Water Costs of Afforestation Agric

research highlights FOREST CARBON analysed geoengineering reporting in news waters around Antarctica — influence the Forest disturbance articles, but little experimental investigation response of sea surface temperatures, and Glob. Change Biol. http://doi.org/s6x (2014) about the effect of different frames on public therefore atmospheric temperature, to views has been carried out so far. greenhouse gas and other forcings. Although It is clear that deforestation leads to the Adam Corner and Nick Pidgeon of the two regions are subjected to similar release of carbon stored in tropical forests Cardiff University, UK, have filled this gap greenhouse gas forcing, the Antarctic is also and a great deal of work has been done to with an online experiment, using 412 UK experiencing ozone depletion. estimate how much carbon is emitted as a participants recruited during early 2013. They conclude that at present the cooling result. The carbon implications of forest Participants read a different description of the Antarctic is associated with effects degradation from human disturbances, of geoengineering. In the experimental related to ozone depletion in the region, such as selective logging, understorey condition, the description was ‘framed’ using which is cancelling the warming due to fires and forest fragmentation, remain an analogy to natural processes (for example greenhouse gases. They suggest that this is less well quantified. the release of millions of small particles that a short-term effect, as ozone recovers and Erika Berenguer from Lancaster reflect sunlight into the highest part of the adds to the warming. In contrast, the Arctic University, UK, and co-workers undertook atmosphere was compared with the cooling is experiencing warming that is enhanced the largest field study of its kind so far effect of a volcanic eruption). In a control by ocean heat transport and this is expected to begin to address this knowledge gap. condition a more standard description was to continue. BW They were particularly interested in used. The results show that participants in understanding the combined effects of the experimental condition were more likely WATER RESOURCES different forms of forest disturbance on to support geoengineering as a solution to Shifting El Niño takes rains the major carbon pools (aboveground, climate change. Geophys. Res. Lett. http://doi.org/s62 (2014) dead wood, litter and soil carbon) in The researchers advise using caution tropical forests. when communicating geoengineering They found that live vegetation — the with natural analogies as it can lead to an largest pool — was the most sensitive to unjustified favourable perception about disturbance, with affected areas containing the technologies. MC on average 40% less aboveground carbon than undisturbed forests. Conversely soil OCEANOGRAPHY stocks seemed to be resistant to disturbance, Polar response asymmetry and the dead wood and litter carbon Phil. Trans. R. Soc. A 373, 20130040 (2014) pools displayed rapid recovery potential. Extrapolating their findings using records Climate change is having different / ALAMY © ZHIEN HUANG of the annual forest disturbance area temperature impacts on the two polar in the Brazilian Amazon indicates that regions. While the Arctic is warming at a Southern China has experienced more the carbon loss from forest degradation greater rate than elsewhere, the Antarctic frequent autumn droughts during the could release 40% more carbon than has predominantly experienced cooling past two decades. Observations show that deforestation alone. AB and sea-ice expansion. John Marshall, of precipitation has been greatly reduced Massachusetts Institute of Technology, since 1990, during this season of transition PSYCHOLOGY USA, and colleagues investigated this from the wet summer monsoon to the dry Geoengineering views phenomenon by considering the role the winter months. Climatic Change http://doi.org/s6z (2014) ocean may play. Wenjun Zhang, of Nanjing University of The authors consider how differences Information Science and Technology, China, Descriptions of new technologies, including in ocean circulation — with surface waters and co-workers studied the causes behind geoengineering, can influence the way the sinking to depth in the high-latitude North this precipitation shift using observations public perceive them. Previous studies have Atlantic compared with upwelling of deep of rainfall, sea surface temperature and atmospheric circulation. They found that MITIGATION there has been an increase in central Pacific El Niño events — where the sea surface Water costs of afforestation Agric. Forest Meteorol. 195–196, 32–37 (2014) temperature anomaly is found in the central Pacific, compared with the more traditional, Afforestation is one way to sequester carbon dioxide from the atmosphere and mitigate or eastern Pacific, location. climate change, but choosing the best location is not always straightforward. This shift in the El Niño location Yang Gao from the Institute of Geographic Sciences and Natural Resources Research, influences precipitation over Southern China, and colleagues investigated the water consumption cost of carbon sequestration China, with very low precipitation during (WCCC) for afforestation projects in China. They find an abrupt change in ecosystem and central Pacific events and excess precipitation plant water-use efficiency coincident with the 400–500 mm average annual precipitation during eastern Pacific events. As global isopleth, where the WCCC is 1 kg H20 per g C. This threshold represents a boundary beyond warming may cause an increase in central which afforestation may lead to land degradation due to water depletion. Pacific El Niño events, this could have Unfortunately China’s major afforestation programmes are mostly concentrated in serious water resource implications for relatively arid areas with a high WCCC to the west of the 400–500 mm precipitation the region. BW isopleth. This illustrates the importance of considering water-use efficiency when selecting sites for afforestation. AB Written by Alastair Brown, Monica Contestabile and Bronwyn Wake. NATURE CLIMATE CHANGE | VOL 4 | JULY 2014 | www.nature.com/natureclimatechange 533 © 2014 Mac mill an Publi shers Li mit ed. All Ri ghts Reserved. .

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