With all due respect to Beyonce, insects were recognized as ‘The Little Things that Run the World‘ by entomologist E.O. Wilson, decades before Beyonce’s 2011 hit song. As Wilson wrote in his iconic perspective piece:
The truth is that we need invertebrates but they don’t need us. If human beings were to disappear tomorrow, the world would go on with little change.
In fact, Wilson noted, the Earth ‘would set about healing itself‘. But if invertebrates were to disappear, Wilson predicts that ‘I doubt the human species could last more than a few months‘.
Insects, the most abundant and numerous of all invertebrate animals, play a particularly important role in our world and in our life. Not counting the enormous contributions of non-native honey bees, which annually help to bring $235 and $577 billion dollar worth of food to the global market, native insects contribute $71 billion dollars (inflation adjusted to 2019) worth of ecological services to our economy and to our society.
These articles covered recent science papers that have caused a lot of concern, and generated a lot of attention. In the ENT 518 class that I am teaching this term (Current Topics in Entomology), our class spent time dissecting and discussing the science papers, as well as popular press coverage of each study.
The first paper, published in 2017 by Hallman and colleagues, documented a 76% decline in insect biomass over a time period spanning nearly three decades. In the peak summer season, the decline was even larger (82%). These researchers had been sampling protected areas in Germany using Malaise traps. This group is working to identify the insects that they collect ~ but, because it takes so much time and specialized expertise to identify most insects to species ~ they also took data on the collective weight of the insects that they collected. This is how they were able to show a 76% decline in insect biomass, between 1989 and 2016.
What caused this massive decline in insect biomass? To address this question, They constructed a series of models to try and identify what factors might explain this precipitous drop in insect biomass (which is being used a proxy for insect abundance). They did not find evidence (from their mathematical models) that climate factors (e.g. temperature, precipitation, wind speed), habitat factors (e.g. site conditions, plant species), or habitat factors (e.g. amount of forest, grassland, water) were responsible for insect declines. Because they did not find evidence that climate change, landscape conversions, or habitat changes reduced insect biomass, they concluded that factors which they did not measure were responsible for insect declines. Specifically, they hypothesize that agricultural intensification (pesticide use, year round tillage, increased use of fertilizers) was a plausible cause.
Students taking the ENT 518 class were mostly convinced that the researchers had documented a large and significant decrease in insect biomass over the time period of the study. Students agreed that the loss of biomass reflects a loss in insect abundance, and probably reflects a loss of insect diversity. Students were more reserved in their assessment of the authors’ suggestion that agricultural intensification was the cause of the decline. Although they agreed that it is a plausible explanation, they wanted to see data to address this hypothesis, rather than having the authors arrive at this conclusion because they eliminated other potential causes of insect decline (e.g. climate change, landscape conversion, habitat change).
The second paper, published in 2019 by Sanchez-Bayo and Wyckhuys, was a review of other papers that studied insect declines. The authors searched science databases for the words ‘insect’ AND ‘decline’ AND ‘survey’, and then reviewed the hundreds of papers (653!) that they found to limit their survey to 73 long-term studies that took place for 10 years of more. The authors then summarize the details of each study, according to major insect groups (e.g. butterflies, bees, beetles, flies). Ultimately, they report that 41% of all insects are in decline, and that across all insect species, the annual rate of decline is 1% per year, and the annual rate of insect extinction is 1% per year. Like the Hallman et al. paper, Sanchez-Bayo and Wyckhuys suggest that agriculture is to blame:
‘Overall, the systemic, widespread and often superfluous use of pesticides in agricultural and pasture land over the past 60 years has negatively impacted most organisms, from insects to birds to bats . . ‘.
The students in ENT 518 honed in on the fact that the authors searched for the words ‘insect’ AND ‘decline’. Accordingly, there was a level of bias in their search procedures. Students seemed convinced that many insect groups are in decline, but were less willing to agree that the overall level of decline, rate of decline, and rate of extinction reported by the authors were accurate estimates. In addition, although students agree that pesticide use is likely to blame for insect declines, they would have been more convinced, if there were better data tying the two together.
Students then discussed how the science papers were translated into a narrative for the NY Times and Atlantic articles. We talked about the elements of a story, and how as scientists, we don’t worry about setting the scene, developing characters, or of conflict in a plot. But, many of us are also science communicators via our work in Extension or through other outreach efforts. If we can paint a picture that people can relate to ~ if we can get them to notice and to share their experience with noticing fewer insects in their yard or their town ~ will they care more about insect conservation?
One of the major reasons that we do the work that we do in the Garden Ecology Lab is because we believe that how we manage our gardens can truly make a difference to insect conservation. If we can take better notice of those ‘little things that run the world’ and share these experiences with our friends and family . . . will that make a difference? I believe that it will. In fact, it is the reason that I come to work, each and every day, excited to learn more about how we can make this world a better place through gardening.