Not in my river

When I was a child, I grew up next to a decent sized river. My wandering started early and I would walk up the river with my mother and sister and splash through, then poke around at the things we found under rocks and in the trees along the banks.

As I got older I walked further afield, and I loved to lie on my belly and take deep gulps of the cold, geosmin flavoured water or cup my fingers tight and get the water to my lips before my hands froze. The bracing cold of the rocky pools was even more exhilarating after running around after sheep and I would float in the water slurping it down as I paddled around after the unfortunate bees that got caught in its swirling currents.


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This was in the ‘80s and ‘90s and at the edge of a national park in the foothills of the Southern Alps of New Zealand. You wouldn’t think this environment would change much in the time since my childhood. After all there has been around 12 000 years of human civilisation and the agriculture that came along with it. How much could really have happened in the last 20 years compared to the last 12 000?


But the reality is that a lot has changed. Change is still happening, and in some areas and ways things are changing faster.


In New Zealand a decrease in some aspects of water quality is occurring rapidly in areas downstream from the foothills – that is everywhere downstream of places like where I grew up. This is down to two things. A change in the intensity of agriculture is taking place—the burnt, brown Canterbury plains of my childhood summers, where a few skinny Merinos spread out across the paddocks to hunt for the grass, has been replaced by vast tracks of irrigated, green dairy country. In New Zealand and other parts of the world, this intensification of agriculture has caused an increase in nutrient concentrations within rivers.


Secondly, more people are moving into previously unmodified/natural areas. In Australia the evidence of this can be seen at many a popular camp site or walking trail. It feels like it has now become uncommon not to find bleached, disintegrating piles of toilet paper strewn around.


Left at the surface, these piles of poo-laden paper slowly break down and are, in all their glory, washed into rivers as soon as the next pulse of rain hits.


There is good news and bad news about this encroachment of people into the wilderness.


If you are looking at things from a human point of view, the news can be viewed as not too bad. The impact of these toilet-paper parcels on water quality isn’t big —research suggests it’s ok to bathe in water near poo-stricken campsites. And the fact that people can’t drink untreated river water is thought to be as much due to bacteria from animal poo as much as it is humans.


But if you are looking at things from an environmental point of view things are not so good. Just as humans can get sick from poor quality water, so too can animals. This seems surprising. We know that animals drink safely from untreated water all the time, and humans are well known to get very sick from doing this!


Well it turns out that humans mostly get sick from water contaminated by human waste. Used as an indicator of water quality, faecal coliforms (bacteria from the guts of warm-blooded animals) in fact do not necessarily mean people can’t drink the water. They are just an indicator, with high concentrations in some cases indicating faecal contamination from non-human sources which may or may not cause people illness.


Animal waste will make people sick if it has a virus, bacteria, parasite or similar pathogen which is not species specific. Vice versa is true for animals and this is where the bad news comes in.


Because of the increase in the number of humans and the domestic animals associated with them encroaching natural areas, and the increasing population density overall, humans and their waste are causing disease in animal populations. The cold sore virus, which is carried by most of humans although they are without symptoms, is deadly to primates. So too is the measles virus, with instances of primates in zoos being killed upon exposure.


The scientific term for this area of research is called zoonanthoponoses, and there is still much that is not known.


For me an area of concern is the impact of human pathogens which survive treatment in sewage treatment plants. These are released from the sewage treatment plants into rivers and oceans, but what happens next? Is some poor wombat right this minute dying of gastric illness, all because he waded up to his belly to drink of water sullied by the humans upstream?


One thing is for sure. Despite the 12 000 years of civilisation on Earth, humans are still having a massive impact on the environment. One can only hope that as rapid as the extinction of species and habitat destruction has been in these 12 000 years, an equally rapid change heralding the end of such destruction can occur in the near future.

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Page last updated 10 July 2020

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