Tag Archives: Rainforests

Amazon is 'at higher risk of tree loss'

FOR IMMEDIATE RELEASE
Part of the Amazon rainforest may be more vulnerable to the effects of climate change than first thought, US researchers say.

LONDON, 21 October – Researchers say the southern part of the Amazon rainforest is at a far higher risk of dieback than the models used in the most recent report by the Intergovernmental Panel on Climate Change (IPCC).

The research team, led by Professor Rong Fu of the University of Texas, say that this is because the forest is drying out much quicker than projected.

If the damage is severe enough, they say the loss of rainforest could cause the release of large volumes of carbon dioxide into the atmosphere, and could also disrupt plant and animal communities in one of the world’s most biodiversity-rich regions, as outlined in the Proceedings of the National Academy of Sciences.

The team used ground-based rainfall measurements from the past three decades. Findings showed that since 1979, the dry season in southern Amazonia lasted about a week longer in each decade.

At the same time, the annual fire seasons have become longer. The researchers say the most likely explanation for the increasingly longer dry seasons is global warming.

“The dry season over the southern Amazon is already marginal for maintaining rainforest,” says Professor Fu. “At some point, if it becomes too long, the rainforest will reach a tipping point.”

She says the length of the dry season is the most important climate factor controlling the southern Amazon rainforest. If it is too long, the forest will not survive.

A study published earlier this year suggested that rainforests worldwide might be able to withstand the impacts of climate change more successfully than thought.

The new results also contrast sharply with forecasts made by the models used by the IPCC: even under future scenarios in which greenhouse gases rise dramatically, those models project the southern Amazon dry season will be at most 10 days longer by the end of the century, and that the risk of climate change-induced rainforest dieback should therefore be relatively low.

Rainfall limited

Professor Fu and her colleagues say the water stored in the forest soil at the end of each wet season is all that the trees have to last them through the dry months. The longer that lasts – regardless of how wet the wet season was – the more stressed the trees become and the more susceptible they are to forest fires.

They say the most likely explanation for the lengthening dry season in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways: It makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above; and it blocks incursions by cold weather fronts from outside the tropics which could trigger rainfall.

The team says the IPCC’s climate models represent these processes poorly, which might explain why they project only a slightly longer Amazonian dry season.

The Amazon rainforest normally acts as a carbon sink, removing atmospheric CO2 and storing it. But during a severe drought in 2005 it went into reverse, releasing one petagram of carbon (one billion tonnes – about one-tenth of annual human emissions) to the atmosphere.

Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate seen in recent decades, the 2005 Amazon drought could become the norm rather than the exception by the end of this century.

Some scientists think the combination of longer dry seasons, higher surface temperatures and more fragmented forests caused by deforestation could eventually convert much of southern Amazonia from rainforest to savanna.

Earlier studies have shown that human-caused deforestation in the Amazon can alter rainfall patterns. But the researchers did not see a strong sign of that in the pattern of increasing dry season length. That was most pronounced in the south-western Amazon, while the most intense deforestation occurred in the south-east.

Because the north western Amazon has much higher rainfall and a shorter dry season than the south, the researchers think it is much less vulnerable to climate change – Climate News Network

FOR IMMEDIATE RELEASE
Part of the Amazon rainforest may be more vulnerable to the effects of climate change than first thought, US researchers say.

LONDON, 21 October – Researchers say the southern part of the Amazon rainforest is at a far higher risk of dieback than the models used in the most recent report by the Intergovernmental Panel on Climate Change (IPCC).

The research team, led by Professor Rong Fu of the University of Texas, say that this is because the forest is drying out much quicker than projected.

If the damage is severe enough, they say the loss of rainforest could cause the release of large volumes of carbon dioxide into the atmosphere, and could also disrupt plant and animal communities in one of the world’s most biodiversity-rich regions, as outlined in the Proceedings of the National Academy of Sciences.

The team used ground-based rainfall measurements from the past three decades. Findings showed that since 1979, the dry season in southern Amazonia lasted about a week longer in each decade.

At the same time, the annual fire seasons have become longer. The researchers say the most likely explanation for the increasingly longer dry seasons is global warming.

