پیامدهای محیطی-‌اکولوژیک خزش شهری در سکونتگاه‌های روستایی پیرامون شهر همدان

Introduction:
Imposition by cities of new roles and functions on peripheral areas has provoked economic, social and spatial disturbances in those areas (Shafiei Sabet & Bozorgniya, 2013). In this regard, major global trends that have fuelled competition over land have also contributed to the development of urban imbalance (Ludlow, 2014). As a result of population density and pressure on resources in cities with rapid expansion, the environment is adversely affected with detrimental impacts on valuable agricultural land. In this regard, Karol argues that ‘urban spraw’ was not problematic at its outset, but the positive effects of this phenomenon are long gone (Lawrence, 2012). Industrialization of the economy has turned villages around cities into unplanned spaces (Deep & Saklani, 2014). This phenomenon raised concerns in connection with the metropolis and the main cities, but the gradual adoption of centralized housing policies and development approach by the state at the regional and local levels contributed to the this issue affecting the middle cities as well (Shafiei Sabet and Haratifard, 2011). Based on this, the present research intends to analyze this phenomenon accurately to help find solutions to mitigate the adverse effects by providing scientific solutions to reduce the damage caused by it in the studied area.
Materials and methods:
A descriptive-analytical method was used to measure accurately the consequences of urban sprawl in the study area. To this end, based on analysis of satellite imagery using Remote Sensing (RS) and the Geographic Information System (GIS), the land use change trends during the three periods of 1990, 2006, and 2015 were investigated for different land uses (residential construction, non-residential construction, changing arid land, agricultural land, gardens, pastures and roads). Then, the effects of urban sprawl on rural settlements around the city of Hamedan and its determinants were investigated. The data collection included the survey of Land sat TM satellite images in 1990, ETM + 2006, HRVIR 2015, and a 1: 50000 map of Hamadan Province for the enhanced detection of phenomena and their comparison with land use changes in subsequent periods.
Results and discussion:
The results suggest that, in Hamedan Province, the urban development and dispersed sprawling growth of the city has caused the highest rate of land use change in agricultural lands over a 27-year period, from 1990 to 2015. As a result, these lands have seen a decrease of 1017 hectares over this period and, at the same time, horticultural lands have also diminished by about 272 hectares. In the meantime, rangelands have dwindled by about 189 hectares. By contrast, residential construction increased by 805 hectares in 2015 compared to 1990, followed by an increase of 346 hectares in non-residential construction and 20 hectares in route and road construction. Moreover, an area of 307 hectares from the total area of 6446 hectares in the study area has been transformed into desert land, and therefore the scene of various construction activities. A comparison of the statistics suggests that residential construction continues to grow, so that the statistical results of three periods indicate an increase of about 17.8% in construction the study area from 1990 to 2015. According to the results, it can be seen that in current situation of Iran, the research undertaken on the marginal area of Hamedan is consistent with the researches of Yagre, Ewing, Morot and Hernandez and other researchers who have discussed environmental issues and the lack of supportive policies to impede the spread of these structures in Europe.
Conclusion:
In studies on spatial development and land use change of agricultural lands, it is important to note the parameters that undergo change progressively as opposed to those that change more rapidly. In this study, it was found that in the study area, farmlands (agro-horticultural lands) have undergone the highest change compared to other lands. Therefore, if policies and measures are not taken to prevent this trend to continue, the environmental damage will be caused by pressure on resources, conversion and land use change, resulting in the destruction of valuable agricultural land.