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Hi Flora & All, Apr 21, 2011
Good to hear from you. As I remarked on Apr 18, much depends upon intensity of use and the temperament of the dog. To judge from the various posts, with an emphasis on interaction (directly or indirectly) of a dog with other dogs or people, the walk or outing being visualized is in a setting with relatively high usage.
Turning now to your points-- and looking at item 1 first, these hypothetical medications, disease organisms, etc. that might be in her feces may either be concentrated in a septic system where a high percolation rate assures penetration to depth and possible contamination of well-water, dumped in a landfill where generations later they may emerge when least expected or they may be thinly scattered in a natural soil (i.e. deposited in the woods) that is well poised to make use of any available resources. For most contaminants is not dilution the solution, especially if biology can deliver the cleanup ?
2) While it is true that a soil profile may become overloaded with nutrients, this takes place in a setting that is orders of magnitude different from even extremely fertile natural soil profiles.
DIGRESSION: Most of my notes are not at hand but I happen to have a chart home that illustrates a seriously overloaded soil. This involved nitrogen and potassium capture by volunteer Reed Canary grass on light sandy loam soil down-slope from a liquid hog manure storage pit. I established plots on this site after having noticed a stand of Agropyron repens (Quack-grass) about 9' tall that flopped over and dissolved after a rain. The nitrogen capture (amount removed in mowed grass) over 4 years was about 2,100 kg N/ha and potassium capture was nearly 2,300 kn K/ha. By way of comparison, an apple orchard trial over 25 years received each year only ~19 kg N/ha (as I recall)+ 1/4 bale of hay mulch/ tree with a few kg/ha of K only in the year of planting.
And less extreme cases of overloading are found when soil (often with no crop removal) is used for disposal of manures; a consequence of specialization and localized concentrations of animal husbandry.
END OF DIGRESSION
But forest soils are always at the far end of the nutrient loading spectrum (unless there is a huge leaky manure pit [or a leaky landfill] just upslope, a Heron colony overhead or exceptional circumstances such that demand is near zero and release is high-- e.g. clearcuts with little or no vegetative cover).
3. As Fred has noted, and you initially noted, runoff is largely a feature of urban conditions. There may be localized runoff from natural woodland but this is mostly during snow-melt or when saturated profiles are hit with a downpour or where very shallow soils are underlain by impermeable barriers (usually leading to barrens, heath, scrub etc. In the urban setting, is it really reasonable to blame the dog for a deplorable system of water mis-management ? If feces are likely to be carried to a storm drain then, I suppose, one should scoop.
But let us think about this a minute. For about 250 years the city of Halifax pumped raw sewage into Halifax harbour (except initial decades when it just ran down the gutter) leaving a ring around the harbour and nearby beaches. Until recent years many sewers in Kentville emptied directly into the Cornwallis, the sewage from the County Home emptied directly into the river, and sewage sludge sometimes just happens to 'leak' into the river due to 'malfunctions'. And a few years ago I was told that in Kings county roughly half of the pumped volume never reaches a treatment plant but instead leaks
out on the way there. Not that I commend any of these practices but against this background, perhaps the odd dog deposit in an urban setting isn't such a big deal.
The solution to problems caused by contiguous acres of impermeable pavement, and the associated need for a normally dry storm-drain system with a huge capacity to deal with the flash-floods of rain events, was devised about 50 years ago by the Franklin Institute; porous pavement oddly enough. Why this solution has been left on the shelf beats me. Porous pavement would also take doggie-do into the root zone where trees or other vegetation could use it.
4. This is a subset of 1 but I will repeat that intensity of usage is fairly important here. If you get well back, especially if you walk cross-country, the chances of some other person or dog even getting close to a fresh deposit is vanishingly small.
In the end of course it is whatever one is comfortable with. I sometimes encounter dogs and dog products when I walk in high-use areas but I don't perceive any of this to be a problem.
Yt, Dave Webster, Kentville
----- Original Message -----
From: Flora Johnson
To: naturens@chebucto.ns.ca
Sent: Tuesday, April 19, 2011 11:28 AM
Subject: Re: [NatureNS] Dogs on walks
Much as I'd love to think that my dog is doing the wilderness a favor by defecating there, sadly this does not appear to be the case. Here's why:
1. Because my dog lives in close association with me, her feces may and very likely do contain contaminants not routinely present in the feces of resident wildlife. These include antibiotics and other medications, potentially harmful strains of E. coli, and other disease-causing organisms that are present in the human environment but not necessarily in the wild.
2. Although it's true that an ecosystem can absorb and even benefit from animal waste, this ability is limited. The quantity of wildlife an ecosystem can support is also limited, so one can hope that a functioning ecosystem will be able to process and the waste products produced by the wildlife it supports. This becomes increasingly less likely once we start to add the waste from our companion animals, whose population is determined by us rather than by the carrying capacity of the local ecosystem.
3. Waste products don't necessarily stay where they were deposited. On the contrary, in environments where there has been a lot of human activity, materials deposited on the soil surface often are washed way by the first rain, ending up in local waterways. This means that even if your dog is defecating in an ecosystem so degraded that it needs the nutrients, there is no guarantee that those nutrients, along with anything else in the dog's feces, won't end up where they're not needed -- namely, in the nearest stream, pond, lake, or shoreline area. In recent years, many outbreaks of E. coli or excessive nitrogen in waterways have been blamed partly or entirely on dog waste.
4. Although I do everything I can to keep my dog healthy, it's still possible that her feces might contain parasites or diseases that could be transmitted to other people's dogs or even, in some cases, to humans and other animals. Even aside from the potential effects on wildlife and the environment, as a responsible pet owner I should not take unnecessary