urban diversity

Bridging citizen science and expert surveys in urban biodiversity monitoring: Insights from insect diversity in Macao

Using insects as a model group, researchers examined the potential of citizen science to uncover undocumented biodiversity.

Guest blog post by Kaiyun Zheng, Mark K. L. Wong, Toby P. N. Tsang, Chi Man Leong

A photo of a cicada emerging from its shell, clinging to a branch among green leaves at night. — Eclosion of *Cryptotympana* sp. during a nighttime bioblitz activity in Macao. Photo courtesy Dr. Danny Chi Man Leong

During a field trip for an ecology course in a city park, lead author Ms Kaiyun Zheng was fascinated by the incredible insect biodiversity surrounding her. Insects serve as important bioindicators—their diversity and assemblage can reveal ecological processes and environmental health. However, sampling insect diversity is often challenging, requiring extensive equipment and field effort. Despite being one of the most species-rich animal groups, insects are undergoing a global decline due to habitat loss, pollution, and urbanization. Traditional insect surveys typically demand significant time and resources and are limited in scope.

Curious to find a more accessible approach, Kaiyun began exploring insect records from both expert-led field surveys and citizen science platforms such as iNaturalist. Together with her supervisor, Dr. Danny Chi Man Leong from Beijing Normal-Hong Kong Baptist University, and co-authors Dr. Mark Wong from The University of Western Australia and Dr. Toby Tsang from University of Toronto Scarborough, they posed a key question: Can citizen science reveal hidden biodiversity beyond what expert surveys have recorded?

A photo of a woman standing outdoors, wearing a white shirt and brown skirt, holding a phone and a hat, with a backpack slung over one shoulder. — Ms. Kaiyun Zheng

A photo of a man with arms crossed, wearing a dark green sweater over a collared shirt, and a watch, standing against a wooden background. — Ms. Kaiyun Zheng

Citizen science involves participation by people without formal scientific training, who contribute to scientific research by collecting and sharing data. In biodiversity documentation, citizen scientists can use smartphones and digital platforms to record species, helping expand scientific knowledge at scale.

Using insects as a model group, the authors examined the potential of citizen science to uncover undocumented biodiversity and discussed how large-scale citizen-contributed data could enhance ecosystem monitoring. To evaluate the strengths and complementarities of different data sources, they compared an expert dataset with a citizen science dataset.

Four panels depicting insect observation data: a map, trend graphs for observations, observers, and species over time. — Spatial distribution of insect observations in Macao from the citizen science dataset (iNaturalist.org) (A), along with cumulative increases in verified identifiers (B), insect observations (C), and recorded insect species (D).

In total, 1,889 insect species were recorded across both datasets, but only 462 species (24%) overlapped. The expert dataset included 1,339 species, of which 877 (65%) were not found in the citizen science records. Conversely, the citizen science dataset documented 1,012 species, with 550 (54%) unique to it. This substantial non-overlap indicates that the two approaches capture different facets of insect diversity. For example, there was relatively high overlap for insect groups such as butterflies and moths (Lepidoptera), likely due to their conspicuous appearance and popularity among observers. In contrast, groups such as wasps, bees and ants (Hymenoptera) and flies (Diptera) were underrepresented in the citizen science dataset, suggesting challenges in detecting smaller or more cryptic species.

Venn diagram showing species counts: 877 expert recorded, 550 citizen science recorded, and 462 shared species. — Venn diagram of insect diversity between expert and citizen science datasets.

These findings highlight the importance of integrating expert surveys with citizen science efforts to achieve a more comprehensive understanding of insect biodiversity, especially in urban areas which benefit from a high participation from citizen scientists.

Their study also highlights the unique strengths of citizen science for urban biodiversity monitoring. Residents living near parks and green spaces are ideally placed to document insect occurrences in real time across a wide range of locations. Notably, the study includes a citizen-contributed record of Mortonagrion hirosei, a Near Threatened damselfly rarely observed in Macao. This example illustrates how citizen science can detect rare or cryptic species, uncovering important biodiversity records and filling gaps left by traditional surveys, making it an indispensable tool for future biodiversity monitoring.

