**2.3. Urban ecology**

Urban areas and ecology are contrary to each other theoretically and as to substance, urban ecology connects with them. Urban ecology was originally developed as a part of human ecology in the 1920s by a small but influential group of sociologists at University of Chicago and they identified urban ecology as "the study of the relation between people and their urban environment" [18]. Urban ecology is a scientific field on the issue of effects on organisms, the interactions among them, and the transformation and flux of energy and matter in urban and urbanizing systems [16]. Urban ecology is ecological research conducted in cities, towns, and urban areas [19]. To understand the structure and dynamics of urban systems, they must be recognized as social-ecological systems that integrate socioeconomic drivers and responses with ecological structures and functions [16].

Basically, "urban" is a term identifying the land use on a place. A common comprehension of "urban" a densely populated urban space characterized by multifunctional land uses. This comprehension seems to be more useful for researches on urban ecology; yet, it is difficult to determine ecological thresholds surrounding urban space. Although ecology is a natural science concerned with the distribution and abundance of organisms, the word has many other meanings as well [19]. Urban ecology is not only a view to urban land from the science of ecology but may include concerns from the social sciences. Urban ecology is a research subject forming a continuum from "pure" ecology in the urban space to an integration of ecology and social sciences to investigate urban systems [19]. Today, the sociological approach to urban ecology continues to exist and evolve [18].

An explicit focus of researches about urban ecology is on sustainability, which includes bio‐ diversity and ecosystem services, energy consumption and carbon footprint for climate change studies [20]. Implementation of nature conservation in the cities will be possible by means of arrangements make harmonic natural–cultural and social environment with each other. Although the conflicting approach on ecology of urban areas focused on ecological footprints, and summaries of citywide species richness, contemporaneous ecosystem ap‐ proaches have begun to integrate physical environment of the nature, including urban cli‐ mate, hydrology, soils, and energetic issues, and to indicate the necessity for comprehension the social dimensions of urban ecology [9]. Urban ecology has increasingly played a signifi‐ cant leading role to overcome the conflicts faced by urban ecosystems. The major focus in many studies about application of urban ecology was on urban green network and its con‐ nection to citizens [20]. Three main goals based on ecology "in reference [9]", "may be ach‐ ieved in urban areas; Firstly, plant ecology can support to improved comprehension of the structure and function of urban ecosystems. Second, ecological function of urban areas must be increased. Third goal is to take advantages to humans of the vegetation elements of ur‐ ban lands" [9].

As emphasized by many scientists and researchers, with an in-depth comprehension of ecology in cities, focusing on the ecology of cities is increasingly being more significant. A framework to put ecological information into practice in urban areas requires interdisciplina‐ ry approaches for enhancing social welfare and providing sustainability in urban areas.
