Mark J McDonnell

Around the world the development and growth of cities and towns are having a significant impact on local and global biodiversity. There is growing interest in the adaptation of nonhuman organisms to urban environments, and we distinguish between the concepts of adaptation and adaptedness. Most of these studies have focused on animals, especially birds. Commonly recorded responses to urban environments include regulatory and acclimatory responses involving changes in behavior, communication, and physiology. Developmental responses tend to be morphological in nature but can also involve cultural learning. There is growing evidence of microevolutionary changes associated with adaptive responses to urban environments. This review also highlights the urgent need to refine the terminology currently used to describe the adaptation of organisms to urban environments in order to improve scientific understanding and more effectively identify and communicate the actions required to create biod...

In order to understand the effect of urban development on the functioning of forest ecosystems, during the past decade we have been studying red oak stands located on similar soil along an urban-rural gradient running from New York City ro rural Litchfield County, Connecticut. This paper summarizes the results of this work. Field measurements, controlled laboratory experiments, and reciprocal transplants documented soil pollution, soil hydrophobicity, litter decomposition rates, total soil carbon, potential nitrogen mineralization, nitrification, fungal biomass, and earthworm populations in forests along the 140 × 20 km study transect. The results revealed a complex urban-rural environmental gradient. The urban forests exhibit unique ecosystem structure and function in relation to the suburban and rural forest stands these are likely linked to stresses of the urban environment such as air pollution, which has also resulted in elevated levels of heavy metals in the soil, the positive...

Question: How does urbanization and associated declines in fire frequency alter the floristic composition of native temperate grasslands? Does it lead to: (1) biotic homogenization, i.e. compositional similarity between remnants increases; (2) biotic differentiation, whereby similarity between remnants declines, or; (3) clustered differentiation, where similarity between remnants remains unchanged, but composition shifts from the historical state? Location: Victoria, Australia. Methods: Using site-level surveys, we examined changes in the floristic similarity of 29 urban grasslands from 1992 to 2013 and compared these changes to those of 63 rural grasslands from 1989 to 2014. Community-level changes in the representation of key functional traits were also examined in urban grasslands, with traits advantaged following disturbance regime change and urban fragmentation predicted to increase in frequency. Results: Our results supported the biotic homogenization hypothesis in urban grasslands. Compositional similarity between grasslands increased principally because of an increase in commonly shared non-native species, with change in native composition comparatively minor. However, no evidence of biotic homogenization was found in rural grasslands, with no significant change in overall composition identified. The most urbanized sites had the highest number of non-native species in both the current and historical data sets, yet non-native composition over the past two decades changed the most in sites on the urban fringe, becoming more similar to sites closer to the urban core. As expected, following declines in fire frequency and increased urbanization, the overall composition of urban grasslands shifted to taller plant species, while native species capable of vegetative reproduction and exotic species with an annual life span increased in frequency. Conclusion: Urbanization was an important driver of biodiversity change in the investigated system, with increasing competition intensity in response to disturbance regime change a likely cause of biotic homogenization. Our results demonstrate that non-native species are a key driver of biotic homogenization, emphasizing the importance of managing non-native immigration and maintaining historical disturbance processes once native ecosystems become urbanized.

There has been much debate about the effectiveness of different sized reserves for nature conservation. However, in human-dominated landscapes such as cities, conservation reserve systems are, by necessity, often determined without using conservation planning principles. This can result in reserve systems that are small, fragmented and disconnected. In this study, we conducted a floristic survey of 68 urban grassland conservation reserves to assess how reserves of different areas contribute to species conservation. Species accumulation curves, species-area relationships, and proportion of native cover were explored. We found that 87% of all native plant species were found in small reserves < 10 ha in size, more small reserves contained a greater number of species than few large reserves of a comparable area, and cover of native species in small reserves was no different than cover in large reserves. However, large reserves harboured more uncommon species than smaller reserves. This research has several important implications for conservation planning and design, highlighting that both small and large reserves can help to conserve native plant species in urban areas. However, a preference for large reserves over small ones is embedded in much conservation planning and management. There is a danger that a normative belief that large reserves are ‘good’ and small reserves are ‘bad’ has become entrenched in conservation thinking. While the theory and evidence showing the conservation benefits of large reserves over small reserves for some organisms is clear, in some cases, small reserves can make a substantial and genuine contribution to conservation outcomes.

ABSTRACT Background/Question/Methods The number and size of cities and towns around the globe are rapidly expanding. There is a tremendous call for information about urban ecosystems in order to address issues related to the conservation of natural resources and the development of sustainable planning and building practices, while also providing a safe and healthy environment for humans. Historically urban ecosystems have not been the object of study by ecologists and thus there is a crucial lack of knowledge regarding the structure and dynamics of these human dominated systems. The use of a comparative approach provides urban ecologists with the ability to quickly develop a greater understanding of the structure, function and dynamics of urban ecosystems. Comparative studies involve the systematic assessment of the similarities and differences between entities or systems. They are a valued and well tested method of developing new understandings in a diversity of disciplines and have been successfully used in ecological and sociological research. To effectively elucidate the multiple dimensions of urban ecosystems and create sustainable cities in the future, urban ecologists need to develop comprehensive ecological and sociological knowledge bases for cities with a range of sizes, developmental histories and at local, regional and global scales. Such knowledge bases can provide important generalities or principles about the relationships between the structure, function and dynamics of urban ecosystems. By making these relationships clear we can progress the study of urban ecology from correlative relationships to the development of a more mechanistic understanding of cities and towns. Results/Conclusions We examined the methods used by urban ecologists to study urban ecosystems over the past 20 years, and assessed their potential contribution to comparative analyses. Case studies that provide a contextual reference offered opportunities for productive meta-analyses. One of the major challenges to successful comparative studies is the identification of standardised, quantitative measures for classifying both the independent (predictor) and dependent (response) variables for meta-analyses and new empirical studies. Comparative ecology allows us to expand our questions beyond the scope of an individual city and begin to ask whether specific ecological patterns and processes are common to most cities. When there are exceptions, a comparative approach also allows us to investigate what social, biophysical or climatic factors are moderating the response. To begin drawing generalisations from urban ecological research, it is imperative that we begin placing a greater research attention on the opportunities that are offered by a comparative ecology approach.

