Book of Abstracts

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life cycle of the built facility. Integrative design processes ensure taking into account seismic aspects together with
other matters of sustainability in order to make sure the building will not only be functional and energy efficient but
also will be able to structurally survive in the event of an earthquake.
For example, architectural decisions dealing with the geometry of the building and the location of different elements
in the plan have a significant impact not only on the building's routine functionality and aesthetics, but also on its
stiffness and dynamic response in the event of a major earthquake at some point in the future. From an energetic
perspective, a seismically resistant configuration may encourage structural solutions which rely, for example, on less
reinforcing steel and as a result may reduce the initial energy embodied in the building’s production – with the
economic and environmental implications of that energy consumption manifest over an extended time frame.
The aim of this study is to examine barriers to the integrated design of resilient buildings by looking at incentives
and disincentives for non-linear co-design processes along the extended building supply chain. The study will use a
novel research approach employing the Delphi technique, a systematic, interactive forecasting method which relies
on panels of experts to identify potential and actualized relationships among industry actors.
Desertification as Catastrophic Regime Shift: Empirical and
Mathematical Aspects
Desertification is commonly viewed as a dynamical transition from a productive stable state to an
alternative less productive stable state. The transition can be induced by an environmental change or by a
disturbance, and becomes feasible near an instability point of the productive state. The session will
address mathematical aspects of such transitions, taking into account the possibility of the productive
state being spatially patchy. Questions to be addressed include mechanisms of desertification, warning
signals for imminent desertification and restoration of decertified areas. The session will also address
field observations of vegetation patterns and pattern dynamics, and attempt confronting model predictions
with empirical data.
Desertification as a gradual regime shift in spatially extended ecosystems
Golan Bel, Hezi Izhaq, Aric Hagberg and Ehud Meron; Department of Solar Energy; Ben-Gurion University of the
Negev; Sede Boqer Campus, Israel; bei@bgu.ac.il
Ecosystem regime shifts are conceived as abrupt global transitions from one stable state to an alternative stable state,
induced by slow environmental changes. Spatially extended ecosystems, however, can also respond to local
disturbances by the nucleation of small domains of the alternative state. Such a response can lead to gradual regime
shifts involving front propagation and coalescence of alternative-state domains. When one of the states is spatially
patterned, a multitude of intermediate stable states appears, ranging from holes in periodic patterns to localized
states, giving rise to step-like gradual shifts. Vegetation dynamics in drylands is a spatially extended ecosystem that
exhibits a bi-stability of patterned and uniform states. We demonstrate the existence of localized states in a
vegetation model that captures two pattern-forming feedbacks, one associated with infiltration contrast between
vegetated areas and bare soil and the other with root-shoot relationships. We further evaluate numerically a
bifurcation diagram that shows the forms of the localized solution branches. It is shown that under certain climatic
conditions, gradual regime shifts involving intermediate localized states, may take place. In addition, the effects of
the two feedbacks on the bifurcation diagram and, hence, on the nature of the regime shifts are studied. We show
that the larger the root-shoot feedback, the more gradual is the degradation of the vegetation and the more abrupt is
the recovery of the vegetation from localized states into a patterned state. We propose indicators to probe gradual
regime shifts and suggest that a combination of abrupt-shift indicators and gradual-shift indicators might be needed
to unambiguously identify regime shifts. Our results are particularly relevant to desertification in drylands where
transitions to bare soil take place from spotted vegetation, and the degradation process appears to involve step-like
events of local vegetation mortality caused by repeated droughts.