“The dry season over the southern Amazon is already marginal for maintaining rainforest,” says Professor Fu. “At some point, if it becomes too long, the rainforest will reach a tipping point.”

She says the length of the dry season is the most important climate factor controlling the southern Amazon rainforest. If it is too long, the forest will not survive.

A study published earlier this year suggested that rainforests worldwide might be able to withstand the impacts of climate change more successfully than thought.

The new results also contrast sharply with forecasts made by the models used by the IPCC: even under future scenarios in which greenhouse gases rise dramatically, those models project the southern Amazon dry season will be at most 10 days longer by the end of the century, and that the risk of climate change-induced rainforest dieback should therefore be relatively low.

Rainfall limited

Professor Fu and her colleagues say the water stored in the forest soil at the end of each wet season is all that the trees have to last them through the dry months. The longer that lasts – regardless of how wet the wet season was – the more stressed the trees become and the more susceptible they are to forest fires.

They say the most likely explanation for the lengthening dry season in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways: It makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above; and it blocks incursions by cold weather fronts from outside the tropics which could trigger rainfall.

The team says the IPCC’s climate models represent these processes poorly, which might explain why they project only a slightly longer Amazonian dry season.

The Amazon rainforest normally acts as a carbon sink, removing atmospheric CO2 and storing it. But during a severe drought in 2005 it went into reverse, releasing one petagram of carbon (one billion tonnes – about one-tenth of annual human emissions) to the atmosphere.

Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate seen in recent decades, the 2005 Amazon drought could become the norm rather than the exception by the end of this century.

Some scientists think the combination of longer dry seasons, higher surface temperatures and more fragmented forests caused by deforestation could eventually convert much of southern Amazonia from rainforest to savanna.

Earlier studies have shown that human-caused deforestation in the Amazon can alter rainfall patterns. But the researchers did not see a strong sign of that in the pattern of increasing dry season length. That was most pronounced in the south-western Amazon, while the most intense deforestation occurred in the south-east.

Because the north western Amazon has much higher rainfall and a shorter dry season than the south, the researchers think it is much less vulnerable to climate change – Climate News Network

Amazon is ‘at higher risk of tree loss’

FOR IMMEDIATE RELEASE Part of the Amazon rainforest may be more vulnerable to the effects of climate change than first thought, US researchers say. LONDON, 21 October – Researchers say the southern part of the Amazon rainforest is at a far higher risk of dieback than the models used in the most recent report by the Intergovernmental Panel on Climate Change (IPCC). The research team, led by Professor Rong Fu of the University of Texas, say that this is because the forest is drying out much quicker than projected. If the damage is severe enough, they say the loss of rainforest could cause the release of large volumes of carbon dioxide into the atmosphere, and could also disrupt plant and animal communities in one of the world’s most biodiversity-rich regions, as outlined in the Proceedings of the National Academy of Sciences. The team used ground-based rainfall measurements from the past three decades. Findings showed that since 1979, the dry season in southern Amazonia lasted about a week longer in each decade. At the same time, the annual fire seasons have become longer. The researchers say the most likely explanation for the increasingly longer dry seasons is global warming. “The dry season over the southern Amazon is already marginal for maintaining rainforest,” says Professor Fu. “At some point, if it becomes too long, the rainforest will reach a tipping point.” She says the length of the dry season is the most important climate factor controlling the southern Amazon rainforest. If it is too long, the forest will not survive. A study published earlier this year suggested that rainforests worldwide might be able to withstand the impacts of climate change more successfully than thought. The new results also contrast sharply with forecasts made by the models used by the IPCC: even under future scenarios in which greenhouse gases rise dramatically, those models project the southern Amazon dry season will be at most 10 days longer by the end of the century, and that the risk of climate change-induced rainforest dieback should therefore be relatively low.

