Carrying capacity

This is a letter from environmental/ecological economist Shelagh Huston, that arose out of discussions initiated by the Sustainable Gabriola group. Shelagh’s note in advance of a meeting to discuss a potential town hall series has changed both the community discussion and the way I [Gabriola trustee Scott Colbourne] look at our role as facilitators/participants in those conversations.


Hello dear friends,

I’m happy that for a long time I’ve been able to be a ‘lurker’ on the Sustainable Gabriola email list. Even though I’ve never been a regular participant (being too insanely over-busy when living there, and now being off-island), I’ve been a huge fan of all you do and have done since the beginning. As a mere by-stander, I haven’t participated in the ongoing conversations. It’s been a source of satisfaction to me that since things are being so extraordinarily competently handled, I can just sit back and cheer you all on.

I’m delighted to see you take on yet another good thing, the planned Town Hall meetings. I understand that all our elected representatives support "holding regular 'town hall' discussions on key issues as identified by the community, recognizing the need to engage in meaningful dialogue intended to take difficult conversations out of the political realm, and to develop an understanding of the context and fears behind controversial issues." 

This is a deeply encouraging sign of the growth into maturity of Gabriola as a community. Now that I live elsewhere, I’m even more convinced that Gabriola has the potential to be a critically-important ‘ark’ of survival and sustainability for the future, especially the possible feared long darkness ahead. What you do seriously matters. 

The Town Hall is “an idea whose time has come” and, I believe, matters quite a lot. The ability to hold public conversations productively may turn out to be one of our most significant tools for survival. I support what was said in the topic on 'Discourse’ in the November notes, as being exactly what’s needed.

I understand the Sustainable Gabriola meeting will consider the agenda for the first Town Hall meeting, and I see that "It has been suggested that an initial focus could be to determine the carrying-capacity of Gabriola,” with full discussion of the parameters this Sunday, and a perhaps more limited scope at the actual Town Hall. 

As a former environmental/ecological economist, I have some thoughts on the idea of “carrying capacity” that I’d like to share with you. I hope my desire to break out of my satisfied-lurker status and share a few quick thoughts on this will be welcomed. Please take my 3-cents-worth mini-essay as another contribution towards holding potentially difficult conversations. If you’d like to share my thoughts at the Sunday meeting, I’d be happy to have them circulated as part of the conversation.

I think that the topic of “carrying capacity” may be a poor foundation for considering the many aspects of sustainability on Gabriola. The concept has been used in the past, including in public conversations on Gabriola that I recall from the 1990’s, as a shorthand way of drawing lines to prevent undesirable and unsustainable development. But it cannot be validly used in this way. This makes it an undependable base-line, and using it opens the discussion to charges of trying to hide a values-based agenda behind a supposedly impregnable 'scientific’ perspective. 

“Carrying capacity” has been defined in various ways, as: 

  • the number of individuals who can be supported in a given area within natural resource limits, and without degrading the natural social, cultural and economic environment for present and future generations. 

These definitions are not identical. The first definition is the original biological concept, applied to a particular species in an ecological niche. This works, to some extent, in cases where the way a species ‘makes a living’ is defined and fixed, such as a measured amount of bamboo shoots per panda per day. The second definition applies the concept to humans, where it has a much less stringent relevance. Even the definition I quoted was followed by the caveat, "The carrying capacity for any given area is not fixed."  


There are a number of problems in applying the idea of carrying capacity to humans. Usually, when people apply the concept, there is an implicit expectation that a specifiable carrying capacity can be found, and can be used in decision-making for determining public policy regarding development and the limits to growth. For example, back in the late ‘90s and early ‘00s, people spent a lot of effort trying to determine how much groundwater there was on Gabriola, with the intention to limit settlement to the number of homes that could be supported by wells drawing on that groundwater, without diminishing or polluting the renewable supply. This seemed both reasonable and objective, a measure with which no-one could argue once the data was established. And the research done did establish that the amount was indeed limited (and put an end to some mythical conceptions of an unlimited supply supposedly coming from Mount Arrowsmith.)  


However, this approach overlooks some vital facts, and the expectation that it is possible to find a definable carrying capacity of a given place to support humans is bound to be disappointed. Applying the notion to people involves making the unwarranted assumptions that humans, like pandas, consume some fixed amount of resources, and that those resources must be found or produced in the same place that they are consumed. It’s obvious that neither are the case.


For humans, who have the ability to transport and store resources, there are, effectively no ‘natural resource limits’ in a given specific land mass such as an island (even though these limits exist for the world as a whole). I remember a time when firewood and water used on Gabriola were only locally sourced, but both are being imported now. And there’s always been enough water on the island, just not in the ground; it comes in large amounts from the sky, and can be stored in cisterns. 


