'Might dogs be harmful to Hampstead Heath?'

A dog in a Hampstead Heath pond

A dog facing up to the swans at Hampstead Heath - Credit: A dog in a Hampstead Heath pond

The Heath is a special place for both people and dogs. Recent studies show that time spent in nature improves our mental health. Walking a dog gives us that opportunity, and dogs get their much needed exercise – a clear win-win.  

But might dog walking have a negative impact on the nature that provides them and us these health benefits? Some conservation organisations think so. 

Should Heath users be concerned? Possibly.  

With the dramatic increase in visits to the Heath, recently estimated at 15 million per year, dog visits must be considerable – perhaps several million per year – and rising.  

Dog ownership in London has increased by an estimated 84% in 2020, which may add to this growth. So it is probably a good time to understand better how dogs might affect nature on the Heath and what we could do about this. 

Two years ago, fellow researchers and I set out to measure the effect of people and dogs on the activity of wild birds and mammals in Heath woodlands.  

A dog in a Hampstead Heath pond

A dog in a Hampstead Heath pond - Credit: Ron Vester

We could not separate the effects of walker and dog, but observed that dogs often rummaged in undergrowth, where wildlife live, while walkers stayed on paths. We learned that some birds, like blackbirds, were significantly less common in areas with high human and dog traffic. In addition, all birds using these areas shifted their foraging to early morning hours.  

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Long-term effects are unclear – if more dogs reduced space and time for wildlife in woodlands, it  could affect their numbers on the Heath. It would certainly reduce our chances of seeing and enjoying this wildlife.  

A dog in a Hampstead Heath pond

A dog in a Hampstead Heath pond - Credit: Ron Vester

A less obvious impact of dog walking is its impact on plant life on the Heath. Dog feces and urine are extremely nutrient rich. A recent study in Belgium has shown that, in natural areas like the Heath, where dogs poo and wee while on walks, this fertilisation is enough to change vegetation and exclude wildflowers. The Heath’s sandy soils are nutrient poor. These once supported extensive “acid grasslands”, which now survive in a few protected patches. Increased dog traffic could fertilise these areas and reduce wild flowers typical of this threatened habitat, like tormentil and heath bedstraw.  

Finally to ponds, where our dogs swim. I need not dwell on the horrific dog attacks we see regularly on waterfowl – this clearly must not be allowed  

A more subtle problem, however, has recently emerged. Britain’s waterways are still showing high levels of certain pesticides banned years ago because they kill honeybees. It turns out they were banned for agricultural but not veterinary use. These neonicotinoids are widely used in flea treatments. Dog washing and swimming can introduce them to waterbodies, where they are lethal to aquatic insects like dragonflies. Last month, these chemicals were confirmed from Heath ponds.  

A dog in a Hampstead Heath pond

A dog in a Hampstead Heath pond - Credit: Ron Vester

Some of these stories point to potential effects, not measured ones. But dog walking seems likely to be having some negative on Heath habitats and wildlife.  

What could we do now to reduce these risks? One positive action would be to keep our dogs strictly to paths in woodlands and rough meadows and out of dense undergrowth. This should reduce disturbance and injury to nesting birds, hedgehogs and other wildlife that nest and rest there. For a well-controlled dog, this should be easy, or a short lead might be used.  

Another possibility is fencing off areas to protect particularly sensitive plants and animals. It is not surprising that Ken Wood, our well-fenced ancient woodland, is also home to many of the Heath’s rabbits, nor that the long-fenced Bird Sanctuary supports healthy numbers of grass snakes. The rare pleasure of seeing a snake, rabbit or hedgehog on the Heath owes much to these existing dog-free areas.  

For ponds, it is also very simple – if we only swim dogs at designated swimming areas, with floating barriers, we should reduce risk to waterfowl and limit poisoning of pondlife by pesticides. 

We can learn a lot from other London green spaces. At Richmond Park, ground-nesting birds like skylarks – long absent from the Heath –  survive because dogs are walked there on short leads. Last year, in response to user groups on Wanstead Flats, City of London rescued their falling skylarks population by fencing off an area of meadow from walkers and dogs.  

Let’s accept that dogs will be dogs. They cannot help disturbing wildlife and degrading natural habitats. That leaves it up to us to protect nature on the Heath, for both our future enjoyment and that of our dogs. 

Jeff Waage is from The Heath and Hampstead Society.