(click to start)

GEO for World Deserts Chapter 1 proposal

Global atmospheric circulation and the distribution of deserts

Ocean upwellings and westerly coastal deserts

California current Coriolis deflection upwelling Tidal flow upwelling tidal mixing

Rain-shadow deserts

Pleistocene glaciations and desert biodiversity

Deserts and Pleistocene Relicts

Fragility of World Deserts In spite of their apparent barrenness, the deserts of the world harbor unique and rare biotas with impressive biological adaptations. The fragmented evolutionary history of the deserts of the world has been the driving force of their biological rarity, of adaptation to local conditions, of specialization to isolated environments. As a result of evolution in isolation from each other, the worlds deserts have high levels of endemism and harbour rare and unique life forms, a fact that makes them ecologically fragile and highly vulnerable to biological extinction.

Cycles, anomalies, and teleconnections

The nurse-plant cycle

periods of extraordinary rainfall SOI Anomaly (°C) a b

r = SOI rainfall anomaly (mm) El Niño conditions La Niña conditions

May 1998

September 2003

time trackers averagers time moisture environmental pulses

Deserts and agriculture Because desert ephemerals grow fast and produce abundant seed in just a few weeks, it comes as no surprise that the earliest archaeological records of agriculture come from dryland regions and that the first domesticated crops evolved from desert annuals. Indeed, the first records of cultivated wheat and barley (two desert ephemerals) come from the Fertile Crescent of the Middle-East some 7–9 thousand years ago.

Deserts and agriculture Similarly, in the American Continent the first agricultural records come from the Tehuacán Valley in southern Mexico, a hot rain-shadow tropical desert where corn, amaranth and squash (all annual, drought-tolerant, fast growers) were first domesticated some 6 thousand years ago. To a large extent, deserts have been the cradle of agriculture.

Deserts and water use

Eficiencia ecológica del uso del agua en cuencas de riego del norte de México Cultivo de maíz: 2.5 m 3 /kg grano cosechado Cultivo de alfalfa: 1.6 m 3 /kg forraje cosechado Carne de vacuno: 31 m 3 /kg de carne

Conversión de eficiencia ecológica a eficiencia energética del uso del agua a.- Elevar 1 L de agua una altura de 1 metro consume 9.8 Joule. b.- Por lo tanto, elevar 1 m 3 de agua desde un acuífero de 100 metros de profundidad, consume aprox. 1 MJoule. c.- Un MJoule es igual a 0.28 kW-h, y es igual a la energía calórica contenida en L de gasolina. d.- Considerando la fricción en las tuberías y la ineficiencia energética de los motores y las bombas, se necesitan aprox. 0.1 L de gasolina para elevar 1 m 3 de agua desde 100 metros de profundidad, o se deben gastar 0.28 kW-h.

Eficiencia energética del uso del agua en cuencas de riego del norte de México Cultivo de maíz: Joule/kg cosechado (aprox L gasolina/kg maíz) Cultivo de alfalfa: Joule/kg cosechado (aprox L gasolina/kg alfalfa) Carne de vacuno: Joule/kg de carne (aprox L gasolina/kg carne)

Los límites de la desalinización del agua de mar Presión osmótica del agua de mar: 2.75 MPa Trabajo teórico para desalinizar 1 m 3 : 2.75 MJ Trabajo real para desalinizar 1 m 3 : 27 MJ = 7.5 kW-h

Coastal ecosystems as water users

Chapter 1: Ecology and evolution of the worlds deserts a. Global distribution of deserts The desert biome, general climatic and geographic conditions Latitudinal desert belts The effect of coastal upwellings on desert evolution Rain-shadows and tropical arid zones

Chapter 1: Ecology and evolution of the worlds deserts b. Evolution, history and biogeography Glacial periods and the evolution of desert biota The expansion of deserts during the Holocene Mountain sky-islands and Pleistocene relicts The evolution and development of pastoralism

Chapter 1: Ecology and evolution of the worlds deserts c. Biological adaptation to aridity Cycles of abundance and scarcity Life-forms and adaptations of plants and animals to aridity Species interactions: pollinators, seed dispersers, facilitation Deserts and agriculture

Chapter 1: Ecology and evolution of the worlds deserts d. Global environmental dynamics and desert ecosystems Ocean/atmospheric/land coupling phenomena Long-term cycles; El Niño anomalies Desert dust in the global atmosphere and its consequences Desertification, albedo changes, and global change