The concept of sustainability is one that is still developing. New information provides new insights and the tools to work towards a future more capable of enduring the tests of time. Until recently, humans believed that all resources could be indefinitely exploited without damage to the system as a whole. This lead to exploitation and many of the negative environmental externalities (e.g. loss of biodiversity, climate change, etc.) facing the world today. This idea led to the concept of simply finding technological replacements for the resources and services that nature provides or weak sustainability, which is the idea that manufactured capital can take the place of natural capital. This means that as long as natural capital is manufactured into something with the equivalent capital value, it can be used without constraint. This view on sustainability does not take into consideration that some services cannot be replaced (ex. what do we do when there is no more ozone layer?).
However, such a feat has proven quite difficult and led to a further evolution of the idea of sustainability, a concept known as strong sustainability, which asserts that existing natural capital cannot be duplicated or replaced. As such, it should be protected, maintained and enhanced in order to continue receiving the benefits of natural capital. Strong sustainability supports the following principles:
- The scale of human activities should be constrained by the actual carrying capacity of the planet. This means addressing issues of sufficiency and efficiency with the implementation of limits to the physical scale.
- Technological development should focus on improving the efficiency of resource use as opposed to increasing the “throughput” (the flow of goods/services from natural to human systems).
- Renewable natural capital should be sustainably managed by harvesting at rates not higher than regeneration rates and keeping waste production to levels that do not exceed the renewable assimilative capacity of the environment.
- Non-renewable natural resources should not be exploited faster than the rate of creation for renewable substitutes. (better suited to weak sustainability)