Cities are true oases of nature – our study shows which species tolerate urbanization best

The Earth is losing animals, plants and other living things so quickly that some scientists consider the planet is nearing all-time low. sixth mass extinctionBut there’s surprisingly excellent news: urban areas may hold the important thing to slowing and even reversing this crisis.

This idea could seem counterintuitive, as studies show that urbanization is a significant driver of Loss of biodiversityCities change the environment through artificial light And Noise pollutionaffecting many species. And urban land cover is anticipated to global increase of two.5% between 2000 and 2030 as increasingly people move to cities.

One measure of urbanization is that half of the European continent is lower than 1.5 kilometers from a Road or railway lineNo place on the continent is greater than 10 kilometers from these features.

But there are opportunities for cities, nature-based solutions to slow the lack of species inside their borders. At a significant international conference on biodiversity loss in 2022, world leaders agreed on ambitious targets for Restoring natural ecosystems all over the worldincluding objectives to “ensure[ing] “biodiversity-integrative urban planning”.

Urban nature-based solutions create, protect and restore natural spaces in cities to support wildlife.

We are conservation And ecology Researchers working in Southern California and other areas. In our recent study, we worked with colleagues to discover areas in Los Angeles that host diverse communities of native species. We even found that some groups of organisms seem to learn from increased urban development. And now we have developed a brand new metric to measure how different species reply to urbanization, which city officials can use to develop local conservation strategies.

Wild Los Angeles

Los Angeles is a city of just about 3.9 million inhabitants and a highly urbanized landscape characterised by its vast network of highways and a mostly quiet and canalized Los Angeles RiverIn the center of the twentieth century, automotive exhaust and industrial emissions produced dense smog which made being outdoors a health risk and ultimately led to the adoption of the Air Quality Control Act of 1970.

Although the sky above town continues to be usually covered in smog, the air in Los Angeles cleaner than at any time within the last 50 yearsAnd town leaders are setting ambitious goals to guard nature throughout town.

In the 2019 “Sustainable City Plan” then-Mayor Eric Garcetti set a goal of achieving no net lack of biodiversity by 2050 – in other words, stopping the lack of living species or offsetting losses by adding recent species. To track progress, town created a individual index for measuring and evaluating biodiversity throughout Los Angeles. We helped calculate a component of this index that measures the connection between native species in Los Angeles and urbanization.

Los Angeles is positioned within the California Floristic Province, a worldwide hotspot of biodiversityIt is one among 36 designated areas worldwide that contain large populations of endemic plants – species found nowhere else on the planet – and are experiencing significant lack of their original plant communities.

Even in essentially the most urbanized parts of town, Angelinos Share the streets with bats, Thousands of birdsand myself large predators resembling mountain lions. However, scientists don’t yet know exactly how the extent of urbanization affects the wide diversity of native animal species that decision Los Angeles home.

Snails lead the pack

To support town’s efforts to evaluate biodiversity and slow regional species loss, we collected Data from iNaturalista free, publicly available app that permits anyone to discover and document animals, plants and other living things. The app has collected over 189 million records and its database is consistently growing.

We filtered these crowdsourced species occurrence data to find out the potential effect of Observer bias – Impact of the way in which individuals collect observations, what may appear in the infoFor example, multiple people could upload sightings of a single animal, making it appear as if multiple animals were sighted. Or people could only upload sightings from areas near roads, making it appear as if there’s more wildlife there, without on the lookout for animals in additional distant areas.

Our filtered dataset included over 500,000 observations recorded by 71,000 scientists, yielding occurrence records for 967 native species inside about 150 kilometers of town of Los Angeles. We modeled species responses to urbanization policies and summarized the typical response of all native species across town.

A scientific community program uses iNaturalist to discover snails and slugs in Southern California.

Overall, we found that the majority native species were more more likely to be present in natural areas around Los Angeles than in urban parts of town. A surprising exception was snails and slugs, which were, on average, more common in urbanized zones than in natural areas. This finding mirrors a 2018 study in Tennessee that also showed that native snail species can persist in highly urbanized environments – perhaps because people supply water to parks and gardens for landscape reasons.

Of all of the native species studied, butterflies and moths in addition to mammals were the least common in heavily built-up areas. The lack of necessary host plants for certain butterfly species could explain why butterflies are relatively rare in highly urbanized areas.

In mammals, our results are much like a 2023 study conducted within the United States. It concluded that mammals, especially large mammals, Extremely urban areas avoided.

Graphic showing how closely 12 groups of organisms were linked to urbanization in a study in the greater Los Angeles area.
Urban tolerance for every of the 12 taxonomic groups. Points in each graph are the responses of individual species; the vertical bar indicates the mean for the group. Positive values ​​indicate that animals usually tend to be present in urbanized areas; negative values ​​indicate groups that prefer natural spaces.
Joseph Curtis, CC BY-ND

Even in essentially the most urban areas, resembling Pershing Square in downtown Los Angeles, we found some species communities that preferred natural spaces. Examples were Wrens (Troglodytes aedon) And urban digging bees (Anthophora urbana).

This suggests that cities can, in some cases, promote native biodiversity. A next step on this research is to know what underlying aspects of the landscape might attract these native species.

Making cities more animal-friendly

Our study shows that small islands of biodiversity can exist even in essentially the most urbanized areas of cities. The urban association metric we developed is meant to function a tool for city managers to develop strategies that allow wild species to proceed to thrive in town.

For example, Los Angeles recently proposed an ordinance that promotes animal-friendly house constructingFor example, residential areas with fences that don’t restrict the movement of untamed animals allow migratory animals to go through.

Data from the iNaturalist app provides researchers with invaluable details about where native species occur and the way common they’re. Anyone who desires to contribute to conservation science can download it and record what they see on a walk, bike ride, ferry ride, or of their garden. You may find more nature in your neighborhood than you expect.

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