Tag Archives: Plants and forests

Carbon emissions from Amazon wildfires could ‘counteract’ deforestation decline

The loss of carbon from wildfires fuelled by drought could “counteract” efforts to cut deforestation in the Amazon rainforest, research suggests.

A new study finds that, while rates of deforestation have sharply fallen in the Amazon over the past decade, the number of wildfires affecting the region has remained stubbornly high – particularly in drought years.

Emissions from wildfires totalled more than 1bn tonnes of CO2 from 2003-2015, the lead author tells Carbon Brief, and climate change, along with forest fragmentation, could cause a further increase in the number of forest fires in the coming decades.

The author adds that, if current efforts to curb deforestation are reversed, the combination of forest fires and deforestation could cause carbon loss from the Amazon to “escalate to proportions never experienced before”.

Three billion trees

The Amazon rainforest is the largest rainforest in the world, spanning an area that is 25 times the size of the UK.

The forest’s three billion trees absorb CO2 from the atmosphere during photosynthesis and then use it to build new leaves, shoots and roots. As they grow, these trees account for a quarter of the CO2 absorbed by the land each year.

The new study, published in Nature Communications, explores how this enormous carbon store is being affected by both deforestation and drought-driven wildfires.

The clearing of trees during deforestation causes previously locked-up carbon to be released back into the atmosphere.

The study finds that, despite remaining a major driver of forest carbon loss, rates of deforestation in the Amazon have fallen by 76% between 2003 and 2015. This reflects efforts by the Brazilian government to curb both legal and illegal deforestation, the study notes.

However, the amount of carbon loss from drought-driven wildfires has remained high, says lead author Dr Luiz Aragão, leader of the tropical ecosystems and environmental sciences group (TREES) at the National Institute for Space Research in Brazil. He tells Carbon Brief:

“This is the first time that we could clearly demonstrate how much widely-spread forest fires during recent droughts influence Amazonian carbon emissions. During these droughts, forest fires can overtake emissions from deforestation.”

Fanning the flames

Glossary

El Niño: Every five years or so, a change in the winds causes a shift to warmer than normal sea surface temperatures in the equatorial Pacific Ocean – known as El Niño. Together with its cooler counterpart, La Niña, this is known as the El Niño Southern Oscillation (ENSO) and is responsible for most of the fluctuations in temperature and rainfall patterns we see from one year to the next.

El Niño: Every five years or so, a change in the winds causes a shift to warmer than normal sea surface temperatures in the equatorial Pacific Ocean – known as El Niño. Together with… Read More

Although wildfires occur regularly in the Amazon, fire incidence is at its highest in drought years.

“Drought years” happen on average every five years in the Amazon and are typically a result of changes to wind and weather patterns brought about by warming in the Atlantic Ocean during events of the climate phenomenon El Niño.

Although droughts have been a natural part of the year-to-year variations in the Amazon’s climate, both the frequency and severity of droughts in the rainforest have been increasing over the last decade because of climate change, Aragão says:

“These natural swings can be intensified by global warming. Another catalyst of this Atlantic oceanic warming is the declining Northern Hemisphere aerosol production, which is also influenced by climate change.”

Previous research (pdf) shows that aerosols influence cloud formation in the rainforest and, therefore, the amount of regional rainfall.

Wildfires are usually sparked by humans clearing land, either for small-scale farming or major deforestation, Aragão says. During drought years, these small fires can quickly spread to large areas of the rainforest.

A lack of rainfall during drought years causes large sections of the lush canopy to dry out and die. These dry, dead leaves can then act as tinder, allowing small fires to spread, says Aragão:

“These forests would not burn naturally. Most of the fires that happen during droughts are human-driven. When the climate is drier, fires that are set for land management are more likely to leak into surrounding forests.”

As large areas of forest burn, huge stores of previously stored carbon are released into the atmosphere. The amount of carbon loss is greatest when fires “leak into” previously pristine forest, which may have been storing carbon for decades or even centuries, Aragão adds.

Assessing the damage

The researchers used satellite data to record the number and regional spread wildfires in the Amazon from 2003-15. The figure below shows the annual fire counts of each year of the study (red bars and numbers), with bold text signifying drought years (2005, 2010 and 2015). The numbers on the x-axis correspond to the fire season months from June (month 6) to December (month 12).

The length of the grey bars corresponds to the sum of all months with more than 10,000 fires. The colour within the grey bar shows the number of fire counts during the year’s “peak month”, with dark red showing a count of more than 40,000 and green showing a count of 10,000 to 15,000.

