12
Feb
Study Predicts Demise of Insects within Decades if Pesticide Dependence Continues
(Beyond Pesticides, February 11, 2019) A new systematic review of insect population studies worldwide reports on “the dreadful state of insect biodiversity in the world, as almost half of the species are rapidly declining and a third are being threatened with extinction.” The study concludes with the dire prediction that insects as a whole will go extinct in the next few decades if patterns of intensive agriculture, in particular pesticide use, continue.
The review, published in Biological Conservation, analyzes 73 insect population studies conducted within the past 40 years, filtered to include only those that quantitatively assess all insect species within a taxa over a span of 10 or more years. Researchers Francisco Sánchez-Bayo, PhD and Kris A.G. Wyckhuys, PhD uncover the disturbing truth behind this mass of data: one in every three insect species monitored worldwide is threatened with extinction. Even more concerning is the finding that 41% of insect species worldwide are in decline, outpacing the more well-publicized vertebrate declines by 200%. Only a few species are expanding in range or occupying vacant niches – not nearly enough to compensate for the massive losses.
In 8% of the studies in the review, citizen science data is analyzed in addition to researcher-collected survey data. The authors recognize that inclusion of citizen science can introduce bias, but note that if anything, citizen science reports would dampen the observed species loss effects due to their bias towards documenting rare species. In short, the authors’ estimates for biodiversity losses are, unfortunately, a conservative lower bound on the true scale of insect declines.
More than half of the studies that Drs. Sánchez-Bayo and Wyckhuys review point directly to intensive agriculture and increased reliance on agrochemicals as causal factors driving insect declines. Several more consider pesticides to be the most likely agent responsible for insect declines, masked under the category of “unexplained factors” in cases where tested variables, such as habitat loss, land use conversion and climate change, are insufficient in explaining losses. “[T]he intensification of agriculture over the past six decades stands as the root cause of the problem, and within it the widespread, relentless use of synthetic pesticides is a major driver of insect losses in recent times,” authors state. Authors emphasize pesticides in particular as the primary culprit: “Several multivariate and correlative statistical analyses confirm that the impact of pesticides on biodiversity is larger than that of other intensive agricultural practices…”
The bulk of evidence implicating pesticide use in the loss of insect biodiversity is both astounding and unsurprising. Insecticides kill insects, often indiscriminately and with devastating consequences for biodiversity, ecosystem stability and critical ecosystem services. Charismatic favorites, among them pollinators like butterflies and bees, are no exception to the rule. Study authors highlight a comprehensive analysis of nearly half a million records from Britain, which reveal that four separate phases of wild bee extinctions followed directly from specific policy changes that expanded the use of chemical fertilizers and pesticides. The review includes so many examples of pesticide-induced mass pollinator declines too numerous to list here, but notable highlights include:
(1) Declines in 80% of 576 species of butterflies studied in Europe are linked to fertilizer and pesticide use.
(2) Declines in California butterflies began sharply following the introduction of systemic neonicotinoid insecticides in 1995.
(3) Bumblebee declines in the US have been steepest in regions with high percentage intensified pesticide use.
(4) Honey bee colony losses began immediately following the introduction of DDT, and spiked again due to compromised immunity induced by neonicotinoids and other systemic insecticides.
The study contains further data on declines across environmental indicator species (such as ground beetles, damselflies, caddisflies and stoneflies), insects that are critical to soil fertility (such as dung beetles and saprophytic beetles, which unlock critical nutrients trapped in wood), and insects that serve as natural enemies to common pests (such as ladybirds and dragonflies). Many of these species also serve as critical food items for vertebrates, such as shrews, moles, hedgehogs, anteaters, lizards, amphibians, bats, birds, and fish.
This comprehensive review confirms devastating declines across diverse classes of insects that are necessary for human sustenance. In the words of the authors, “As insect biodiversity is essential for the proper functioning of all ecosystems, the current trends are disrupting – to varying degree – the invaluable pollination, natural pest control, food resources, nutrient recycling and decomposition services that many insects provide.”
It is easy to feel overwhelmed by the astounding degree of evidence corroborating massive declines across diverse taxa in study regions throughout the world. More overwhelming still are the predictions authors make about the future with continued reliance on agrochemicals: complete extinction of the insects that form the base of the entire ecosystem.
The authors offer a solution to the sobering reality they present. “A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide.” Beyond Pesticides holds the position that reduction is not sufficient. We must move beyond reduction and commit to complete transformation of our agricultural system if we hope to stave off the dire fate this study predicts.
Beyond Pesticides is a resource for activists pushing to end pesticide use and adopt least-toxic, organic practices. Join the movement to end destructive pesticide use by engaging at the local, state and federal levels to transform our agricultural system. See previous Daily News citing researcher David Goulson, PhD and his conclusion, “We appear to be making vast tracts of land inhospitable to most forms of life, and are currently on course for ecological Armageddon,” which he told The Guardian.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Biological Conservation
