by The most significant predictors of bug biodiversity in Los Angeles are proximity to the mountains and year-round temperature stability, according to a study we conducted in collaboration with Brian V. Brown of the Los Angeles Museum of Natural History and colleagues at Southern University California. and California State University.
The project used data from the museum’s BioSCAN project, in which volunteers across Los Angeles agreed to install insect traps on their properties between 2014 and 2018.
The analysis revealed some surprising results. For example, land values had little effect on the overall diversity of arthropods, particularly spiders and insects. This finding challenges the “luxury hypothesis,” the notion that wealthier neighborhoods, which tend to have more trees, always have more biodiversity—an assumption that generally holds true for birds and mammals, including bats.
The BioSCAN study identified more than 400 different bug species across the Greater Los Angeles Area, many of which have survived despite trail and habitat loss.
Indeed, urban environments can be attractive to some invasive arthropod species. Often called urban opportunities, such species often come in waves that replace or restrict existing species. For example, about 20 years ago, native black widow spiders of Los Angeles (Latrodectus hesperus) started brown spiders (Latrodectus geometricus). Recent evidence indicates that these mediators are replaced by false noble widow spiders (Steatoda nobilis).
Why is it important
Bug populations are essential to humans, who depend on them to provide pollination, decompose plant and animal matter and control pest insects. These services are as important in cities as they are in rural environments – and insects provide them for free.
Imagine a city without organic waste such as dead animals or rotting plant matter. A city without insects would also mean an environment without birds and most other types of wildlife, many of which depend on insects for food. Flowers, fruits or vegetables would also not grow in such a place. In fact, a world without humans would be a world without insects.
Low arthropod diversity can lead to ecosystem imbalance. A 2022 study found that pests, like sap-feeding aphids, can get out of control in urban areas because there aren’t enough predators like beetles and spiders to keep them under control.
Most biodiversity studies are done in natural or even protected areas, but more and more, scientists are recognizing that urban areas can harbor many species. Understanding biodiversity in urban areas is important as cities are expected to continue to spread – with the United Nations predicting that urban populations will grow by 2.5 billion by 2050.
What is not known yet
Although we now know the factors that most influence arthropod diversity in Los Angeles, we do not fully understand how this diversity translates into healthy urban ecosystems.
Scientists know that more species lead to healthier urban ecosystems, but not all species contribute equally. For example, planting pollinator-friendly plants in urban environments is a relatively easy intervention, but it will not benefit all insect species.
What lies ahead
As part of the BioSCAN project, volunteers have also allowed bioacoustic monitors to be installed on their properties, so that future studies can include bats, which are also vital for pollination and pest control in cities.
Additionally, researchers at the University of Southern California are continuing to study the same data set to understand seasonality in urban arthropod communities. In a warming climate, this information could help predict future changes in the bug population.
Overall, insights from these studies could help inform urban planning and development to support bug biodiversity, particularly as cities expand through urban sprawl.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by: Laura Melissa Guzman, USC Dornsife College of Letters, Arts and Sciences; Charles Lehnen, USC Dornsife College of Letters, Arts and Sciencesand Teag Baiotto, University of Southern California
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Laura Melissa Guzman receives funding from the Foundation for Conservation, Food and Health.
Charles Lehnen receives funding from external sources Iguanas in the Balance Grant and Gold Family Fellowship as well as internal USC funding sources USC Provost Fellowship, USC Graduate Travel/Research Award, PhD Academy Scholarship & Research Fund, and Student Government Postgraduate USC GSG Professional Development Fund.
Teagan Baiotto does not work for, consult with, or own shares or receive funding from any company or organization that would benefit from this article this, and has not disclosed any relevant connections beyond their academic appointment.
