Vermin and spiders are not typically associates of comfort around people. Arthropods, defined by their hard exoskeletons and jointed legs, play a crucial part in ecosystems that humans rely on, even when their presence is not welcomed.
Urban areas with high biodiversity have been documented in diverse scientific studies. Benefits include improved air quality, lower flood risk, and even enhanced mental health. Greater biodiversity also leads to healthier, more resilient urban ecosystems.
Arthropods account for roughly 84% of described animal species, with over 1.3 million named species, most of them insects around a million. Consequently, the diversity of arthropods in a given place largely shapes local biodiversity.
As urbanization accelerates, most of the world’s growing population concentrates in cities. The spread of urban areas has important biodiversity consequences; yet, abiotic drivers of urban arthropod biodiversity remain poorly defined.
Specimen of the family Syrphidae (flower flies). Pixabay
Given its vast diversity, limited distribution, and strong dispersal ability, arthropods offer an excellent model for investigating which factors most accurately predict urban biodiversity.
A study published in Scientific Reports examines how human activity alters biodiversity among arthropods and how non-biological factors, such as everyday temperature fluctuations and proximity to the ocean, influence arthropod biodiversity in city environments.
Bees, flies, moths and spiders
Research conducted in Los Angeles (United States) reveals surprising results and points to ways homeowners, landscape architects, and city planners can foster a healthy mix of small but vital neighbors.
Scientists collected flying arthropods including bees, flies, and moths, as well as spiders and other creatures. They counted arthropods to gauge the diversity of groups present in each study area over a year. The findings were unexpected.
“We anticipated that most arthropod groups would respond similarly to environmental factors such as forested landscapes or dense urban pavements. Instead, we observed a broad spectrum of responses, even among closely related groups and across distant ones”, notes lead researcher Melissa Guzmán.
Spiders adapt very well to cement and concrete surfaces.
For example, the prevalence of hard surfaces like concrete and asphalt produced different effects on various insect populations. The diversity of fruit flies from the Drosophilidae family rose, while the diversity of flies from the Tipuloidea superfamily declined.
Interestingly, spider diversity remained high in areas with hard materials. Temperature also influenced the diversity of fungus gnats in the Mycetophilidae family and the Syrphidae family of bee-like flies; higher temperatures correlated with reduced diversity for these groups.
50 new species discovered
Researchers suggest that higher summer temperatures dry out plants eaten by aphids, the food source for many hoverflies. Additionally, non-native bees forage more as temperatures rise, competing for resources with some hoverflies.
To understand how variation among species relates to land value, ground cover, and heat, scientists say the insights could help urban planners and developers adjust projects to boost biodiversity and deliver benefits to all residents.
What surprised the researchers most was the discovery of many unknown arthropod species in the study area, including 50 species previously undocumented by science.
The skyline of Los Angeles serves as the backdrop for this work, which adds a new dimension to how biodiversity is viewed in cities. An entomologist from the study, Brian Brown, notes that the total number of species living in the city may be far higher than previously thought.
Among recommendations to increase urban biodiversity, the study highlights two main priorities: prioritizing green spaces and reducing pesticide use. It also offers guidance for urban planners and builders to create microhabitats that support a wider variety of species.
While the Los Angeles study centers on that city, researchers believe similar patterns could apply to other urban communities with comparable contexts.
Reference work: Nature Scientific Reports 2023. Citation: Nature Scientific Reports 2023.
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