**3. Complete role of non-native invasive species**

Biological invasions must be considered within the larger set of environmental issues [3]. Knowing the complex ecology and different potential harms and benefits to society, in general invasive species, can teach us important lessons about how we use the planet [13]. Some authors [16] state that alien species as newcomers in urban areas are not a threat to urban ecosystems; in contrast, there is a chance for increasing biological diversity and thus achieving conservation objectives [12]. In the past half century, biological invasions together with other related environmental problems have become interesting study subjects because they provide natural experiments at temporal and spatial scales [3]. There has been an explosive development in the science of invasion in recent years, and many symposiums, articles and books have been prepared. However, there is still substantial controversy regarding the role of invasions in natural as well as human-shaped environments.
