The lesser long-nosed bat (Leptonycteris curasuae yerbabuenae) feeds exclusively on the fruit and nectar of agave and night-blooming cacti such as saguaro and organpipe, pollinating flowers in the process. Photo Courtesy of Bruce Taubert.

Authors: Sophia Ruger, ASU Undergraduate Student Researcher, and Kelli L. Larson, Professor of Geography and Sustainability at ASU, with input from Andrew Trgovac.

Sophia Ruger is completing her Sustainability degree and a certificate in Geographic Information Science. She hopes to provide applicable solutions for significant environmental and health-related issues in cities across the globe. If she’s not busy at school, she is out rock climbing, wakeboarding, or sewing at home. She is searching for internships or professional experiences, so feel free to connect with her through LinkedIn.

Kelli Larson is a Professor at Arizona State University who moved to the Sonoran Desert in 2005 and regularly engages students in her research. Her work focuses on how people interact with nature and manage urban landscapes and the environment. When she is not working, Kelli practices yoga and loves to hike, paddle, and otherwise explore nature and different places throughout Arizona and elsewhere. She also enjoys spending time with her dogs, going to plays, and cooking. You can learn more about Kelli or contact her through ASU.

The story begins in 1972 when the first wildlife habitat in Arizona was certified in Prescott on August 21st. This was the year before the National Wildlife Federation (NWF) officially launched their wildlife gardening program. Since then, thousands of properties have been certified statewide, although the frequency of certifications remained low until the 2000s. When our team at Arizona State University started analyzing data on certified wildlife gardens from the NWF in May 2024, over 4,000 properties—including residential yards and other types of properties—had been certified in Arizona to provide shelter, food, water, and places for wildlife to raise their young. 

The Arizona Wildlife Federation (AWF) is one of the 26 state affiliates active in promoting gardening for wildlife through the Certified Wildlife Habitat® program. Our team is collaborating with both AWF and NWF to understand: how and why have wildlife-certified gardens expanded over time, and who and where are these gardeners? 

As seen in the chart below, the years 2006 and 2023 saw the most certifications in the state, with a peak of 296 in 2023 alone. Mary Phillips, who leads the national Garden for Wildlife/Certified Wildlife Habitat® program, explains: “The national program celebrated its 50^th anniversary in 2023, and both AWF and NWF received high levels of media attention and engaged in outreach that year, resulting in more awareness and certification applications.” Although we do not yet know what caused the peaks prior to 2015, when Mary started working with NWF, we are exploring the factors underlying the rise and decline of wildlife-certified gardens over time. The mortgage crisis of 2007-2010 may be one factor leading to declines since the number of certifications between 2011 and 2016 decreased dramatically. With the emergence of the COVID-19 pandemic around 2020, we later saw a surge. Mary adds, “With people at home, gardening, and sustainable practices surged nationwide as they were inspired to do something positive that generated visible increases in butterflies, birds, and bees to support and enjoy where they live. In Arizona, the use of drought-tolerant native plants is an added appeal to residents in their quest to conserve water and support AZ wildlife.”   

Just as we see temporal patterns in the rise and fall of certified habitats in the state, interesting geographic patterns are also evident in the data. Across 190 cities and towns in Arizona with at least one or more certified properties, the top 20 (highlighted in the map below) contain 72% of the total (at around 3000 habitats), and the top 10 contain 50% of the certified habitats in the state.

Larger circles represent more community gardens per resident.

With 976 gardens, Tucson contains the most (23%) Certified Wildlife Habitat® in the state; this translates into approximately 18 gardens for every 10,000 residents in Tucson. Coming in second, Phoenix — as the largest city in the state — has 11% (470), which amounts to fewer than 3 gardens per 10,000 residents. Along with these large cities in the top 20 are other municipalities in the metro Phoenix area including Scottsdale, Mesa, Tempe, Glendale, Chandler, and Gilbert. Other top towns are Prescott, Sedona, and Flagstaff to the north and Bisbee and Ajo to the south. 

It is not surprising that cities and their suburbs with some of the largest populations in the state have the most gardens, but what is happening in smaller towns like Ajo, Bisbee, Sierra Vista, and Hereford? Perhaps conservation initiatives around the San Pedro River or the birding culture in the region contribute to the cluster of garden efforts in southeastern Arizona. With further research, our team aims to identify the factors leading to certifications in particular places across the state.