The chart also displays annual deforestation rates in the Amazon (khaki bars), which were derived from the Brazilian government.

The chart shows how the number of forest fires tends to spike in drought years. For example, during the 2015 drought, fire incidence was 36% higher compared to the average for the previous 12 years, the study finds.

Annual absolute fire counts (red bars) and deforestation rates (khaki bars) in the Amazon from 2003-15. Number of fires during drought years (2005, 2010, 2015) are shown in bold. The length of the grey bars corresponds to the sum of all months with more than 10,000 fires. The colour within the grey bar shows the number of fire counts during the year’s “peak month”, with dark red showing a count of more than 40,000 and green showing a count of 10,000 to 15,000. Source: Aragão (2018)

The results show that, while deforestation rates are decreasing, forest fire counts have not seen a similar decline.

This suggests that the role that deforestation plays in sparking forest fires is diminishing over time, says Aragão:

“Before we used to observe that fires in Amazonia were strongly related to deforestation. Now this relationship is weak. We think that there are few explanations, but a strong one is that because the Amazon is more fragmented, there are more edges between the deforested land and forests. This increases the chances of fires from open lands to propagate into forests.”

The effect of fragmentation could be magnified by future climate change, which is expected to bring more extreme droughts to the Amazon, he says:

“We expect that drought intensity and frequency will increase towards the end of the century. So, with more droughts it is very likely that fire incidence will also increase if no policy actions are taken to curb ignition sources.”

The researchers also used satellite data to record the total amount of CO2 released as a result of deforestation and wildfires over the study period.

The results are shown on the chart below, which shows annual CO2 emissions in teragrams (one teragram is equal to 1m tonnes of CO2) for forest fires (dark green) and deforestation (light green).

Over the course of the study period, emissions from wildfires in drought years alone totalled more than 1bn tonnes, Aragão says. The release of CO2 during forest fires could increase further as the climate warms, he adds.

Annual CO2 emissions in teragrams (1m tonnes) of forest fires (dark green) and deforestation (light green) in the Amazon from 2003 to 2015. Source: Aragão (2018)

‘Compelling’ results

The “comprehensive” study raises concerns over the growing threat of wildfires in the Amazon, says Prof Guido van der Werf from Vrije University in the Netherlands, who was not involved in the study. Van der Werf was part of a team that developed the Global Fire Emissions Database. He tells Carbon Brief:

“What is particularly compelling to me is the observed decoupling of fire and deforestation; they used to go hand in hand as fire was the cheapest tool in the deforestation process, but in recent years fires are observed more outside the deforestation regions, especially during drought years.

“Controlling these forest fires may be more difficult than controlling deforestation as it only takes one simple ignition to burn down a large area and many fires occur in secondary forests which may be less well monitored.”

The research uses a “sound methodology” but relies on statistics from the Brazilian government, which research suggests could be overstating recent deforestation reductions, says Dr Richard Birdsey, a senior scientist specialising in quantifying forest carbon budgets from the Woods Hole Research Centre, who also wasn’t involved in the research. He tells Carbon Brief:

“Some studies question the official statistics of deforestation in Brazil, suggesting that the reduction over previous decades may be overestimated. If deforestation is higher than the estimate used in this paper, then the relative effect of drought-induced fire would not be as large as stated here, and the decoupling of fire incidence from deforestation rates would not be as significant.”

Another factor not considered in the study is that forests tend to recover more quickly from wildfires than deforestation, he adds:

“Fires create young forests that will rather quickly recover significant amounts of lost biomass and usually have higher productivity compared with old-growth for several decades. Thus, considering the effects of fires over decades is an important consideration not addressed in this paper.”

Further carbon loss as a result of drought-driven wildfires could “counteract” efforts to curb deforestation in the Amazon, says Aragão. And, if efforts to stop deforestation are unsuccessful, the scale of carbon loss from the Amazon could reach “unprecedented” levels, he says:

“The main worry is that if deforestation increases, in combination with the increase fragmentation, increase in drought probability [caused by climate change] and the use of fires by humans, carbon emissions could escalate to proportions never experienced before.”

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Rainforests: Scientists concerned climate change is altering the tropical life cycle

Climate change could be causing shifts to the natural cycle of life in the tropical rainforest, scientists have suggested.

A rise in global temperatures may be driving trees and plants to produce fruit and flowers earlier or later than before, researchers have found. This could have large consequences for a diverse range of animals that rely on tropical rainforests for food and shelter.