Urbanisation can cause local and sometimes global extinction of plant species. Using a plant functional trait approach may help to distinguish species that persist in urban areas from those that have become extinct. We analyzed historical and recent survey data from 11 cities ...

Background/Question/Methods The number and size of cities and towns around the globe are rapidly expanding. There is a tremendous call for information about urban ecosystems in order to address issues related to the conservation of natural resources and the development of sustainable planning and building practices, while also providing a safe and healthy environment for humans. Historically urban ecosystems have not been the object of study by ecologists and thus there is a crucial lack of knowledge regarding the structure and dynamics of these human dominated systems. The use of a comparative approach provides urban ecologists with the ability to quickly develop a greater understanding of the structure, function and dynamics of urban ecosystems. Comparative studies involve the systematic assessment of the similarities and differences between entities or systems. They are a valued and well tested method of developing new understandings in a diversity of disciplines and have been su...

ABSTRACT Ordóñez, C., (2012). Adapting urban forests to climate change. Proceedings of Canadian Urban Forest Conference 10 (CUFC 10) (National), 2nd-5th October, 2012, London, ON, Canada (published online: http://treecanada.ca/en/resources/publications/cufc10-london-october-2-4-2012/)

There is a need to establish permanent vegetation plots to study vegetation dynamics in urban and suburban landscapes. The construction and installation of a simple and inexpensive below-ground marker suitable for areas with high levels of human activity are described. These markers have been used effectively over the past decade to establish permanent plots in forests in New York City.

ABSTRACT Introduction: Over the past 20 years the study of urban ecology has made great progress. Our understanding of urban ecosystems and their influence on ecological patterns and processes is advancing to where we can begin to formulate some generalities. Many of these advances in understanding have been due to comparative studies at a local scale, such as those using a gradient approach within a metropolitan area. However, very few of the studies to date have taken a regional or global comparative approach, and therefore, many remain as little more than case studies. Comparative research between urban areas will allow us to test the applicability of these findings and generalities in cities with different social, historical and environmental contexts. They can also identify new research questions and help focus research on important components of urban ecosystems that require further attention (McDonnell and Hahs, Chapter 5; Lehvävirta and Kotze, Chapter 31). The aim of this book, and the workshops leading up to it, was to begin a dialogue on the value (i.e. opportunities and challenges) of comparative studies in advancing our knowledge of ecology in cities and towns, and how we might begin to foster a larger number of regional and global comparative studies. Therefore, this book should be seen as an exploration of the work that has been done so far, and a discussion about how we might move our science forward.

The growth of cities and towns together with the associated increase in their ecological ‘footprint’ is one of the most serious ecological problems facing the world today. The increase in the number of people living in cities and towns, coupled with the magnitude and intensity of human activities, has resulted in what Likens (1991) refers to as human-accelerated environmental change. This includes changes in land use, toxification of the biosphere, invasion of exotic species and loss of biotic diversity. These changes are most evident in major cities, but significant changes are also occurring in peri-urban areas, in small towns and especially in coastal settlements. The rate of change associated with the expansion and creation of cities and towns is particularly high in developing countries (Lee, 2007). Human-accelerated environmental change is occurring at small and large spatial scales throughout the world, but the true magnitude of the impact of these changes is difficult to envisage because of uncertainties in the predicted effects of global climate change (IPCC, 2001). We face many challenges and potential conflicts if we are to manage current day-to-day problems and attempt the bigger task of creating sustainable cities and towns in the future. Although cities and towns are dominated by humanbuilt structures and activities (buildings, vehicles, impermeable surfaces, parks,

... Titre du document / Document title. Spatial heterogeneity during succession : a cyclic model of invasion and exclusion Auteur(s) / Author(s). ARMESTO JJ ; PICKETT STA ; MCDONNELL MJ ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). Univ. Chile, fac. cienc., lab. ...

culture Figure 7.2. Conceptual model~xtended version. Note: The term "biosphere" in this diagram refers to all aspects of the biosphere other than those incorporated under the general heading "human society." In reality, of course, humans and their artifacts are all part of the

Urbanization contributes to the loss of the world's biodiversity and the homogenization of its biota. However, comparative studies of urban biodiversity leading to robust generalities of the status and drivers of biodiversity in cities at the global scale are lacking. Here, we compiled the largest global dataset to date of two diverse taxa in cities: birds (54 cities) and plants (110 cities). We found that the majority of urban bird and plant species are native in the world's cities. Few plants and birds are cosmopolitan, the most common being Columba livia and Poa annua . The density of bird and plant species (the number of species per km 2 ) has declined substantially: only 8% of native bird and 25% of native plant species are currently present compared with estimates of non-urban density of species. The current density of species in cities and the loss in density of species was best explained by anthropogenic features (landcover, city age) rather than by non-anthropogenic...