Biotic effects of climate change in urban environments: The case of the grey-headed flying-fox (Pteropus poliocephalus) in Melbourne, Australia

doi:10.1016/j.biocon.2005.01.035

Biological Conservation

Volume 124, Issue 2, July 2005, Pages 267-276

https://doi.org/10.1016/j.biocon.2005.01.035 Get rights and content

Abstract

Urban climates are known to differ from those of the surrounding rural areas, as human activities in cities lead to changes in temperature, humidity and wind regimes. These changes can in turn affect the geographic distribution of species, the behaviour of animals and the phenology of plants. The grey-headed flying-fox (Pteropus poliocephalus) is a large, nomadic bat from eastern Australia that roosts in large colonies known as camps. Historically a warm temperate to tropical species, P. poliocephalus recently established a year-round camp in the Royal Botanic Gardens Melbourne. Using a bioclimatic analysis, we demonstrated that on the basis of long-term data, Melbourne does not fall within the climatic range of other P. poliocephalus camp sites in Australia. Melbourne is drier than other summer camps, and cooler and drier than other winter camps. The city also receives less radiation, in winter and annually, than the other summer and winter camps of P. poliocephalus. However, we found that temperatures in central Melbourne have been increasing since the 1950s, leading to warmer conditions and a reduction in the number of frosts. In addition, artificial watering of parks and gardens in the city may contribute the equivalent of 590 mm (95% CI: 450–720 mm) of extra rainfall per year. It appears that human activities have increased temperatures and effective precipitation in central Melbourne, creating a more suitable climate for camps of the grey-headed flying-fox. As demonstrated by this example, anthropogenic climate change is likely to complicate further the task of conserving biological diversity in urban environments.

Introduction

The construction of cities and the daily activities of their human inhabitants can have pronounced effects on the local climate. For example, the urban heat island effect (Manley, 1958) was first documented in the early 19th century by Howard (1833) following his observations that overnight minimum temperatures in central London were higher than in the surrounding countryside. The maximum difference in temperature between a large city and the surrounding rural area can be as much as 12 °C on calm, clear nights when the urban heat island effect is most pronounced (Oke, 1979, Landsberg, 1981). Urban environments can also have their own wind fields, increased cloudiness and rainfall, and enhanced thunderstorm activity (Landsberg, 1981, Bridgman et al., 1995, Changnon, 2001, Liu et al., 2002).

Climate change in urban areas is likely to affect the habitat available for plant and animal species, both indigenous and introduced. It may also lead to changes in the behavioural patterns of animals and the phenology of plants. For example, climatic warming resulting from extensive urban development near Basel, Switzerland is implicated in the local extinction of eight populations of the land snail Arianta arbustorum (Baur and Baur, 1993). The hatching success of the snail’s eggs decreases with exposure to temperatures of 22 °C and above, demonstrating one mechanism by which elevated urban temperatures can affect the distribution of species. In the early 1980s, magnolias bloomed two weeks earlier in central Washington, DC than in the surrounding suburbs (Landsberg, 1981), while plants as diverse as snowdrops and apple trees generally flower earlier in urban than in rural areas of central Europe (Roetzer et al., 2000).

The grey-headed flying-fox (Pteropus poliocephalus), historically a warm temperate to tropical species, established a regular camp (colonial roost) at the Royal Botanic Gardens Melbourne in 1981 (Menkhorst and Dixon, 1985). Prior to this, the species was only an occasional visitor to Melbourne. The camp in the Fern Gully at the Gardens was apparently occupied year-round between December 1985 and March 2003 (Aston, 1987, Menkhorst, 1995), and represented the southernmost camp of any flying-fox species in the world (Tidemann, 1999). In this paper, we investigate: (a) whether Melbourne falls within the climatic range of camp sites of P. poliocephalus on the basis of long-term data; and (b) whether Melbourne has moved into the climatic range of the species as a result of urban development and human activities in the city. We discuss the implications of our study for the conservation of indigenous flora and fauna in urban environments.

