Croplands and pastures cover about a 1/3 of the Earth’s ice free surface. Foley et al in their PNAS commentary Our share of the planetary pie illustrate the uses of this agricultural production. Their map shows the percentage of crop NPP used to produce food that humans consume directly (blue) or indirectly in processed products (orange-red). The majority of the nonfood portion is feed for livestock, but also includes fiber or luxury crops, such as cotton and coffee. Note the differences between agriculture is rich (feed for livestock) and poor countries (food).
Click on map for a larger verison.
The map is based on data from:
Monfreda, C., N. Ramankutty, and J. A. Foley (In Press), Farming the Planet. 2: The Geographic Distribution of Crop Areas, Yields, Physiological Types, and NPP in the Year 2000, Global Biogeochemical Cycles, doi:10.1029/2007GB002947.
Is the home of polar bears, seals and Inuit communities already doomed? asks Jon Foley in Tipping Points in the Tundra a recent commentary Science. According to him, several recent sources of evidence show that feedback mechanisms seem to be kicking into high gear as the Arctic warms up. Temperature data illustrate, for example, that from the 1960’s to the 1980’s, the Arctic warmed by 0.15 degrees Celsius per decade, but since then the warming has been nearly 0.3 to 0.4 degrees per decade.
Recent evidence comes from Terry Chapin and his co-workers who have analyzed Arctic data on surface temperature, cloud cover, energy exchange, albedo, and changes in snow cover and vegetation. They concluded that the recent changes in the length of the snow-free season have triggered a set of interlinked feedbacks that will amplify future rates of summer warming. One of these feedbacks relate to that the snowmelt has advanced by around 2.5 days per decade which has lead to an increase in the amount of energy that is absorbed and transferred to the atmosphere. The resulting regional increase in temperature is estimated to be comparable (per unit area) to the global atmospheric heating that is projected from a doubling of CO2 levels in the atmosphere.
Chapin et al. also analyses the role of vegetation change for triggering positive feedbacks. Tall shrublands have increased rapidly in the surrounding region of the Arctic. Tree lines have also moved further north. Although the estimated contributions these have on warming were found to be small, the authors expect that they will continue to increase disproportionally in the future.
Continue reading ‘Is the Arctic Already Lost?’