[naturenews] from [nature.com]
[naturenews]
Published online 19 August 2009 | Nature | doi:10.1038/news.2009.842
News
Forest definition comes under fire
Ecologists accuse framework convention of barking up the wrong tree.
Natasha Gilbert
Ecologists have questioned the UNFCCC's definition of a forest.PunchstockThe health of the world's forests — and their capacity to lock away carbon — could be jeopardized by logging if the United Nations Framework Convention on Climate Change (UNFCCC) definition of a forest is not changed, a study warns.
A future climate deal could see developing countries financially compensated for preserving their forests. The UNFCCC defines a forest as an area of land 0.05–1 hectare in size, of which more than 10–30% is covered by tree canopy. Trees must also have the potential to reach a minimum height of 2-5 metres.
Countries participating in the UNFCCC can choose how they want to define a forest from within those ranges. For example, in Brazil a forest is defined as an area of land greater than 1 hectare, with more than 30% canopy cover and a minimum tree height of 5 metres. By contrast, Ghana defines a forest as an area of land greater than 0.1 hectare, with more than 15% canopy cover and a minimum tree height of 2 metres.
But a report1 in the journal Conservation Letters, says that the UNFCCC has set the proportion of land that must be covered by tree canopy too low. Nophea Sasaki, a forest ecologist at Harvard University, and an author of the study, says that woodland could be "severely degraded" but still be classified as a forest under the current UNFCCC definition.
{“Our main concern is that people will take it as a threshold and keep logging until they reach it.”
Nophea Sasaki
Harvard University}
"Our main concern is that people will take it as a threshold and keep logging until they reach it," he says. So even though the region could lose a lot of biodiversity and a large proportion of its carbon stock, it would still be regarded as a forest. Sasaki says that loggers tend to target the bigger, more mature tree species, which hold the most carbon.
In a case study of an evergreen forest in Cambodia, Sasaki and his co-author Francis Putz from the University of Florida in Gainsville use inventory data for plots of trees with trunks wider than 5 centimetres to estimate that the forest holds 121.2 tonnes of carbon per hectare. Of this, 71.4 tonnes is in trees that have trunks wider than 45 centimetres — the trees that loggers are most likely to target. So if all these larger trees were harvested, the carbon stock would be depleted by almost 40%, yet the forest would still be considered a forest under the UNFCCC definition, the study says.
Copenhagen concerns
Sasaki says that the minimum threshold for canopy cover should be raised to 40%, the minimum tree height should be 5 metres and that natural forests should be differentiated from plantations.
Read more about the climate at the Road to Copenhagen special.His proposed threshold for canopy cover, he says, is based not on calculations that show forest degradation would be avoided at these levels, but rather on the definition used by the Food and Agriculture Organization of the United Nations, as this is likely to be acceptable to participating countries and "40% has to be better than 30%".
Sasaki is also concerned that forest degradation will be "disregarded" in the post-Kyoto agreement on climate change due to be negotiated in Copenhagen in December. But Sasaki says that several prominent studies ignore the issue of degradation of forests and their long-term sustainability — including a report2 from the Harvard University project on international climate agreements which was presented to the UNFCCC in Poznań, Poland, in December last year.
Neil Burgess, a conservation scientist at the University of Cambridge, UK, says that part of the problem is that degradation is not easy to measure. Unlike deforestation, which can be measured by remote-sensing methods such as satellites, degradation is evaluated through on-the-ground studies that assess what types of tree species are growing and estimate the forest's carbon stock.
Burgess says Sasaki's paper has not proven why its proposed definition of a forest would be optimal, but that "the more canopy cover you have, the more intact the forest is, so the more carbon it is retaining".
"Working out the amount of degradation that would be tolerable in a post-Kyoto agreement would be useful. People at the Copenhagen meeting will have to worry about this to some extent," Burgess says.
References
1. Sasaki, N. & Putz, F. E. Conserv. Lett. advance online publication doi:10.1111/j.1755-263x.2009.00067.x (2009).
2. Aldy, J. E. & Stavins, R. N. Designing the Post-Kyoto Climate Regime: Lessons from the Harvard Project on International Climate Agreements (Harvard Project on International Climate Agreements, 2008).
[naturenews]
Published online 19 August 2009 | Nature | doi:10.1038/news.2009.844
News
Gravity waves 'around the corner'
Sensitive search fails to find ripples in space, but boosts hopes for future hunts.
Calla Cofield
The hunt for gravitational waves may not have found the elusive ripples in space-time predicted by Albert Einstein, but the latest results from the most sensitive survey to date are providing clear insight into the origins and fabric of the Universe.
General relativity predicts that gravitational waves are generated by accelerating masses. Violent yet rare events, such as a supernova explosion or the collision of two black holes, should make the biggest and most detectable waves.
