The term “tragedy of the commons” pops up on many environmentally themed sites when discussing sustainability, but sometimes it’s not explained.

The tragedy of the commons refers to the diminishing of a shared resource by people acting based on their own self-interest. Simply put, it’s a form of greed, usually fueled by either ignorance or a feeling of self-entitlement.
 
While the general concept has been recognised for thousands of years, the common term came into being in 1968 via the pen of ecologist Garrett Hardin in an essay of the same name.
 
Tragedy of the commons scenarios are numerous – to some degree, most of us participate in one or more each day. 
  
For example, driving a gas powered vehicle erodes the quality of the air that we share with others. Buying goods we don’t need can steal resources away from future generations and impact the environment from which they are taken. 
 
Even the decision to have children, often seen as a right, is not one Nature has granted – and each extra person is an additional load on our already heavily stressed planet, competing for dwindling resources. Hardin didn’t pull any punches on this issue. 
 
According to Wikipedia, “Hardin argued that welfare provides for children and supports overbreeding as a fundamental human right, malthusian catastrophe is inevitable.”
 
Hardin went so far as to say:

“The only way we can preserve and nurture other and more precious freedoms is by relinquishing the freedom to breed, and that very soon.”

Ouch, that’s not going to sit well with some readers, but I understand where he was coming from as overpopulation is a pressing issue.

I’ve been a child sponsor for over a decade now. It’s wonderful to know the girl I sponsor in Africa now has opportunities she may never have had. But I also wonder if I’m just helping to perpetuate a cycle of future impoverished generations. However, the fact she is receiving an education encourages me as it’s education that has been shown to have a knock-on effect of reducing birth rates. In that respect, I’m not sure if Hardin was spot-on in his conclusion as welfare can be very beneficial if it’s properly directed, but the general spirit of his thoughts on overpopulation was probably – and unfortunately – correct. 
 
Another example he gave, from which the essay drew its name, related to herders grazing their animals on commonly-held pasture. One herder may allow his flock to grow as large as possible to generate as much personal benefit as he can, to the detriment of other herders and the landscape in general.
  
So there you have it – a basic understanding of the concept behind the tragedy of the commons. You no longer need to look bewildered when it’s mentioned and you can nod sagely when the topic is raised in dinner conversation.
  
But seriously, what is knowledge without the chance to apply or at least share it?
 
Regardless of some of the examples Hardin may have used (other scenarios have been hotly debated too), that’s all nit-picking really; the essence remains solid. The depletion of a resource by one individual can have a marked negative impact on the wider environment and all the organisms that live within it. And that’s something we can bear in mind as we go about our lives.
   
If you’re curious to learn more of what Mr. Hardin had to say back in 1968, read the full text of the Tragedy Of The Commons.