Rainfall limited

Professor Fu and her colleagues say the water stored in the forest soil at the end of each wet season is all that the trees have to last them through the dry months. The longer that lasts – regardless of how wet the wet season was – the more stressed the trees become and the more susceptible they are to forest fires. They say the most likely explanation for the lengthening dry season in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways: It makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above; and it blocks incursions by cold weather fronts from outside the tropics which could trigger rainfall. The team says the IPCC’s climate models represent these processes poorly, which might explain why they project only a slightly longer Amazonian dry season. The Amazon rainforest normally acts as a carbon sink, removing atmospheric CO2 and storing it. But during a severe drought in 2005 it went into reverse, releasing one petagram of carbon (one billion tonnes – about one-tenth of annual human emissions) to the atmosphere. Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate seen in recent decades, the 2005 Amazon drought could become the norm rather than the exception by the end of this century. Some scientists think the combination of longer dry seasons, higher surface temperatures and more fragmented forests caused by deforestation could eventually convert much of southern Amazonia from rainforest to savanna. Earlier studies have shown that human-caused deforestation in the Amazon can alter rainfall patterns. But the researchers did not see a strong sign of that in the pattern of increasing dry season length. That was most pronounced in the south-western Amazon, while the most intense deforestation occurred in the south-east. Because the north western Amazon has much higher rainfall and a shorter dry season than the south, the researchers think it is much less vulnerable to climate change – Climate News Network

FOR IMMEDIATE RELEASE Part of the Amazon rainforest may be more vulnerable to the effects of climate change than first thought, US researchers say. LONDON, 21 October – Researchers say the southern part of the Amazon rainforest is at a far higher risk of dieback than the models used in the most recent report by the Intergovernmental Panel on Climate Change (IPCC). The research team, led by Professor Rong Fu of the University of Texas, say that this is because the forest is drying out much quicker than projected. If the damage is severe enough, they say the loss of rainforest could cause the release of large volumes of carbon dioxide into the atmosphere, and could also disrupt plant and animal communities in one of the world’s most biodiversity-rich regions, as outlined in the Proceedings of the National Academy of Sciences. The team used ground-based rainfall measurements from the past three decades. Findings showed that since 1979, the dry season in southern Amazonia lasted about a week longer in each decade. At the same time, the annual fire seasons have become longer. The researchers say the most likely explanation for the increasingly longer dry seasons is global warming. “The dry season over the southern Amazon is already marginal for maintaining rainforest,” says Professor Fu. “At some point, if it becomes too long, the rainforest will reach a tipping point.” She says the length of the dry season is the most important climate factor controlling the southern Amazon rainforest. If it is too long, the forest will not survive. A study published earlier this year suggested that rainforests worldwide might be able to withstand the impacts of climate change more successfully than thought. The new results also contrast sharply with forecasts made by the models used by the IPCC: even under future scenarios in which greenhouse gases rise dramatically, those models project the southern Amazon dry season will be at most 10 days longer by the end of the century, and that the risk of climate change-induced rainforest dieback should therefore be relatively low.

Rainfall limited

Professor Fu and her colleagues say the water stored in the forest soil at the end of each wet season is all that the trees have to last them through the dry months. The longer that lasts – regardless of how wet the wet season was – the more stressed the trees become and the more susceptible they are to forest fires. They say the most likely explanation for the lengthening dry season in recent decades is human-caused greenhouse warming, which inhibits rainfall in two ways: It makes it harder for warm, dry air near the surface to rise and freely mix with cool, moist air above; and it blocks incursions by cold weather fronts from outside the tropics which could trigger rainfall. The team says the IPCC’s climate models represent these processes poorly, which might explain why they project only a slightly longer Amazonian dry season. The Amazon rainforest normally acts as a carbon sink, removing atmospheric CO2 and storing it. But during a severe drought in 2005 it went into reverse, releasing one petagram of carbon (one billion tonnes – about one-tenth of annual human emissions) to the atmosphere. Fu and her colleagues estimate that if dry seasons continue to lengthen at just half the rate seen in recent decades, the 2005 Amazon drought could become the norm rather than the exception by the end of this century. Some scientists think the combination of longer dry seasons, higher surface temperatures and more fragmented forests caused by deforestation could eventually convert much of southern Amazonia from rainforest to savanna. Earlier studies have shown that human-caused deforestation in the Amazon can alter rainfall patterns. But the researchers did not see a strong sign of that in the pattern of increasing dry season length. That was most pronounced in the south-western Amazon, while the most intense deforestation occurred in the south-east. Because the north western Amazon has much higher rainfall and a shorter dry season than the south, the researchers think it is much less vulnerable to climate change – Climate News Network

