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GEO for World DesertsGEO for World Deserts

Chapter 1 proposalChapter 1 proposal

Global atmospheric circulation Global atmospheric circulation and the distribution of desertsand the distribution of deserts

Ocean upwellings and westerly Ocean upwellings and westerly coastal desertscoastal deserts

California current

Coriolis deflection

upwelling

Tidal flow

upwelling

tidalmixing

Rain-shadow desertsRain-shadow deserts

Pleistocene glaciations and Pleistocene glaciations and desert biodiversitydesert biodiversity

Deserts and

Pleistocene Relicts

Fragility of World DesertsFragility of World DesertsIn 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 world’s 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 Cycles, anomalies, and teleconnectionsteleconnections

The nurse-plant cycle

periods of extraordinary rainfall

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La Niña conditions

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environmental pulses

Deserts and agricultureDeserts and agricultureBecause 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 agricultureDeserts and agricultureSimilarly, 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 useDeserts and water use

Eficiencia ecológica del uso del agua en cuencasEficiencia ecológica del uso del agua en cuencasde riego del norte de Méxicode riego del norte de México

Cultivo de maíz: 2.5 m3/kg grano cosechado

Cultivo de alfalfa: 1.6 m3/kg forraje cosechado

Carne de vacuno: 31 m3/kg de carne

Conversión de eficiencia ecológica a eficiencia energética del Conversión de eficiencia ecológica a eficiencia energética del uso del aguauso del agua

a.- Elevar 1 L de agua una altura de 1 metro consume 9.8 Joule.

b.- Por lo tanto, elevar 1 m3 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 0.046 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 m3 de agua desde 100 metros de profundidad, o se deben gastar 0.28 kW-h.

Eficiencia energética del uso del agua en cuencasEficiencia energética del uso del agua en cuencasde riego del norte de Méxicode riego del norte de México

Cultivo de maíz: 7.4 106 Joule/kg cosechado(aprox. 0.34 L gasolina/kg maíz)

Cultivo de alfalfa: 4.6 106 Joule/kg cosechado(aprox. 0.21 L gasolina/kg alfalfa)

Carne de vacuno: 91.9 106 Joule/kg de carne(aprox. 4.21 L gasolina/kg carne)

Los lLos líímites de la desalinización del agua de marmites de la desalinización del agua de mar

Presión osmótica del agua de mar: 2.75 MPa

Trabajo teórico para desalinizar 1 m3: 2.75 MJ

Trabajo real para desalinizar 1 m3: 27 MJ = 7.5 kW-h

Coastal ecosystems as water users

Chapter 1: Ecology and evolution of the Chapter 1: Ecology and evolution of the world’s desertsworld’s 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 Chapter 1: Ecology and evolution of the world’s desertsworld’s 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 Chapter 1: Ecology and evolution of the world’s desertsworld’s 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 Chapter 1: Ecology and evolution of the world’s desertsworld’s 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