In a recently published study, scientists identify the best ways to manage your garden pond to provide a haven for aquatic species such as insects and snails in urban areas.
The researchers provide recommendations on the best sizes for ponds, the importance of aquatic plants and how to manage its “conductivity” – a measure of how well pond water can pass an electrical current. They also consider the possible impact of predation by fish.
Another key recommendation is that pond owners should form community groups to provide macroinvertebrates with a mix of environments, helping them to thrive across their neighbourhoods.
The findings have been published in the journal Insect Conservation and Diversity.
“There are an estimated two and a half to three and a half million garden ponds in the UK and they can add to local biodiversity if they are managed correctly,” said Dr Matthew Hill, Lecturer in Ecology at Bournemouth University, who led the study. “Many ponds are managed for aesthetics reasons or fishkeeping, rather than as habitats for wildlife. But if we can add biodiversity into the ornamental designs, they could provide an important freshwater resource in urban areas,” he added.
In the new study, the Freshwater Habitats Trust carried out surveys of thirty ponds in Oxfordshire to collect data on the make-up of each habitat and the number of species living there. The data was then analysed by Dr Hill which led to the following recommendations:
Have as big a pond as possible: The surface area of a pond should be at least five square metres to increase the number of bugs and snails that live there. Although pond-keepers need to understand any safety implications of having a bigger pond.
Increase the number of native plants in the pond: Plants are vital for providing food and keeping a balanced ecosystem in ponds. While some non-native plants are popular for ornamental reasons, they should be in the minority because of the risks that they carry other species not native to the UK. Non-native plants to avoid include Crassula helmsii (also known as New Zealand pigmyweed) Lagarosiphon major (curly waterweed), Elodea nuttallii (western waterweed) and Myriophyllum aquaticum (parrot's feather).
Top up with rainwater to reduce conductivity of the water. Simple devices are available to measure a pond’s conductivity. Lower conductivity levels will enable environmentally sensitive species to thrive in the garden ponds. Fish food, potting compost from plants as well as natural contaminants can affect its conductivity.
Although ornamental fish will feed on bugs, the researchers did not find evidence of them affecting the diversity of species, however they note that all ponds in the study had low to moderate numbers of fish. Plants can provide a hiding place to reduce the risk of predation from fish.
Whilst Dr Hill and the team believe that it is important to have ponds with a rich array of species, they also advise that it is important to manage ponds that are more ecologically unique – those that may not have as many types of bugs but do contain species that are not found in other ponds.
“On the one hand, we want to increase the size and plant richness to increase macroinvertebrate richness, but we also want to manage those unique ponds because they are also contributing to the species pool,” explained Dr Hill.
This is where they believe that pond-keepers can come together to form community groups.
“People generally manage their ponds on an individual basis,” Dr Hill explained. “It would better if they could be managed collectively as a group of ponds. We don’t want every pond to be the same, we want a wide range of environmental conditions. This has been recommended before for terrestrial garden management and could now be taken further to include water habitats,” he concluded.
