An exchange in the comments on this question got me thinking: what is the standard definition for sustainable?
Does it include such things as:
- Geographic extent
- Time frame
- Other factors?
There isn't really a single agreed-upon definition of sustainability. Everyone has a basic idea of what it is, but the exact meaning differs from person to person.
Most common definition
The most common and often-cited definition of sustainability, or to be more precise that of sustainable development, is the one in the Brundtland report "Our common future":
development that meets the needs of the present without compromising the ability of future generations to meet their own needs
Although this definition does give some direction, it is not very usable. What exactly is a 'need'? Where do we draw the line between a need and a want? How can we know the needs of future generations?
Context and time dependent
The exact meaning of sustainability often depends on the context. A sustainable supply chain for example usually considers primarily the economics of it, whereas a sustainable building is usually about energy-efficiency and perhaps also about the environmental impact of the used construction materials.
The meaning of sustainability also changes with time. In the 'early days' sustainability was all about environmental protection. Nowadays a common view on sustainability is that of the 'triple bottom line' or the 3 pillars;
This is also referred to as the 3 Ps; people, planet, profit. Although this view is widely accepted, for some it doesn't go far enough and they propose to add culture as a 4th pillar of sustainability.
Sustainability on this website
On Sustainable Living SE we've tried to define sustainability by describing its relations with other concepts (which is the purpose of the defining-sustainability tag). Since sustainability can mean many things, when an OP refers to sustainability in a question without further clarification, it is recommended to ask what aspect of sustainability he/she is interested in. When answering questions, it is a good idea to mention what aspects of sustainability you've taken into account in your answer.
Sustainable: To continue a practice over a long period with little or no impact on the underlying resource.
I don't think that "sustainable" is an absolute. And too many people are using it that way. E.g. "Meat animals are unsustainable" "Coal power is unsustainable" "Organic farming is unsustainable due to weed issues" "Zero till is unsustainable due to chemical use."
Sustainable is better used as a relative measure, used with a given metric, and usually a handful of caveats. This will make the word unusable in sound-bite journalism.
Often a an adjective needs to come first.
e.g. Managed timber leases, where a single company has century long management of a block of land, and is responsible for maintaining a cutting policy that keeps more or less constant inventory on a decade long time scale is more economically sustainable than the U.S. Forests Service policy of auctioning off timber blocks.
This leaves open whether or not it is ecologically sustainable.
The time frame is important. Often the present practice will result in the destruction of the underlying resource in a short or medium period of time. E.g. Slash and burn agriculture in tropical rain forests. This results in infertile parking lots or mudscapes in a few years. Conventional plough, disk and harrow agriculture in many climates loses top soil at a rate of inches per century. By this metric PDH temperate agriculture is more sustainable than S&B tropical agriculture.
The ultimate measure of sustainability is to be able to continue the practice over geologic time.
Imho, if you are talking about sustainability, you should care about each factor that is connected to an object you use or an activity you do.
It's clear that you can't be always sustainable on everything you do, but it is already good if you know more in detail about things that happen around you.
Regarding your post, it must be clear, that the production of meat is not sustainable at all. You need to produce or buy additional food for them, the people working in this field have to get payed and then you still have the distribution taking a lot of effort till the meat is at the customers home. I think it would be better to find a different lifestyle regarding food we eat and even discover the real diversity that is out there instead of just talking about meat all the time. I also eat meat from time to time but I don't have to talk about it all the time and I know it is not sustainable.
And you also have the same problem with all the other things, that you can purchase, that have been produced in another place or with the everything that you do. To be sustainable, you have to be aware of what you consume and how you do it, the quantity. And that's the hardest thing, because we do not all have a correct relation to our consumption. Also because everybody has a different way to live.
Being sustainable means to consume in a level that gives even generations after us the possibility to live and have enough of everything. In a level that everybody has the same possibilities to do it, everywhere in the world.