The economic circle of sustainability is founded on the concept of maximizing the flow of income from a stock of capital while maintaining the stock yielding this income. The concept encompasses traditional theory on economic growth, that is, determining optimal economic growth with a given capital. The premise is that future generations can only be better off if they have more capital per capita than we have today. It is immediately obvious that population growth is inimical to sustainable development since it 'dissipates' the capital stock. Technological change, on the other hand, enables a given capital stock to generate more wellbeing per unit of the stock. An easy way to think of it, then, is to say that future generations will be no worse off if capital stocks are 'constant' and for the rate of technological change to just offset the rate of population growth. If technological progress is faster than population change, then future generations could still be as well off as we are today with a lower capital stock, and so on.
1. natural (or environmental) capital, which provides a continuing income of ecosystem benefits, such as biological diversity, mineral resources, forests, wetlands, and clean air and water;
2. built (or productive) capital, such as machinery, buildings, and infrastructure (roads, housing, health facilities, energy supply, water supply, waste management, etc);
3. human capital, in the form of knowledge, skills, health, cultural endowment, and economic livelihood (small enterprise development, literacy, health care, inoculation programs, etc.);
4. social capital, the institutions and structures that allow individuals and groups to develop collaboratively (training, regional planning, decision sharing culture, etc.); and
5. financial capital, the value of which is simply representative of the other forms of capital.
This broadening of the concept of capital is critical to an understanding of sustainable development. It is now easy to see that the total capital stock could be rising while any one form of capital is declining. The idea that forms of capital substitute for each other is embodied in the notion of weak sustainability. If, on the other hand, forms of capital are not substitutable then the requirement that the total stock be constant (rising) has to be supplemented by the requirement than the relevant specific capital stock should also be non-declining. In the literature, this has been termed strong sustainability.As the professional manufacturer of complete sets of mining machinery, such as hammer crusher, Henan Hongxing is always doing the best in products and service.
The social circle of sustainability addresses issues such as poverty, health, education, local empowerment and maintaining culture and heritage. Although social norms change over time, sustaining social and cultural systems is important. Social sustainability has obvious linkages with economic development in terms of addressing poverty and local input into economic decision-making. Linkages with environment development focus on the allocation and distribution of natural resources to future generations as well as local empowerment over natural resource management.
The ecological circle of sustainability is concerned with maintaining the physical/chemical and biological environment to preserve resilience and the ability of natural systems to adapt to change, protecting from degradation the ecological processes, functions and cycles that are fundamental to life on Earth. An obvious linkage with economic development is through the supply of raw materials for production and the use of the environment as the final waste sink. One linkage with social sustainability is through the level of local participation in natural resource management. Closely related to ecological sustainability is the concept of carrying capacity, both in terms of human population that can be supported by Earth and the ability of our environment to assimilate final waste products.