Biodiversity: Making wildlife welcome in urban areas

Careful design of the green spaces in cities will benefit both wild animals and humans.
  1. Travis Gallo  Is a corresponding author
  2. Mason Fidino  Is a corresponding author
  1. Lincoln Park Zoo, United States

Can we think of a world in which wild animals wander down our streets? It may be difficult to picture such a scene because cities have historically been designed and built with people, rather than biodiversity or wildlife, in mind. And as urban areas grow – it is expected that 95% of population increase over the next decade will be in cities (Acuto et al., 2018) – it becomes even harder to conceive that humans and wildlife could co-exist in urban landscapes. However, there are some grounds for optimism and now, in eLife, Arielle Parsons of the North Carolina Museum of Natural Sciences and North Carolina State University, and colleagues report new insights about the wildlife that live in cities (Parsons et al., 2018).

The team used remotely triggered wildlife cameras in two cities – Washington, DC and Raleigh, North Carolina – to compare mammal diversity and habitat use across a range of environments: urban, suburban, exurban (i.e., commuter towns beyond the suburbs) and wild spaces. While the diversity was low in the most urban areas, there was little difference in the number of species and the habitat use of wild mammals between suburban areas and more natural settings. Most of the animals that lived in the wider region were also found in suburban areas, thus offering new insights in the ways that wildlife can co-exist with humans in an urbanizing world.

However, the suburbs of today are likely to be the urban areas of tomorrow. In Chicago for instance, the human population is expected to grow by another 2.4 million people by 2040, with suburban areas absorbing 64% of that increase. As suburbia becomes densely populated, what can be done to protect biological diversity? Parsons et al. point to the answer: in their study, mammals were more likely to occupy areas with higher levels of urban green space. This result adds to a growing body of research highlighting that these green areas are important habitats for biodiversity (Figure 1; Aronson et al., 2014; Aronson et al., 2017; Ives et al., 2016; Hall et al., 2017).

Wildlife can persist in urban areas when habitats are avaliable.

A coyote (Canis latrans; left) captured on a trail camera in a cemetery in the Uptown neighborhood of Chicago, Illinois. A ringtail (Bassariscus astutus; right) captured on a trail camera near downtown Austin, Texas. Parsons et al. studied wildlife in two cites – Washington, DC and Raleigh, North Carolina – and found that, as the human population density increased, the amount of green spaces available became more important for urban wildlife. Photographs: Urban Wildlife Institute, Lincoln Park Zoo; Amy Belaire.

Yet, not all the green spaces in cities are created equal for wildlife. For example, with colleagues we have shown that urban parks in Chicago, with their mature trees embedded in a sea of turf grass, are relatively poor habitats for mammals. In comparison, cemeteries or golf courses, which often are surrounded by additional vegetation and have open water areas, hosted more species (Gallo et al., 2017). Understanding what makes certain urban green spaces friendly to wildlife can help us to design parks that attract a wider range of animals. Ultimately, people also benefit from city parks, which purify the air, cool the temperature, and provide a space to engage in physical activity that can increase well-being and reduce chronic diseases like childhood obesity (Wolch et al., 2014).

Another compelling aspect of the study by Parsons and colleagues – who are based at universities and institutes across the United States – is that the results came from a large-scale citizen science project, where 557 volunteers operated 1427 cameras in their own backyards or in green spaces near their homes. While urban ecologists and conservation scientists primarily study the ecological form and function of cities, many practitioners also hope to connect urban dwellers with their natural surroundings. Experiences explicitly focused on biodiversity – such as citizen science projects – help people develop a greater global conservation ethic compared to schemes like community gardens, where biodiversity is raised more implicitly (Prévot et al., 2018). Although Parsons et al. did not measure the outreach and stewardship potential of their work, it is possible that the study increased the ecological knowledge of urban and suburban residents, deepening their understanding of global conservation issues and having a broader impact on urban conservation than expected.

Cities create near permanent changes to the landscape and they can seriously damage global biodiversity. However, as scientists like Parsons and colleagues show, nature can – and does – find a way to adapt to urban spaces. Therefore, by taking a social and ecological approach to urban planning, we can create environments that see people thrive, and wild animals roam.


Article and author information

Author details

  1. Travis Gallo

    Travis Gallo is at the Urban Wildlife Institute, Lincoln Park Zoo, Chicago, United States.

    For correspondence
    Competing interests
    No competing interests declared
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2877-9848
  2. Mason Fidino

    Mason Fidino is at the Urban Wildlife Institute, Lincoln Park Zoo, Chicago, United States

    For correspondence
    Competing interests
    No competing interests declared

Publication history

  1. Version of Record published: October 2, 2018 (version 1)


© 2018, Gallo et al.

This article is distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use and redistribution provided that the original author and source are credited.


  • 5,343
    Page views
  • 211
  • 4

Article citation count generated by polling the highest count across the following sources: Crossref, PubMed Central, Scopus.

Download links

A two-part list of links to download the article, or parts of the article, in various formats.

Downloads (link to download the article as PDF)

Open citations (links to open the citations from this article in various online reference manager services)

Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)

  1. Travis Gallo
  2. Mason Fidino
Biodiversity: Making wildlife welcome in urban areas
eLife 7:e41348.
  1. Further reading

Further reading

  1. Some mammals have successfully adjusted to life in urban environments.

    1. Ecology
    2. Evolutionary Biology
    Jason P Dinh, SN Patek
    Research Article Updated

    Evolutionary theory suggests that individuals should express costly traits at a magnitude that optimizes the trait bearer’s cost-benefit difference. Trait expression varies across a species because costs and benefits vary among individuals. For example, if large individuals pay lower costs than small individuals, then larger individuals should reach optimal cost-benefit differences at greater trait magnitudes. Using the cavitation-shooting weapons found in the big claws of male and female snapping shrimp, we test whether size- and sex-dependent expenditures explain scaling and sex differences in weapon size. We found that males and females from three snapping shrimp species (Alpheus heterochaelis, Alpheus angulosus, and Alpheus estuariensis) show patterns consistent with tradeoffs between weapon and abdomen size. For male A. heterochaelis, the species for which we had the greatest statistical power, smaller individuals showed steeper tradeoffs. Our extensive dataset in A. heterochaelis also included data about pairing, breeding season, and egg clutch size. Therefore, we could test for reproductive tradeoffs and benefits in this species. Female A. heterochaelis exhibited tradeoffs between weapon size and egg count, average egg volume, and total egg mass volume. For average egg volume, smaller females exhibited steeper tradeoffs. Furthermore, in males but not females, large weapons were positively correlated with the probability of being paired and the relative size of their pair mates. In conclusion, we identified size-dependent tradeoffs that could underlie reliable scaling of costly traits. Furthermore, weapons are especially beneficial to males and burdensome to females, which could explain why males have larger weapons than females.