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GEO for World DesertsChapter 1 proposal

Global atmospheric circulation and the distribution of deserts

Ocean upwellings and westerly coastal deserts

Rain-shadow deserts

Pleistocene glaciations and desert biodiversity

Deserts and Pleistocene Relicts

Fragility 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 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

May 1998

September 2003

trackersaveragersenvironmental pulses

Deserts 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 79 thousand years ago.

Deserts and agricultureSimilarly, in the American Continent the first agricultural records come from the Tehuacn 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 ecolgica del uso del agua en cuencasde riego del norte de MxicoCultivo de maz: 2.5 m3/kg grano cosechadoCultivo de alfalfa: 1.6 m3/kg forraje cosechadoCarne de vacuno: 31 m3/kg de carne

Conversin de eficiencia ecolgica a eficiencia energtica del uso del aguaa.- 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 acufero de 100 metros de profundidad, consume aprox. 1 MJoule.c.- Un MJoule es igual a 0.28 kW-h, y es igual a la energa calrica contenida en 0.046 L de gasolina.d.- Considerando la friccin en las tuberas y la ineficiencia energtica 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 energtica del uso del agua en cuencasde riego del norte de MxicoCultivo de maz: 7.4 106 Joule/kg cosechado(aprox. 0.34 L gasolina/kg maz)

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 lmites de la desalinizacin del agua de marPresin osmtica del agua de mar: 2.75 MPaTrabajo terico para desalinizar 1 m3: 2.75 MJTrabajo real para desalinizar 1 m3: 27 MJ = 7.5 kW-h

Coastal ecosystems as water users

Chapter 1: Ecology and evolution of the worlds deserts

a. Global distribution of desertsThe desert biome, general climatic and geographic conditionsLatitudinal desert beltsThe effect of coastal upwellings on desert evolutionRain-shadows and tropical arid zones

Chapter 1: Ecology and evolution of the worlds deserts

b. Evolution, history and biogeographyGlacial periods and the evolution of desert biotaThe expansion of deserts during the HoloceneMountain sky-islands and Pleistocene relictsThe evolution and development of pastoralism

Chapter 1: Ecology and evolution of the worlds deserts

c. Biological adaptation to aridityCycles of abundance and scarcityLife-forms and adaptations of plants and animals to ariditySpecies interactions: pollinators, seed dispersers, facilitationDeserts and agriculture

Chapter 1: Ecology and evolution of the worlds deserts

d. Global environmental dynamics and desert ecosystemsOcean/atmospheric/land coupling phenomenaLong-term cycles; El Nio anomaliesDesert dust in the global atmosphere and its consequencesDesertification, albedo changes, and global change