What kind of wildlife flourishes in cities?

The High Line in New York City, a former elevated railroad trestle converted to a public park. Image: Shinya Suzuki/Flickr/creative commons.

Biodiversity refers to the variety of all living things on Earth, but people often have very specific ideas of what it means. If you run an online search for images of biodiversity, you are likely to find lots of photos of tropical rainforests and coral reefs.

Those ecosystems are invaluable, but biodiversity also exists in many other places. More than half of the people on Earth live in cities, and that number is growing, so it is especially important to understand how biodiversity patterns occur in our man-made environments.

As an ecologist specializing in urban systems, I spend a lot of time investigating biodiversity in parks, residential areas and abandoned zones in and around the city of Baltimore. My main interests are seeing how urban dwellers invest in biodiversity, which species persist in cities and what kinds of biodiversity can thrive in green spaces.

In spite of the substantial environmental changes that humans have caused in cities, research shows that they still contain many forms of life. And we can develop and maintain habitat to support them.

Human impacts

Human activities such as farming and building roads disturb the environment. This changes habitats, causes plants and animals to move and alters biodiversity patterns.

In cities many of these shifts are obvious. Cats and coyotes are now the top predators in many urban areas, perhaps replacing species that dominated before these areas were settled. Humans have introduced exotic species such as tree of heaven, and pests such as the emerald ash borer. And our living patterns have promoted eruptive growth of some species, such as white-tailed deer.

Razing a vacant row home in Baltimore, Maryland. This kind of activity creates habitat. Image: author provided.

It is common to assume that few other species remain in disturbed urban environments. But in fact, there are many pockets of biodiversity in and around cities, such as frogs living in stormwater detention ponds and trees in restored streamside forests. Landscapes that people create in and around their homes support many ornamental herbaceous and woody plant species.

Our research group works to understand the relationship between people and urban biodiversity patterns. The most prominent feature of the urban environment is that it is fragmented into many small zones. Human activity creates more patches of smaller size and greater edge lengths between types of habitats than we would expect to see in undisturbed areas.

This benefits species that thrive at edges, like white-tailed deer and nuisance vines, but harms others that require larger interior habitats, such as certain birds. As human activities create a more fragmented environment, it becomes increasingly important to create linkages between natural areas, such as preserved forests, to maintain populations and their biodiversity.

Humans also modify dispersal patterns. We place preferred plants in our yards and gardens, transplant wild shrubs from forests to suburban yards and trap nuisance animals such as beavers and relocate them to forests.

Two vacant lots where row homes once stood in Baltimore, Maryland. Each plot was cleared and seeded with native species. Even after one year on these poor soils, native plants established. Image: author provided.

Work from our research group has successfully related people’s management practices to understand how species are gained or lost from one location to the next. This concept, which we call “species turnover,” is a major way in which biodiversity increases in cities. Where people make many different types of choices, we have found that the trees people manage change a lot. This tells us that what one person sees as valuable differs from the views of another, which increase biodiversity in these areas. In “ignored” or less managed areas, such as vacant land, we see a less diverse mix of species on average.


How past actions influence the present

Ecologists can also understand biodiversity in cities by studying how humans have altered and then abandoned some areas, and how plants and animals have responded. Such human legacies are profound in old cities like Baltimore.

Our research group has studied these impacts on patches of land where buildings once stood. There are more than 14,000 vacant lots in Baltimore where houses have been razed, which adds up to a lot of habitat.

We have found that buildings’ footprints have very different soils from the areas around them that once were backyards. Footprint soils are compact and comprise mainly building rubble, while backyards have healthier soils. Although these habitats are close together, they support different plant communities. Plants growing on building footprints tend to be similar, while there is very high species turnover in former back yards.

Helping urban ecosystems thrive

Every species has traits, such as a plant’s nitrogen fixation rate and flower color. These characteristics support the services that the species can offer – for example, providing habitat for songbirds. As cities move toward more green practices, knowing about species’ traits can help planners choose which plants, animals, birds and insects to support.

In West Baltimore, my research group has cleared and seeded vacant lots with different mixes of native plants that reflect different traits to learn which species combinations can confer the most ecosystem services. In urban areas, valuable ecosystem services include supporting bees and other pollinators and improving soil quality.

We have found that native plant species can become established and persist even on poor urban soils. Working with local high school students, we have carried out pollinator surveys over two years, which show that these plants support more abundant and more diverse communities of pollinators, including bumblebees and butterflies. Over the next five to 10 years, we plan to expand this work across 65 plots on vacant land so that we can understand the full range of ecosystem services that native plants provide.