A more pervasive yet weaker source of waves should be the stochastic gravitational wave background (SGWB) that was mostly created in the turmoil immediately after the Big Bang, and which has spread unhindered through the Universe ever since.
The Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, based in Washington state and Louisiana, look for these cosmic gravitational waves by measuring any slight disturbance to laser beams that shuttle between heavy mirrors held kilometres apart. Whereas the gravitational wave signal from a distinct event, such as a black-hole merger, would appear as a spike in the LIGO data, the SGWB is a murmur that is more difficult to detect.
{“For 40 years they've been saying that gravity waves are around the corner ... I think for the first time that's actually a true statement.”
Michael Turner
University of Chicago, Illinois}
Working with the Virgo Collaboration, which runs a gravitational wave detector near Pisa, Italy, the LIGO team has now analysed what their own detector saw between November 2005 and September 2007. Although LIGO did not find any waves, the teams conclude in Nature1 that the SGWB is even smaller than LIGO can currently detect. This result rules out some theoretical models of the early Universe that would generate a relatively large background of gravitational waves.
Cosmic predictions
"This is the first time that an experiment directly searching for gravitational waves is essentially going and making a statement about cosmology, about the evolution of the Universe," says Vuk Mandic, an astrophysicist at the University of Minnesota in Minneapolis, and part of the LIGO team. The data also exclude certain cosmological models involving cosmic strings — hypothetical cracks in the fabric of space that are thinner than an atom but have immense gravitational fields.
The LIGO results reduce the upper limit for the size of the SGWB, which had previously been set by indirect measurements. A relatively large SGWB in the very early Universe, for example, would have had a measurable effect on both the cosmic microwave background radiation left over from that time, and the relative amounts of light elements — such as hydrogen, helium and lithium — created within minutes of the Big Bang.
The LIGO and Virgo collaborations are in the process of merging their scientific efforts, and the teams plan to include data and collaborative work from both experiments in all of their future papers. Detector improvements should help Virgo to match LIGO's sensitivity in the next few years, and a series of upgrades to both experiments should increase their sensitivity to the SGWB by more than a thousand times by 2014 — which astrophysicists say is almost certain to be enough to pin down its quarry at last.
"For some 40 years they've been saying that gravity waves are around the corner," says Michael Turner, an astrophysicist at the University of Chicago in Illinois, who was not involved in the research. "And I think for the first time in 40 years that's actually a true statement."
References
1. The LIGO Scientific Collaboration & The Virgo Collaboration. Nature 460, 990-994 (2009). | Article
[naturenews]
Published online 19 August 2009 | Nature | doi:10.1038/news.2009.842
News
Forest definition comes under fire
Ecologists accuse framework convention of barking up the wrong tree.
Natasha Gilbert
Ecologists have questioned the UNFCCC's definition of a forest.PunchstockThe health of the world's forests — and their capacity to lock away carbon — could be jeopardized by logging if the United Nations Framework Convention on Climate Change (UNFCCC) definition of a forest is not changed, a study warns.
A future climate deal could see developing countries financially compensated for preserving their forests. The UNFCCC defines a forest as an area of land 0.05–1 hectare in size, of which more than 10–30% is covered by tree canopy. Trees must also have the potential to reach a minimum height of 2-5 metres.
Countries participating in the UNFCCC can choose how they want to define a forest from within those ranges. For example, in Brazil a forest is defined as an area of land greater than 1 hectare, with more than 30% canopy cover and a minimum tree height of 5 metres. By contrast, Ghana defines a forest as an area of land greater than 0.1 hectare, with more than 15% canopy cover and a minimum tree height of 2 metres.
But a report1 in the journal Conservation Letters, says that the UNFCCC has set the proportion of land that must be covered by tree canopy too low. Nophea Sasaki, a forest ecologist at Harvard University, and an author of the study, says that woodland could be "severely degraded" but still be classified as a forest under the current UNFCCC definition.
{“Our main concern is that people will take it as a threshold and keep logging until they reach it.”
Nophea Sasaki
Harvard University}
"Our main concern is that people will take it as a threshold and keep logging until they reach it," he says. So even though the region could lose a lot of biodiversity and a large proportion of its carbon stock, it would still be regarded as a forest. Sasaki says that loggers tend to target the bigger, more mature tree species, which hold the most carbon.
In a case study of an evergreen forest in Cambodia, Sasaki and his co-author Francis Putz from the University of Florida in Gainsville use inventory data for plots of trees with trunks wider than 5 centimetres to estimate that the forest holds 121.2 tonnes of carbon per hectare. Of this, 71.4 tonnes is in trees that have trunks wider than 45 centimetres — the trees that loggers are most likely to target. So if all these larger trees were harvested, the carbon stock would be depleted by almost 40%, yet the forest would still be considered a forest under the UNFCCC definition, the study says.
Copenhagen concerns
Sasaki says that the minimum threshold for canopy cover should be raised to 40%, the minimum tree height should be 5 metres and that natural forests should be differentiated from plantations.
