There is a petition doing the rounds at the moment hosted by the 38 Degrees organisation calling for a ban on leaf blowers, citing their detrimental effect on insects as the raison d’etre. I’ve signed it, mainly because of the noise and the air pollution effects, especially as “Leaf Blower Man” goes past my office frequently at this time of year😊
The Leaf Blower Man in action outside my office and the aftermath – I wonder what happens to the leaves next?
You may, (or perhaps not), be wondering what has brought about this most recent media outburst against leaf blowers. Taking this as a great opportunity to procrastinate still further, I tracked down the first media mention about the dangers of leaf blowers to a newspaper article published in the German newspaper Augsburger Allgemeine on November 14th in which it reported a press release, dated the 16th October, from The German Ministry for the Environment and Nature Conservation, strongly advising people not to use leaf blowers because of the danger they cause to the environment, not just from pollution but because of the harm they do to insects and other small animals.
“Der Bund für Umwelt und Naturschutz (BUND) fordert nun nicht nur Privatleute, sondern auch die Kommunen zum Verzicht auf den Einsatz auf: „Laubbläser sind nicht nur ohrenbetäubend laut und verschmutzen die Luft durch ihre Verbrennungsmotoren, sie schaden auch der Bodenbiologie gravierend“, sagt die Artenschutzexpertin des BUND, Silvia Bender. „Denn neben Blättern werden auch Insekten und Spinnen aufgesaugt und gehäckselt sowie Pflanzensamen zerstört.“ Ohnehin seien die Geräte überflüssig: „Wir empfehlen daher Grundstücksbesitzern und auch Kommunen dringend, auf Laubbläser und Laubsauger zu verzichten und stattdessen wieder zu Rechen und Harke zu greifen.“”
“The Federal Government for the Environment and Nature Conservation (BUND) now demands not only private individuals, but also the communities to abandon the use: “Leaf blowers are not only deafening loud and pollute the air through their internal combustion engines, they also harm the soil biology seriously,” says the species protection expert of the BUND, Silvia Bender. “In addition to leaves and insects and spiders are sucked up and chopped and plant seeds destroyed.” Anyway, the devices are superfluous: “We therefore recommend landowners and communities urgently to dispense with leaf blower and leaf vacuum and instead to rake and rake again.”
If you want to read the original source it is here; it also extols the virtues of the exercise you gain from raking up your leaves 😊
Although it had taken almost a month for the German press to latch on to the story, presumably they were waiting for autumn to properly kick-in; BBC World ran with the story on 15th November and the first British Newspapers by 18th November and a feature piece by Kate Bradbury in the Daily Telegraph appeared on November 26th which finally prompted me to put fingers to keyboard 😊
Kate mentioned in her article that there was no scientific evidence that leaf blowers directly harmed insects and after spending some time with Google Scholar and Web of Science, I can confirm this. Perhaps someone might like to do a project on it? I’m sure it might appeal to a keen undergraduate or MSc student. Kate correctly points out that leaves form leaf litter and as she aptly puts it “are natures’ winter blanket” providing shelter for countless animals. Including vertebrates. Those insects that overwinter on the ground, or in the upper layers of the soil, despite their fantastic anti-freeze chemistry (Leather et al., 1983) are also very grateful for a nice thick layer of leaves to help buffer the effects of a cold winter and keep them hidden from natural enemies (Thomas et al., 1992). Additionally, leaf litter also provides a valuable food source for the very important, and often overlooked ecological recyclers such as the soil dwelling flies (Frouz, 1999) and of course, the invaluable and underappreciated earthworms (Cothrel et al., 1997). An example of how important leaf litter is for insect survival, is the way in which the horse chestnut leaf miner can be controlled in gardens and parks by the removal of the leaves from under infested trees as soon as leaf fall has ended (Kehrli & Bacher, 2003). Leaf blowers may not be harming insects and other invertebrates physically, (although I imagine that being blasted by what must seem like a hurricane, can’t be a totally benign experience), but they certainly have the potential to reduce their populations, which given the current worries about Insectageddon (Leather, 2018), Is not something we should be happy to encourage.
