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Principles of Riverine Health, by Frederick Schueler

One of the triumphs of the 2014 Ontario Rivers Alliance (ORA)  Annual General Meeting was the realization that, while the fight against the misguided Feed in Tariff (FIT) meso-scale hydro projects was an ongoing struggle, we could see light at the end of the tunnel.  We needed to begin to implement a broader consideration of the health of rivers that we’re mandated to address, perhaps working towards a publication on criteria of health for Ontario rivers.

Googling riverine health brings up two sets of criteria. These either suggest that “minimally altered watersheds are intrinsically healthy, because their key process regimes are, by definition, within the natural range of variation,”[1] or they tend to emphasize the services the “healthy” stream can provide to human observers or exploiters.

Ever since I had my mind blown by the density of ideas in Valerius Geist’s classic Life strategies, human evolution, environmental design: toward a biological theory of health,[2] I’ve valued his definition of organic health as phenotypic development that maximizes the expression of the characteristics that distinguish a species from its relatives (in the case of humanity including large brain, high capacity for exercise due to evaporative cooling, manual & bodily dexterity, highly developed intellect & language, music, tool manufacture & use, dance, visual mimicry, role playing, altruism, humor, self-control, complex traditions, and long life span).

If we import Geist’s biological criterion into the “health” of rivers, it’s clear that  what makes them different from other habitats is that they are lentic (flowing) rather than lotic (standing). This means that what we’re looking for in a healthy stream is expressions of the consequences of water moving downstream. On this basis, I’ve come up with a 3-point conceptualization. The first two points are consequences of the flow itself, and the third is about differentiation among rivers:

1) Continuity (channel, flow regimes, migration, long-lived species) – The connectedness of rivers can be broken in either time or space. In its early years ORA has mostly been defending continuity, since dams break dispersal and flow in diverse ways (and by creating impoundments, reduce the difference between the river and standing water). Lakes, the alternative kind of water, are geologically temporary, since they fill in with sediment or drain when their sills are eroded down, but as long as rain falls, rivers will flow, and almost always in the channels that they have flowed in before. All our lakes date from the recent retreat of the Ice, but at least north to the Arctic Watershed, Ontario rivers are geologically confluent with streams which have been flowing south across North America since the Paleozoic. Another aspect of healthy continuity – or indication that continuity has been preserved – is long-lived stream creatures with complex life histories, such as Unionid mussels, Sturgeon, Eels, Turtles, and Mudpuppies.

2) Oligotrophy (net watershed ombrotrophy, filter-feeding, wetlands) –  One of the primary goals of conventional river conservation has been preventing organic and nutrient pollution, whether from point sources or through runoff or groundwater. The reason such nutrient loading is unnatural is that mature  terrestrial plant communities characteristically strip most of the mineral nutrients out of the water they process, so the biota of a river is adapted to water that has a lower concentration of nutrients than precipitation – what I’ve called ‘net ombrotrophy.’[3] Another consequence of flow is that there’s minimal nutrient recycling in any particular reach of a river – photosynthetic production and filter-feeding both depend on extracting nutrients from the thin broth that’s flowing downstream, and anything that gets up into the current is lost downstream unless it’s moved back upstream in the body of some current-breasting creature.

3) Endemicity (biogeographic integrity, biodiversity, native rather than alien species) – Because they flow for so long in constrained channels, which many of their creatures either can’t or won’t leave, rivers and streams provide venues for evolutionary adaptation to local conditions. South of the limits of glaciation the number of species of locally endemic fish, Unionid mussels, Crayfish, and Salamanders is astonishing.  In Ontario we don’t have species-level differentiation, but we do have different faunas dependent on how species colonized through post-glacial lakes, and every local population is specially adapted to its situation, and every twist and reach of a stream has its own community. Maintaining the distinctiveness of a river means working to prevent extinction of local populations, and avoiding the introduction of alien species that will make all invaded streams more similar to each other.

All of this converges on the conventional idea that “minimally altered watersheds are intrinsically healthy, because their key process regimes are, by definition, within the natural range of variation,” and the resulting idea that a measure of “health” would “appropriately be based on the extent to which watershed process regimes are modified relative to the baseline, or their natural ranges of variation,”[4] but I think it helps to think about riverine health in these three categories, just as we conventionally think of human health as being determined by the physical conditions of life, social environment, and exposure to pathogenic organisms.

So the lesson for river lovers is to rejoice in whatever you’ve got, but when there’s a chance, move towards a healthier state. This is just a first sketch of  these ideas: if this approach and these points stand up to scrutiny we’ll need to expound them and find ways to make nontechnical readers comfortable enough with the language that they can assimilate the meaning of the points and apply them in practical conservation.

You can contact Fred [email protected]


[1]    Atlantic Ecology Division, National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency. 2011. Healthy Watersheds Integrated Assessments Workshop Synthesis. contribution AED-11-051, December 2011, 81 pp.\zyfiles\Index%20Data\11thru15\Txt\00000003\P100DXBV.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h|-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p|f&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&ZyPURL
[2]   1978, New York, Springer-Verlag, 495 pp
[3]   Schueler, Frederick W. 1989. Feeding from the clouds: Net ombrotrophy as a measure of the health of landscapes. Trail & Landscape 23(3):122-125 –
[4]   link to the same document as #1

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