Wildlife will find a pond if you build one. But how exactly?
An unexpected swarm of eels wriggled at the bottom of the drained pond. This body of water was enormous, and it had been designed as an outdoor swimming pool by whoever had previously lived in the house. However, the former owner soon decided that it was too cold to swim in. Instead, they had filled it with ornamental goldfish.
Lydia Massiah, now a former teacher and aspiring writer, and her family moved to the property years ago and decided the pond was far too large for the garden. So they began the draining process. She recalls that someone came to take the goldfish away. But she never expected to find eels hiding in the pool’s deepest recesses. “They would have crossed a road and come across two fields from the river,” she says, still amazed at how they slithered over land and climbed into the pond, which was also raised 2ft (0.6m) above ground level. They quickly vanished after being discovered, presumably back towards the river, Massiah adds.
Ponds are unique because of this mysterious property of water in gardens – how it attracts wildlife so successfully. Massiah and her family made certain that another, more ecologically balanced, wildlife pond in the back garden remained intact in the hope that it would continue to benefit local species.
Of course, not all ponds are biodiverse, but the recent wildlife gardening craze has brought them to the forefront. Even those with limited outdoor space are encouraged to participate, with several environmental organisations recommending mini-versions made from half-sunken washing up bowls. There is a growing recognition that, when thoughtfully designed, they can act as lifelines, increasing the resources available to native plants and animals.
According to the Wildlife Trusts, there are approximately three million garden ponds in the United Kingdom. Researchers estimate that there are millions of artificial ponds in the United States, though some of these are agricultural rather than recreational. But how significant are they for wildlife? How do animals find their way to them? What else should you consider when designing a pond to support local species?
“It’s like magic,” says Jenny Steel, an author and plant ecologist, of ponds’ ability to attract wildlife. “Within about 12 hours of filling that first big pond I made myself, there were dragonflies.”
Aside from the frogs and aquatic insects that many gardeners hope to see in their ponds, these watering holes occasionally attract more unusual visitors, such as tawny owls, grass snakes, and even kingfishers.
Steel recalls summer evenings spent watching swallows and house martins swoop and soar above her garden ponds, picking off airborne insects on the wing. You don’t even need a massive lagoon. Steel has a small pond in part of an old barrel on her patio, which attracts animals. “That little barrel pond is constantly used by birds,” she says, describing how they enjoy bathing in it.
It begs the question of how these creatures detect ponds from a distance. Some have observed that you can simply take the “build it and they will come” strategy. But how does Mother Nature know?
Many flying creatures search for light or sound reflected by bodies of water. Dragonflies are drawn to polarised light that bounces off the surface of water, according to researchers in Hungary. These insects appear to prefer dark or light ponds to lay their eggs in, depending on species, and may do so by looking for differences in the polarised light reflected by watery habitats. The draw of this light is so strong that some dragonflies may become confused. According to one 2007 study, they can mistake the reflective surfaces of polished gravestones in cemeteries for ponds.
Birds may also mistake the polarised light reflected by asphalt for water.
Other animals will most likely use their sense of smell to find their next aquatic home. Experiments show that amphibians, such as salamanders, can detect water in the dark solely through scent.
“My advice is always that any water is better than no water at all in a wildlife garden,” says Steel.
But you don’t have to rely entirely on nature. There are many things you can do to increase your chances of attracting and benefiting native species if you are thinking about establishing a wildlife pond or making an existing pond in your garden more wildlife-friendly, says Steel. And the effort is worthwhile.
For one thing, it’s best to fill the pond with rainwater rather than tap water because tap water contains additives like chlorine and contaminants like nitrates that can harm wildlife. According to Steel, nutrients in tap water can also be problematic because they promote excessive algae growth.
Steel also emphasises the significance of including a diverse range of native aquatic plants. and possibly some terrestrial vegetation along the pond’s margins, which will benefit a variety of species. It’s critical to include some plants that will grow underwater and help to oxygenate the pond – they’ll do this naturally as they photosynthesise. Shining pondweed, which is native to North America and Europe (though there are several species, so make sure you get a native one), and hornwort, which is also native to both continents, are two classic examples.
Plants and animals require oxygen, so ensuring a sufficient supply will benefit the pond’s ecosystem as a whole. If you want to support a variety of different species, you should also avoid having fish in your pond. While fish are often important in natural freshwater ecosystems, they can easily dominate and eat too many of the other inhabitants in small ponds.
Matt Hill, a freshwater ecologist and senior lecturer in geography at the University of Huddersfield in the United Kingdom, emphasises that pond builders should avoid placing them in heavily shaded areas, as this will deter many species. Furthermore, he recommends that people prioritise variability in their pond designs whenever possible – This entails creating some deeper areas, perhaps up to 1m (3.3ft), but also shallow banks, as these are used by creatures such as aquatic insects. He says it’s fine to put stones around a portion of the pond, but you should avoid completely encircling it to allow smaller wildlife to get in and out.
“For me, the key message is that variability is to be expected – and encouraged. You want various environmental conditions, “He adds that your pond life may differ from your neighbor’s. Some people may notice an abundance of snails, while others may notice an abundance of dragonflies. The important thing is that hundreds or even thousands of different ponds scattered throughout a district or county will serve a diverse range of plants, insects, amphibians, mammals, and birds, according to Hill. Together, they should benefit the environment throughout the region.
