Cristina E. Ramalho

Time for a change: dynamic urban ecology.

Contemporary cities are expanding rapidly in a spatially complex, non-linear manner. However, this form of expansion is rarely taken into account in the way that urbanization is classically assessed in ecological studies. An explicit consideration of the temporal dynamics, although frequently missing, is crucial in order to understand the effects of urbanization on biodiversity and ecosystem functioning in rapidly urbanizing landscapes. In particular, a temporal perspective highlights the importance of land-use legacies and transient dynamics in the response of biodiversity to environmental change. Here, we outline the essential elements of an emerging framework for urban ecology that incorporates the characteristics of contemporary urbanization and thus empowers ecologists to understand and intervene in the planning and management of cities.

Complex effects of fragmentation on remnant woodland plant communities of a rapidly urbanizing biodiversity hotspot

In many cities worldwide, urbanization is leading to the rapid and extensive fragmentation of native vegetation into small and scattered urban remnants. We investigated the effects of fragmentation on plant species richness and abundance in 30 remnant Banksia woodlands in the rapidly expanding city of Perth, located in the southwestern Australian global biodiversity hotspot. We considered a comprehensive set of factors characterizing landscape fragmentation dynamics (current and historical remnant area and connectivity, time since isolation, and trajectories of landscape change), disturbance regimes (fire frequency, grazing, and intensity of human activities), and local environmental conditions (soil nutrient status and litter depth). We used generalized linear mixed models to determine the interactive effects of time since remnant isolation and remnant area on plant species richness, and structural equation models to disentangle the direct and indirect effects of landscape and local factors on plant species richness and abundance. Fragmentation impacts were most rapid in smaller remnants. Indeed, in the small remnants, native plant species richness was halved in only a few decades after isolation, suggesting an underlying rapid loss of habitat quality. We found that richness and abundance of woody species were higher in historically large remnants and lower in the rural areas, despite these rural remnants showing greater connectivity. Richness of native herbaceous species declined with time since isolation, mainly in the smaller remnants, and this was associated with altered soil properties. Furthermore, increased litter depth (possibly indicating higher productivity) and increased abundance of nonnative herbaceous species in the older and smaller remnants was associated with a decline in the abundance of native herbaceous species. Our study suggests that in rapidly expanding cities, landscape fragmentation can have major and complex effects on remnant vegetation. Yet these impacts might take several decades to manifest themselves. Hence, understanding the long-term conservation capacity of newly formed remnants, which is key to setting conservation priorities, requires consideration of landscape fragmentation and land use history. Moreover, the smaller and older remnants may already display changes due to fragmentation, providing clues for urban planning and ecosystem management that help to protect urban remnant plant diversity.

A climate change context for the decline of a foundation tree species in south-western Australia: insights from phylogeography and species distribution modelling

BACKGROUND AND AIMS A worldwide increase in tree decline and mortality has been linked to climate change and, where these represent foundation species, this can have important implications for ecosystem functions. This study tests a combined approach of phylogeographic analysis and species distribution modelling to provide a climate change context for an observed decline in crown health and an increase in mortality in Eucalyptus wandoo, an endemic tree of south-western Australia. METHODS Phylogeographic analyses were undertaken using restriction fragment length polymorphism analysis of chloroplast DNA in 26 populations across the species distribution. Parsimony analysis of haplotype relationships was conducted, a haplotype network was prepared, and haplotype and nucleotide diversity were calculated. Species distribution modelling was undertaken using Maxent models based on extant species occurrences and projected to climate models of the last glacial maximum (LGM). KEY RESULTS A structured pattern of diversity was identified, with the presence of two groups that followed a climatic gradient from mesic to semi-arid regions. Most populations were represented by a single haplotype, but many haplotypes were shared among populations, with some having widespread distributions. A putative refugial area with high haplotype diversity was identified at the centre of the species distribution. Species distribution modelling showed high climatic suitability at the LGM and high climatic stability in the central region where higher genetic diversity was found, and low suitability elsewhere, consistent with a pattern of range contraction. CONCLUSIONS Combination of phylogeography and paleo-distribution modelling can provide an evolutionary context for climate-driven tree decline, as both can be used to cross-validate evidence for refugia and contraction under harsh climatic conditions. This approach identified a central refugial area in the test species E. wandoo, with more recent expansion into peripheral areas from where it had contracted at the LGM. This signature of contraction from lower rainfall areas is consistent with current observations of decline on the semi-arid margin of the range, and indicates low capacity to tolerate forecast climatic change. Identification of a paleo-historical context for current tree decline enables conservation interventions to focus on maintaining genetic diversity, which provides the evolutionary potential for adaptation to climate change.

The potential of ecologically enhanced urban parks to encourage and catalyze densification in greyfield suburbs

Abstract This paper explores the potential of a strategy for achieving infill development in Australian greyfield suburbs in which redesigned, ecologically enhanced urban parks, in areas with reasonable access to public transport, are employed to encourage, catalyze, and ultimately support, residential densification. This process involves the upzoning of a walkable catchment of selected greyfield urban parks to higher residential densities than the market is currently delivering. To encourage this upzoning in the local community, local parks are redesigned using an ecological-oriented approach that seeks to enhance both their ecological and social values. The parks’ redesign is likely to lead to an increase in land values, which, in turn, is anticipated to catalyze redevelopment. In combination with increased zoning densities, this strategy is hypothesized to lead to greater densification. It is proposed that, as the densification occurs, a needs-based assessment is conducted to determine the park equipment required by the increased park catchment population. The potential of this process is explored in an illustrative planning exercise in the local government area of Bayswater (Perth, Western Australia), which has significant infill targets and a large amount of sports field-dominated parkland. The paper concludes by arguing that a strategy of densification around public open space could potentially aid in greyfield suburbs achieving their infill targets, as well as lead to improved social and ecological outcomes.

