Tag Archives: Forest fires

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

Temperature rise will fan forest flames

FOR IMMEDIATE RELEASE The forest fires raging through states in the western US are among the worst on record, but latest research indicates that they will get even worse in future as temperatures rise. LONDON, 2 September − As fire crews battle to control the forest fires that have been devastating areas of the western US, a bleak warning has been issued that such fires in future are likely to break out over longer periods and wider areas each year, and create up to twice as much smoke. Forest wildfires are a regular event in California and other states in the western US, but this year’s conflagrations are being described as some of the worst on record. One fire, which has threatened California’s Yosemite National Park, was at one stage spread over nearly 200,000 acres, or more than 300 square miles. Environmental scientists at Harvard School of Engineering and Applied Sciences (SEAS) fed data into a number of models to come up with predictions about how such fires will behave in future. The data included not only historical records of fires but also seasonal temperatures, relative humidity levels, and amounts of brush and dry fuel on the forest floor over six “ecoregions” in the western states. The models were matched with data from the fourth Intergovernmental Panel on Climate Change (IPCC) report on possible future atmospheric and climatological conditions for the year 2050. Based on this multi-model approach, the Harvard team was then able to calculate the likely extent of fires in mid-century, and to gauge areas that would be burned. “We weren’t altogether certain what we would find when we started this project,” says Loretta J Mickley, the study’s co-author and a senior research fellow in atmospheric chemistry at Harvard SEAS.

Conducive to fires

“In the future, we expect warmer temperatures, which are conducive to fires, but it’s not apparent what the rainfall and relative humidity will do. Warmer air can hold more water vapour, for instance, but what does this mean for fires? “It turns out that, for the western US, the biggest driver for fires in the future is temperature, and that result appears robust across models. When you get a large temperature increase over time, as we are seeing, and little rainfall, fires will increase in size.” Among the study’s forecasts for fires in the western US in 2050 are:

  • Areas burned in the month of August could increase by 65% in the Pacific Northwest, nearly double in the Eastern Rocky mountains, and quadruple in the Rocky Mountains Forest region.
  • Probability of large fires could increase by factors of two or three.
  • The start dates of the “fire season” could be earlier (late April instead of mid-May) and the end date could be later (mid-October instead of early October).

During the last 40 years, air quality has improved considerably over much of the US, mainly due to government efforts on regulating emissions. However, the study predicts that, due to more fires, smoke levels could increase by between 20% and 100% by 2050. “I think what people need to realise is that embedded in those curves showing the tiny temperature increases year after year are more extreme events that can be quite serious,” Mickley  says.  “It doesn’t bode well.” − Climate News Network

FOR IMMEDIATE RELEASE The forest fires raging through states in the western US are among the worst on record, but latest research indicates that they will get even worse in future as temperatures rise. LONDON, 2 September − As fire crews battle to control the forest fires that have been devastating areas of the western US, a bleak warning has been issued that such fires in future are likely to break out over longer periods and wider areas each year, and create up to twice as much smoke. Forest wildfires are a regular event in California and other states in the western US, but this year’s conflagrations are being described as some of the worst on record. One fire, which has threatened California’s Yosemite National Park, was at one stage spread over nearly 200,000 acres, or more than 300 square miles. Environmental scientists at Harvard School of Engineering and Applied Sciences (SEAS) fed data into a number of models to come up with predictions about how such fires will behave in future. The data included not only historical records of fires but also seasonal temperatures, relative humidity levels, and amounts of brush and dry fuel on the forest floor over six “ecoregions” in the western states. The models were matched with data from the fourth Intergovernmental Panel on Climate Change (IPCC) report on possible future atmospheric and climatological conditions for the year 2050. Based on this multi-model approach, the Harvard team was then able to calculate the likely extent of fires in mid-century, and to gauge areas that would be burned. “We weren’t altogether certain what we would find when we started this project,” says Loretta J Mickley, the study’s co-author and a senior research fellow in atmospheric chemistry at Harvard SEAS.

Conducive to fires

“In the future, we expect warmer temperatures, which are conducive to fires, but it’s not apparent what the rainfall and relative humidity will do. Warmer air can hold more water vapour, for instance, but what does this mean for fires? “It turns out that, for the western US, the biggest driver for fires in the future is temperature, and that result appears robust across models. When you get a large temperature increase over time, as we are seeing, and little rainfall, fires will increase in size.” Among the study’s forecasts for fires in the western US in 2050 are:

  • Areas burned in the month of August could increase by 65% in the Pacific Northwest, nearly double in the Eastern Rocky mountains, and quadruple in the Rocky Mountains Forest region.
  • Probability of large fires could increase by factors of two or three.
  • The start dates of the “fire season” could be earlier (late April instead of mid-May) and the end date could be later (mid-October instead of early October).

During the last 40 years, air quality has improved considerably over much of the US, mainly due to government efforts on regulating emissions. However, the study predicts that, due to more fires, smoke levels could increase by between 20% and 100% by 2050. “I think what people need to realise is that embedded in those curves showing the tiny temperature increases year after year are more extreme events that can be quite serious,” Mickley  says.  “It doesn’t bode well.” − Climate News Network