As followers of this blog know, one of my big interests is evidence-based, environmental decision-making. I care that good scientific data is being used to make informed policy decisions. As such the recent “insects are vanishing” meme that is spreading through my social media feeds has me concerned. Most of these stories derive from a single paper that recently came out in “Biological Conservation” titled Worldwide decline of the entomofauna: A review of its drivers by Francisco Sánchez-Bayo and Kris A.G.Wyckhuys. This paper provides a classic example of how a search algorithm designed to answer one question can result in a skewed output dataset when asked to answer a different question. Now most of the time this type of study has little effect on public policy; unfortunately, this study is the exception to that rule. As such it is important to understand what this paper did both wrong and right and what this paper can and can’t tell us about global insect population trends. Ultimately this is important because of how it informs future environmental policy decisions.
Reading the paper it becomes clear that the authors appear to have started their work simply seeking to understand the general drivers that influence insect population decline, where those declines are being observed. Somehow over the course of their research (and possibly the peer review process) they decided to extrapolate their results to make more globalized generalizations. The problem was that their initial dataset was not the appropriate tool to make these types of generalizations. The result is a paper that makes broad claims that are unsupported by the underlying data.
What do I mean by that? Well let’s look at the search algorithm used in their study:
we performed a search on the online Web of Science database using the keywords [insect*] AND [declin*] AND [survey], which resulted in a total of 653 publications.
They then used tools to winnow down that initial list of 653 papers to a smaller group of
73 reports on entomofauna declines in various parts of the world (Fig. 1) and examines their likely causes (Table S1). Because the overwhelming majority of long-term surveys have been conducted in developed countries, particularly in the northern hemisphere, this review is geographically biased and does not adequately cover trends in tropical regions, where information on insect biodiversity is either incomplete or lacking (Collen et al., 2008).
The problem with the reporting on this paper is that it ignores all these provisos and instead makes huge claims based on scant evidence. So let’s start with the biggest failing of the paper: the original search algorithm.
The search algorithm looked only for papers that included some variation on insect, declin[e] and survey and then used that collection of papers in their further analyses. The problem is that is a pretty limited dataset. Would this search algorithm find a paper like:
The search algorithm only looked for papers where populations were declining not where they were increasing or were observed to be relatively stable. To be absolutely clear here, I don’t know if global insect populations are decreasing, increasing or stable, but this search algorithm won’t help anyone find that information out. It only looked for studies that found declining populations.
To help my readers understand let’s use a different example. Imagine you did a search of newspaper headlines for [Vancouver Canucks] and [loss*] and . That search would give you a list of Vancouver Canucks losses. Does that mean the Canucks never won a game? No, but that wasn’t what you were looking for.
Going back to the paper, they provide an incredibly important proviso in the methodology section but this proviso is virtually ignored in the reporting of its results. I included it above but it bears repeating.
Because the overwhelming majority of long-term surveys have been conducted in developed countries, particularly in the northern hemisphere, this review is geographically biased and does not adequately cover trends in tropical regions, where information on insect biodiversity is either incomplete or lacking (Collen et al., 2008).
Take a look at the geographic distribution of their papers:
Talk about a Eurocentric paper. Any Biologist will tell you that most insect diversity is observed in the Tropics and yet the article’s data density in the Tropics is virtually non-existent. Looking in their Supplemental Data we find that the paper includes less than a handful of papers dealing with the Tropics.
Let’s think about this. Is there any field of study where we would extrapolate ecological conditions in Europe to indicate global conditions? Europe is a horrible model for any ecological study because Europe has been heavily populated, intensively farmed and disturbed for centuries. If you were looking for the worst place to extrapolate world ecological trends from, Europe would be an excellent choice.
So you are probably wondering why I care some much about this topic? The answer is because when you use bad data as an input into a policy development process you get bad policies as an output. The one thing this paper makes clear is that human land use decisions are the biggest driver of insect population declines, where they have been observed. Sure climate change is a minor driver but the bigger problem is how humans manipulate our environment to make it more comfortable for other humans.
I have said time-and-again at this blog that one of my biggest concerns is habitat preservation and with insect populations we have another topic where habitat preservation appears to be the key. The paper makes it clear that preserving habitat is the single best way to help protect insect populations. To do that we need to reduce our ecological footprint by densifying our populations and changing our farming practices. From a practical perspective we need to stop relying on biofuels that eat up valuable potential wild spaces to produce liquid fuels or biomass for electricity. We need to stop building huge solar farms and even bigger wind farms that eat up valuable potential wildlands and instead massively increase the number of small solar collectors and “small wind” vertical turbines in our urban environments.
This is the Ecomodernist mantra I have repeated throughout my blogging. We need to change the way humans make use of the planet. We need to use a smaller part of it more intensely so we can leave a larger area for nature to do its thing with minimal human interference or influences.
As for all these blaring headlines about the insect apocalypse; well this paper is not supportive of them. Only in the activist press could a study with this limited reach and breadth be used to extrapolate world conditions.
To conclude, I can’t say it enough. I don’t know whether insect populations planet-wide are increasing, decreasing or are stable. But neither do the authors of this paper and neither do the activists who are using the headline from this paper to beat decision-makers over the head. Good environmental decision-making needs good data and while this paper helps describe certain phenomena, mostly in Europe, it does little to add to our understanding of worldwide insect conditions. Moreover, what it does tell us is that if we want to keep our insect populations healthy we need to change the way humans interact with our natural environment. We need to reduce our ecological footprint and give nature the space it needs to thrive.