Demographic and genetic viability of a medium-sized ground-dwelling mammal in a fire prone, rapidly urbanizing landscape

The rapid and large-scale urbanization of peri-urban areas poses major and complex challenges for wildlife conservation. We used population viability analysis (PVA) to evaluate the influence of urban encroachment, fire, and fauna crossing structures, with and without accounting for inbreeding effects, on the metapopulation viability of a medium-sized ground-dwelling mammal, the southern brown bandicoot (Isoodon obesulus), in the rapidly expanding city of Perth, Australia. We surveyed two metapopulations over one and a half years, and parameterized the PVA models using largely field-collected data. The models revealed that spatial isolation imposed by housing and road encroachment has major impacts on I. obesulus. Although the species is known to persist in small metapopulations at moderate levels of habitat fragmentation, the models indicate that these populations become highly vulnerable to demographic decline, genetic deterioration, and local extinction under increasing habitat connectivity loss. Isolated metapopulations were also predicted to be highly sensitive to fire, with large-scale fires having greater negative impacts on population abundance than small-scale ones. To reduce the risk of decline and local extirpation of I. obesulus and other small- to medium-sized ground-dwelling mammals in urbanizing, fire prone landscapes, we recommend that remnant vegetation and vegetated, structurally-complex corridors between habitat patches be retained. Well-designed road underpasses can be effective to connect habitat patches and reduce the probability of inbreeding and genetic differentiation; however, adjustment of fire management practices to limit the size of unplanned fires and ensure the retention of long unburnt vegetation will also be required to ensure persistence. Our study supports the evidence that in rapidly urbanizing landscapes, a pro-active conservation approach is required that manages species at the metapopulation level and that prioritizes metapopulations and habitat with greater long-term probability of persistence and conservation capacity, respectively. This strategy may help us prevent future declines and local extirpations, and currently relatively common species from becoming rare.

Effects of fragmentation on the plant functional composition and diversity of remnant woodlands in a young and rapidly expanding city

Questions How do plant functional trait abundance and diversity in urban remnants of a rapidly urbanizing city change with fragmentation? Is there a delayed functional response to fragmentation? Location Thirty remnant Banksia woodlands, Perth, Australia. Methods We used GLMM to examine the effects of remnant age and area, and their interaction, on the relative abundance and functional diversity (FD) of five plant functional traits: growth form, pollination, seed dispersal, nutrient acquisition and regeneration strategies. We then used fourth-corner analysis to examine the influence of a wider set of fragmentation-related factors on trait abundances. Results The functional composition and diversity of Banksia woodlands changed with remnant age, particularly in the smaller remnants. Plants more prone to decline with remnant age were the growth form shrubs, root-clustered trees, herbaceous obligate seeders and understorey species that are insect-pollinated, have seeds dispersal internally by animals and have arbuscular or ericoid mycorrhizas. In contrast, plants more prone to persist were growth forms trees, sedges and rushes, ectomycorrhizal trees, herbaceous resprouters, wind-pollinated and root-clustered understorey species. FD increased with remnant age in the growth forms and overstorey, but declined among the herbaceous and shrub pollination and nutrient acquisition traits. Conclusions Functional traits that consistently signalled the plant community response to fragmentation were growth form, pollination and dispersal. This functional response was largely delayed, suggesting a ″functional extinction debt″, which will lead to a further decline of plants with vulnerable trait states in the future, especially in the small- and medium-sized remnants. Our study illustrates the vulnerability of small remnants to changes in community assembly and ecosystem function due to fragmentation. Furthermore, it exemplifies how a functional trait approach is valuable to understand the impacts of urbanization on remnant plant communities, before local extinctions may occur. Finally, the study shows how cities’ fragmentation history and biogeographic settings provide an important context influencing plant functional responses to urbanization-related processes.

A Climate-Oriented Approach to Support Decision-Making for Seed Provenance in Ecological Restoration

There is increasing awareness that the long-term success of ecological restoration efforts can be compromised if projected climate change is not effectively incorporated in restoration planning. We propose an approach that aims to support the decision-making process for seed provenance selection in ecological restoration when clear genetic-based guidelines for seed transfer are not available. The approach takes advantage of the increasing availability and refinement of user-friendly web-based GIS interfaces that allow non-experts to directly access biodiversity and environmental data, and build species distribution models. It offers an easily accessible desktop method that land managers and practitioners can use to gain insight: 1) on the overall spatial implications of projected climate change to their restoration project; 2) whether assisted gene flow through climate-adjusted provenance may be appropriate for a given species at a given restoration site; and 3) how far away and in which direction from the restoration site seeds should be collected from. This approach should be used in the early stages of the restoration project to help frame the decision-making process in a climate change context, and can also be used as a platform where other lines of evidence are integrated. We advocate that, in the context of rapid climate change, the climate-adjusted provenance is a promising approach to seed sourcing in ecological restoration, and we suggest its refinement in a way that hedges against uncertainty in climatic projections.