Many gardeners now actively garden with wildlife in mind. A welcome development, but what does the gardener hope to get out of it? Is it enough simply to know that wildlife is thriving in your garden, or do you have to see visible evidence of that?
The problem is that the wildlife you will see in your garden is only the tip of the iceberg; the bees, birds and butterflies are only about five per cent of even the larger inhabitants of the average garden. Most of the earthworms, slugs, snails, woodlice, centipedes, millipedes, harvestmen, spiders, bugs, flies, sawflies, wasps, beetles, moths and ants are inevitably going to escape attention. And yet that lot, along with a larger and even less visible cast, make up the functioning, living, breathing garden ecosystem that ultimately supports the birds, the hedgehogs and the frogs.
The invertebrates we need to appreciate
Nematodes
Most garden wildlife escapes attention because it’s too small, too nocturnal, or (especially) too subterranean. Few people realise that at least half of all animal biomass on the planet is found below ground. Which all seems a bit less unlikely when you consider that by far the most abundant animals on Earth are nematodes (or roundworms).
Nematodes are tiny, just about visible with the naked eye, but there are about 4.4 x 1020 nematodes (or about 55 billion for every human) in the world’s soils, and four out of every five individual land animals are nematodes.
Most nematodes are an important – and large – part of the soil ecosystem
One reason nematodes are so successful is that they have adopted every possible means of making a living in soil. Some eat bacteria or other microbes, some eat fungi, some are herbivores and others are predators, sometimes of animals much larger than themselves.
To the gardener, a handful of nematodes are enemies (for example, plant parasitic eelworms), while a few are valuable friends, such as the nematodes you can buy to control slugs or vine weevils. But most are just an important – and large – part of the soil ecosystem.
Ants
Ants are another group of animals that are more abundant than you realise. There are probably around 20 x 1015 individual ants worldwide, with a total weight greater than all wild birds and mammals combined.
I know many gardeners don’t like ants, but like other invertebrates they’re food for larger animals, and if you ever see a green woodpecker in your garden, ants are probably the reason.
Some plants also rely on ants for seed dispersal, with fatty structures called elaiosomes attached to their seeds to persuade ants to disperse them. If you’ve ever planted a Cyclamen hederifolium in one corner of the garden, and now there are seedlings everywhere, ants are probably responsible.
Spiders
OK, so you’re thinking, ‘Spiders aren’t invisible – my garden is full of spiders.’ And so it is, but you still probably fail to notice most of them. On a misty autumn morning, the world may seem to be one giant spider’s web, but although all spiders make silk, not all spin webs – at least not big, noticeable ones – and there are plenty of other spiders the presence of which is not at all obvious.
Globally, there are at least 45,000 species of spider, and all of them are predators, overwhelmingly of insects. To put that into perspective, the world’s spiders consume annually a weight of insects about the same as the weight of meat and fish consumed by the human population.
Many of those insects may be useful, and most have no direct impact on you and me at all, but some of them would like to eat your plants, and there would be a lot more if it weren’t for spiders.
There would be a lot more plant-eating insects in your garden if it weren’t for spiders
Spiders are also important food for many garden birds, including wrens, robins, blackbirds, tits, dunnocks and goldcrests. Not only that, but long-tailed tits and goldfinches use spider webs to help build their nests.
The webs that are so obvious in autumn belong to money spiders and orb-web weavers, including the ubiquitous garden spider. But many British spiders don’t build webs to catch their prey. For example, the woodlouse spider, usually found hiding under stones by day, is a nocturnal hunter that specialises in eating woodlice. Its enormous fangs are very distinctive, and it’s one of very few British spiders that can give you a proper bite.
Another non-web spinner, and one of very few spiders that might even be described as ‘cute’, is the zebra spider. One of several jumping spiders, its zebra stripes, short legs and bank of four huge eyes, like searchlights, are unmistakable. It’s often seen patrolling on sunny walls or fences, stalking and finally jumping on to its prey from a surprisingly long distance.
Help invertebrates in your garden
Looking after your soil animals is simple: lots of plants, lots of organic matter, and go easy on the digging. But what can gardeners do for spiders? Well, essentially, gardening for wildlife is gardening for spiders. If your garden is good for lots of other invertebrate wildlife, most of which you will never notice, the spiders that also go unnoticed will reward you by eating them, and both will be eaten by the wildlife you do notice, and everyone will be happy.
Read Ken's piece on why plants with bad reputations are actually good for your garden.