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Credit: Kuo-Jung Chao
Credit: Kuo-Jung Chao

Amazon’s carbon uptake declines as trees die faster

The most extensive land-based study of the Amazon to date reveals it is losing its capacity to absorb carbon from the atmosphere.  From a peak of two billion tonnes of carbon dioxide each year in the 1990s, the net uptake by the forest has halved and is now for the first time being overtaken by fossil fuel emissions in Latin America.  

The results of this monumental 30-year survey of the South American rainforest, which involved an international team of almost 100 researchers and was led by the University of Leeds, are published in the journal Nature.

Over recent decades the remaining Amazon forest has acted as a vast ‘carbon sink’ – absorbing more carbon from the atmosphere than it releases – helping to put a brake on the rate of climate change. But this new analysis of forest dynamics shows a huge surge in the rate of trees dying across the Amazon.

Lead author Dr Roel Brienen, from the School of Geography at the University of Leeds, said: “Tree mortality rates have increased by more than a third since the mid-1980s, and this is affecting the Amazon’s capacity to store carbon.”

Initially, an increase in carbon dioxide in the atmosphere – a key ingredient for photosynthesis – led to a growth spurt for the Amazon’s trees, the researchers say. But the extra carbon appears to have had unexpected consequences.

Study co-author Professor Oliver Phillips, also from the University’s School of Geography, said: “With time, the growth stimulation feeds through the system, causing trees to live faster, and so die younger.”

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Nature / Alberto Seveso
Nature / Alberto Seveso

Epoch-defining study pinpoints when humans came to dominate planet Earth

The human-dominated geological epoch known as the Anthropocene probably began around the year 1610, according to new research published today in Nature.

Previous epochs began and ended due to factors including meteorite strikes, sustained volcanic eruptions and the shifting of the continents. The researchers behind the new study have concluded that humans have become a geological power and suggest that human actions have produced a new geological epoch.

Lead author Dr Simon Lewis, a geographer at the University of Leeds and UCL, said: “In a hundred thousand years, scientists will look at the environmental record and know something remarkable happened in the second half of the second millennium. They will be in no doubt that these global changes to Earth were caused by their own species.

“Today we can say when those changes began and why. The Anthropocene probably began when species jumped continents, starting when the Old World met the New. We humans are now a geological power in our own right – as Earth-changing as a meteorite strike.”

The paper ‘Defining the Anthropocene’ appears in the 12 March edition of Nature.

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Human trafficking and slavery in the UK

Louise Waite and Hannah Lewis were invited to speak at Parliament on Tuesday 10 March 2015. They addressed the All Party Parliamentary Group on Global Uncertainties on the topic of ‘Human Trafficking and Slavery in the UK’, chaired by John Glen MP. They spoke alongside Kevin Hyland; the UK’s first Independent Anti-Slavery Commissioner. The audience comprised MPs and Lords together with representatives from the National Crime Agency, the Home Office, and many NGOs and think-tanks including Anti-Slavery International, Refugee Council, Joseph Rowntree Foundation, CentreForum, Chatham House and the Centre for Social Justice.

Hannah & Louise profiled their ESRC funded research on the Experiences of forced labour among refugees and asylum seekers and a follow on project, also funded by ESRC, on Tackling forced labour among refugees and asylum seekers. Their presentation communicated their key message that amidst the burgeoning amount of research on forced labour and unfreedom in recent years, there is a missing focus on the particular experiences of asylum seekers and refugees living in the UK. Their research reveals for the first time that refugees and asylum seekers are a group of migrants vulnerable to exploitation in various forms of severely exploitative and, in some cases, forced labour in the UK. Hannah and Louise closed their presentation by outlining their key recommendations to tackle forced labour among refugees and asylum seekers:

  • End the enforced destitution of asylum seekers by restoring their right to work.
  • Ensure all workers irrespective of immigration status are protected from forced labour through universal access to basic employment rights.
  • Stop criminalising asylum seekers and undocumented migrants for working to meet basic survival needs by ending criminal prosecutions for new cases and wiping previous convictions from existing records.
  • Allow all refugees to exercise their rights to family reunion without the pressure to take up exploitative work by reinstating legal aid.

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Most carbon dense ecosystem in Amazonia mapped for first time

Amazonian forests are known to harbour large stores of carbon locked up in their trees. However, results from a new study show surprisingly that the parts of Amazonia with the highest concentration of carbon store most not as wood, but below the ground, as peat.

The study was undertaken by researchers from the Universities of Leeds, St Andrews, Edinburgh (UK), and Turku (Finland), in collaboration with the Research Institute of the Peruvian Amazon (IIAP) and is published today in the journal Environmental Research Letters. The authors mapped and quantified the carbon stored in the largest area of peatland forest in Amazonia within a geological basin almost the size of England (120,000 km2). The researchers estimated that over three billion tons of carbon are stored within this ecosystem, with 90 % stored below the ground as peat.

“Peatland forests are different from other Amazonian forests as they are typically dominated by small-statured trees or palms. We can see these differences not only on the ground but also from space using satellite imagery. These differences allowed us to map the extent of the peatlands and distinguish the different types of peatland forest. Crucially this approach allowed us to distinguish a type of forest dominated by small trees, or ‘pole’ forest – the most carbon-dense peatland type” explains lead author Freddie Draper, a PhD student at the University of Leeds. “Combining this satellite data with extensive field data we have been able to provide spatially explicit estimates of the amount of carbon stored in these ecosystems for the first time”.

