What are the benefits of snails ? Surely they are only a menace and deserve to be stomped on ? Yet there they are in almost every garden. They must serve some purpose !
This series of articles on snails was stimulated by frustration with the enormous snail population in my garden and the question I asked myself about it. As with so many other aspects of gardening, was I engaging in wrong thinking trying to 'get rid' of some irritation, before I had explored what this thing may be doing to help me ?
Take for example 'weeds' and 'insects'. By now we all know that using biocides in the garden to get rid of them is doing more harm than good, that many weeds and insects are beneficial, and so forth. But we need to learn and self educate to realize this. I decided to apply the same inquiry to snails, to discover the benefits of snails.
I found three useful answers : Firstly, like earthworms, they are active soil builders, secondly they are useful indicators of ecosystem health and last but not least, in a wildlife garden they are useful as food for other animals higher up the food chain, supporting a wide diversity of creatures in your garden.
If you google 'worms and soil' you will find 24 million results on how worms benefit your soil. Google 'snails and soil' and you will find 15 million results on how to get rid of snails and no mention of their good work.
Snails are doing up to 33% of the decomposition of organic matter in the garden. They are building soil structure and dispersing soil organisms. Their feces make a mineral and nitrogen rich contribution to the soil, say some authors.
In one case study, worms increased soil phosphates and the root nodulation and cover of Trifolium dubium, a nitrogen fixing clover, by suppressing grasses and Asteraceae through burying the seeds. Compared to worms, foraging snails increased plant litter while they decreased the Trifolium cover, therefore reducing soil nitrogen. This effect of reducing nitrogen compared to worms may only be due to them working against a nitrogen fixing plant, rather than somehow removing nitrogen from the soil, because they are known to add nitrogen.
In the Negev desert where soil nitrogen is very low, snails were important in the nitrogen cycle. Snails feeding on lichens that penetrate rocks (endolithic lichens) ingest rock and lichen and their faeces contribute 22-27mg N per m2 per year, or 11% of soil nitrogen inputs and 18% of soil creation in this habitat. This is probably important for plant growth.
Snails may be a nuisance to the farmer, but a study on snail populations revealed that their number in agricultural soils is actually low. In tilled soil there is decreased food and moisture, and they are exposed to physical disturbance and toxins. The population of snails in woods and grassland is much higher. Thus one more of the benefits of snails is that they are an indicator of ecosystem and soil health.
I can confirm with personal observation the research that snails thrive in forests and are indicators of soil health. In my food forest garden there is a massive snail population. Growing juicy greens as a ground cover doesn't work too well. I'm forced to build raised beds isolated from the forest for my European vegetables.
We notice snails eating our garden plants, but take a closer look and you will see that almost all common garden snails and slugs actually prefer dead and decaying plant detritus. The more you remove dead plant matter to clean up your garden beds, the more likely they are to go for your lettuces.
To provide balanced nutrition in my vegetable beds, one of the sources of manure will be snail manure. I harvest all the snails I find and put them in a farm or container cage, on netting, there they can eat to their hearts' content on garden waste I've chosen to feed them, and I can harvest their feces as they fall down through the netting. But the control of the situation is an illusion of course. Gastropods rule, and every gardener knows it ! However, it helps to make friends with that, to know of the good they do, and how to tweak your system to lessen the damage.
Please let me know if you have any questions, comments or stories to share on gardening, permaculture, regenerative agriculture, food forests, natural gardening, do nothing gardening, observations about pests and diseases, foraging, dealing with and using weeds constructively, composting and going offgrid.
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Snail predators are very diverse. Snails thus support a garden's faunal diversity, serving as indicators of ecosystem health, while the predators control snails