24
Oct
Agricultural Intensification over Last Three Decades Reduces Insect Population by 75%
(Beyond Pesticides, October 24, 2017) Over 75% of insect abundance has declined over the last 27 years, according to new research published by European scientists in PLOS One. The 
dramatic drop in insect biomass has led to equally dramatic pronunciations from highly respected scientists and entomologists. “We appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon,” study coauthor David Goulson, Ph.D. of Sussex University, UK, told The Guardian. “If we lose the insects then everything is going to collapse.” Looking at the range of mechanisms that could be driving this slow moving catastrophe, researchers could suss out only one plausible large-scale factor: agricultural intensification.
The current study, which looked at 63 nature preserves located in Germany, follows a similar study released in 2013 that was conducted in a singular German nature preserve. That study, originally published only in German, but available translated by Boulder County Beekeepers, found that 75% of insect biomass declined in the Orbroich Bruch Nature Reserve in Krefeld, Germany from 1989 to 2013. That study was limited to a singular nature preserve, and while scientists who worked on the study described their results as “frightening,” because of the small sample size, it was easy for other researchers to brush off the results as an anomaly, or one-off event.
This new study is not so easy to ignore. Researchers used Malaise traps, large, tent-like nets that can trap a range of flying insects. All traps were situated in protected areas, and samples were taken at different sites throughout the course of the study. Most sites were sampled once, though some were sampled two or more times. During the sampling process, traps were emptied once every 11 days on average from spring to early fall, and catches were stored in solution and weighed to determine insect biomass. Researchers also recorded data on weather, land use, and habitat type.
Researchers found that insect biomass declined significantly in mid-summer, compared to samples in early spring or fall. Despite average temperature increases due to climate change, which scientists indicated would likely increase insect biomass, declines persisted. And despite substantial variation in the abundance of insects trapped between different habitats, with, for example, nutrient-rich grasslands having higher trapped insect biomass than nutrient poor dunes or shrubland, rates of decline were similar across all habitat types.
Given this information, authors indicated that climate change and landscape factors were unlikely to explain the dramatic declines, as they would have expected to see stronger relationships. Only one factor was identified as plausible: agricultural intensification. Scientists note that, typical of fragmented landscapes across Europe, 94% of preserve sites tested were enclosed by agricultural fields. In the authors’ words, “Part of the explanation could therefore be that the protected areas (serving as insect sources) are affected and drained by the agricultural fields in the broader surroundings (serving as sinks or even as ecological traps).”
Massive declines in insect populations is an issue that will affect all life on the planet, from reptiles and birds, to mammals and humans. “As entire ecosystems are dependent on insects for food and as pollinators, it places the decline of insect eating birds and mammals in a new context,” said lead author of the study Hans de Kroon, PhD, of Radboud University.
An international team of scientists, The Task Force on Systemic Pesticides, has identified neonicotinoids and other systemic poisons as culpable not only for declines in insect pollinators, but global biodiversity writ large. In the U.S., increases in herbicide use have been attributed to declines in Monarch butterfly populations.
This trend can be reversed, researchers indicate, by taking simple steps. “We need to do less of the things that we know have a negative impact, such as the use of pesticides and the disappearance of farmland borders full of flowers,” Dr. de Kroon told The Guardian. While these changes are simple in practice, they are complicated only because of political cowardice to fully account for the dangers of chemical intensive agriculture. If the negative effects of conventional farming on ecosystem services and biodiversity were fully considered in the price of food, the true cost of the world’s prevailing approach to agriculture would come into sharp focus.
In the meantime, consumers can make the decision to support regenerative, ecologically based farming practices by supporting organic agriculture. Read here why organic is the right place to put your food dollars. And for more information on pesticides and their effect on biodiversity, view our Bee Protective and Wildlife program pages.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Phys.org, The Guardian, PLOS One