Ajo and Bisbee are two small towns in Arizona with around 100 recorded habitats, which amounts to more than 1% of their residents gardening for wildlife (compared to only 0.03% in Phoenix). The high Certified Wildlife Habitat® count among these relatively small towns indicates a significant effort to provide wildlife habitat in these communities. With Bisbee’s population of 5,008 residents and 104 gardens, the town hosts two gardens per 100 residents (or 2% of the community). With Ajo’s population of 2,922 and 96 gardens, they host the highest number of gardens per capita at 3% (or three gardens for every 100 residents). 

So, why do Ajo and Bisbee have a relatively large number of Certified Wildlife Habitat® relative to their populations? One reason is that both towns have been certified through the NWF’s Community Wildlife Habitats®, which requires a certain number of habitats. This community-level program extends the gardening for wildlife effort beyond individual properties by bringing together committed gardeners to expand habitat for wildlife in their municipalities. As Keith Ashley, the Deputy Director of the Arizona Wildlife Federation explains, “When you take a close look at the data like this, you can really see the impact that a small group of changemakers like "Project Wildlife Bisbee" can have. When they decided to get their community certified, they inspired so many people to get involved with habitat creation and maintenance. Imagine what a difference it would make if we had a few Arizona communities becoming certified each year for the next few decades!”

Finally, we are exploring: who are the people behind Certified Wildlife Habitat®? Specifically, based on the data we have available from NWF (as shown in the pie chart below), which landowners are certifying their properties as wildlife habitat across the state? Mostly, so far, they are residents like you. That is, more than 90% of all habitats certified since 1972 (3,448 total) were established by residents at their homes, and 40 additional habitats are located in community gardens.   

Among the other 7% of non-residential habitats (227; see the pie chart below), 34% are located in schoolyards (represented by teal), especially at K-12 institutions. Certified Wildlife Habitat® at schoolyards makes good sense because many people visit schoolyards, and these habitat gardens can be educational for students learning biology and other subjects. Additional habitats are managed by private entities (in yellow) including farms (23% of non-residential property) and churches (18%) are the next most common types of property. Relatively few certified habitats are on other types of properties, as shown in the graph. 

In moving forward with our research, our ASU-based team hopes to better understand the reasons for designing and maintaining Certified Wildlife Habitat® in residential yards and other types of property. By identifying barriers or challenges with gardening for wildlife, moreover, we can provide information and other resources to overcome them. By doing so, we hope to expand wildlife habitat across Arizona and the U.S. in collaboration with the National Wildlife Federation and our state chapter. As we learn more, this information could help NWF and AWF, among other organizations, to support habitat gardeners. Based on previous research, we know that certified habitats make a real difference by increasing biodiversity by hosting a larger variety of vegetation and bird species. 

To get certified or learn more, visit https://certifiedwildlifehabitat.nwf.org/.

Learn about the biodiversity impacts of Certified Wildlife Habitat®

Read more about constraints to wildlife gardening and associated tips

Be sure to sign up for Arizona Wildlife Federation’s E-News to receive regular updates on Gardening for Wildlife in Arizona!

Meet the ASU Team

Critical to American agriculture, this non-native European honey bee (Apis mellifera) is visiting a saguaro cactus blossom. Honey bees can compete with native bees for resources, which presents complicated conservation questions. Photo Courtesy of Bruce Taubert.

Authors: Sharika Kapur, ASU Undergraduate Student Researcher, and Kelli L. Larson, Professor of Geography and Sustainability at ASU

Sharika Kapur is majoring in Sustainability with a concentration in Society and Sustainability. She aspires to leverage her education to drive positive social and ecological change. Beyond her academic pursuits, she loves to express herself creatively through painting and sculpting. She would love to connect with others passionate about environmental health. You can reach her via LinkedIn.

Kelli Larson is a Professor at Arizona State University who moved to the Sonoran Desert in 2005 and regularly engages students in her research. Her work focuses on how people interact with nature and manage urban landscapes and the environment. When she is not working, Kelli practices yoga and loves to hike, paddle, and otherwise explore nature and different places throughout Arizona and elsewhere. She also enjoys spending time with her dogs, going to plays, and cooking. You can learn more about Kelli or contact her through ASU.