The animals most at risk include those that rely on flower nectar for survival, including bees and hummingbirds, as well as animals that feed on the fruit of tropical trees, including great apes, monkeys and parrots.

However, a lack of historical data and ongoing research in the tropics means that the scale of these changes is yet to be fully understood, scientists told Carbon Brief at a Royal Society conference held in Buckinghamshire earlier this month.

Changing seasons

In every part of the world, plants rely on cues from their environment, including changes in sunshine, temperature and rainfall, to determine when to start producing leaves, flowers or fruit. The study of this phenomenon is known as plant “phenology”.

Primary rainforest Langkawi Malaysia. Credit: David Noton Photography / Alamy Stock Photo.

In temperate regions, including the UK and North America, plants tend to time their natural cycles to the changing of the seasons. For instance, plants respond to warming temperatures and increasing daylight hours in the spring by sprouting new leaves.

However, rainforests do not have well-defined seasons, such as spring, summer, autumn, and winter, says Prof Patricia Morellato from São Paulo State University in Brazil. Morellato chaired a session on the possible future of tropical phenology research at the conference. At the sidelines of the event, she told Carbon Brief:

“In the tropics, we don’t have sharp seasons, so it’s more difficult to track changes. Instead, we have to know the cycle and, over time, see if the cycle is changing.”

Most rainforests have a wet and a dry season, which is caused by annual changes in rainfall. But many tropical plants do not time events, such as flowering, in accordance with these seasons, says Dr Joseph Wright, from the Smithsonian Tropical Research Institute in Panama. At the conference, Wright presented a talk on the environmental controls of leaf fall and flowering in tropical rainforests. He told Carbon Brief:

“I work on a 16 sq km site in Panama with 2,000 plant species. Every month of the year, there are several hundred species flowering. At the peak month, there’s probably a thousand species flowering. But even in the minimum month, there’s 200 species flowering.”

Because tropical plants do not time their life cycles according to the seasons, it is more difficult to work out what environmental cues could be causing the plants to begin flowering, Wright said:

“It could be unusually low temperature. It could be the beginning of the rainy season. Or it could be sunlight. These hypotheses are very vague.”

Data drought

Another limitation in the tropics is a lack of long-term climate and plant data, the researchers said.

In Europe and North America, scientists and nature enthusiasts alike have been recording the date of the first bud, leaf and flower for thousands of species for more than a century.

This long record has enabled researchers to track how plants are responding to global warming. Recent research (pdf) from the Met Office finds that spring is currently advancing at a rate of 2.5 days per decade across Europe.

However, in the tropics, there are very few known historical records and little funding available for research to be conducted, Wright said:

“There’s an incredible north-south divide. The northern hemisphere is rich and there’s tonnes of excellent universities and national research councils and so, as a consequence, in the northern temperate zone we have an incredible knowledge base. There’s tonnes of scientists and there’s very few species.

“You go to the tropics, we have the opposite situation. Countries are poor, each country might have one national university and the vast majority have no national research programme. But there’s thousands of species, there’s a hundred times more species and three orders of magnitude fewer scientists.”

Measuring mismatch

Despite a lack of historical knowledge, a growing number of researchers are trying to find new ways of understanding how climate change could affect the natural cycle of tropical rainforests.

One key area of this new research is to understand how shifts in forest cycles could affect the unique community of animals that live in the tropics.

It is still unclear how climate change may affect rainfall patterns in much of the tropics, but research (pdf) suggests that rainforests could experience longer dry periods by the end of the century.

A research paper published by Morellato and her colleagues in 2016 in the journal Biological Conservation attempts to evaluate how a longer dry season caused by climate change could affect the timings of key events in the rainforest.

It suggests that a longer dry season could cause plants to start flowering later on in year. This is shown in the chart below, where blue bars show the amount of monthly rainfall, while blue lines show the percentage of plants that are producing flowers. Red lines show the percentage of plants producing fruit.

On the chart, red-dashed arrows show how a longer dry season caused by climate change could lead to later plant reproduction via flowering. Later flowering could lead to less time available for plant pollination, which will result in fewer plants producing fruit the following year.

Schematic diagram showing the effects of climate change in tropical rainforests. On the top chart, blue bars show monthly rainfall, blue lines show the percentage of plants flowering and red lines show the percentage of plants producing fruit. The bottom chart shows the overlap (black) and non-overlap (striped) of the activity timing of flowers and pollinators (blue) and fruit and fruit-eating animals (red). Caption: Morellato et al. (2016)

Beneath the chart, a diagram shows how a later flowering period caused by climate change could lead to a smaller overlap between the activity time of flowers and their pollinators (shown in blue).

