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Urban biodiversity: is there such a thing?

Le courrier du CNRS, n° 82, 1996, pp.102-104.
Philippe Clergeau

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1In recent years, landscapes have undergone profound transformations - the destruction of natural habitats, fragmentation, increased uniformity due to intensive agriculture, urban sprawls, etc. - which have had a strong impact on plant and animal life and on biological systems. Species able to live only in one type of habitat, or to survive only on one type of food are gradually disappearing, whereas others, more adaptable, are breeding at a fast pace. Although the decline of biological diversity seemed at first to concern mainly areas of urban growth or intensive farming, research recently carried out in urban environments (generally based on the study of birds, considered good bioindicators), has shown that on the contrary, cities show a complex biological gradient and rare species may even be found in them. Certain neighbourhoods are even more biologically diverse than some rural areas, and species threatened elsewhere often find refuge in cities. Cities also attract animals which are capable of using what humans, directly or indirectly, produce: they nest or rest on buildings, feed on waste and lawns, etc. Other than pigeons, rats or cockroaches, familiar and long-time urban residents, certain bird species such as gulls or starlings are now settling down in cities, to sleep or even to breed. Two issues may be addressed through the study of these birds. First, that of ecological studies applied to a heterogeneous environment, in other words the study of the relationship between population dynamics and landscape structures; and secondly, the environmental issue of space and species “control”:

A feathered invasion

2Our first research findings on the night-time behaviour of starlings in Brittany can be divided into two categories.

3First, it has been observed that over the past twenty years, starlings have changed their habits: because of landscape transformations, they now prefer to alight on coniferous trees rather than on reeds as they used to. They also tend to converge on fallow lands located in suburban outskirts, usually on land about to be built up. Urban growth generates fallow land on the outskirts of cities and as such, it influences the starlings' choice of sleeping grounds. Landscape transformation is a key factor: for starlings, sleeping on the outskirts of a city may be preliminary to settling down in the increasingly numerous and woody parks and gardens within the city itself. By observing their movements from city (where they sleep) to countryside (where they feed) and back, we were able to determine the geographical scale to be taken into account and we realized the importance of not separating urban and rural milieus. Our research has also shown that birds are able to breed and feed their brood in cities thanks to the many lawns which have replaced the vegetable gardens of old. The massive presence of starlings is thus fostered by the fact that urban environments are now less exclusively mineral (trees and lawns in city centres; fallow land, old trees and lawns on the outskirts).

4Secondly, urban residents tend to complain more and more frequently about starlings; the real cause of these complaints however, cannot be strictly ascribed to an increase in the presence of these birds. People tend to complain about the filth and noise and about the epidemiological risks supposedly caused by their presence, although in fact, it has been proved that starlings are not serious germ carriers and that only a very large flock can be distinctly heard against the noisy background of city life. A sociological study devoted to people living near starling sleeping grounds revealed two important factors: people tend to express their feeling of social unease by taking out their problems on birds and secondly, these become a complaint issue because of social cohesion factors (people only send in complaints through community-based organizations, groups or associations, for instance).

Of birds and men

5Our research focuses on how city-dwellers perceive biological diversity. We chose to use the perception of birds as an indicator of the relationship between man and nature. Several neighbourhoods of Rennes and Quebec were selected according to their position on an urbanization gradient (from city centre to neighbouring countryside). Our expected results will be derived from a combined analysis of spatial and human factors (history, professional status and density of population, neighbourhood structure, etc.), ecological factors (bird population, dynamic development in space and time of certain species), and sociological factors (perception of nature, perception and ability to recognize different animal species, urban policy, etc.). More specifically, our aim is to see whether city dwellers react to a greater variety of birds, what causes changes of opinion or attitude (for instance, why some people will feed a titmouse but drive away starlings) and whether density of population, buildings, green areas, or birds (either in quantity or frequency of overhead movements) can be considered a key factor for analysing these perceptions. So far, our initial results have confirmed what we already know about the relationships between fauna and habitat and highlight the different types of reactions that human beings, intruders in the natural world, may have towards birds, intruders in the city.

Has the relationship between man and nature really changed?

6Doubtless, the presence of nature in cities is both necessary and desired, as shown by the popularity of the term “urban ecology”, which has yet to be defined. We are not speaking here of a nature made to be clean and artificial, as in the hygienist tradition, but of a “wild” nature, whereby biodiversity becomes an avowed goal of urban management; this is precisely what the cities of Rennes and Orléans are now working on. Their efforts seem successful since the diversity of species in these cities has considerably increased. However, the proliferation of undesirable species has caused much discontent. In fact, the fear of nature, a well-known human feeling, seems to be resurfacing. People will not tolerate what they consider to be the threatening or offending presence of nature. Brambles and nettles, crows and starlings, wasps or ants are not welcome in man's environment, and even less so in such an entirely man-made habitat as the city. According to this interpretation, the opposition between nature (seen as wild, non-social) and city (seen as artificial and social) would seem to be a fact of life.

7A solution to the conflict between the “wish for nature” and the “fear of the wild” can be found in the control of “nature” in cities. Urban dwellers will tolerate nature only if they can control it and if it is relatively clean, in other words if it is not wild. The situation with starlings illustrates this attitude: after the above-mentioned results were made public, fallow lands, which as it is have negative connotations, were immediately done away with. As a result, we have encountered difficulties in promoting our proposal to drive the birds away from the city centre towards certain isolated fallow lands.

8The question we are now faced with is whether encouraging greater biological diversity in cities actually makes any sense. There is a risk that certain “good” species will be favoured while others will be repressed. However, the implications of this issue reach far beyond the question of this or that species: what we must look at are the overall ecological processes underlying the transformation of our landscape. Understanding and preserving biodiversity means taking into account the spatial organization of different types of habitat which include both urban areas and surrounding countryside in one entity. This scope of analysis can also be simultaneously applied to the control of species (whether threatened or threatening) and the organization of space (for instance, should green areas be dispersed or connected to the countryside through green corridors ?)

9Lastly, most human beings live and will go on living in cities; for this reason, environmental planning and more specifically the question of urban fauna are strongly influenced by urban residents' perceptions of nature. Developing urban biological diversity could thus include programmes aimed at increasing contacts between man and “wild” species.

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Clergeau P. (dir.), De nouveaux oiseaux dans la ville ? Colonisation des zones urbaines par les étourneaux, Rapport du Programme “Ecologie Urbaine”, Services de la recherche, Ministère de l'équipement et Ministère de l'environnement, 1995.

Clergeau P., “Importance of multiple scale analysis for understanding distribution and for management of an agricultural bird pest”, Landscape and Urban Planing, 31, 281-289, 1995.

Micoud A., “Vers un nouvel animal sauvage ?”, Natures-Sciences-Sociétés, 1,  202-210, 1993.

Terrasson F., La peur de la Nature, Paris, Éditions Sang de la Terre, 1991.

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Electronic reference

Philippe Clergeau, « Urban biodiversity: is there such a thing? », Cybergeo : European Journal of Geography [Online], Topics, Online since 12 April 1996, connection on 08 July 2020. URL : ; DOI :

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About the author

Philippe Clergeau

IngénieurINRA, chercheur à l'unité Fonctionnement des écosystèmes et biologie de la conservation (URA 1853 CNRS), Université Rennes I, avenue du Général Leclerc, 35042 Rennes Cedex.

By this author

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