Even the aspect of not "degrading the natural social, cultural and economic environment for present and future generations”  depends vitally on how ‘degradation’ is defined, and for who and where. Bringing water to Gabriola doesn’t degrade Gabriola, no matter what it may do to the water source. And what constitutes ‘degradation’ depends on value judgements. At a time when these matters were being vigorously discussed, it was pointed out that Gabriola could, in fact, survive with a far higher human population - it would just be very different than it is now. (For a light-hearted look at this, see "Gabriola and Manhattan—Two Islands", SHALE 6, pp.3–8, April 2003, 


This is not to say that putting several million people on Gabriola would be a good idea - I think it would be a disaster, especially for most of the nonhuman species who call our island home - only that it’s possible. So, we are forced into asserting what we believe would be good, or ethical, or preferable, which are subjective value judgements - not a supposedly ‘objective’ measure of ‘facts’. And I strongly believe that making value judgements is both inevitable, and totally appropriate. We have been misled for many years by people hiding determinations of preferences under false pretences of being ‘objective’ and ‘factual’.

For humans, the level of resources used, and more significantly the environmental impacts of that use on both ‘sources and sinks’, is not a straightforward result of the number of people in a place. One of the earliest attempts to describe the role of multiple factors in determining environmental degradation was the IPAT equation, I = P x A x T (Barry Commoner, 1972.) This states that environmental impact (I), expressed in terms of resource depletion or waste accumulation, may be described by multiplying population (P), the size of the human population, by affluence (A), the level of consumption by that population, and by technology (T), the processes used to obtain resources and transform them into useful goods and wastes. 

The IPAT equation probably arose from another attempt to define objective limits to sustainability. And it too has failed in that regard, since it has not been able to identify sustainable limits to either individual or composite environmental impacts. But it’s a useful conceptual tool which demonstrates that there are multiple ways of reducing undesirable effects. A given community could reduce their level of consumption (A), reduce their population (P), or make their technologies more efficient (T) - likely all three would be needed, in different ratios for different starting conditions. 
And as a planet, we need to do all these things. One of the striking aspects of the climate change disaster is that the location of the source of the excess carbon makes no difference - the impacts are global. 


I’m taking up your time on this, not because the details matter, but because the basis on which we hold these conversations about the future really does matter to the outcome. Even for this community, where we've spent years trying to learn how to talk and listen to each other, it’s depressingly easy for disagreements to get shrill, for trust to be eroded, and for partisanship and divisiveness to raise their heads. Even if we don’t realize we’re doing it, if we try to push through our preferred outcome by making indefensible pseudo-scientific claims, we risk losing the mutual goodwill that keeps the social fabric from unraveling. 


So, even if ‘carrying capacity’ looks like a handy and capacious container for a bunch of important issues, I think it’s the wrong place to start from. Or, to mix metaphors, this road may look smooth, but I want to warn you there's a washed-out bridge ahead. 


I was always told as a kid not to complain about something unless I had could offer a better idea. Unfortunately, I don’t know if I can come up with an alternative. One idea, I don’t know if it’s better or not, would be to perhaps work together at the Town Halls to develop some kind of community ’indicators’. Wikipedia says (

Community indicators are "measurements that provide information about past and current trends and assist planners and community leaders in making decisions that affect future outcomes". They provide insight into the overall direction of a community: whether it is improving, declining, or staying the same, or is some mix of all three.

In essence, indicators are measurements that reflect the interplay between social, environmental, and economic factors affecting a region’s or community’s well-being. Community indicators projects typically are conducted by nonprofit organizations within a community, although in some cases they are initiated by the public sector."

Back in 2002, I was briefly involved as a workshop participant in the development of some environment and sustainability indicators for Canada (see State of the Debate: Environmental and Sustainable Development Indicators for Canada, NRTEE, 2005. The National Round Table on Economy and Environment did some great work until 2013, when Harper pulled the plug on it.) And I studied the use of indicators as part of my interest in Community Economic Development. They can be a good participatory focus for discussing and grounding values-based and evidence-based community intentions, in a format that can help policy-makers know if they’re going in the right direction. Anyway, just a thought, to avoid negative dumping on someone’s idea without suggesting any alternatives!


I want to uphold you in doing this very important work. Anything which gets the general public actually talking to each other, fruitfully, without degenerating into toxic trolldom, matters much more now than it ever has. We’re not just trying to do a fuzzy kumbaya hippy exercise here - it’s survival which is at stake, in a world of extreme danger. May all you do continue to serve to keep our home safe and thriving for generations to come.


With love and solidarity and blessings,




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