This “mismatch” could greatly threaten the survival of pollinators, including insects and birds, who rely on flowers for both food and shelter.

The animals most at risk are those which feed on the nectar of just a small number of plant species, such as many bees and hummingbirds, the study notes:

“The reliable and continuous availability of floral resources in the tropics has enabled strong and diverse adaptations in flower visitors, maintaining rich assemblages of highly specialised floral foragers, such as bees and hummingbirds.”

On top of this, a reduction in fruit availability in the following year as a result of climate change could cause a “mismatch” in the activity time of fruit trees and fruit-eating animals, which are known as “frugivores”. The paper reads:

“Frugivorous animals critically rely on fruits, and fundamental aspects of their ecology – including diet, population size, social behaviour reproduction, and movements – depend on fruit abundance and seasonality.”

A wild, young male orangutan climbs trees in the rainforest to find red berries to eat. Credit: Lillian Tveit / Alamy Stock Photo.

Such animals include great apes, smaller monkey species, as well as a range of tropical birds, including parrots, the paper adds.

‘Critical to every organism’

Although recent research outlines the species most at risk from shifts to the tropical cycle, it is likely that such changes will affect almost every animal found in the rainforest in some way, Morellato said:

“In the tropics, almost all species rely, at some point in their lives, on a plant in flower or in fruit. Changes in phenology will affect the animal community in forests, that’s for sure.”

Fully understanding how climate change is affecting plant phenology will be key to protecting rainforest wildlife, Wright said:

“Primary producers [plants] are critical to every organism, every animal, every consumer in the forest. The more we’re able to get some understanding on what the link between what climate and the plant response is, the more we’re going to be able to make predictions about their chances of survival.”

 

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Climate change and deforestation threaten world’s largest tropical peatland

Just over a year ago, scientists announced the discovery of the world’s largest intact tropical peatland in a remote part of the Congo’s vast swampy basin.

The Cuvette Centrale peatlands stretch across an area of central Africa that is larger than the size of England and stores as much as 30bn tonnes of carbon.

Now, the same research team has published a new study finding that future climate change, along with deforestation, could threaten the peatlands’ ability to soak up and store large amounts of carbon.

If left unaddressed, these threats could cause the Congo peatlands to turn from a carbon sink to a carbon source, the study says. This means that the peatlands could contribute to climate change by releasing more carbon than they are able to absorb.

Protecting the peatlands from climate change will require “an international effort to reduce greenhouse gas emissions”, the lead author tells Carbon Brief.

Peat power

The Cuvette Centrale, which spans both the Republic of the Congo and the Democratic Republic of Congo (DRC) (see map below), is the second-largest tropical wetland in the world.

Location of the Cuvette Centrale wetlands in Africa (in green) Source: Dargie et al. (2017)

The peatlands within the Cuvette Centrale covers 145,500 sq km and contains 30% of the world’s tropical peatland carbon, according to the 2017 Nature paper. This is equivalent to about 20 years’ worth of US CO2 emissions from burning fossil fuels.

Across the world, peat covers just 3% of the land’s surface, but stores one-third of the Earth’s soil carbon.

Peat is a wetland soil made of partially decomposed plant debris. It is usually found in cooler, waterlogged environments, explains Dr Greta Dargie, a research fellow from the University of Leeds and lead author of the study published in the journal Mitigation and Adaptation Strategies for Global Change. She tells Carbon Brief:

“Under waterlogged conditions, the usual decomposition of dead trees and leaves is slowed, meaning there is a build-up of carbon-rich material which we call peat. A long slow build-up means that peatlands store enormous quantities of carbon.”

Heating up

Glossary

RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation and carbon dioxide removal technologies mean atmospheric CO2 concentration peaks and then falls during this century. By 2100, CO2 levels increase to around 420ppm – around 20ppm above current levels – equivalent to 475ppm once other forcings are included (in CO2e). By 2100, global temperatures are likely to rise by 1.3-1.9C above pre-industrial levels.

RCP2.6: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP2.6 (also sometimes referred to as “RCP3-PD”) is a “peak and decline” scenario where stringent mitigation… Read More

Future climate change presents one of the largest threats to the Congo peatlands, the new study finds.

