Once fire-proof Amazon rainforests have become flammable, thanks to climate change

A forest fire in the Amazon. Image: Getty.

The Amazon rainforest is described as the planet’s lungs for good reason. So much carbon is locked up in its trees that protecting the forest is a must if we want to do something about global warming. However, reducing the CO₂ that is emitted when a tropical forest is destroyed depends not only on stopping the actual deforestation, but also on fighting wildfires within the forest.

In a new study published in Nature Communications we show that forest fires are responsible for a huge portion of the carbon emitted from the Brazilian Amazon. During drought years, these fires can emit around a billion tonnes of CO₂. That alone is double the amount of carbon effectively emitted through deforestation in the Amazon.

Humans are throwing vast amounts of CO₂ into the planet’s atmosphere. While in developed countries such as the US and UK most of the emissions come from industrial activities, in developing tropical countries such as Brazil, most come from forests being chopped down and burnt.

Yet while deforestation is already recognised as an important driver of carbon emissions, wildfires under the forest canopy present a less visible but still pernicious threat. To figure out just how bad the problem is, we combined satellite data on the current climate, atmospheric carbon content and the health of forest ecosystems. Our work revealed that emissions from tropical forest fires are growing, even though they are still not normally accounted for in estimates of national emissions.

Wildfires – but not natural fires

Wildfires in the Amazon are not natural events, but are instead caused by a combination of droughts and human activities. Both anthropogenic climate change and regional deforestation are linked to increases in the intensity and frequency of droughts over Amazonia.

Fires spreads into the forest during the 2015 drought. Image: Erika Berenguer/author provided.

This kicks off a nasty cycle: as trees have less water during such droughts, their growth slows and they’re less able to remove CO₂ from the atmosphere through photosynthesis. Trees then shed extra leaves or even die, which means more wood and leaves are ready to burn on the forest floor and, without a dense canopy to retain moisture, the forest loses some of the humidity which acted as natural fire prevention.

These changes are exacerbated by “selective logging” of specific tree species, which opens up the canopy and further dries out the understory and forest edges, which are drier than the interiors. The result: normally fire-proof rainforests become flammable.

A fiery future?

The resulting wildfires have reached a worrying level, burning millions of hectares during the recent El Niño. But the worst could still be to come, as the unusually warm conditions in the Atlantic or Pacific oceans that have caused previous droughts are expected to intensify.

So far this century the Amazon has already experienced three “droughts of the century”, in 2005, 2010, 2015-2016. If the climate science is accurate, and if no action is taken to efficiently predict and avoid fires occurring, we expect that carbon emissions from forest fires would be sustained even if deforestation ended overnight.

Smouldering tree trunk after a forest fire during the 2015 drought in eastern Amazonia. Image: Erika Berenguer/author provided.

As one of the signatories to the Paris agreement on climate change, Brazil is committed to reducing its emissions to 37 per cent below 2005 levels by 2025. A major reduction in deforestation rates over the past decade is a great start. However, deforestation policy doesn’t help reduce forest fires and consequently isn’t fully efficient in mitigating carbon emissions from the Amazon.

Brazil has made substantive advances in reporting emissions from deforestation. It now needs urgently to focus on incorporating CO₂ losses from wildfires into its estimates. After all, those fire emissions are expected to increase in future, thanks to more extreme droughts, an expansion of selective logging, and the ongoing use of fire to manage pasture or to remove regrowing vegetation on farmlands.

Kilometres of burned forests (magenta) spread across old-growth forests (green) in eastern Amazonia. White patches are clouds. Image: Celso Silva-Junior/USGS/author provided.

Given that fire is an essential part of many smallholders’ livelihoods, it is critically important to implement sustainable and socially-just policy responses. Brazil should start by reversing the budget cut to the organisation that oversees its only existing fire-prevention programme. It should also avoid selective logging in regions that are prone to fires, and ensure forest management always factors in long-term fire-prevention.

The ConversationIn summary, these findings are not only critical for policymakers in Brazil to strengthen the efforts of effectively quantifying and limiting carbon emissions from forest fires in the years ahead, but also to other tropical nations to tackle the potential impacts of drought-induced fires on their carbon budget. These new findings bring critical information for nations to help prepare for urgent actions aiming to mitigate the potential increase of fire emissions in response to the intensification of droughts in tropical ecosystems.

Luiz Aragão, Senior Lecturer in Earth Systems Sciences, University of Exeter; Jos Barlow, Professor of Conservation Science, Lancaster University, and Liana Anderson, Research Associate in Land Cover Dynamics and Carbon Emissions, University of Oxford.

This article was originally published on The Conversation. Read the original article.


 

 
 
 
 

Marseille and Paris are crawling with rats. But it’s your problem too

A Parisian rat. Image: Getty.

You can very easily have a fine time in Marseille, but it is likely to be interrupted by rats.