The lawn-care industry has globally promoted neat, uniform, and weed-free turfgrass landscapes, often characterized by lush, hyper-green lawns. However, these lawns not only reduce biodiversity but also demand a significant amount of water to survive, particularly in semi-arid regions like Arizona. Instead of managing monocultural lawns —that is, landscapes comprising a single species of turfgrass, residents can transform their yards into habitat to support wildlife and improve biodiversity in neighborhoods. Perhaps now is the time to make your yard do more — for wildlife and you.

Research conducted at Arizona State University shows promise for people adopting yards to support local wildlife across the U.S. Several studies conducted by Kelli Larson, a Professor of geography and sustainability at ASU, reveal insights on residents’ yard preferences and priorities. Much of Larson’s research has focused on metro Phoenix, but her work also includes surveying residents across six metropolitan areas including Los Angeles, Miami, Baltimore, Boston, and Minneapolis–Saint Paul. Across these regions and elsewhere, evidence suggests that many residents are willing to support alternative yard designs, though residents face certain constraints that slow the shift towards wildlife-supporting landscapes.

The rufous hummingbird (Selasphorus rufus) migrates as far as 3,900 miles (one way!) and requires nectar at every stop on its journey. While non-native thistles can be invasive, at least 13 species are native to Arizona and an important food source for pollinators. Photo Courtesy of Bruce Taubert.

Author: Alexandra (Lexi) Cegielski, ASU Undergraduate Student and Researcher

Lexi Cegielski is an undergraduate student at Arizona State University majoring in Sustainability and Urban Planning. She is passionate about creating sustainable cities and preserving wildlife. Growing up in Arizona, Lexi spends her free time enjoying the outdoors with friends and family. In her spare time, she loves baking vegan desserts, hiking, and practicing yoga. To learn more about Lexi’s work and passions, visit her LinkedIn. 

Did you know that residential yards cover roughly 30% of land in the United States? This is one reason why the Arizona Wildlife Federation seeks to expand gardening for wildlife in people’s yards and neighborhoods. This includes a certification program —led by the National Wildlife Federation — that promotes the provisioning of food, water, and shelter (i.e., wildlife habitat) in residential and other gardens. You may be wondering: can residents’ yards benefit wildlife and related conservation efforts? The short answer is yes — and scientific evidence has proven it. 

Researchers affiliated with Arizona State University and the U.S. Forest Service, among others, have evaluated vegetation and bird diversity in NWF-Certified Wildlife Habitat®. Focusing on residential yards, the research team compared biodiversity in certified habitats and different types of lawns and natural areas in six U.S. cities. Specifically, the team collected data on vegetation and bird species in metropolitan Phoenix, as well as Los Angeles, Miami, Baltimore, Boston, and Minneapolis–St. Paul.

Researchers collected data on vegetation and bird species in three types of residential yards and two types of natural areas, as shown in the graph to the right below. The yard types included NWF-certified habitat and two types of lawns (defined as yards covered by at least 75% turfgrass): those fertilized (called high-input lawns) and not fertilized (low-input lawns). For each yard type, several different residential properties were surveyed in each of the six metro regions.

The team also surveyed two types of parks as “reference sites.” The idea here was to compare vegetation and bird diversity in these relatively undeveloped areas that contain wildlife habitat. Interstitial parks were sites within the metropolitan region that are managed as parks compared to relatively unmanaged nature preserves (i.e., representing native ecosystems such as the Sonoran Desert in Phoenix). For each type of reference site, 4 or 5 parks were evaluated from each metro region for a total of more than 25 natural sites.

So, what did the biodiversity surveys entail? Imagine going into your own yard and counting all of the different types of plants and birds you see. How many different species would you see? This approach essentially mirrors the methodology the researchers used to assess the diversity of species across different landscape types. This method of field research is known as community ecology surveys, and the goal is to document every unique species of bird and vegetation. In inventorying vegetation, the researchers documented cultivated vegetation including purposely planted trees, shrubs, and herbaceous (non-woody) plants. The team also inventoried “weeds”, which they consider “spontaneous vegetation” (i.e., since they are not intentionally cultivated). The field surveys generated various measures of biodiversity, including species richness — which is the number of different species of vegetation or birds found at each site. The researchers then compared species richness across the different types of yards and reference sites.