The latest assessment report (pdf) from the Intergovernmental Panel on Climate Change (IPCC) finds that the region could warm by around 0.5C from 2000 to the end of the century under a low-emissions scenario (RCP2.6) and by 4.5C under a high-emissions scenario (RCP8.5).

It is less clear how global warming could affect rainfall in the region, but research (pdf) suggests that the peatlands could experience an overall reduction in rainfall and an increase in the number of dry periods as the climate warms.

Glossary

RCP8.5: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP8.5 is a scenario of “comparatively high greenhouse gas emissions“ brought about by rapid population growth, high energy demand, fossil fuel dominance and an absence of climate change policies. This “business as usual” scenario is the highest of the four RCPs and sees atmospheric CO2 rise to around 935ppm by 2100, equivalent to 1,370ppm once other forcings are included (in CO2e). The likely range of global temperatures by 2100 for RCP8.5 is 4.0-6.1C above pre-industrial levels.

RCP8.5: The RCPs (Representative Concentration Pathways) are scenarios of future concentrations of greenhouse gases and other forcings. RCP8.5 is a scenario of “comparatively high greenhouse gas emissions“ brought about by rapid population growth,… Read More

A combination of less rainfall and higher temperatures could cause parts of the peatlands to dry out, which could reduce the rate of plant decomposition and, therefore, the rate that the peatlands can absorb carbon from the atmosphere.

Drier conditions could also prompt the peatlands to start releasing larger amounts of carbon, says Prof Simon Lewis, a study author from the University of Leeds and University College London, and one of Carbon Brief’s contributing editors. He tells Carbon Brief:

“The critical insight here is that the central Congo peatlands are probably maintained by rainwater. So, even modest reductions in dry season water-logging, perhaps through rising temperatures and increasing evaporation rates, would mean the whole system moves from a carbon sink to a carbon source.”

In other words, climate change could cause the Congo peatlands to start releasing more carbon into the atmosphere than it is able to absorb.

Forest under threat

Another threat to Congo’s peatlands could come from a potential rise in deforestation for wood and palm oil production in the region, the study notes.

The removal of trees from above peatlands can leave large areas of ground exposed to the sun, which can cause the boggy ground to dry out. This can cause the peatlands to release carbon at a faster rate.

At present, government officials from the DRC have granted logging access to 20% of the forested peatlands. The extent of the logging concession agreements (red outlines) is shown on the chart below, where dark grey indicates peatland and light grey shows other types of land cover.

At least one concession agreement (shown in shaded red) has also been approved for the construction of an oil palm plantation in the Republic of the Congo part of the peatlands, which would take up 4,200km sq of forested peatlands.

Extent of logging concessions (red outlines) and oil palm concessions (shaded red) granted in the Cuvette Centrale. Dark grey shows the location of the Cuvette Centrale peatlands, while light grey shows other types of land cover. Source: Dargie et al. (2018)

Despite these agreements being reached, logging operations are yet to commence in the peatland forests. This is likely to be because the DRC introduced a national ban on logging in 2002, the study notes.

However, the country’s government is currently considering lifting this ban, which would mean logging could be permitted across large areas of the peatland region.

Plans to lift the ban are being driven forward by the French Development Agency (AFD) with financial support from the Norway-led Central African Forests Initiative (CAFI), Lewis says. These groups argue that lifting the ban could aid social development in the region and make it easier to curb illegal and unregulated deforestation.

On top of this, the peatlands could also be affected by plans to construct hydroelectric dams in region, including the Grand Inga hydropower project. Such projects could divert water away from the wetlands, the study notes.

Overall, the peatlands face an immediate risk from deforestation and land-use change and a more long-term threat from climate change, Lewis says:

“The competing threats of direct land-use change and climate change are difficult to compare. The speed with which land can be converted is fast and can quickly kill large areas of swamp forest. But other areas would probably remain unaffected. The speed of climate change is slower than the movement of bulldozers, but could affect the entire peatland.”

Protecting peat

To protect the peatlands in the short term, policymakers should consider introducing new environmental protections to the region, the authors write in their paper:

“Further research, therefore, needs to integrate knowledge from local communities, the natural sciences and social sciences, to develop a more holistic understanding of the Cuvette Centrale peatlands and facilitate local communities and their governments to manage and protect this globally significant region.”

However, protecting the peatlands from the threat of climate change will require a long-term “international effort”, Dargie says:

“With climate change, there is also the added complication that Republic of the Congo and DRC government policies and interventions alone will not be enough to avoid any negative impacts on the Congo Basin peatlands. That will require an international effort to reduce greenhouse gas emissions.”

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