Research article:

Zheng K, Wong MKL, Tsang TPN, Leong CM (2025) Bridging Citizen Science and Expert Surveys in urban biodiversity monitoring: Insights from insect diversity in Macao. Biodiversity Data Journal 13: e153402. https://doi.org/10.3897/BDJ.13.e153402

How quickly do flower strips in cities help the local bees?

Insects rely on a mix of floral resources for survival. Populations of bees, butterflies, and flies are currently rapidly decreasing due to the loss of flower-rich meadows. In order to deal with the widespread loss of fauna, the European Union supports “greening” measures, for example, the creation of flower strips.

A group of scientists from the University of Munich, led by Prof. Susanne S. Renner, has conducted the first quantitative assessment of the speed and distance over which urban flower strips attract wild bees, and published the results of the study in the open-access Journal of Hymenoptera Research.

Flower strips are human-made patches of flowering plants that provide resources for flower-visiting insects and insect- and seed-feeding birds. Previous experiments have proved their conservation value for enhancing biodiversity in agricultural landscapes.

The success of flower strips in maintaining populations of solitary bees depends on the floristic composition, distance from suitable nesting sites, and distance from other habitats maintaining stable populations of bees. To study the attractiveness of the flower strips in urban landscapes, the scientists used an experimental set-up of nine 1,000 sq. meters flower strips recently established in Munich by a local bird conservation agency.

“We identified and counted the bees visiting flowers on each strip and then related these numbers to the total diversity of Munich’s bee fauna and to the diversity at different distances from the strips. Our expectation was that newly planted flower strips would attract a small subset of mostly generalist, non-threatened species and that oligolectic species (species using pollen from a taxonomically restricted set of plants) would be underrepresented compared to the city’s overall species pool,”
shared Prof. Susanne S. Renner.

Bees need time to discover new habitats, but the analysis showed that the city’s wild bees managed to do that in just one year so that the one-year-old flower strips attracted one-third of the 232 species recorded in Munich between 1997 and 2017.

Surprisingly, the flower strips attracted a random subset of Munich’s bee species in terms of pollen specialization. At the same time, as expected, the first-year flower-strip visitors mostly belonged to common, non-threatened species.

The results of the study support that flower strip plantings in cities provide extra support for pollinators and act as an effective conservation measure. The authors therefore strongly recommend the flower strip networks implemented in the upcoming Common Agricultural Policy (CAP) reform in the European Union.

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Original source:

Hofmann MM, Renner SS (2020) One-year-old flower strips already support a quarter of a city’s bee species. Journal of Hymenoptera Research 75: 87-95. https://doi.org/10.3897/jhr.75.47507

Ottawa confirmed as the biodiversity hotspot for a subfamily of wasps in North America

What usually comes to mind when speaking about biodiversity hotspots are tropical regions, pristine areas and magnificent forests. Meanwhile, it is quite rare that a city in a temperate zone is considered significant in terms of biodiversity, much less mentioned as a hotspot. Yet, the city of Ottawa together with its surroundings, despite having population surpassing 1 million people, is now confirmed to be the locality in North America with the most recorded species of braconid wasps in the subfamily Microgastrinae, a group of parasitic insects that attack caterpillars and play an important role in the natural biocontrol of agriculture and forestry pests.

A study published in ZooKeys reports 158 species within 21 different genera of Microgastrinae for Ottawa. “To put this into perspective,” says Dr. Jose Fernandez-Triana, affiliated with the Canadian National Collection of Insects and lead author of the paper, “if Ottawa (a relatively small area of less than 7,800 km2) would be considered as a country itself, its species total would rank 17th among all countries in the world.”

