Urban refugia sheltering biodiversity across world cities

Abstract

Over the last years, world cities have emerged as multiple and complex habitats hosting numerous and varied urban refugia for biodiversity. Therefore, the published literature was systematically reviewed to investigate the increasingly acknowledged role of many urban habitats to function as refugia for species. Many plants and animals were reported to colonize a variety of urban environments: Urban forest/grassland (natural/seminatural), City park, Historical park (villa garden, botanical gardens, cemeteries, etc.), Green spaces (abandoned areas, railways, line of trees, etc.), Water body, and Built area. Refugia were found in over a hundred world cities, especially in medium- to very big-size cities. The number of papers focusing on animals (n = 66) were higher than those regarding plants and mushrooms (n = 19 and n = 1, respectively); however, the number of species recorded within refugia were the highest for plants. Plants exhibited the highest frequency (7 out of 19 papers) in Historical park, while animals in Urban forest/grassland (20 out of 66 papers). In most studies (25.9%), urban refugia were linked to Urban forest/grassland that is terrestrial natural and seminatural sites widespread within or around cities. The 22.3% of studies referred to generic Green spaces of several types interspersed within cities, both public and private. The 14.1% of refugia were found in Built area (artificial). About the 33% of studies reported the presence of species worthy of conservation (rare, endemic, endangered, or protected) for a total of 365 species. The 20% of investigated papers reported the presence of alien species for a total of 879 species. Invasive alien species recorded within refugium areas should be subjected to control measures to prevent degradation to refugia. Overall, the capability for urban areas to host a huge amount of biodiversity needs to be acknowledged by city planners so that management practices that maintain and support such diversity can be pursued. Recording and monitoring species along with their refugial habitats is fundamental to achieve this goal.

Tourist Trampling on a Peripheral Plant Population Restricted to an Urban Natural Area in the Capo Sant’Elia Promontory (Sardinia, W-Mediterranean Basin)

“…Plants such as G. alypum , which has phytogeographical importance in Sardinia, are often restricted to specific areas. In this particular instance, the urban setting can be seen as a special refugium that offers vital habitats and new opportunities for species to survive in an environment marked by disturbance and stress [ 12 , 62 , 63 , 64 ]. Isolated populations have unique biological and ecological requirements, making them of interest in ecology, evolutionary biology, and genetics.…”

“…An increasing number of scientific studies have considered many sites within cities as places that have the ability or the potential to provide refugia for numerous native species. Therefore, several species, due to the abundance of unique, unusual, and intricate habitats found in urban landscapes, can find refuge in these habitats, which are very different from those that surround cities [ 12 ]. The biodiversity found within natural areas has become one of the primary attractions for prospective visitors, who find themselves enjoying the beauty that biodiversity provides and the consequent sense of place that derives from it [ 7 ], raising public awareness of the need to conserve it [ 13 , 14 , 15 , 16 , 17 ].…”

Vascular flora of Punta Arenas city: comparative analysis of composition, life forms, and biogeographic origins

“…To compare the composition of urban flora in Punta Arenas with other cities in the country (i.e., La Serena, Santiago, Valparaíso, Rancagua, and Talca), floristic similarity was calculated between these cities, considering only the woody tree flora. To do this, a species × city matrix was created, including all species and encoding their presence-absence in each city with values one (1) and zero (0), respectively. Then, we used the Simpson's index (β sim = a × (a + min{ b,c}) -1 ) [36] that measures dissimilarity between pairs of samples [37], and whose advantage over other indices is that it better reflects compositional differences -rather than richness-between samples (i.e., cities) [38].…”

“…The process of urbanization establishes new conditions and habitat opportunities for biodiversity [1,2]. This is particularly true in the case of the urban vascular flora [3], whose distribution and abundance within cities are governed by environmental factors (e.g., precipitation, temperature, geography) as well as by public and private decisions made by citizens that determine which species to plant where [4].…”