So, if they are not physically damaging our invertebrate friends, and there is, as yet, no scientific evidence that they do so, how are leaf blowers harming insects and their allies. Leaf litter is an invaluable resource, it not only provides nutrients for plants and helps sequester carbon (Berg & McLaugherty, 2008), and as I mentioned earlier, it provides livelihoods for fungi, bacteria, insects and other invertebrates, and the litter grazers in turn, provide tasty meals for other invertebrates further up the food chain* (Scheu, 2001; Miyashita et al., 2003). By removing fallen leaves to satisfy health and safety directives and/or some folks preferences for tidy pavements and lawns, we are at the same time as we pollute our atmosphere with nasty hydrocarbons, depriving these useful organisms of much-needed resources ☹ Whilst I sympathise with local councils and their desire to keep their citizens safe from potentially slips and falls, I really don’t see the need for leaf-free lawns and parks.
Shiny, leaf-free (almost), and safe for humans versus beautiful, leaf strewn and good for earthworms and their ilk and aesthetically pleasing (to me at any rate).
And if you must keep your pavements leaf-free then why not use a quieter and less polluting alternative such as a human with a stiff broom or if a mechanical alternative is the only option, then an electrically powered mechanical road-sweeper is an acceptable substitute.
I like this one as it is a Scarab 😊
Leaf blowers have been used to harm insects, albeit on a larger scale than that wielded by the local council worker or gardener, and in conjunction with a vacuum device. Inspired by the use of tractor driven vacuum machines developed to control Lygus bugs in strawberry fields (Pickel et al., 1994), Phyllis Weintraub and colleagues (Weintraub et al., 1996) developed a tractor-propelled blower-vacuum combi to manage insect pests in celery and potato crops. The insects are first dislodged by a blower and then vacuumed up for later disposal ☹ More recently, a similar technique has been used to control Colorado Potato Beetles.
There may be no scientific evidence to show that leaf blowers used as intended are bad for insects but on the other hand there is no evidence that shows the opposite, and given the noise and atmospheric pollution they produce and the undoubted harm they cause by litter, my sympathies lie with those wanting to ban the things.
I think that most entomologists would say that the only good leaf blower is one that has been reverse engineered to be a G-Vac and used for insect sampling. I suspect that insects would have a different opinion as most of those insects we catch usually end up dead, even if it is for the good of science 😊
My colleague Andy Cherrill demonstrating his patent G-vac or ‘Chortis’ as we call it 😊
Berg, B. & McClaugherty, C. (2008) Plant Litter – Decomposition, Humus Formation, Carbon Sequestration. Springer, Berlin 338 pp.
Cothrel, S.R., Vimmerstedt, J.P. & Kost, D.A. (1997) In situ recycling of urban deciduous litter. Soil Biology &Biochemistry, 29, 295-298.
Frouz, J. (1999) Use of soil dwelling Diptera (Insecta, Diptera) as bioindicators: a review of ecological requirements and response to disturbance. Agriculture, Ecosystems & Environment, 74, 167-186.
Kehrli, P. & Bacher, S. (2003) Date of leaf litter removal to prevent emergence of Cameraria ohridella in the following spring. Entomologia experimentalis et applicata, 107, 159-162.
Leather, S.R. (2018) “Ecological Armageddon” – more evidence for the drastic decline in insect numbers. Annals of Applied Biology, 172, 1-3.
Leather, S.R., Bale, J.S. & Walters, K.F.A. (1993) The Ecology of Insect Overwintering. Cambridge University Press, Cambridge.
Miyashita, T., Takada, M. & Shimazaki, A. (2003) Experimental evidence that above ground predators are sustained by underground detritivores. Oikos, 103, 31-36.
Pickel, C., Zalom, F.G., Walsh, D.B. & Welch, N.C. (1994) Efficacy of vacuum machines for Lygus Hesperus (Hemiptera: Miridae) control in coastal California strawberries. Journal of Economic Entomology, 87, 1636-1640.
Scheu, S. (2001) Plant and generalist predators as links between the below-ground and above-ground system. Basic & Applied Ecology, 2, 3-13.
Thomas, M.B., Sotherton, N.W., Coombes, D.S. & Wratten, S.D. (1992) Habitat factors influencing the distribution of polyphagous predatory insects between field boundaries. Annals of Applied Biology, 120, 197-202.
Weintraub, P.G., Arazi, Y. & Horowitz, A.R. (1996) Management of insect pests in celery and potato crops by pneumatic removal. Crop Protection, 8, 763-769.
*apropos providing resources and at a different scale than leaves, I remember reading somewhere (probably in one of the late great Oliver Rackham’s books) that the ‘park’ mentality that pervaded modern UK forestry management for several decades resulting in the removal of dead wood from the forest and woodland floor, meant that the top height achieved by modern oak trees is considerably less than that of oak trees harvested in the 16th, 17th and 18th centuries.