Plant population success across urban ecosystems: A framework to inform biodiversity conservation in cities

Abstract

In a rapidly urbanising world, the ability of plant species to survive and build self‐sustaining populations in urban environments is increasingly important for biodiversity conservation. Yet, the contribution of cities to biodiversity conservation remains unclear because ecologists have studied biodiversity patterns, largely without considering the population establishment of plants and the ways in which different kinds of urban ecosystems harbour native and endangered plant species. These limitations can mislead conservation policies for cities. To better understand how urban ecosystems can contribute to biodiversity conservation, we propose a framework that links the population status (casual or established) of plant species with ecosystem novelty and highlights barriers to population establishment in different types of urban ecosystems, from natural remnants to novel ecosystems. To quantify the relative importance of natural remnants vs. human‐shaped ecosystems for the conservation of self‐sustaining urban plant populations. we re‐analyse a unique dataset from a metropolitan region in Europe with information on the population status of 1,199 plant species. Results demonstrate that urban ecosystems harbour many established native and endangered species although a considerable share (37%) of species of conservation concern are confined to natural remnants. In hybrid and immature novel ecosystems, high species numbers reflect many species with only casual populations. The role of novel ecosystems as habitats for native and endangered plant species increases as novel ecosystems mature. Synthesis and applications. General information about plant species richness in urban environments may mislead conservation policies as different kinds of urban ecosystems can play different roles in harbouring species of conservation concern. Moreover, presence/absence data can mask establishment failures of species. This proposed framework helps to distinguish between casual and established populations of plant species, and highlights barriers to population persistence in urban ecosystems, reflecting different land uses and land use histories over time. Revealing the role of natural remnants vs. hybrid vs. novel ecosystems as habitats for species of conservation concern illustrates opportunities for biodiversity conservation in all urban ecosystems and can support setting priorities for conservation.

When cities are the last chance for saving species

“…But the potential for conservation gains in unconventional landscapes is often unrecognized (Shwartz et al . ; Kowarik and von der Lippe ). For many urban‐restricted threatened species, sites that are small, that have been highly modified, or that no longer support remnant vegetation are rarely prioritized – yet these are often the areas where species recovery efforts must occur.…”

“…It is increasingly recognized that areas of intensive human land use often coincide with biodiversity hotspots, threatened species, and ecosystems of conservation concern (Ives et al . ; Kowarik and von der Lippe ; Threlfall and Kendal ) and that conservation action in such landscapes is critical (Miller and Hobbs ; Dunn et al . ; Blaustein ).…”

“…However, conservation research and action in urban landscapes is still an emerging field (Shwartz et al . ; Kowarik and von der Lippe ). Given that “urban” is often considered to be the opposite of “natural”, urban environments suffer from a persistent stigma (Klaus ; Salomon Cavin ; Soanes et al .…”

Plants in the city: understanding recruitment dynamics in urban landscapes

“…Second, urban ecologists should also seek to extend experiments over multiple years and establish long‐term research projects that record basic demographic data on plant populations. Although such work has begun (eg Kowarik and von der Lippe ), very little is known about the transition probabilities between life‐history stages for urban plants, especially after seedling stages. Collecting basic demographic data on urban plant populations will enable the development of comparative models and generation of new hypotheses on urban plant community dynamics.…”

“…Research should also consider recruitment limitation in different categories of urban environments, from remnant patches to constructed or designed natural areas. Understanding recruitment limitation for a range of sites may inform the potential for cities to support broader conservation goals related to native species and habitat (Kowarik and von der Lippe ).…”