‘’Ponds have been around commonly and continuously for millions of years’’
Ponds provide a unique biodiversity resource, that is also an important part of our history,
culture, a visual focus in many landscapes and an amenity for many communities. They can
provide a focus for villages, schools and communities as well as added wildlife interest. There are approximately 500,000 ponds in the UK, but there has been a dramatic loss of
ponds over the last 100 years, so their preservation has never been more important.
So why are ponds so important and what makes them hotspots for biodiversity? It has often been assumed that large waterbodies, like rivers and lakes, have a higher conservation value than ponds. In fact, this is not true. In a study comparing the number of invertebrate animal species collected from 600 rivers and 150 ponds across Britain, it was found that, in total, ponds supported more invertebrate species than rivers. The ponds also had a greater number of rare animals. Nationally, around two thirds of all Britain’s freshwater plants and animals can be found somewhere in permanent and temporary ponds.
Ponds are also a last refuge for some species. As a result of ‘crayfish plague’, which was
brought in with imported crayfish, the native, White-Clawed Crayfish, has almost been
completely lost from many rivers, but ponds can provide refuges.
Before we go any further, we should define what a pond is. Ponds are natural or man-made
waterbodies between 1m 2 and 2 ha in area which hold water for 4 months of the year or more. This is a deliberately broad definition and includes even very small waterbodies, which can sometimes have a high conservation value. It also includes semi-seasonal and temporary ponds, which often dry up in summer, but can support both specialised and valuable pond communities.
Why are ponds so good for wildlife? One of the reasons that ponds are such rich habitats is
because they provide a very natural type of habitat. Ponds have been around for millions of
years, and during this time many species of plants and animals have become adapted to the
conditions that they provide. Fortunately, ponds (although now mostly man-made) are still
quite common features, even in our modern landscape. This is fortunate, as many freshwater species now depend on ponds for their survival.
So, how many freshwater invertebrate species can be found in ponds? It has been assumed
that since ponds are small, they cannot be particularly important. However, ponds can be
extremely biodiverse habitats.
Invertebrates (animals without backbones), include dragonflies, mayflies, snails, water fleas
and many others. There are at least 4000 species of freshwater invertebrate in the UK, and
around 70% of these live in ponds. Amongst these are many rare, vulnerable and endangered species. In a diverse pond there may be over 100 of the larger invertebrate species, such as beetles, dragonflies, snails and caddisflies. In highly diverse ponds, over 150 species may be
supported.
Around the margins of ponds in the zone between the water and dry land, many wetland
invertebrates also live. However, there have been few studies into these damp ground
communities. Studies that have been conducted, have suggested these zones can contain very uncommon animals. Rare invertebrates are often found in what seems to be on first sight, unpromising habitats. These can include habitats such as wooded and seasonal ponds, ponds with floating mats of rushes and reeds, or muddy, damp ground at the water’s edge. Exceptional ponds can have over 15 species of dragonfly.
Our native amphibians (frogs, toads and newts) are pond specialists. They use these small
waterbodies as their main breeding habitat. As adults, amphibians utilize ponds in different ways. Young amphibians can stay close to their home pond and others might hibernate over winter. Common Toads prefer to live in deep ponds together with fish as the tadpoles are distasteful to fish. Great Crested Newts, better survive in ponds which dry out occasionally, as this prevents fish preying on their larvae.
The grass snake is one of our native reptiles which also loves ponds, mainly because frogs
and sometimes fish are amongst its favourite foods.
Most of our larger wetland plants can be found in ponds, with the rarest species depending
exclusively on them.
Ponds can also be an important habitat for wetland mammals. Water Voles now use ponds
more exclusively now that Mink abounds in many of our rivers and streams. The Otter also use ponds as a habitat to catch fish and amphibians. Bats, too, hunt around ponds, taking
emerging insects.
Permanent ponds often have healthy populations of fish. With natural densities, these can
coexist with plants and animals. Ponds that are well connected by ditch or stream systems can be important for Eels, although once common, have been undergoing a global decline.
Certain types of pond won’t support fish. For example, ponds which are naturally acid, and
shallow ponds that occasionally dry out don’t support fish.
Ponds are also important habitats for birds, the open water as well as the margins. Shallow,
muddy ponds known as ‘Scrapes’, are often dug for waders. Many bird species, including
Swallows and House Martins, hunt over ponds, picking off insects emerging from the water.
Others, including terns and grebe use them as a source of fish.
So, next time you’re out and about and see a seemingly uninteresting piece of water, go take a closer look – you may be surprised as to what you may find within this often undervalued and overlooked habitat.