Ordinarily in tropical forests, the vast majority of carbon is emitted back to the atmosphere as carbon dioxide, as trees die and decompose. However, waterlogging in peatlands means that decomposition is very slow so the carbon accumulates as peat.

Dr Tim Baker, co-author and Associate Professor at the School of Geography, University of Leeds presented the results to policymakers at ’Voices for Climate’ on the margins of the recent UN Climate Change Conference COP20 in Lima, Peru. “Mapping and quantifying the amount of carbon stored in these ecosystems is an important part of prioritising national strategies to mitigate climate change. For example, these peatlands occupy just 3 % of the forested area of Peru, but contain almost 50 % of the total amount of carbon stored above the ground in all Peruvian forests”.

“The peatlands we studied are largely intact, in contrast to tropical peatlands in Southeast Asia that have been exposed to decades of destruction, leading to huge carbon emissions and biodiversity losses” added co-author Dr Katherine Roucoux, lecturer at the University of St Andrews. “However, most of the peatland area, including the most carbon-dense peatland type, currently lies outside of the protected areas and threats are increasing. If these carbon-rich forests could be protected too, then large emissions of carbon to the atmosphere could be prevented.”

Funding for the project came primarily from the UK Natural Environment Research Council (NERC).

http://www.bbc.com/news/science-environment-30448519

Climate change was not to blame for the collapse of the Bronze Age

Scientists have proven definitively that climate change could not have been responsible for a huge population collapse in Europe at the end of the Bronze Age.

Archaeologists and environmental scientists from the University of Leeds, the University of Bradford, University College Cork and Queen’s University Belfast have shown that the changes in climate that scientists believed to coincide with the fall in population in fact occurred at least two generations later.

Their results, published today in the Proceedings of the National Academy of Sciences, show that human activity starts to decline after 900 BC, and falls rapidly after 800 BC, indicating a population collapse. But the climate records show that colder, wetter conditions didn’t occur until around two generations later.

Dr Graeme Swindles, from the School of Geography, University of Leeds and a co-author of the study, said: “We found clear evidence for a rapid change in climate to much wetter conditions, which we were able to precisely pinpoint to 750 BC using statistical methods.”

Fluctuations in human activity levels through time are reflected by the numbers of radiocarbon dates for a given period. The team used new statistical techniques to analyse more than 2000 radiocarbon dates, taken from hundreds of archaeological sites in Ireland, to pinpoint the precise dates that Europe’s Bronze Age population collapse occurred.

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Study supervised by Jon Lovett shows the severe environmental impacts of armed conflicts on the Lebanon

Armed conflicts are responsible for severe environmental impacts due to both the direct effects of destruction and indirect effects resulting from the break down of law and social order. Northern Lebanon has experienced repeated conflicts over the last three decades, and in a recently published study resulting from a collaboration between Jon Lovett from the School of Geography, Leeds and the Universities of Balamand and Twente analyses change over time to demonstrate land degradation resulting from conflict. Mapping and monitoring land degradation are essential for designing and implementing post-conflict recovery plans and informed policy decisions.

The aim of the work was to evaluate the effect of repetitive armed conflicts on land degradation along the coastal zone of North Lebanon using multi-temporal satellite data. The specific objectives were to:

  • identify a list of indicators for use in conjunction with satellite remote sensi
  • monitor land cover change throughout repetitive events of armed conflicts and
  • model the effect of repetitive armed conflicts on land degradation.

The work involved the use of multi-temporal Landsat images and literature review data in Geographic Object-Based Image Analysis (GEOBIA) approach, together with 26 field visits to confirm interpretation of the images. The work resulted in the development of

  • a list of indicators to be employed,
  • land cover change detection maps with the use of multi-temporal Landsat images and, consequently, a fire risk associated with changes in vegetation cover throughout repetitive armed conflict events, and
  • an integrated approach for modelling the effect of repetitive armed conflicts on land degradation with the use of a composite land degradation index (CLDI).

The final synthetic map showed four classes of exposure to land degradation associated with repetitive armed conflicts. Data collected from field visits showed that the final classification results highly reflected (average of 90 %) the effect of repetitive armed conflicts on the different classes of exposure to land degradation.

Link to paper

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Grouse moor burning causes widespread environmental changes

Evidence of the environmental effects of moorland burning is published today in the first authoritative scientific study on the subject, with the aim of relieving tensions on both sides of the grouse moor management debate.

The EMBER (Effects of Moorland Burning on the Ecohydrology of River basins) project has shown that heather burning on moorland, which is practised predominantly to support red grouse populations for gun sports, has significant negative impacts on peat hydrology, peat chemistry and physical properties, river water chemistry and river ecology.

A report on the five-year EMBER project is published online today – the first day of the moorland burning season, which will run until 15 April 2015.

Dr Lee Brown, from the School of Geography at the University of Leeds, who led the study, said: "Until now, there was little evidence of the environmental impacts of moorland burning. Yet, many moorland owners and individuals who hold sporting rights to the land have felt pressured by regulators and conservationists to change their burning regimes.

“Unsurprisingly, a push away from moorland burning – a practice that started in the UK about 100-150 years ago – without solid scientific evidence to back up the need for change has created a lot of tension. The findings from the EMBER project now provide the necessary evidence to inform policy.”

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