There are close to 200 species of microgastrine wasps known from Canada and around 350 – from North America. Thus, the fauna in Ottawa equals to three quarters of the total recorded for the entire country, and almost half of all species in the Nearctic region. In fact, the diversity in the Canadian capital represents by far the highest number of species ever recorded for a locality in North America, a consequence of the city being a transition from an eastern deciduous forest biome to a boreal biome, with small areas of unusual habitats like dunes, alvars, floodplains and bogs.

Based on the analysis of almost 2,000 specimens, collected between 1894 and 2010, and housed in the Canadian National Collection of Insects, the paper also reports two new species for North America and two additional species records for Canada and Ontario, as well as dozens of new additions to the regional fauna. Seasonal distribution showed several peaks of activity, in spring, summer, and early fall.

The study highlights the incredible diversity of parasitoid wasps and how much remains to be discovered, even in temperate areas and/or city environments. “It is possible that southern localities in North America are eventually found to be more diverse than Ottawa,” notes Dr. Fernandez-Triana. “But for that to happen one would need to find an area that has a variety of habitats and has also been thoroughly sampled over the years, with thousands of specimens available for study.”

“In the meantime,” jokes the scientist, “the citizens of the Canadian capital will have the bragging rights in North America, at least for microgastrine wasp diversity.”

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Original source:

Fernandez-Triana J, Boudreault C, Buffam J, Mclean R (2016) A biodiversity hotspot for Microgastrinae (Hymenoptera, Braconidae) in North America: annotated species checklist for Ottawa, Canada. ZooKeys 633: 1-93. https://doi.org/10.3897/zookeys.633.10480

The city of angels and flies: 12 unknown scuttle fly species have been flying around L.A.

Although the second-largest and rather concrete metropolis in the United States might not be anywhere near one’s immediate association for a biodiversity hotspot, the fly fauna of Los Angeles is quite impressive. As part of BioSCAN, a project devoted to exploring the insect diversity in and around the city, a team of three entomologists report on their latest discovery – twelve new scuttle fly species. Their study is published in the open access Biodiversity Data Journal.

Launched in 2013, the Natural History Museum of Los Angeles County‘s project BioSCAN seems to never cease to amaze with large numbers of newly discovered species. The first phase of the study finished with 30 species of flies new to science from sites in 27 backyards, 1 community garden, the Los Angeles Ecovillage, and the Nature Gardens at the Museum. In recognition to the residents, who had literally let the scientists in their homes, each of those flies was named after the relevant site’s host.

When they decided to revisit the specimens they had collected during the first year of the project as well as older museum collections, the authors of the present paper were in fact quite certain they were about to find a new batch of unknown flies.

Having already described so many new scuttle fly species, the latest twelve had initially gone undercover, all being rare and often represented by only one specimen among the total of 43,651 collected individuals.

“The remarkable diversity of biologies of these flies makes them a varied and essential group to document in any ecosystem,” the entomologists explain.

The extensive BioSCAN project is still ongoing thanks to its passionate staff, international collaborators and advisors, as well as the large number of students and volunteers. Being especially grateful for their help, the scientists have named one of the fly species M. studentorum and another one – M. voluntariorum. The project is currently in its second phase of collecting.

“These volunteers are critical to our operation, and have contributed to everything from public outreach in the NHM Nature Lab to specialized work on phorid flies,” point out the authors.

In the end, the researchers hope that they will get their message across to other taxonomists, funding agencies, institutions and the public alike. Urban environments with their fast-changing conditions and biodiversity profile, need constant attention and scientific curiosity.

“There is an enormous taxonomic deficiency, including, or, perhaps, especially, in rapidly changing urban environments,” they say. “Taxonomists and their funding agencies must give time, attention and money to the environments surrounding their towns and cities.”

“Baseline collections of urban fauna must be established in the present if there is hope for understanding the introductions and extinctions that will occur in the future,” they stress.

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Original source:

Hartop E, Brown B, Disney R (2016) Flies from L.A., The Sequel: A further twelve new species ofMegaselia (Diptera: Phoridae) from the BioSCAN Project in Los Angeles (California, USA).Biodiversity Data Journal 4: e7756. doi: 10.3897/BDJ.4.e7756