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    Mongabay, a leading resource for news and perspectives on environmental and conservation issues related to the tropics, has launched Tropical Conservation Science - a new, open access academic e-journal. It will cover a wide variety of scientific and social studies on tropical ecosystems, their biodiversity and the threats posed to them. Tropical Conservation Science - March 8, 2008.

    At the 148th Meeting of the OPEC Conference, the oil exporting cartel decided to leave its production level unchanged, sending crude prices spiralling to new records (above $104). OPEC "observed that the market is well-supplied, with current commercial oil stocks standing above their five-year average. The Conference further noted, with concern, that the current price environment does not reflect market fundamentals, as crude oil prices are being strongly influenced by the weakness in the US dollar, rising inflation and significant flow of funds into the commodities market." OPEC - March 5, 2008.

    Kyushu University (Japan) is establishing what it says will be the world’s first graduate program in hydrogen energy technologies. The new master’s program for hydrogen engineering is to be offered at the university’s new Ito campus in Fukuoka Prefecture. Lectures will cover such topics as hydrogen energy and developing the fuel cells needed to convert hydrogen into heat or electricity. Of all the renewable pathways to produce hydrogen, bio-hydrogen based on the gasification of biomass is by far both the most efficient, cost-effective and cleanest. Fuel Cell Works - March 3, 2008.

    An entrepreneur in Ivory Coast has developed a project to establish a network of Miscanthus giganteus farms aimed at producing biomass for use in power generation. In a first phase, the goal is to grow the crop on 200 hectares, after which expansion will start. The project is in an advanced stage, but the entrepreneur still seeks partners and investors. The plantation is to be located in an agro-ecological zone qualified as highly suitable for the grass species. Contact us - March 3, 2008.

    A 7.1MW biomass power plant to be built on the Haiwaiian island of Kaua‘i has received approval from the local Planning Commission. The plant, owned and operated by Green Energy Hawaii, will use albizia trees, a hardy species that grows in poor soil on rainfall alone. The renewable power plant will meet 10 percent of the island's energy needs. Kauai World - February 27, 2008.

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Thursday, September 18, 2008

Plants soak up less CO2 as planet warms - reforestation or conservation to combat climate change may not work

Plants are unlikely to soak up more carbon dioxide from the air as the planet warms, new research suggests. A large team of scientists found that grassland took up less CO2 than usual for two years following temperatures that are now unusually hot, but may become common. The conclusion parallels a real-world finding from Europe's 2003 heatwave, when the continent's plant life, including forests, became a net producer, not absorber, of CO2. This latest study is published as the cover story of the current issue of Nature.

The findings make the case for the creation or maintenance of 'carbon sinks' through reforestation or conservation efforts problematic. A lot of faith is being placed in some circles in this capacity of plants to maintain absorption of CO2 as concentrations of the gas rise, or even to use the extra CO2 to grow faster and absorb more of it. It is one of the reasons behind the recent upsurge of interest in having western governments pay to protect tropical forests.

But the new research is one of a growing number of pieces of evidence (here, here, here, here and here) suggesting this will not always work. Some ecosystems might continue to absorb carbon dioxide, and perhaps increase the rate of absorption; others may react to warming by releasing the greenhouse gas and become part of the problem, not the solution. Careful studies will be needed to see whether it makes sense to use land to grow trees or grasses on it as a carbon sequestration technique.

Researchers extracted four intact segments of grassland, about 3 sq m in area and weighing about 12 tonnes each, from the prairies of Oklahoma, and placed them in special chambers at the Desert Research Institute (DRI) in Reno, Nevada. Conditions in the chambers, such as temperature, moisture and sunlight, could be precisely controlled.

Two of the four chambers were given a set of conditions mimicking what actually happens, on average, on the wild prairies. Temperatures rose and fell with days and nights and seasons, and "rainfall" was injected in a realistic pattern. The other two chambers received the same prescription with the exception that for a whole year, temperatures were always 4°C higher.

The warmer plots saw a shortfall in carbon dioxide uptake of about 30% during the warm year and the one following.
In the warm year, the temperature goes up and causes more evapotranspiration from the plants. But plants have evolved to 'know' that when it gets dry they should curb their water loss, so they reduce the apertures of their stomata [pores] to conserve water, and that constrains the amount of CO2 they can take up [by photosynthesis]. - Professor Jay Arnone, Desert Research Institute, lead author
This response has been understood for some time. But what happened in the following year, when temperatures returned to 'normal', was not so familiar. Even during the warm year with its meagre amount of photosynthesis, plants had put carbon in the soil. So during the normal year following, soil microbes had extra carbon to process, which they did, emitting more carbon dioxide into the air.

Same story in Europe

By complete coincidence, the study mimicked fairly closely events on the other side of the Atlantic. As DRI researchers were turning up the heat in 2003 in their experimental plots, in Europe it was happening for real, with temperatures in some places reaching 6°C above normal.

An analysis led by French researchers, published in 2005, showed that as the continent became hotter, Europe's plants changed from being net overall absorbers of CO2 to net producers:
:: :: :: :: :: :: :: :: :: :: ::

The consequences of these findings are wide-ranging, and particularly worrying for those who see a future in mitigating climate change by creating and conserving forests or grasslands. As the planet warms, these ecosystems may become part of the problem instead of a solution.

Different types of ecosystems will react differently to warming and elevated atmospheric CO2 levels, which is why they need targeted scrutiny.
We conducted this study under current ambient levels of CO2 so we don't know for sure what'll happen in the future. But we don't anticipate a huge effect of [elevated] CO2 on these systems. As high temperatures become more commonplace, you might expect a persistent reduction in the uptake of CO2 by natural ecosystems, and that may mean that the net rate of CO2 elevation may increase. - Professor Arnone
There is growing evidence that Northern forests are far less effective carbon sinks than tropical forests (previous post), even though some studies have suggested even tropical rainforests may become carbon emitters under warming conditions. But at least, this effect is offset by the fact that these humid forests generate clouds, which have a high albedo, reflecting sunlight back into space, and thus cooling the planet.

For grasslands, the findings have been less consistent, which is why the current study is so important: it is the first analysis showing the CO2 cycle response of grass to a warmer environment.

The large collaborative study involved scientists from the DRI; University of Nevada, Reno; University of Oklahoma in Norman, Okla.; University of New Hampshire; the National Center for Atmospheric Research in Boulder, Colo., and Rice University in Houston, Texas. The study was funded by the U.S. National Science Foundation's Division of Environmental Biology under the program, "Integrated Research Challenges in Environmental Biology".

: The grassland plots were grown in DRI's EcoCELL facility. Credit: DRI.

John A. Arnone III, et al. "Prolonged suppression of ecosystem carbon dioxide uptake after an anomalously warm year", Nature 455, 383-386 (18 September 2008) | doi:10.1038/nature07296

Biopact: Northern forests less effective carbon sinks than tropical forests - June 22, 2007

Biopact: Plant a tree and save the planet? Let's think again. - December 13, 2006

Eurekalert: Experiment suggests limitations to carbon dioxide 'tree banking' - August 7, 2007.

Eurekalert: Trees to offset the carbon footprint? - April 9, 2007.


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