The bloated and brazen beasts are so utterly convinced they own the place that they barely register any human presence to distract from their hedonistic excesses – throwing wild street parties, burrowing holes in overflowing bins, and darting in and out of exclusive harbourfront restaurants. We only really intrude when the occasional, blissfully oblivious rat is splattered across the cobblestones by a scooter.

For many residents, the whiskery foes have gone some way beyond a nuisance to represent a genuine menace. Rats have infested schools and taken over canteens. Pest control services claim they have broken into cars and gnawed through cables, which may have contributed to accidents. It is also alleged that they have caused Internet outages by attacking fibre-optic cables – continuing the venerable horror movie tradition of cutting the power seen in Aliens and Jurassic Park. Rats are also infamous and prolific traffickers of disease and have raised the threat of Leptospirosis.

Rat populations are fiendishly difficult to quantify, given their nocturnal lifestyle and that many live off-grid in the sewers; but by some estimates they now outnumber Marseille’s human inhabitants. Distress calls from the public to the city’s sanitation department and pest control services have increased, and the unofficial fifth emergency service has expanded its operations in response, laying poison traps and sweeping the gutters.

Several factors have contributed to the rat supremacy. Marseille’s Mediterranean climate has always been hospitable to rats, and a series of unusually warm summers – often passing 30°C – have made it more so. (Rats tend to stop breeding when it’s cold.)

City officials also bemoan the wanton waste disposal habits of their citizens, which have allowed large and easily accessible piles of appetising trash to accumulate. Marseille’s councillor for hygiene Monique Daubet recently complained the city has become a “five-star restaurant for rats”.

Others have suggested a series of strikes by garbage collectors gave the rat population a turbo charge it barely needed. A single pair of brown rats can spawn more than a thousand descendants within a year.

That formidable birth rate is one indicator of what the city is up against: the urban rat is almost a perfect predator. Millennia of human ingenuity has failed to remove them from our midst or negate the threats they pose. Rats are supreme survivors – scientists marvel at their survival on nuclear test sites – and they thrive in the most inhospitable environments. They can eat practically anything, but are neophobic, meaning they shy away from all but the most devious poison traps. The rodents are intelligent, resilient, and their ability to colonise new habitats rivals our own.

Faced with this adversary, the local authority has assigned more resources to the fight, through both the city’s sanitation department and the private extermination service A3DS. Both are reluctant to discuss their tactics and whether they are having an impact. But officials are also taking a tough line on public responsibility, insisting that residents dispose of trash after 7pm in sealed bags or face fines. The city has also proposed measures such as mobile dumps and new model bins that rats should find harder to access.

The Marseillais are also keeping a close eye on events in the capital: Paris’ rat problem may be even more severe, driven by flooding from the River Seine that has forced the rodents to seek higher ground. In recent years, rats have overrun the Louvre and forced the closure of public parks, as well as starring in viral video nasties that do little for the city’s image as the capital of romance.


Paris mayor Anne Hidalgo has sounded the alarm and invested millions of euros in a campaign against rats, which has seen thousands of raids in hundreds of parks and buildings, as well as the introduction of more secure bins, and fines levied against people accused of feeding the enemy. Her administration has also despatched an envoy to New York to study the city’s approach to its own notorious rodent community.

An international approach makes sense given that rats are on the march all around the world. Reported sightings have shot up in New York, Chicago, Boston, San Francisco, and Washington. One study estimated that rats inflict $19 billion of economic damage each year in the US alone. London has also seen an increase in reported sightings. Leading rodentologist Bobby Corrigan says the same patterns are playing out in the major cities of the Americas, Europe, Asia, and Australia.

And for much the same reasons. Contributing factors include “too few resources allocated an organised program for rat control,” says Corrigan. “Also, more people in our cities means more refuse, more overloading of the city’s sanitation budgets, less thorough removal of the kind of food shrapnel that escapes typical garbage collection. Each rat only needs about 30 grams of food per 24 hours to thrive and reproduce.” A warming climate also plays a part.

Poison traps and culls can only go so far, says the rodentologist, arguing that a holistic approach is required to head off the growing threat. “The best measure is a city organised in addressing the rats across all agencies,” says Corrigan. That means mobilising departments of sanitation, parks, housing, health, and sewers, as well as mayoral administrations themselves.

Society-wide civic participation is also essential. “Controlling rats takes everyone: every homeowner, shop owner, restaurant, grocery store, airport, and so on. Not to do so invites the risk of a “new and/or highly virulent virus” developing among our old enemies, he adds.

Research into sterilisation programmes offers some hope of a new weapon to repel and reduce the rodent hordes. But not enough for us to evade responsibility while rat populations grow and the threat increases. “If we don’t work together as the wise species we claim to be and present a scientific, multi-faceted organised effort against this very smart and organised smaller mammal, we can have no hope of defeating it,” says Corrigan. Time to man the barricades.