14
Oct
Study Documents Aggregate Insecticide Load for Pollinators in Real-World Analysis
(Beyond Pesticides. October 14, 2022) A team of researchers has taken on the challenge of integrating data from multiple and disparate sources in order to devise tools with which scientists can evaluate pollinator pesticide exposures and impacts more effectively at “landscape scale” (and at real-life exposure levels). Accessing data that are useful and relevant at this landscape level has been a significant problem for researchers and conservationists. This “zoomed out” view is critical because pollinators are highly mobile across thousands of meters of foraging area. A functional understanding of the risks pollinators encounter in their territories requires integrated data at this level, as opposed to the large geographic areas across which pesticide use is typically tracked. The team’s paper on their work — Putting pesticides on the map for pollinator research and conservation — was published in Nature.com in mid-September.
Pollinators are essential to healthy ecosystems and to a third of human food sources, as well as to plants used for commercial seed production. As the authors note, nearly 90% of flowering plant species benefit from the services of pollinators that help plants set their seeds and produce flowers and fruit (this last term includes foods widely considered to be “vegetables,” but which are the product of pollination). But for years, pollinators and insects broadly have been in dramatic decline, making worse the biodiversity crisis we face globally.
Pesticides are a chief driver of pollinator decline, along with habitat fragmentation and loss caused by human development and encroachment; these drivers are, according to the study authors, most documented for honey bees (including managed colonies), wild bees, and butterflies. The loss of appropriate habitat reduces food and nesting resources for these populations, and pesticide exposures can outright kill pollinators or lead to behavioral, immunological, and/or reproductive impacts. In addition, herbicide use can mitigate against pollinator health by reducing their plant food sources. Neonicotinoid and organophosphate insecticides are among the worst pesticides for these and other insect populations — and are commonly used; see here and here.
The coauthors explain their mission: “Scientists’ and conservationists’ ability to [evaluate pollinator decline] has been limited by a lack of accessible data on pesticide use at relevant spatial scales and in toxicological units meaningful to pollinators. Here, we synthesize information from several large, publicly available datasets on pesticide use patterns, land use, and toxicity to generate novel datasets describing pesticide use by active ingredient . . . and aggregate insecticide load . . . for state–crop combinations in the contiguous U.S. Furthermore, by linking pesticide datasets with land-use data, we describe a method to map pesticide indicators at spatial scales relevant to pollinator research and conservation.”
The datasets they have created include these, for 10 major crops (or crop groups) in each of the 48 contiguous U.S. states.
- average application rate of more than 500 common pesticide active ingredients (1997–2017)
- aggregate bee toxic load (honey bee lethal doses) of all insecticides combined (1997–2014); note that this dataset ends in 2014 because after that year, data on seed-applied pesticides were excluded, and these contribute significantly to bee toxic load
- reclassification tables relating these pesticide-use indicators to land use/land cover classes, enabling the creation of maps predicting annual pesticide loading (at 30–56 m resolution)
According to the study paper, researchers have heretofore generated useful models for predicting pollinator abundance and ecosystem services as a function of the landscape, especially for wild and honey bees, and monarch butterflies. But the subject researchers assert that these models could be vastly improved by integrating into them metrics on patterns of pesticide use, in the geographic areas under consideration, at landscape scale.
The team identifies several hurdles encountered in their work: (1) U.S. data on pesticide use, land use, and pesticide toxicity are spread across “disparate government databases, each with idiosyncratic nomenclature and organization”; (2) available pesticide use data are reported as averages at primarily county, state, or national scales, whereas data on pollinator populations are structured at smaller scales, e.g., hundreds or thousands of meters (for foraging ranges); and (3) because there are hundreds of commonly used active pesticide ingredients, the available data do not generally capture the relevant toxicity “doses” to which pollinators are exposed; translating pesticide use data into relevant “units of toxicity” would help researchers evaluate aggregate/cumulative and synergistic impacts.
The researchers tackle these obstacles, and created datasets and methods that allow mapping of pesticide use estimates to extant land use data. They recommend “matching state-level, crop- and year-specific pesticide use averages to land use estimated through remote sensing.” Through these methods, they say, it is “possible to generate maps of predicted bee toxic load and individual active ingredients at 30 m resolution, a finer spatial grain than reported in our county-level analysis, and one more suited to landscape research on pollinator populations and communities. . . . Moreover, while this work is motivated primarily by the effects of pesticides on pollinators, the estimates and mapping method we describe have potential application in a wide array of settings ranging from water quality monitoring to human epidemiology.”
The researchers note that their focus on bee toxic insecticides was largely because (1) the quality of available data on insecticides is both higher and more consistent than that for herbicides and fungicides; (2) insecticides have greater acute toxicity than the other two categories (“insecticides account for > 95% of bee toxic load nationally, even when herbicides and fungicides are included, and even though insecticides make up only 6.5% of pesticides applied on a weight basis”); and (3) focusing metrics on insecticides “increases their interpretability, reflecting efforts directed toward insect pest management, rather than a mix of insect, weed, and fungal pest management.”
To support other researchers and conservationists (and other interested parties) in exploring insecticide use patterns, the team created an interactive website: https://insecticideexplorer.shinyapps.io/insecticideexplorer/. It allows users to generate graphs showing trends in national and state-level insecticide use, and to download reclassification tables for bee toxic load for particular state–year combinations.
This research team tackled a troublesome byproduct of how pesticide use is evaluated — the “siloing” of information, which relates to how science “works.” For all the utility of the scientific norm of isolating variables, there is also great risk in making this the sole means of scientific inquiry. Traditionally, scientists break down phenomena into constituent parts, and look for mechanistic, linear causality. But the work of both Rachel Carson (on pesticide impacts) and Theo Colborn (on endocrine disruption and later, the dangers of fracking), for example, demonstrates that this “narrowed field” lens is not adequate to the systemic and highly interactive problems of our globalized, technological, and chemically saturated world. This is eminently so for attempts to understand the multiplicity of factors, among which pesticide use looms large, that attend the dramatic decline in pollinator populations and health, and the broader and global “insect apocalypse.”
Beyond Pesticides has long worked toward adoption of more holistic and precautionary approaches to evaluating and regulating pesticides. Beyond our clamor for more-comprehensive risk assessment and more-protective regulation stands the genuine solution for which we advocate: “eschewing pesticide use, and focusing on soil health, diversification, and sustainable practices — [essentially,] organic and regenerative farming and land management” practices that can help reverse the decline of pollinator health and populations. The public can contribute to this effort by purchasing organic whenever possible (whether at the supermarket or, even better, from local farms and CSA [Community Supported Agriculture] programs), planting diverse, pesticide-free habitat on your property, and encouraging local communities to follow suit.
Source: https://www.nature.com/articles/s41597-022-01584-z
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