Plant Diversity

Plant ecologist Dr. Josep Padullés Cubino, who formerly was affiliated with the University of Minnesota but now is a professor at the Autonomous University of Barcelona, led the assessment of vegetation diversity. Dr. Padullés Cubino discovered that NWF-certified gardens hosted the highest total number of vegetation at 1,408 species, followed by low-input lawns, then high-input lawns, and reference natural areas. While we might expect higher plant variety in natural areas versus yards, the opposite was found to be true. The higher species richness per unit area in residential yards compared to natural areas is due to the introduction and maintenance of non-native species found at nurseries.

A graphic related to vegetation diversity is known as a species accumulation curve (below right), which shows the differences in the number of species between each landscape type. From the figure, we clearly see that NWF-certified gardens host a larger number of species than other landscape types, including both types of lawns and the two reference sites. In fact, notice how the top line is still on an upward trend at 25 sampled plots. This indicates that even more species would have been found if the team continued to collect data from additional gardens.  

Certified wildlife yards also excelled compared to various-input lawns because of the higher variation inseed mass. Higher seed mass essentially means more food sources for birds and other wildlife available. Additionally, seed mass increases the ability of plants to reproduce. In all, plant diversity in a garden is crucial for wildlife to feast and live. 

Ensuring your wildlife garden contains various plants is an exceptional start to a successful wildlife garden. From the words of the expert himself, Josep Padullés Cubino reminds you that, “Wildlife gardening is a process that takes time. Be patient and take time to observe the changes in your garden and the wildlife it attracts.”

Bird Diversity

Wildlife ecologist Dr. Susannah Lerman, who is a Research Ecologist with the U.S. Forest Service, is passionate about native birds. In a publication she led with Dr. Desiree Narango, the team demonstrated that residential yards — regardless of the type — supported a greater number of bird species compared to the reference natural areas (i.e., parks). Unlike vegetation diversity, yards with NWF-certified habitats hosted similarly high species richness in the bird communities as the low- and high-input lawns. Yet community turnover — another measure of biodiversity — was uniquely highest in wildlife-certified yards compared to other yard types. Community turnover evaluates the magnitude of changes in the species present from one yard to another. What this essentially means is that in high-input lawns, we are likely to find the same common species — for example, rock pigeons, house sparrows, and great-tailed grackles — from one lawn to the next. But in NWF-certified yards, we see more changes in bird species from one NWF-certified yard to another. For instance, in one certified yard, you might see an Abert’s towhee, Anna’s hummingbird, and verdin, yet in the next, you might also see cactus wren, and in the next a curve-billed thrasher, and yet in another, a greater roadrunner. The image below, designed by Dr. Lerman, demonstrates the idea of community turnover with bird species common in the U.S. While lawn after lawn we see pigeons, sparrows, and grackles, the species in certified yards vary more greatly from habitat to habitat (i.e., a robin, cardinal, and woodpecker may be in one certified habitat yard, but in the next we see a robin along with wood thrush and chickadee, and in additional residential habitats we pick up additional species such as a grey catbird and yellow warbler. 

Dr. Lerman and colleagues’ research also found that neighborhoods withabundant tree canopy feature more diverse birds, and especially in warmer regions such as Arizona, trees can be a great way for species to stay cool and protected from threats. Meanwhile, impervious surfaces can exacerbate heat and lower biodiversity. Thus, in addition to managing yards as a wildlife habitat by following NWF’s certification guidelines, additional tips for attracting birds include increasing tree cover and reducing impervious surfaces such as patios. 

Lerman’s team also found that residential wildlife habitats tend to attract bird species with “high public interest,” or in other words, birds that people tend to appreciate and enjoy seeing. Example species include the Gilded Flicker and Costa’s Hummingbird. In contrast, the natural areas, or parks, tend to support “species of conservation concern,” which are birds that are imperiled due to declines in their populations. Example species of concern are the Cactus Wren and Gambel’s Quail. As a result, Dr. Lerman and colleagues advocate for both “land sparing” and “land sharing” approaches to conservation; while land sparing involves protecting natural areas in parks and preserves, land sharing entails residents creating wildlife habitat to share their yards with wildlife. Through both land sparing and sharing, human-dominated landscapes such as cities can protect wildlife and help preserve biodiversity.

