[1
]The Mitrani Department of Desert Ecology; Swiss Institute for Dryland Energy and Environmental
Research; Blaustein Institutes for Desert Research; Ben-Gurion University; Sde Boqer
Campus Israel
[2
]Department of Environmental Science Policy & Management; University of California;
Berkeley California 94720 USA
[3
]Institute of Mathematics; Hebrew University of Jerusalem; Givat Ram., Jerusalem 9190401
Israel
[4
]Department of Ecology, Evolution and Behavior; Hebrew University of Jerusalem; Givat
Ram., Jerusalem 9190401 Israel
[5
]School of Mathematical Sciences; University of KwaZulu-Natal; PB X54001 Durban 4000
South Africa