dissolve easily in water, but do not break down quickly in the environment. This means they are likely to be transported away in runoff from the fields where they were first applied to nearby surface water and groundwater bodies.
In all, nine rivers and streams, including the Mississippi and Missouri Rivers, were included in the study. The rivers studied drain most of Iowa, and parts of Minnesota, Montana, Nebraska, North Dakota, South Dakota, and Wisconsin. These states have the highest use of neonicotinoid insecticides in the Nation, and the chemicals were found in all nine rivers and streams.
Of the three most often found chemicals, clothianidin was the most commonly detected, showing up in 75 percent of the sites and at the highest concentration. Thiamethoxam was found at 47 percent of the sites, and imidacloprid was found at 23 percent. Two, acetamiprid and dinotefuran, were only found once, and the sixth, thiacloprid, was never detected.
Instead of being sprayed on growing or full-grown crops, neonicotinoids can be applied to the seed before planting. The use of treated seeds in the United States has increased to the point where most corn and soybeans planted in the United States have a seed treatment (i.e., coating), many of which include neonicotinoid insecticides.
“We noticed higher levels of these insecticides after rain storms during crop planting, which is similar to the spring flushing of herbicides that has been documented in Midwestern U.S. rivers and streams,” said USGS scientist Michelle Hladick, the report’s lead author. “In fact, the insecticides also were detected prior to their first use during the growing season, which indicates that they can persist from applications in prior years.”
One of the chemicals, imidacloprid, is known to be toxic to aquatic organisms at 10-100 nanograms per liter if the aquatic organisms are exposed to it for an extended period of time. Clothianidin and thiamethoxam behave similarly to imidacloprid, and are therefore anticipated to have similar effect levels. Maximum concentrations of clothianidin, thiamethoxam and imidacloprid measured in this study were 257, 185, and 42.7 nanograms per liter, respectively.
The U.S. Environmental Protection Agency has classified all detected neonicotinoids as not likely to be carcinogenic to humans.
Meanwhile, Invertebrate numbers nearly halve as human population doubles
Invertebrate numbers have decreased by 45% on average over a 35 year period in which the human population doubled, reports a study on the impact of humans on declining animal numbers. This decline matters because of the enormous benefits invertebrates such as insects, spiders, crustaceans, slugs and worms bring to our day-to-day lives, including pollination and pest control for crops, decomposition for nutrient cycling, water filtration and human health.
The study, published in Science and led by UCL, Stanford and UCSB, focused on the demise of invertebrates in particular, as large vertebrates have been extensively studied. They found similar widespread changes in both, with an on-going decline in invertebrates surprising scientists, as they had previously been viewed as nature’s survivors.
The decrease in invertebrate numbers is due to two main factors – habitat loss and climate disruption on a global scale. In the UK alone, scientists noted the areas inhabited by common insects such as beetles, butterflies, bees and wasps saw a 30-60% decline over the last 40 years.
The diminishing status of invertebrate populations greatly compromise nature’s ability to provide us with what we need. In economic terms, they provide us with important services, often worth billions of GBP£:
- Pollination – insect pollination is required for 75% of all the world’s food crops and is estimated to be worth ~10% of the economic value of the world’s entire food supply. Globally, pollinators appear to be strongly declining in both abundance and diversity.
- Pest control – in the US alone, the value of pest control by native predators is estimated at $4.5 billion annually, these costs could escalate with the decline in predator number.
- Nutrient cycling and decomposition – insects and vertebrates (birds, for example) are important for cycling nutrients and moving them over long distances, without which the integrity of other ecosystem functions such as plant productivity could be compromised.
- Water quality – declines in amphibian populations has led to increased algae and the biomass of waste matter, which in turn reduces nitrogen uptake.
- Human Health – decreasing invertebrate numbers are known to compromise food production due to reduced pollination, seed dispersal and insect predation but the impact the continuing loss of animals, including invertebrates, has on the spread of human disease needs to be better understood as a priority.
Scientists believe there is a growing understanding of how ecosystems are changing but to tackle these issues, better predictions of the impact of changes are needed together with effective policies to reverse the losses currently seen. Using this approach, conservation of species can be prioritised with the benefit of protecting processes that serve human needs, and successful campaigns scaled-up to effect a positive change globally.
Dr Ben Collen (UCL Biosciences), last author of the study, said: “We were shocked to find similar losses in invertebrates as with larger animals, as we previously thought invertebrates to be more resilient. While we don’t fully understand what the long-term impact of these declining numbers will be, currently we are in the potentially dangerous position of losing integral parts of ecosystems without knowing what roles they play within it.
“Prevention of further declines will require us to better understand what species are winning and losing in the fight for survival and from studying the winners, apply what we learn to improve conservation projects. We also need to develop predictive tools for modelling the impact of changes to the ecosystem so we can prioritise conservation efforts, working with governments globally to create supportive policy to reverse the worrying trends we are seeing.”
Professor Rodolfo Dirzo (Stanford Woods Institute for the Environment), lead author of the study, said: “Where human density is high, you get high rates of defaunation, high incidence of rodents, and thus high levels of pathogens, which increases the risks of disease transmission. Who would have thought that just defaunation would have all these dramatic consequences, but it can be a vicious circle.
“We tend to think about extinction as loss of a species from the face of Earth, and that’s very important, but there’s a loss of critical ecosystem functioning in which animals play a central role that we need to pay attention to as well. Ironically, we have long considered that defaunation is a cryptic phenomenon, but I think we will end up with a situation that is noncryptic because of the increasingly obvious consequences to the planet and to human well-being.”
