Investigating the sustainability of the ecosystem by combining two approaches of ecological footprint and evaluation of ecosystem services (Case study: city of Nowshahr)

Natural capital is essential for human survival and achieving sustainable development goals. Therefore, a scientific framework is required to evaluate regional natural capitals consumption and their capacity to ensure sustainable development. Natural capitals represent the limiting and irreplaceable factors in human well-being and sustainability of every developmental intervention. Degradation of the accumulation and flows of the natural capitals are the fundamental issues in the discussion of environmental sustainability. The current research has been conducted with the aim of investigating the state of ecosystem sustainability by adopting two approaches of ecological footprint and ecosystem services, and in other words, comparing the amount of demand for resources with the supply of goods and services provided by the ecosystem.

In this research, to investigate the sustainability of Nowshahr's natural and urban ecosystem as the case study, first, the trend of land use changes and its associated phenomena in the region have been investigated using ENVI 5.6 software for processing the satellite images. In order to investigate the change process of the study area, Landsat satellite reference images, TM, ETM+ and OLI sensors were used for the time scale of 2002, 2013 and 2020. Then, the classic ecological footprint of the region was calculated for six types of productive ecosystems, including agricultural lands, pastures, fishing areas, forests, built-up lands, and the carbon demand. The areas of these six land cover types were converted into global hectares using yield and equivalence factors. Subsequently, the maximum amount of ecosystem service flow per global hectare was estimated. And after that, the amount of consumption of natural capital accumulation and the occupation of capital flow in the region were investigated. Finally, the ecosystem stability of the study area was investigated using indicators such as the ecological pressure index (EPI), ecological sustainability index (ESI), ratio of capital stock to flows index, flow occupation ratio index, and excessive natural capital flow index.

According to the research results in the city of Nowshahr, during the period of 2011-2019, the amount of ecological footprint, ecological deficit and pressure have gradually increased, resulting in a reduction of the ecological balance and stability. Only the pasture, forest and fishing areas are in a stable state meaning that the supply of ecological resources is more than the demand, and the pressure is still within the carrying capacity of the ecosystem. In the period of investigation, the amount of use of stock to natural capital flow has increased and has reached almost four times of natural capital flow.

Measuring human demand for natural capital and nature's supply is essential for tracking progress, setting goals, and orientating sustainability policies. By combining the two approaches of evaluating ecosystem services and ecological footprint, it is possible to track human demand and nature's supply from a precise subset of ecosystem services, and therefore ecological balance and sustainability can be examined at the local level. Based on the results of the research, the stability of the region and the status of its ecosystem services is threatened by the cultivated land, and mainly the consumption of fossil energy. Based on the results of the research, in the period of investigation, the stability of the city of Nowshahr has decreased and the status of its ecosystem services are threatened by the cultivated land, and mainly the consumption of fossil energy. During this period and considering factors such as land use level, ecological deficit, footprint depth, ecosystem service flow, ecological pressure index, and ecological sustainability index, agricultural land use was the most unsustainable and fishing was the most sustainable use in city of Nowshahr.