Signs of forests adapting to growing CO2 levels

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network  

FOR IMMEDIATE RELEASE LONDON, 9 August – Trees may be getting more efficient in the way they manage water. They could be exploiting the higher levels of carbon dioxide in the atmosphere, growing foliage from a lower uptake of groundwater. If so, then the carbon dioxide fertilisation effect – predicted by theorists and observed in laboratory experiments – could be real. This is a provisional finding, because it is pretty difficult to measure the precise economy of a whole forest or an open wilderness. But Trevor Keenan  – of Macquarie University in Australia and at present at Harvard University in the US – and colleagues report in Nature that they used an indirect measure, called the eddy-covariance technique, to monitor the way managed forests handle two important gases: carbon dioxide and water vapour. Carbon dioxide levels in the atmosphere were once 280 parts per million; they are now 400 ppm and still rising. For more than 20 years, rigs have towered above the world’s forests recording eddy co-variance, measuring carbon uptake and water-use over areas of a square kilometre. Keenan and his fellow-researchers looked at the data from 21 temperate and boreal forests in the northern hemisphere and found a remarkably consistent trend: as the years rolled by, and carbon dioxide levels rose, forests used water more efficiently, and this was true for all 21 sites. This so-called fertilisation effect has been independently confirmed in arid zones, again by indirect research, through the work of an Australian team studying satellite data, and also seems consistent with a finding reported in Nature Climate Change that tropical forest trees are now producing more flowers, even though the observed temperature rises in the tropics have so far only been modest. The implication of the most recent research from the boreal and temperate forests is that plants could be partially closing their stomata to keep their carbon levels at a constant level. This finding, like much in science, raises as many questions as it answers. How plants “know” what to do in such circumstances, and how they do it, is still a mystery: Plants exploit atmospheric carbon dioxide so it should be no surprise that a better supply leads to more efficient growth. But more carbon dioxide also means higher temperatures, more evaporation, more precipitation and more cloud cover, so it has been difficult to observe the impact. Whether this will turn out in the long run to be a positive feedback that could, to some slight extent, slow global warming is uncertain. Plants are also sensitive to extreme heat and drought, two other unwelcome companions of climate change due to human emissions of greenhouse gases such as carbon dioxide, so it is too soon to suggest that forests will emerge as the winners. Other scientists still have to confirm the effect, and measure its scale more accurately. But the latest research does suggest trees are responding to change. “Our analysis suggests that rising atmospheric carbon dioxide is having a direct and unexpectedly strong influence on ecosystem processes and biosphere-atmosphere interactions in temperate and boreal forests,” says one of the authors, Dave Hollinger of the US Forest Service. – Climate News Network  

Warming 'may harm rainforests less'

FOR IMMEDIATE RELEASE
The world’s rainforests may be able to weather the assaults of climate change more robustly than scientists had earlier thought, says a new study.

LONDON, 12 March – Scientists think they have found some good news for the Amazon and other tropical forests. They say they appear more able to withstand the effects of climate change than previous studies had suggested.

The research team, including climate scientists and tropical ecologists from the UK, USA, Australia and Brazil, concluded that the forests are less likely to lose biomass – plants and plant material – in response to greenhouse gas emissions over the rest of this century.

In what they say is the most comprehensive assessment yet of the risk of tropical forest dieback caused by climate change, the scientists say their results have important implications for the future evolution of rainforests, including the role they play in the global climate system and carbon cycle. The study is published online in Nature Geoscience.

To remain effective, programmes such as the United Nations’ Reducing Emissions from Deforestation and Degradation+ scheme (REDD+) require rainforest stability, in effect locking carbon within the trees.

The research team was led by Dr Chris Huntingford from the Centre for Ecology & Hydrology in the UK. He and his colleagues used computer simulations with 22 climate models to explore the response of tropical forests in the Americas, Africa and Asia to greenhouse gas-induced climate change.

They found loss of forest cover in only one model, and only in the Americas. The researchers found the largest source of uncertainty in the projections to be differences in how plant physiological processes are represented, rather than the choice of emission scenario and differences between various climate projections.

