How simple grazing rules can lead to persistent boundaries in vegetation communities.

Natural landscape boundaries between vegetation communities are dynamically influenced by the selective grazing of herbivores. Here we show how this may be an emergent property of very simple animal decisions, without the need for any sophisticated choice rules etc., using a model based on biased diffusion. Animal grazing intensity is coupled with plant competition, resulting in reaction-diffusion dynamics, from which stable boundaries spontaneously emerge. In the model, animals affect their resources by both consumption and trampling. It is assumed that forage consists of two heterogeneously distributed competing resource species, one that is preferred (grass) over the other (heather) by the animals. The solutions to the resulting system of differential equations for three cases a) optimal foraging, b) random walk foraging and c) taxis-diffusion are presented. Optimal and random foraging gave unrealistic results, but taxis-diffusion accorded well with field observations. Persistent boundaries between patches of near-monoculture vegetation were predicted, with these boundaries drifting in response to overall grazing pressure (grass advancing with increased grazing and vice versa). The reaction-taxis-diffusion model provides the first mathematical explanation for such vegetation mosaic dynamics and the parameters of the model are open to experimental testing.

The State, Compartmentalization and the Turn to Local Community: A Critique of the Political Thought of Alasdair MacIntyre

Alasdair MacIntyre condemns modern politics, specifically liberalism and the institutions of the liberal state, as irredeemably fallen. His core argument is that the liberal state encourages a disempowering ‘compartmentalization’ of people’s everyday roles and activities that undermines the intersubjective conditions of human flourishing. MacIntyre’s alternative is an Aristotelian politics centred on the notion of “practice.” Defined by justice and solidarity, this politics can only be realized, he claims, within local communities which oppose and resist the dictates of the administrative state and capitalist market. Here it is argued that MacIntyre’s notion of “practice” represents a compelling ethical-political ideal. However, the belief that this ideal is best realized within local communities is rejected. In privileging local community, MacIntyre relies on a reductive view of modern states and overlooks the institutional conditions of a just polity. Against this, it is argued that a politics of human flourishing cannot succeed without an emancipatory transformation of large-scale, trans-communal institutions, in particular the state.

Cities of God? Medieval urban forms and their Christian Symbolism

Situated in the context of recent geographical engagements with 'landscape', this paper combines 'morphological' and 'iconographic' landscape interpretations to examine how urban forms were perceived in late medieval Europe. To date, morphological studies have mapped the medieval city either by classifying urban layouts according to particular types, or by analysing plan forms of particular towns and cities to reveal their spatial evolution. This paper outlines a third way, an 'iconographic' approach, which shows how urban forms in the Middle Ages conveyed Christian symbolism. Three such 'mappings' explore this thesis: the first uses textual and visual representations which show that the city was understood as a scaled-down world â?? a microcosm â?? linking city and cosmos in the medieval mind; the second 'mapping' develops this theme further and suggests that urban landscapes were inscribed with symbolic form through their layout on the ground; while the third looks at how Christian symbolism of urban forms was performed through the urban landscape in perennial religious processions. Each of these 'mappings' points to the symbolic, mystical significance urban form had in the Middle Ages, based on religious faith, and they thus offer a deepened appreciation of how urban landscapes were represented, constructed and experienced at the time.

Mapping cosmopolis: moral topographies of the medieval city

Cosmopolis is a concept that has a long history in many cultures around the globe. It is a mirroring of the 'social' and 'natural' worlds, such that in one is seen the order and the structures of the other -- a mutual 'mapping'. In this paper I examine how the presence of cosmopolis -- a Christianised cosmopolis of the European Middle Ages -- was made evident in the representation and formation of cities at that time. I reveal a dualism between the social and spatial ordering of both city and cosmos which defined and reinforced social and spatial boundaries in urban landscapes, evident for example in the 11th and 12th centuries. Recently, Toulmin (1992) has taken the idea of cosmopolis to argue that it has been a persistent presence in Western - Enlightenment science, philosophy, and religion -- a 'hidden agenda of modernity'. I contend that, as an idea, cosmopolis has a much earlier circulation in European thinking, not least in the Middle Ages. Locating cosmopolis in the medieval and the modern periods then begs a question of what is it that really makes the two distinct and separate? All too often human geographers have emphasised discontinuities between the 'medieval' and 'modern' age, locating the 'rise of modernity' some time in the Enlightenment period. However, what 'mapping' cosmopolis reveals are continuities, binding time and space together, which when looked at begin to help query the modernity concept itself.