People and Trees: Assessing the US Urban Forest Resource

Nowak, David J.; Noble, Mary Heather; Sisinni, Susan M.; Dwyer, John F.

doi:10.1093/jof/99.3.37

Cited by 90 publications

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The importance of street trees to urban avifauna

Wood

Esaian

2020

Ecological Applications

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Street trees are public resources planted in a municipality's right-of-way and are a considerable component of urban forests throughout the world. Street trees provide numerous benefits to people. However, many metropolitan areas have a poor understanding of the value of street trees to wildlife, which presents a gap in our knowledge of conservation in urban ecosystems. Greater Los Angeles (LA) is a global city harboring one of the most diverse and extensive urban forests on the planet. The vast majority of the urban forest is nonnative in geographic origin, planted throughout LA following the influx of irrigated water in the early 1900s. In addition to its extensive urban forest, LA is home to a high diversity of birds, which utilize the metropolis throughout the annual cycle. The cover of the urban forest, and likely street trees, varies dramatically across a socioeconomic gradient. However, it is unknown how this variability influences avian communities. To understand the importance of street trees to urban avifauna, we documented foraging behavior by birds on native and nonnative street trees across a socioeconomic gradient throughout LA. Affluent communities harbored a unique composition of street trees, including denser and larger trees than lower-income communities, which in turn, attracted nearly five times the density of feeding birds. Foraging birds strongly preferred two native street-tree species as feeding substrates, the coast live oak (Quercus agrifolia) and the California sycamore (Platanus racemosa), and a handful of nonnative tree species, including the Chinese elm (Ulmus parvifolia), the carrotwood (Cupaniopsis anacardioides), and the southern live oak (Quercus virginiana), in greater proportion than their availability throughout the cityscape (two to three times their availability). Eighty-three percent of streettree species (n = 108, total) were used in a lower proportion than their availability by feeding birds, and nearly all were nonnative in origin. Our findings highlight the positive influence of street trees on urban avifauna. In particular, our results suggest that improved street-tree management in lower-income communities would likely positively benefit birds. Further, our study provides support for the high value of native street-tree species and select nonnative species as important habitat for feeding birds.

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The importance of street trees to urban avifauna

Wood

Esaian

2020

Ecological Applications

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Residential yard management and landscape cover affect urban bird community diversity across the continental USA

Lerman

Narango

Avolio

et al. 2021

Ecological Applications

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Urbanization has a homogenizing effect on biodiversity and leads to communities with fewer native species and lower conservation value. However, few studies have explored whether or how land management by urban residents can ameliorate the deleterious effects of this homogenization on species composition. We tested the effects of local (land management) and neighborhood‐scale (impervious surface and tree canopy cover) features on breeding bird diversity in six US metropolitan areas that differ in regional species pools and climate. We used a Bayesian multiregion community model to assess differences in species richness, functional guild richness, community turnover, population vulnerability, and public interest in each bird community in six land management types: two natural area park types (separate and adjacent to residential areas), two yard types with conservation features (wildlife‐certified and water conservation) and two lawn‐dominated yard types (high‐ and low‐fertilizer application), and surrounding neighborhood‐scale features. Species richness was higher in yards compared with parks; however, parks supported communities with high conservation scores while yards supported species of high public interest. Bird communities in all land management types were composed of primarily native species. Within yard types, species richness was strongly and positively associated with neighborhood‐scale tree canopy cover and negatively associated with impervious surface. At a continental scale, community turnover between cities was lowest in yards and highest in parks. Within cities, however, turnover was lowest in high‐fertilizer yards and highest in wildlife‐certified yards and parks. Our results demonstrate that, across regions, preserving natural areas, minimizing impervious surfaces and increasing tree canopy are essential strategies to conserve regionally important species. However, yards, especially those managed for wildlife support diverse, heterogeneous bird communities with high public interest and potential to support species of conservation concern. Management approaches that include the preservation of protected parks, encourage wildlife‐friendly yards and acknowledge how public interest in local birds can advance successful conservation in American residential landscapes.

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The more things change: species losses detected in Phoenix despite stability in bird–socioeconomic relationships

et al. 2019

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The science of urban ecology has increasingly grappled with the long‐term ramifications of a globally urbanized planet and the impacts on biodiversity. Some researchers have suggested that places with high species diversity in cities simply reflect an extinction debt of populations that are doomed to extinction but have not yet disappeared. The longitudinal studies conducted to date have found species composition shifting with urbanization but have not always documented continued species extirpations post‐urbanization. We used long‐term monitoring data on birds from the greater metropolitan area of Phoenix, Arizona, to measure changes in residential bird communities, species–habitat relationships, and human perceptions of bird species diversity over a five‐year period. Bird richness, occupancy, and abundance decreased, as did the percentage of respondents satisfied with bird variety in their neighborhoods. As in previous analyses for this region, we found that desert specialist species were associated with neighborhoods with xeric landscaping consisting of gravel groundcover, and drought‐tolerant, desert‐adapted vegetation. These species were also found in neighborhoods with high per capita income rates and lower percentages of renters and Hispanic/Latinx residents. Non‐native species were positively associated with neighborhoods containing mesic yards with grass and other water‐intensive vegetation. The proportions of yards in our surveyed neighborhoods with these distinct landscaping types likewise remained relatively stable over five‐year period. Although habitat–species relationships remained unchanged, we detected significant loss of species across the sampling period. Declines were not confined to desert specialist species but included generalist and invader species as well. The parallel reduction in residents’ satisfaction suggests that people perceive some aspect of this environmental degradation. Further investigation into the mechanisms underlying these species losses may reveal options for retaining some desert specialist species, and the uniqueness they contribute to urban fauna.

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People and Trees: Assessing the US Urban Forest Resource

Cited by 90 publications

References 0 publications

The importance of street trees to urban avifauna

The importance of street trees to urban avifauna

Residential yard management and landscape cover affect urban bird community diversity across the continental USA

The more things change: species losses detected in Phoenix despite stability in bird–socioeconomic relationships

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