Although this work suggests that the risk of climate-induced damage to tropical forests will be relatively small, the team does list where the considerable uncertainties remain in defining how ecosystems respond to global warming.

Dr Huntingford said: “The big surprise in our analysis is that uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections.

Other factors involved

 

“Despite this we conclude that, based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas (Amazonia and Central America), Africa and Asia.”

Co-author Dr David Galbraith, from the University of Leeds, UK, said: “This study highlights why we must improve our understanding of how tropical forests respond to increasing temperature and drought.

“Different vegetation models currently simulate remarkable variability in forest sensitivity to climate change. And while these new results suggest that tropical forests may be quite resilient to warming, it is important also to remember that other factors not included in this study, such as fire and deforestation, will also affect the carbon stored in tropical forests.

“Their impacts are also difficult to simulate. It is therefore critical that modelling studies are accompanied by further comprehensive forest observations.”

Co-author Dr Lina Mercado from the University of Exeter, UK, and the Centre for Ecology & Hydrology said one of the big remaining challenges was to include, in Earth system models, a full representation of how the rainforests respond and adapt to warming.

Debate over how resilient the rainforests may be is not new. A 2010 study, funded by Nasa, said the worst drought in the Amazon for more than a century had had little impact on the forest’s vegetation.

The Intergovernmental Panel on Climate Change (IPCC) has said that up to 40% of the Amazon forest could react drastically to even a small reduction in rainfall, and the result could be the replacement of the trees by tropical grassland.

One feature of this study is the confidence it has in climate projections and its acknowledgement that there is still much more to learn about plant physiology and ecosystem response.

Dr Huntingford told the Climate News Network the fertilisation effect of the large quantities of CO2 being absorbed by the forests was dominant, with the detrimental effects of climate change less important.

But the release of carbon dioxide into the atmosphere would overtake the process of photosynthesis. He said: “We do realise the story is changing as time passes, and all we can do is to try to present the facts as best we can and reflect the way the climate is changing, and the physical response to that now and in the future.” – Climate News Network

FOR IMMEDIATE RELEASE
The world’s rainforests may be able to weather the assaults of climate change more robustly than scientists had earlier thought, says a new study.

LONDON, 12 March – Scientists think they have found some good news for the Amazon and other tropical forests. They say they appear more able to withstand the effects of climate change than previous studies had suggested.

The research team, including climate scientists and tropical ecologists from the UK, USA, Australia and Brazil, concluded that the forests are less likely to lose biomass – plants and plant material – in response to greenhouse gas emissions over the rest of this century.

In what they say is the most comprehensive assessment yet of the risk of tropical forest dieback caused by climate change, the scientists say their results have important implications for the future evolution of rainforests, including the role they play in the global climate system and carbon cycle. The study is published online in Nature Geoscience.

To remain effective, programmes such as the United Nations’ Reducing Emissions from Deforestation and Degradation+ scheme (REDD+) require rainforest stability, in effect locking carbon within the trees.

The research team was led by Dr Chris Huntingford from the Centre for Ecology & Hydrology in the UK. He and his colleagues used computer simulations with 22 climate models to explore the response of tropical forests in the Americas, Africa and Asia to greenhouse gas-induced climate change.

They found loss of forest cover in only one model, and only in the Americas. The researchers found the largest source of uncertainty in the projections to be differences in how plant physiological processes are represented, rather than the choice of emission scenario and differences between various climate projections.

Although this work suggests that the risk of climate-induced damage to tropical forests will be relatively small, the team does list where the considerable uncertainties remain in defining how ecosystems respond to global warming.

Dr Huntingford said: “The big surprise in our analysis is that uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections.

Other factors involved

 

“Despite this we conclude that, based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas (Amazonia and Central America), Africa and Asia.”

Co-author Dr David Galbraith, from the University of Leeds, UK, said: “This study highlights why we must improve our understanding of how tropical forests respond to increasing temperature and drought.

“Different vegetation models currently simulate remarkable variability in forest sensitivity to climate change. And while these new results suggest that tropical forests may be quite resilient to warming, it is important also to remember that other factors not included in this study, such as fire and deforestation, will also affect the carbon stored in tropical forests.

