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An Uncertain Future for Soil Carbon
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Predictions of how rapidly the large amounts of carbon stored as soil organic matter will respond to warming
are highly uncertain (1). Organic matter plays a key role in determining the physical and chemical properties of soils and is a major reservoir for plant nutrients. Understanding how fast organic matter in soils can be built up and lost is thus critical not just for its net effect on the atmospheric CO2 concentration but for
sustaining other soil functions, such as soil fertility, on which societies and ecosystems rely. Recent analytic advances are rapidly improving our understanding of the complex and interacting factors that control the age
and form of organic matter in soils, but the processes that destabilize organic matter in response to disturbances (such as warming or land use change) are poorly understood
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Carbon Storage with Benefits
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Biochar—a material related to charcoal—has the potential to benefit farming as well as mitigate climate change.
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A-maize-ing Diversity
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Analysis of a new maize resource reveals that a large number of genetic loci with small effects may underlie the wide variation seen in traits such as flowering time.
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A Measurable Planetary Boundary for the Biosphere
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Terrestrial net primary (plant) production provides a measurable boundary for human consumption of Earth’s biological resources.
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Approaching the Limits: A book review in Science
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Excerpts: "In Harvesting the Biosphere, Vaclav Smil traces the historical development of human consumption of biological resources and evaluates whether we could be approaching important global limits. Smil (an economist at the University of Manitoba) has written several books on global energy and other resource issues; here, he focuses on human consumption of the plant and animal life and whether current trends are sustainable." And "Full of recent references and statistics, Harvesting the Biosphere adds to the growing chorus of warnings about the current trajectory of human activity on a finite planet, of which climate change is only one dimension. One can quibble with some assumptions or tweak Smil’s calculations, but the bottom line will not change, only the time it may take humanity to reach a crisis point. Systems ecology teaches that the human population and consumption trajectories need a stronger feedback control than currently exists. Either we are smart enough to craft that feedback mechanism ourselves, or the Earth system will ultimately provide it."
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Carbon Mitigation by Biofuels or by Saving and Restoring Forests?
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The carbon sequestered by restoring forests is greater than the emissions avoided by the use of the liquid biofuels.
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Accounting for Environmental Assets
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A country can cut down its forests, erode its soils, pollute its aquifers and hunt its wildlife and fisheries to extinction, but its measured income is not affected as these assets disappear. Impoverishment is taken for progress
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Can a collapse of global civilization be avoided?
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Environmental problems have contributed to numerous collapses of civilizations in the past. ... But today, for the first time, humanity’s global civilization—the worldwide,increasingly interconnected, highly technological society in which we all are to one degree or another, embedded—is threatened with collapse by an array of
environmental problems. Humankind finds itself engaged in what Prince Charles described as ‘an act of suicide on a grand scale’ [4], facing what the UK’s Chief Scientific Advisor John Beddington called a ‘perfect storm’ of environmental problems [5]. The most serious of these problems show signsof rapidly escalating severity, especially climate disruption.
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Carbon debt of Conservation Reserve Program (CRP) grasslands converted to bioenergy production
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Over 13 million ha of former cropland are enrolled in the US Conservation Reserve Program (CRP), providing well-recognized biodiversity, water quality, and carbon (C) sequestration benefits that could be lost on conversion back to agricultural production. Here we provide measurements of the greenhouse gas consequences of converting CRP land to continuous corn, corn–soybean, or perennial grass for biofuel production. No-till soybeans preceded the annual crops and created an initial carbon debt of 10.6 Mg CO2 equivalents (CO2e)·ha−1 that included agronomic inputs, changes in C stocks, altered N2O and CH4 fluxes, and foregone C sequestration less a fossil fuel offset credit. Total debt, which includes future debt created by additional changes in soil C stocks and the loss of substantial future soil C sequestration, can be constrained to 68 Mg CO2e·ha−1 if subsequent crops are under permanent no-till management. If tilled, however, total debt triples to 222 Mg CO2e·ha−1 on account of further soil C loss. Projected C debt repayment periods under no-till management range from 29 to 40 y for corn– soybean and continuous corn, respectively. Under conventional tillage repayment periods are three times longer, from 89 to 123 y, respectively. Alternatively, the direct use of existing CRP grasslands for cellulosic feedstock production would avoid C debt entirely and provide modest climate change mitigation immediately. Incentives for permanent no till and especially permission to harvest CRP biomass for cellulosic biofuel would help to blunt the climate impact of future CRP conversion.
land-use change | renewable energy | carbon balance | agriculture | nitrous oxide
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A safe operating space for humanity
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Identifying and quantifying planetary boundaries that must not be transgressed could help prevent human activities from causing unacceptable environmental change, argue Johan RockstrÖm and colleagues.
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