Section snippets

Pteropus poliocephalus

Flying-foxes (Megachiroptera: Pteropodidae) are large bats that feed on fruit, nectar, pollen and other plant products, and navigate by sight rather than echolocation. P. poliocephalus is one of eight species of flying-fox known from Australia (Hall and Richards, 2000). It is listed as Threatened in Victoria, and Vulnerable in New South Wales and nationally (New South Wales Threatened Species Conservation Act 1995; Victoria Flora and Fauna Guarantee Act 1988; Environment Protection and

Bioclimatic analysis of camp sites

The BIOCLIM analysis of long-term climate data indicated that Melbourne is outside the climatic range of the other summer and winter camps of P. poliocephalus (Fig. 1(b) and (c)). Compared to the other summer camps, Melbourne is drier on an annual basis and receives less radiation per year and during the coldest quarter (Table 1). In the climatic space defined by the mean annual temperature and annual precipitation at the summer camps (Fig. 2(a)), Melbourne is at the cooler, drier end of the

Climate change in Melbourne and climatic suitability for P. poliocephalus

The warming trend observed in Melbourne since the 1950s is likely to be the result of both a general warming trend observed across Australia (Torok and Nicholls, 1996) and an increase in the urban heat island effect with Melbourne’s increasing population (Torok et al., 2001, Lenten and Moosa, 2003). Using data from 149 weather stations located outside urban centres (i.e., towns with a population greater than 10,000), Torok and Nicholls (1996) calculated an upward trend in Australian-average

Acknowledgements

We are very grateful to John Nelson and Patrina Birt for providing information on the location of flying-fox camps, Janet Stein, Jane Elith and Jenny Kestevens for their assistance with BIOCLIM, and Jeannie Campbell for gathering elevation data for the flying-fox camps. We thank Tim Forster from the Bureau of Meteorology for providing weather data for the Melbourne Regional Office and Peter Symes for providing data on irrigation at the Royal Botanic Gardens Melbourne. The following people

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Biotic effects of climate change in urban environments: The case of the grey-headed flying-fox (Pteropus poliocephalus) in Melbourne, Australia

Abstract

Introduction

Section snippets

Pteropus poliocephalus

Bioclimatic analysis of camp sites

Climate change in Melbourne and climatic suitability for P. poliocephalus

Acknowledgements

Trends in Ecology and Evolution

Environmental Modelling and Software

Biological Conservation

Biological Conservation

Australian rainforests

Influx of the grey-headed flying fox Pteropus poliocephalus (Chiroptera, Pteropodidae) to the Melbourne area, Victoria, in 1986

Victorian Naturalist

Body temperature, oxygen consumption, and heart rate in three species of Australian flying foxes

Physiological Zoology

Climatic warming due to thermal-radiation from an urban area as possible cause for the local extinction of a land snail

Journal of Applied Ecology

Urban biophysical environments

BIOCLIM – a bioclimate analysis and prediction system

Flight physiology of flying foxes, Pteropus poliocephalus

Journal of Experimental Biology

Remnant Bushland of South East Queensland in the 1990s: its distribution, loss, ecological consequences, and future prospects

Assessment of historical thunderstorm data for urban effects: the Chicago case

Climatic Change

The Australian weather book

Pest, or passenger pigeon? The New South Wales Scientific Committee’s assessment of the status of the grey-headed flying-fox

Threatening processes and conservation priorities

Seasonal movements of grey-headed flying foxes, Pteropus poliocephalus (Chiroptera: Pteropodidae), from two maternity camps in northern New South Wales

Wildlife Research

The biology and management of flying foxes in New South Wales

Managing the grey-headed flying-fox Pteropus poliocephalus as a threatened species: a context for the debate

Managing the grey-headed flying-fox Pteropus poliocephalus as a threatened species in New South Wales: adjusting to a long-term vision

The distribution, abundance and vulnerability to population reduction of a nomadic nectarivore, the grey-headed flying-fox Pteropus poliocephalus in New South Wales, during a period of resource concentration

Australian Zoologist

The status of rainforests in northern New South Wales

Flying foxes: fruit and blossom bats of Australia