1. Ecological footprint theory
The concept of “Ecological Footprint” was first proposed by Canadian ecological economist W. Reis in 1992 and perfected by M. Weiknerg in 1996, and is a method to measure the degree of human utilization of natural resources and the life support services provided by nature for human beings. The significance of the ecological footprint is to judge whether the development of a country or region is within the scope of ecological carrying capacity, whether it has large ecological security, and whether the ecological security foundation of social and economic development is sustainable and stable and can support the sustainability of social and economic development.
Human survival and development require the support of resources, and various resources consumed by people’s basic survival needs such as clothing, food, housing, and transportation are all related to the land with ecological productivity. By calculating the amount of resources and energy and waste consumed by a person, a specific group of people, and a group of people, can be extended to “a giant foot carrying the cities and factories created by human beings, and the footprints left on the earth”. This can be said to be the concept of ecological footprint.
In the early 1990s, Canadian ecological economist William Rees and his doctoral student Mathis Wackernagel proposed a method to measure the degree of sustainable development – ecological analysis, which divides the land with ecological productivity into six categories: cultivated land, forest land, pasture land, water area, construction land and energy land. As a method to measure the degree of sustainable development, the ecological footprint analysis method calculates the size of the ecological footprint (DEF) from the demand side, and calculates the size of the ecological carrying capacity (SEF) from the supply side, and compare the land area of the two to evaluate the sustainable utilization of land resources of the calculation object. The land area here is expressed in “Global Hectare”, which is equivalent to 1hm2 of ecological land with a global average yield.
For a real ecosystem, if its SEF is greater than DEF, there will be an ecological surplus, indicating that human pressure on the natural ecosystem is within the ecological carrying capacity provided by the system, the ecosystem is safe, the development of the socio-economic system is sustainable, and the land sustainable use of resources; conversely, there is an ecological deficit, indicating that the demand for ecologically productive land for human survival and social and economic development in this system has exceeded the supply provided by the ecosystem, the ecosystem is unsafe, and the use of land resources is in the unsustainable category.
The calculation of ecological footprint is based on the following two basic facts: (1) Humans can determine the amount of most of the resources they consume and the amount of waste they produce; (2) These resources and wastes can be converted into corresponding biological production areas. Therefore, the ecological footprint of any known population (an individual, a city, or a country) is the total biological production area (including land area and water area) required to produce all the resources consumed by those populations and absorb all the wastes produced by these populations.
The formula for calculating the ecological footprint is
where i is the type of consumer commodities and inputs; Pi is the average production capacity of i consumer goods; Ci is the per capita consumption of i commodities; aai is the biological production area converted to i trade commodities per capita; N is the population; Ef is the per capita Ecological Footprint; EF is the total Ecological Footprint.
2. Decoupling development theory
Decoupling theory is mainly used to analyze the response relationship between economic development and resource consumption. A large number of studies on the relationship between economic growth and material consumption show that in the early stage of industrial development of a country or a region, the total material consumption increases year-on-year with the growth of the total economic volume, or even higher; but there will be changes after a certain stage. When the economy grows, material consumption does not increase synchronously, but slightly lowers, and even begins to show a downward trend, showing an inverted “U” shape. Therefore, concepts and indicators such as resource productivity proposed in the formulation of decoupling development strategies by European countries can be used for reference, by greatly improving resource productivity and environmental productivity, so as to achieve better economic and social development with less water, land, energy, material consumption and less pollution discharge.
3. “Roller Coaster” theory (EKC hypothesis)
In 1991, economists G. Grusman and A. Krueger conducted a study on the changes in air pollutants (1979-1990) and water pollutants (1977-1988) in 66 countries and regions and found that there is an inverted U-shaped relationship between the changing trends of most pollutants and the changing trends of per capita national income. They proposed the Environmental Kuznets Curve (En-vironmental Kuznets Curve, EKC) (Figure 1) hypothesis, arguing that along a country’s development trajectory, especially in the take-off stage of industrialization, there will inevitably be a certain degree of environmental degradation; after per capita income reaches a certain level, economic development will be conducive to the improvement of environmental quality.