Final Thoughts

In sum, scientific evidence from field research confirms that NWF-certified habitats in people’s yards enhance conservation by hosting diverse vegetation, which in turn supports varied bird species that people appreciate. Thus, residents can directly make a difference in their own yards by managing bird habitats. Not only does wildlife gardening provide shelter and resources for diverse wildlife, but people also reap related benefits. As Dr. Lerman notes, “There's also a lot of joy that comes from seeing different kinds of birds in your backyard.” 

To find out how to get certified or otherwise garden for wildlife, visit www.nwf.org/CERTIFY

Learn more about certified wildlife gardens in Arizona

Get tips on how to make your wildlife garden beautiful and low-maintenance

Be sure to sign up for Arizona Wildlife Federation’s E-News to receive regular updates on Gardening for Wildlife in Arizona!

Meet the ASU Team

Sources 

Lerman, S. B., Narango, D. L., Avolio, M. L., Bratt, A. R., Engebretson, J. M., Groffman, P. M., Hall, S. J., Heffernan, J. B., Hobbie, S. E., Larson, K. L., Locke, D. H., Neill, C., Nelson, K. C., Padullés Cubino, J., & Trammell, T. L. E. (2021). Residential yard management and landscape cover affect urban bird community diversity across the continental USA. Ecological Applications, 31(8), e02455. https://doi.org/10.1002/eap.2455

Lerman, S.B., K.L. Larson, D.L. Narango, M.A. Goddard, and P.P. Marra. 2023. Humanity for habitat: Residential yards as an opportunity for biodiversity conservation. Bioscience. 73: 671-689. https://doi.org/10.1093/biosci/biad085

Padullés Cubino, J., Cavender-Bares, J., Groffman, P. M., Avolio, M. L., Bratt, A. R., Hall, S. J., Larson, K. L., Lerman, S. B., Narango, D. L., Neill, C., Trammell, T. L. E., Wheeler, M. M., & Hobbie, S. E. (2020). Taxonomic, phylogenetic, and functional composition and homogenization of residential yard vegetation with contrasting management. Landscape and Urban Planning, 202, 103877. https://doi.org/10.1016/j.landurbplan.2020.103877

Note: the species accumulation curve above was Figure 2 published by Elsevier in https://www.sciencedirect.com/science/article/abs/pii/S0169204620300323?via%3Dihub

Queen butterfly (Danaus gilippus). Photo Courtesy of Bruce Taubert.

Author: Kelli Larson, Professor of Geography and Sustainability at ASU

Kelli Larson is a Professor at Arizona State University who moved to the Sonoran Desert in 2005 and regularly engages students in her research. Her work focuses on how people interact with nature and manage urban landscapes and the environment. When she is not working, Kelli practices yoga and loves to hike, paddle, and otherwise explore nature and different places throughout Arizona and elsewhere. She also enjoys spending time with her dogs, going to plays, and cooking. You can learn more about Kelli or contact her through ASU.

From forested mountains to desert landscapes, wildlife travel far and wide to seek the best habitat for their survival. As urban and residential areas expand, wildlife increasingly finds their way into our backyards and neighborhoods. Although urbanization and other human activities degrade wildlife habitat worldwide, people can positively impact wildlife where they live. In particular, gardening for wildlife in residential yards and neighborhoods can provide crucial habitat for birds, bees, and other animals, thereby helping to protect wildlife and conserve biodiversity. 

Based at Arizona State University in Tempe, my research team has been collaborating with other researchers and conservationists to answer a variety of questions related to the environmental impacts of residents’ yards, broadly defined as the outdoor areas of homes inclusive of lawns (i.e., turfgrass), other plant species, gravel or wood mulch, patio areas, pools, and other natural or built features. Yards are particularly prevalent in neighborhoods with “single-family” or detached homes, in contrast to “multi-family” homes such as apartments and condos. You might ask: just how widespread are yards, and do they really matter? The short answer is yes — and in the U.S., residential areas cover about 30% of land, and among the U.S. housing stock, about two-thirds constitute single-family housing with yards, which we also refer to as residential landscapes or gardens. Since the design and management of these residential landscapes can significantly impact the environment, my research broadly examines: how and why do residents design and manage their yards in various ways, and what are the environmental as well as societal implications? 

