One or two people have commented about the increase in duck weed in Yalden Spring over the last few months and asked if this is to do with the prevention of dogs going for a swim. We thought we’d publish some information on why the duck weed isn’t a bad thing, and why we have built the dead hedging to prevent dogs going into the pond…

Many of you will know that Yalden Spring is an incredibly rare habitat, and a very important part of Limpsfield Common. Being a spring, it is naturally uncontaminated and we are incredibly lucky to have such a unique habitat in our area, and should be doing our utmost to protect it.

Unfortunately, the increase in numbers of dogs (and their humans!) in the pond (and on the common in general) over recent years has had a detrimental effect on the resident wildlife and we want to do all we can to encourage flora and fauna to return, and bring the spring back to SSSI standards.
[SSSI stands for Site of Special Scientific Interest – areas of land and water that we consider best represent our natural heritage in terms of their flora and fauna.]

When it comes to duck weed, any perceived increase is not due to the fencing or the prevention of dogs; it’s more to do with the climate we have had over the summer months and the natural fluctuation as a result of the increase in water temperature, creating suitable conditions for the plant’s reproduction. As winter arrives, the lowering of the overall temperature will mean that the duck weed naturally starts to dissipate.

In fact, the disturbance (by dogs) of the sediment in the water column actually means that the surface flora (duck weed) has a significantly higher chance to thrive than any plants that grow from under the water.

Duck weed is a natural pond plant, and acts as shelter and a great source of food for inhabitants of, and visitors to the pond. Whilst a complete blanket on the water surface is detrimental to the habitat (preventing light from getting below the water surface and outcompetes other flora for nutrients), duck weed also provides some good ecological benefits when managed well: It is a great oxygenator and provides filtration for nitrogen and phosphorus, helping reduce algae growth and improve water quality. It also offers a valuable food source for frogs, newts, insects and many other creatures that live around the area, particularly in the months leading into winter.

It’s a bit of a balancing act, and in fact, the fencing may help to gradually reduce the amount of pond weed.

Unfortunately, there are no benefits from dogs splashing about in Yalden Spring! This has an extremely damaging effect on the pond’s resident flora and fauna, and this is why we’ve had to stop them going for a swim.

How dogs negatively affect the pond

When dogs enter the pond, aside from severely disturbing and potentially injuring or killing the resident frogs, newts, tadpoles and invertebrates living there (as well as affecting pretty much all other animals that rely on the pond as a habitat), they “poach” (tread into the sediment) and severely stir up the silt and clay the particles of which are then released and persist in the water column, preventing any sunlight from penetrating the water and drastically reducing the chance for any aquatic flora to establish, grow and stabilise.

Unfortunately splashing around isn’t the only reason dogs destroy pond life…

Did you know that any flea and tick treatment applied to dogs within a month of going in the water will leach those chemicals into the water upon entering? These chemicals are indiscriminate, not just targeting fleas and ticks, but also killing off any aquatic invertebrates in the immediate area.

It’s also important to note that dogs can pick up illnesses from ponds, so it’s not a great idea to let them in for their own health anyway. Most dog walkers we talk to are very understanding and happy their dogs can’t go in, because their animals smell a lot better for it…and so do their cars!

We hope the above helps to explain why the new dead hedge structure is positive and plays a vital role in our plan for the habitat recovery of Yalden Spring, which extends over to both sides of the bridge. This will help to protect the pond and encourage the oxygenating marshy flora and provide a safe habitat for the local wildlife, with the long term aim of both protecting and expanding this locally rare and important ecosystem.

Duck weed aside, you may have also noticed the increase in pond life recently. As well as the frog breeding spectacle (in February) over the last couple of years, we have been really pleased to see a marked increase in various dragonfly species and even grass snakes (the apex predator of the habitat!), which are all great indicators of a return to a healthy habitat, and that’s what it’s all about from a conservation point of view.

Crispin Scott, a NT Nature Conservation Advisor recently visited and was very impressed with the work we are doing to help bring Yalden Spring back to SSSI standards.

“You seem to have got stuck in and done some really good work, especially around the pond that we first visited…The dead hedging seems to be a really good and attractive dog barrier too. Well done!”