“Their impacts are also difficult to simulate. It is therefore critical that modelling studies are accompanied by further comprehensive forest observations.”

Co-author Dr Lina Mercado from the University of Exeter, UK, and the Centre for Ecology & Hydrology said one of the big remaining challenges was to include, in Earth system models, a full representation of how the rainforests respond and adapt to warming.

Debate over how resilient the rainforests may be is not new. A 2010 study, funded by Nasa, said the worst drought in the Amazon for more than a century had had little impact on the forest’s vegetation.

The Intergovernmental Panel on Climate Change (IPCC) has said that up to 40% of the Amazon forest could react drastically to even a small reduction in rainfall, and the result could be the replacement of the trees by tropical grassland.

One feature of this study is the confidence it has in climate projections and its acknowledgement that there is still much more to learn about plant physiology and ecosystem response.

Dr Huntingford told the Climate News Network the fertilisation effect of the large quantities of CO2 being absorbed by the forests was dominant, with the detrimental effects of climate change less important.

But the release of carbon dioxide into the atmosphere would overtake the process of photosynthesis. He said: “We do realise the story is changing as time passes, and all we can do is to try to present the facts as best we can and reflect the way the climate is changing, and the physical response to that now and in the future.” – Climate News Network

Warming ‘may harm rainforests less’

FOR IMMEDIATE RELEASE The world’s rainforests may be able to weather the assaults of climate change more robustly than scientists had earlier thought, says a new study. LONDON, 12 March – Scientists think they have found some good news for the Amazon and other tropical forests. They say they appear more able to withstand the effects of climate change than previous studies had suggested. The research team, including climate scientists and tropical ecologists from the UK, USA, Australia and Brazil, concluded that the forests are less likely to lose biomass – plants and plant material – in response to greenhouse gas emissions over the rest of this century. In what they say is the most comprehensive assessment yet of the risk of tropical forest dieback caused by climate change, the scientists say their results have important implications for the future evolution of rainforests, including the role they play in the global climate system and carbon cycle. The study is published online in Nature Geoscience. To remain effective, programmes such as the United Nations’ Reducing Emissions from Deforestation and Degradation+ scheme (REDD+) require rainforest stability, in effect locking carbon within the trees. The research team was led by Dr Chris Huntingford from the Centre for Ecology & Hydrology in the UK. He and his colleagues used computer simulations with 22 climate models to explore the response of tropical forests in the Americas, Africa and Asia to greenhouse gas-induced climate change. They found loss of forest cover in only one model, and only in the Americas. The researchers found the largest source of uncertainty in the projections to be differences in how plant physiological processes are represented, rather than the choice of emission scenario and differences between various climate projections. Although this work suggests that the risk of climate-induced damage to tropical forests will be relatively small, the team does list where the considerable uncertainties remain in defining how ecosystems respond to global warming. Dr Huntingford said: “The big surprise in our analysis is that uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections.

Other factors involved

  “Despite this we conclude that, based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas (Amazonia and Central America), Africa and Asia.” Co-author Dr David Galbraith, from the University of Leeds, UK, said: “This study highlights why we must improve our understanding of how tropical forests respond to increasing temperature and drought. “Different vegetation models currently simulate remarkable variability in forest sensitivity to climate change. And while these new results suggest that tropical forests may be quite resilient to warming, it is important also to remember that other factors not included in this study, such as fire and deforestation, will also affect the carbon stored in tropical forests. “Their impacts are also difficult to simulate. It is therefore critical that modelling studies are accompanied by further comprehensive forest observations.” Co-author Dr Lina Mercado from the University of Exeter, UK, and the Centre for Ecology & Hydrology said one of the big remaining challenges was to include, in Earth system models, a full representation of how the rainforests respond and adapt to warming.

