Mass Insect Deaths: Findings In 2017

Of all the insect biodiversity and environmental impact studies that came out this year, two stand out as particularly important.

The first is Hallmann et al.‘s More than 75 percent decline over 27 years in total flying insect biomass in protected areas, published in PLoS ONE. It’s the publication of a monumental long-term monitoring effort: they used Malaise traps – tents that trap low-flying insects – at 63 environmentally-protected areas around Germany, and report the weights of insects collected between March and October over 27 years, from 1989 through 2016.

The main result is spoiled by the title, and you can see it depicted graphically above: blue are the earliest years (1989) going to yellow are recent (2016). While it’s expected and known from previous studies that disturbed and agricultural lands have lower insect biodiversity and abundances, that there was a decline of 76.7% in protected areas is a real shock, and a wake-up call that we’re really not doing enough conservation work.

The causes of the decline cannot be pinpointed from just this dataset. Given that these are protected areas, there are no direct habitat changes (the authors confirm this using historical satellite imagery). Climate effects cannot be considered using their limited weather data. The most likely culprit is agriculture: as is typical in Europe, these protected areas are completely surrounded by farmland, and are thus highly-fragmented, and everything that goes on in those farmlands (e.g. pesticide use) affects the protected areas – the extent of these effects is just very, very surprising.

The paper is chock full of data and statistics, and it’s all open access, so I encourage everybody to go and dig through, especially environmental skeptics.


The second important paper is centered on honeybees and agriculture: A worldwide survey of neonicotinoids in honey, published in Science by Mitchell et al..

Neonicotinoids are a popular family of insecticide, accounting for a third of insecticides used globally, even with EU restrictions. They typically affect an insect’s nervous system, and will result in many sublethal effects even at low doses. Importantly, they are systemic pesticides, meaning that they spread to all the tissues of the plant, and so are able to affect a diversity of insects, not just the ones that come into touch with it on leaves. This is why they’re so linked to the honeybee collapse story: even though honeybees are just pollinators, they will ingest neonicotinoids because it will accumulate in nectar and pollen – and this is terrible, because honeybees are definitely not a target insect.

Mitchell et al. see just how far this accumulation goes by collecting data on the concentrations of five neonics (acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam) in 198 honeys from around the world.

It turns out that three quarters of honeys are contaminated with at least one neonic. Doesn’t matter where it’s from, although Africa and South America have markedly lower concentrations than Europe and North America – despite the stringent regulations and bans in the EU. Don’t worry, they’re not even close to being dangerous to humans. The world doesn’t revolve around you. The worry here is for the effects this has on colonies – remember that the honey is the colony’s food, and their food is now toxic to a certain degree. The results on this paper say that 48% of the honey samples are contaminated to such a degree that they cause acute effects on ingestion, not just sublethal ones, like alterations to behaviour that disrupt a colony’s functioning.

Not good at all. The paper has all the breakdowns of which neonics are found where to what degree. It’s a shame it’s paywalled, but feel free to email me for a copy, including all the juicy supplementary data ;)


All doom and gloom, basically. But hey, nothing that will affect you personally right this moment (we’ll have a different talk in a few years when food prices skyrocket). So to cap this off rightly, here’s a lovely review by Hauke & Herzig: Dangerous arachnids – fake news or reality? Arachnids are technically all venomous, but can they affect us? If the media is to be believed, spiders are going to kill us all.

To end on a positive note, that’s mostly fake news… except if you live in North Africa, the Middle East, Mexico, the Amazon, or southern Brazil… and even there, a very small number of species can actually sting/bite you with any lethal effect, and antidotes exist for everything. Nevertheless, the authors compile a very liberal list of potentially dangerous arachnids, comprising known lethal species and including other species in their genus. The final list comes up to 248 spiders (0.5% of known spiders) and 537 scorpions (23.1% of known scorpions). Basically, stay away from scorpions; pictured above are some of the confirmed dangerous ones (if you need that picture, then you will not have time to ID them in the field anyway, so just stay away. Really. I’ve been stung by a scorpion, it’s unpleasant).

Besides this list, the paper is an extremely useful reference on arachnid venoms and their effects on humans, so if this is within your interest, do check it out.

References:

Hallmann CA, Sorg M, Jogejans E, Siepel H, Hofland N, Schwan H, Stenmans W, Müller A, Sumser H, Hörren T, Goulson D & de Kroon H. 2017More than 75 percent decline over 27 years in total flying insect biomass in protected areasPLoS ONE 12, e0185809.

Hauke TJ & Herig V. 2017Dangerous arachnids—Fake news or reality? Toxicon 138, 173-183.

Jeschke P, Nauen R, Schindler M & Elbert A. 2011Overview of the Status and Global Strategy for NeonicotinoidsJournal of Agricultural and Food Chemistry 59, 2897-2908.

Mitchell EAD, Mulhauser B, Mulot M, Mutabazi A, Glauser G & Aebi A. 2017A worldwide survey of neonicotinoids in honeyScience 358, 109-111.

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