What do we know (and need to know) about the role of urban habitats as ecological traps? Systematic review and meta-analysis Jesús Zuñiga-Palacios a , Iriana Zuria a, ⁎, Ignacio Castellanos a , Carlos Lara b , Gerardo Sánchez-Rojas a a Centro de Investigaciones Biológicas, Universidad Autónoma del Estado de Hidalgo, Pachuca, Hidalgo, Mexico b Centro de Investigación en Ciencias Biológicas, Universidad Autónoma de Tlaxcala, Tlaxcala, Mexico HIGHLIGHTS • Urban habitats can be representing eco- logical traps and/or safe habitats for urban species • A meta-analysis indicates that urban zones are not ecological traps for many species • However, outcomes are affected by the type of approach used to measure habi- tat preference and fitness • Birds are the most studied group, thus more studies with other groups are im- perative • Studies in more biodiverse and less studied countries are also necessary GRAPHICAL ABSTRACT abstract article info Article history: Received 7 January 2021 Received in revised form 9 March 2021 Accepted 13 March 2021 Available online 18 March 2021 Editor: Jose Julio Ortega-Calvo Keywords: Safe habitats Fitness Habitat preference Urbanization Behavior Urban areas represent a spectrum that goes from being safe habitats for biodiversity (i.e., habitats more or equally preferred, without costs to fitness) to being ecological traps (i.e., habitats more or equally preferred, but with costs to fitness). Given the imminent urban expansion, it is valuable to assess how biodiversity is responding to urbanization and thus generate timely conservation strategies. We systematically review the urban ecology literature to analyze how much do we know about the role of urban areas as ecological traps. Using a formal meta-analytical approach, we test whether urban areas are functioning as ecological traps or as safe habitats for different taxonomic groups. We generated a data set of 646 effect sizes of different measures of habitat pref- erences and fitness from 38 papers published between 1985 and 2020. The data set covered 15 countries and 47 urban areas from four continents, including 29 animal species. Studies from North America and Europe were best represented, and birds were the most studied taxa. Overall, the meta-analysis suggests that urbanized habitats are functioning more as safe sites than as ecological traps, mainly for certain species with characteristics that have allowed them to adapt well to urban areas. That is, many of the studied species prefer more urbanized hab- itats over other less urbanized sites, and their fitness is not modified, or it is even increased. However, there was high heterogeneity among studies. We also performed meta-regressions to identify variables accounting for this heterogeneity across studies and we demonstrate that outcomes may depend on methodological aspects of stud- ies, such as study design or the approach used to measure habitat preference and fitness. More research is needed for poorly studied regions and on a wider range of species before generalizations can be made on the role of urban areas for biodiversity conservation. © 2021 Elsevier B.V. All rights reserved. Science of the Total Environment 780 (2021) 146559 ⁎ Corresponding author at: Km. 4.5 carr. Pachuca-Tulancingo s/n, Col. Carboneras, Mineral de la Reforma, Hidalgo 42184, Mexico. E-mail address: izuria@uaeh.edu.mx (I. Zuria). https://doi.org/10.1016/j.scitotenv.2021.146559 0048-9697/© 2021 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect Science of the Total Environment journal homepage: www.elsevier.com/locate/scitotenv