Debate over how resilient the rainforests may be is not new. A 2010 study, funded by Nasa, said the worst drought in the Amazon for more than a century had had little impact on the forest’s vegetation. The Intergovernmental Panel on Climate Change (IPCC) has said that up to 40% of the Amazon forest could react drastically to even a small reduction in rainfall, and the result could be the replacement of the trees by tropical grassland. One feature of this study is the confidence it has in climate projections and its acknowledgement that there is still much more to learn about plant physiology and ecosystem response. Dr Huntingford told the Climate News Network the fertilisation effect of the large quantities of CO2 being absorbed by the forests was dominant, with the detrimental effects of climate change less important. But the release of carbon dioxide into the atmosphere would overtake the process of photosynthesis. He said: “We do realise the story is changing as time passes, and all we can do is to try to present the facts as best we can and reflect the way the climate is changing, and the physical response to that now and in the future.” – Climate News Network

FOR IMMEDIATE RELEASE The world’s rainforests may be able to weather the assaults of climate change more robustly than scientists had earlier thought, says a new study. LONDON, 12 March – Scientists think they have found some good news for the Amazon and other tropical forests. They say they appear more able to withstand the effects of climate change than previous studies had suggested. The research team, including climate scientists and tropical ecologists from the UK, USA, Australia and Brazil, concluded that the forests are less likely to lose biomass – plants and plant material – in response to greenhouse gas emissions over the rest of this century. In what they say is the most comprehensive assessment yet of the risk of tropical forest dieback caused by climate change, the scientists say their results have important implications for the future evolution of rainforests, including the role they play in the global climate system and carbon cycle. The study is published online in Nature Geoscience. To remain effective, programmes such as the United Nations’ Reducing Emissions from Deforestation and Degradation+ scheme (REDD+) require rainforest stability, in effect locking carbon within the trees. The research team was led by Dr Chris Huntingford from the Centre for Ecology & Hydrology in the UK. He and his colleagues used computer simulations with 22 climate models to explore the response of tropical forests in the Americas, Africa and Asia to greenhouse gas-induced climate change. They found loss of forest cover in only one model, and only in the Americas. The researchers found the largest source of uncertainty in the projections to be differences in how plant physiological processes are represented, rather than the choice of emission scenario and differences between various climate projections. Although this work suggests that the risk of climate-induced damage to tropical forests will be relatively small, the team does list where the considerable uncertainties remain in defining how ecosystems respond to global warming. Dr Huntingford said: “The big surprise in our analysis is that uncertainties in ecological models of the rainforest are significantly larger than uncertainties from differences in climate projections.

Other factors involved

  “Despite this we conclude that, based on current knowledge of expected climate change and ecological response, there is evidence of forest resilience for the Americas (Amazonia and Central America), Africa and Asia.” Co-author Dr David Galbraith, from the University of Leeds, UK, said: “This study highlights why we must improve our understanding of how tropical forests respond to increasing temperature and drought. “Different vegetation models currently simulate remarkable variability in forest sensitivity to climate change. And while these new results suggest that tropical forests may be quite resilient to warming, it is important also to remember that other factors not included in this study, such as fire and deforestation, will also affect the carbon stored in tropical forests. “Their impacts are also difficult to simulate. It is therefore critical that modelling studies are accompanied by further comprehensive forest observations.” Co-author Dr Lina Mercado from the University of Exeter, UK, and the Centre for Ecology & Hydrology said one of the big remaining challenges was to include, in Earth system models, a full representation of how the rainforests respond and adapt to warming.

Debate over how resilient the rainforests may be is not new. A 2010 study, funded by Nasa, said the worst drought in the Amazon for more than a century had had little impact on the forest’s vegetation. The Intergovernmental Panel on Climate Change (IPCC) has said that up to 40% of the Amazon forest could react drastically to even a small reduction in rainfall, and the result could be the replacement of the trees by tropical grassland. One feature of this study is the confidence it has in climate projections and its acknowledgement that there is still much more to learn about plant physiology and ecosystem response. Dr Huntingford told the Climate News Network the fertilisation effect of the large quantities of CO2 being absorbed by the forests was dominant, with the detrimental effects of climate change less important. But the release of carbon dioxide into the atmosphere would overtake the process of photosynthesis. He said: “We do realise the story is changing as time passes, and all we can do is to try to present the facts as best we can and reflect the way the climate is changing, and the physical response to that now and in the future.” – Climate News Network