7x7 meter experimental plots where 15 abandoned row houses once stood. These plots are being seeded with different mixes of native plants. Image: author provided.

Residents who live near our research plots are happy to see areas that were unmanaged and largely neglected turn green. Even small “pocket parks” can brighten communities.

The ConversationWe have many other questions about urban biodiversity. How do city dwellers living in cities think about biodiversity? What traits of different animals and plants do people find attractive, and do those traits provide desirable ecosystem services? By analysing these issues, we can learn more about which animals and plants do the most to enhance city life and how we can help them thrive here.

Christopher Swan is professor of geography and environmental systems at University of Maryland, Baltimore County.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

CityMetric is now City Monitor! Come see us at our new home

City Monitor is now live in beta at citymonitor.ai.

CityMetric is now City Monitor, a name that reflects both a ramping up of our ambitions as well as our membership in a network of like-minded publications from New Statesman Media Group. Our new site is now live in beta, so please visit us there going forward. Here’s what CityMetric readers should know about this exciting transition.  

Regular CityMetric readers may have already noticed a few changes around here since the spring. CityMetric’s beloved founding editor, Jonn Elledge, has moved on to some new adventures, and a new team has formed to take the site into the future. It’s led by yours truly – I’m Sommer Mathis, the editor-in-chief of City Monitor. Hello!

My background includes having served as the founding editor of CityLab, editor-in-chief of Atlas Obscura, and editor-in-chief of DCist, a local news publication in the District of Columbia. I’ve been reporting on and writing about cities in one way or another for the past 15 years. To me, there is no more important story in the world right now than how cities are changing and adapting to an increasingly challenging global landscape. The majority of the world’s population lives in cities, and if we’re ever going to be able to tackle the most pressing issues currently facing our planet – the climate emergency, rising inequality, the Covid-19 pandemic ­­­– cities are going to have to lead the way.

That’s why City Monitor is now a global publication dedicated to the future of cities everywhere – not just in the UK (nor for that matter just in the US, where I live). Our mission is to help our readers, many of whom are in leadership positions around the globe, navigate how cities are changing and discover what’s next in the world of urban policy. We’ll do that through original reporting, expert opinion and most crucially, a data-driven approach that emphasises evidence and rigorous analysis. We want to arm local decision-makers and those they work in concert with – whether that’s elected officials, bureaucratic leaders, policy advocates, neighbourhood activists, academics and researchers, entrepreneurs, or plain-old engaged citizens – with real insights and potential answers to tough problems. Subjects we cover include transportation, infrastructure, housing, urban design, public safety, the environment, the economy, and much more.

The City Monitor team is made up of some of the most experienced urban policy journalists in the world. Our managing editor is Adam Sneed, also a CityLab alum where he served as a senior associate editor. Before that he was a technology reporter at Politico. Allison Arieff is City Monitor’s senior editor. She was previously editorial director of the urban planning and policy think tank SPUR, as well as a contributing columnist for The New York Times. Staff writer Jake Blumgart most recently covered development, housing and politics for WHYY, the local public radio station in Philadelphia. And our data reporter is Alexandra Kanik, whose previous roles include data reporting for Louisville Public Media in Kentucky and PublicSource in Pittsburgh, Pennsylvania.

Our team will continue to grow in the coming weeks, and we’ll also be collaborating closely with our editorial colleagues across New Statesman Media Group. In fact, we’re launching a whole network of new publications, covering topics such as the clean energy transition, foreign direct investment, technology, banks and more. Many of these sectors will frequently overlap with our cities coverage, and a key part of our plan is make the most of the expertise that all of these newsrooms combined will bring to bear on our journalism.

Please visit citymonitor.ai going forward, where you can also sign up for our free email newsletter.


As for CityMetric, some of its archives have already been moved over to the new website, and the rest will follow not long after. If you’re looking for a favourite piece from CityMetric’s past, for a time you’ll still be able to find it here, but before long the whole archive will move over to City Monitor.

On behalf of the City Monitor team, I’m thrilled to invite you to come along for the ride at our new digs. You can follow City Monitor on LinkedIn and on Twitter. If you’re interested in learning more about the potential for a commercial partnership with City Monitor, please get in touch with our director of partnerships, Joe Maughan.

I want to thank and congratulate Jonn Elledge on a brilliant run. Everything we do from here on out will be building on the legacy of his work, and the community that he built here at CityMetric. Cheers, Jonn!

To our readers, on behalf of the City Monitor team, thank you from all of us for being such loyal CityMetric fans. We couldn’t have done any of this without you.

Sommer Mathis is editor-in-chief of City Monitor.