As a Professor of Geography and Sustainability at Arizona State University (ASU), I have been conducting social science research on residential landscapes for nearly twenty years, particularly within metropolitan Phoenix and other urban regions of the U.S. My early research on yards primarily focused on water conservation in our arid region, since lawns and other landscape features (e.g., pools) in residential areas consume a significant amount of water. In fact, did you know that, collectively, residents’ irrigation of lawns and other plants — coupled with other outdoor water uses (including evaporation from pools) — constitute up to two-thirds of all water consumed in municipal (urban areas) of Arizona? Did you know that in Arizona's urban areas, up to two-thirds of all municipal water is consumed through outdoor uses, including lawn irrigation, plant watering, and pool evaporation? However, since the 1980s, cities like Phoenix and others in the southwestern U.S. have been transitioning away from mesic (wet) lawns to what researchers call xeric (dry) yards.

Xeric yards — which contain gravel or rock groundcover (instead of turfgrass, or lawns) — are often planted with native vegetation or climate-adapted, low water-use plants. As these landscapes have grown and replaced lawns in recent decades, the region has substantially lowered per-capita water use. This shift in residential (and other) landscapes not only conserves our state’s water resources; they can also have a positive impact on wildlife. So, over the last decade, I have been collaborating with ecologists and other social scientists to investigate: who is gardening for wildlife, and why? In other words, what factors motivate people to design and manage their yards in ways that provide habitat for wildlife, and what barriers exist to the adoption and expansion of wildlife-friendly yards? Meanwhile, I collaborate with ecologists and other scientists to examine how different yard designs and management practices affect the environment, including wildlife. 

From left to right: Diadasia diminuta, Lucifer sheartail hummingbird (Calothorax lucifer), and lesser longnosed bat (Leptonycteris curasuae yerbabuenae). Photos Courtesy of Bruce Taubert.

In a series of blog posts, my team will be sharing research on residential yards with you. The research projects we feature involve partnerships between ASU, the Arizona Wildlife Federation (AWF), and the National Wildlife Federation (NWF), especially their programs focused on gardening for wildlife. If you are unfamiliar with these programs, they include certification programs that acknowledge residents' efforts to provide food, water, and shelter to wildlife, which you can read more about on the AWF and NWF websites. In a previous project funded by the National Science Foundation, an interdisciplinary team of social and ecological scientists collected data in NWF-certified habitats in residential yards and other types of landscapes to measure plant and bird biodiversity. During this project, I also led the analysis of social survey data to better understand who is gardening for wildlife and what is motivating them relative to people with traditional lawns or other types of landscapes. More recently, we have been analyzing where Certified Wildlife Habitats® are located in the state, and how many yards and other types of properties have been certified over the last 50 years. In this blog series, we present the results and welcome your feedback. 

The ASU team includes three bright undergraduate students — all of whom are majoring in sustainability with links to geographical sciences and urban planning. All three are passionate about wildlife and conservation: Alexandra (Lexi) Cegielski, Sharika Kapur, and Sophia Ruger. Each student has co-written a blog post to share past and recent research findings.

First, Lexi details the biodiversity impacts of Certified Wildlife Habitats® in people’s yards compared to other types of yards and parks based on research by my colleagues, Drs. Padu Cubinos, who is a biogeographer, and Susannah Lerman, who is an ecologist.

Next, Sharika explains how aesthetics and maintenance concerns dominate when residents are making decisions about their yards. By extension, we provide tips for designing beautiful yards that are easy to maintain.

Lastly, Sophia Ruger presents our preliminary geospatial and temporal analyses of the Certified Wildlife Habitats® in Arizona, partly using Geographic Information Systems which enable mapping and spatial analysis. In addition to showing that the vast majority of certifications are in people’s yards, some years have experienced relatively high and low numbers of Certified Wildlife Habitats®, which are prevalent in some Arizona communities more than others.

We hope you enjoy learning about our work!