**3.3 Improvement of cities carrying capacity under the sustainable development goals**

The spatial carrying capacity transmitted from the planetary boundary scale to the national downscaling is increased to achieve the sustainable development goals. Sustainable development requires the use of natural resources by humans to be kept within environmental limits [8], this means that on the basis of recognizing that human activities continue to cause major global environmental changes. As a criterion and important influencing factor of carrying capacity, it is necessary to fully account for the various public, exclusive and irreversible risks arising from the ever-increasing global climate change, water resource changes, and the fragility of ecosystems. In particular, the global climate change caused by the spatial diffusion of carbon dioxide-based greenhouse gases, which determining to environmental governance should shift from the original biosphere level to the global level planetary scale. The sustainable development and other national decomposition of goals can be achieved to need a multi-scale systematic approach [9]. Downscaling transmission from the planetary boundary scale to the national level can be realized by means of consume of good and services basing on carbon footprint [10].

The coordinated resource and environmental carrying capacity provide best standards of practice for China. In 2019, the "Several opinions on establishing spatial planning system and supervising its implementation" clarified the basic role of the evaluation of "resources and environmental carrying capacity and spatial suitability" based on bottom-line management and control [11]. In 2020, "Resources and Environment Carrying Capacity and Space Development Suitability Evaluation Technical Guidelines (Trial Version)" established standards of practice in provinces, cities (districts) in China. Delineate urban growth boundaries, baseline of farmland, resource and environment through the evaluation system to achieve management and control of urban units; through the economic scale, population forecast and demand update in urban development, and at the same time integrate ecosystem units to achieve urban identity flexible management and control; by responding to the spatial layout of various elements in different scales of space, it can be achieved to realized the carrying capacity and scale of elements to sustainable development nationally.

The technological innovation should be used to improve the carrying capacity of resources and environment. A basic assumption of economics is the scarcity of resources, as the supply of resources is limited to the needs of human beings, mainly including the limitation of quantity, quality, time, space, structure, capital and environmental capacity, there is no exception for both natural and social resources. However, technological innovation can improve the utilization efficiency of resources, which alleviating the scarcity of resources to a certain extent, reducing the dependence on natural resources, damaging to the ecological environment, and improving the carrying capacity of resources and environment.