Read more about the climate at the Road to Copenhagen special.His proposed threshold for canopy cover, he says, is based not on calculations that show forest degradation would be avoided at these levels, but rather on the definition used by the Food and Agriculture Organization of the United Nations, as this is likely to be acceptable to participating countries and "40% has to be better than 30%".
Sasaki is also concerned that forest degradation will be "disregarded" in the post-Kyoto agreement on climate change due to be negotiated in Copenhagen in December. But Sasaki says that several prominent studies ignore the issue of degradation of forests and their long-term sustainability — including a report2 from the Harvard University project on international climate agreements which was presented to the UNFCCC in Poznań, Poland, in December last year.
Neil Burgess, a conservation scientist at the University of Cambridge, UK, says that part of the problem is that degradation is not easy to measure. Unlike deforestation, which can be measured by remote-sensing methods such as satellites, degradation is evaluated through on-the-ground studies that assess what types of tree species are growing and estimate the forest's carbon stock.
Burgess says Sasaki's paper has not proven why its proposed definition of a forest would be optimal, but that "the more canopy cover you have, the more intact the forest is, so the more carbon it is retaining".
"Working out the amount of degradation that would be tolerable in a post-Kyoto agreement would be useful. People at the Copenhagen meeting will have to worry about this to some extent," Burgess says.
References
1. Sasaki, N. & Putz, F. E. Conserv. Lett. advance online publication doi:10.1111/j.1755-263x.2009.00067.x (2009).
2. Aldy, J. E. & Stavins, R. N. Designing the Post-Kyoto Climate Regime: Lessons from the Harvard Project on International Climate Agreements (Harvard Project on International Climate Agreements, 2008).
[naturenews]
Published online 19 August 2009 | Nature | doi:10.1038/news.2009.844
News
Gravity waves 'around the corner'
Sensitive search fails to find ripples in space, but boosts hopes for future hunts.
Calla Cofield
The hunt for gravitational waves may not have found the elusive ripples in space-time predicted by Albert Einstein, but the latest results from the most sensitive survey to date are providing clear insight into the origins and fabric of the Universe.
General relativity predicts that gravitational waves are generated by accelerating masses. Violent yet rare events, such as a supernova explosion or the collision of two black holes, should make the biggest and most detectable waves.
A more pervasive yet weaker source of waves should be the stochastic gravitational wave background (SGWB) that was mostly created in the turmoil immediately after the Big Bang, and which has spread unhindered through the Universe ever since.
The Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, based in Washington state and Louisiana, look for these cosmic gravitational waves by measuring any slight disturbance to laser beams that shuttle between heavy mirrors held kilometres apart. Whereas the gravitational wave signal from a distinct event, such as a black-hole merger, would appear as a spike in the LIGO data, the SGWB is a murmur that is more difficult to detect.
{“For 40 years they've been saying that gravity waves are around the corner ... I think for the first time that's actually a true statement.”
Michael Turner
University of Chicago, Illinois}
Working with the Virgo Collaboration, which runs a gravitational wave detector near Pisa, Italy, the LIGO team has now analysed what their own detector saw between November 2005 and September 2007. Although LIGO did not find any waves, the teams conclude in Nature1 that the SGWB is even smaller than LIGO can currently detect. This result rules out some theoretical models of the early Universe that would generate a relatively large background of gravitational waves.
Cosmic predictions
"This is the first time that an experiment directly searching for gravitational waves is essentially going and making a statement about cosmology, about the evolution of the Universe," says Vuk Mandic, an astrophysicist at the University of Minnesota in Minneapolis, and part of the LIGO team. The data also exclude certain cosmological models involving cosmic strings — hypothetical cracks in the fabric of space that are thinner than an atom but have immense gravitational fields.
The LIGO results reduce the upper limit for the size of the SGWB, which had previously been set by indirect measurements. A relatively large SGWB in the very early Universe, for example, would have had a measurable effect on both the cosmic microwave background radiation left over from that time, and the relative amounts of light elements — such as hydrogen, helium and lithium — created within minutes of the Big Bang.
The LIGO and Virgo collaborations are in the process of merging their scientific efforts, and the teams plan to include data and collaborative work from both experiments in all of their future papers. Detector improvements should help Virgo to match LIGO's sensitivity in the next few years, and a series of upgrades to both experiments should increase their sensitivity to the SGWB by more than a thousand times by 2014 — which astrophysicists say is almost certain to be enough to pin down its quarry at last.
"For some 40 years they've been saying that gravity waves are around the corner," says Michael Turner, an astrophysicist at the University of Chicago in Illinois, who was not involved in the research. "And I think for the first time in 40 years that's actually a true statement."
References
1. The LIGO Scientific Collaboration & The Virgo Collaboration. Nature 460, 990-994 (2009). | Article
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