There has been a flurry of recent commentary concerning Amazon drought – some of it good, some of it not so good. The good stuff has revolved around a recently-completed interesting field experiment that was run out of the Woods Hole Research Center (not to be confused with the Woods Hole Oceanographic Institution), where they have been examining rainforest responses to drought – basically by using a very large rainproof tent to divert precipitation at ground level (the trees don’t get covered up). As one might expect, a rainforest without rain does not do well! But exactly what happens when and how the biosphere responds are poorly understood. This 6 year long field experiment may provide a lot of good new data on plant strategies for dealing with drought which will be used to improve the models and our understanding of the system.
The not-so-good part comes when this experiment is linked too directly to the ongoing drought in the southern Amazon. In the experiment, older tree mortality increased markedly after the third year of no rain at all (with around 1 in 10 trees dying). Since parts of the Amazon are now entering a second year of drought (possibly related to a persistent northward excursion of the ITCZ), the assumption in the Independent story (with the headline ‘One year to save the Amazon’) was that trees will start dying forest-wide next year should the drought continue.
This is incorrect for a number of reasons. Firstly, drought conditions are not the same as no rain at all – the rainfall deficit in the middle of the Amazon is significant, but not close to 100%! Secondly, the rainfall deficits are quite regionally variable, so a forest-wide response is highly unlikely. Also, the trees won’t all die in just one more year and could recover, depending on yearly variation in climate.
While this particular article is exaggerated, there are, however, some issues that should provoke genuine concern. Worries about the effects of the prolonged drought (and other natural and human-related disturbances) in the Amazon are indeed widespread and are partly related to the idea that there may be a ‘tipping point’ for the rainforest (see this recent article for some background). This idea is exemplified in a study last year (Hutrya et al, 2005) which looked at the sharp transition between forest and savannah and related that to the coupling of drought incidence and wild fires with the forest ecosystem. Modelling work has suggested that the Amazon may have two vegetation/regional climate equilibria due to vegetation and climate tending to reinforce each other if one is pushed in a particular direction (Oyama and Nobre, 2003). The two alternative states could be one rainforested and wet like today, the other mainly savannah and dry in the Eastern Amazon. Thus there is a fear that too much drought or disturbance could flip parts of the forest into a more savannah-like state. However, there is a great deal of uncertainty in where these thresholds may lie and how likely they are to be crossed, and the rate at which change will occur. Models go from predicting severe and rapid change (Cox et al, 2004), to relatively mild changes (Friedlingstein et al (2003)). Locally these responses can be dramatic, but of course, these changes also have big implications for total carbon cycle feedback and so have global consequences as well.
Part of that uncertainty is related to the very responses that are being monitored in the WHRC experiment and so while I would hesitate to make a direct link, indirectly these results may have big consequences for what we think may happen to the Amazon in the future.
Special thanks to Nancy Kiang for taking the time to discuss this with me.
Update: WHRC comments on the articles below.
128 Responses to "Amazonian drought"
cat black says
Periodic droughts, even if non-fatal, will certainly not promote carbon uptake while trees are not actively growing. I wonder too if areas of relative dryness might become attractive to farmers and loggers, since the drier forests would be more easily accessed by heavy equipment for more days during the year. If these rainfall patterns persist long enough for people on the ground to take advantage, it could well direct human activity toward those areas and accelerate their demise via exploitation, just as if the rainfall had actually stopped and the trees had died in place for that reason. The overlap in climate and economic models might be more important than either acting alone.
Jim Torson says
I am a bit surprised that you listed the first article (Amazon Rainforest ‘could become a desert’) in the “good” category. Is this really a good description of the research?
It would be useful to hear what the Woods Hole Research Center folks have to say about these articles discussing their research.
Hank Roberts says
Many thanks, Gavin, for finding this. I looked hard and didn’t find it by searching the web myself earlier.
A couple of questions (I also emailed these to the contact link at the research page, with a pointer to this discussion, hoping someone from there will contribute).
The panels at ground level “diverted 6′ of water.” What was the total rainfall in the area? With the visible gaps between panels, some would certainly get to the ground. Knowing total rainfall would tell us what portion was diverted.
Is there any way to estimate how much water the trees absorb from their leaves, since the leaves got full exposure to rainfall? (Maybe a radioactive tracer….)
The experiment and control plots are quite close together and the website for the study does report the trees drew from quite deep underground, so again groundwater levels would not be at 100 percent drought condition.
These may be trivial amounts — I can’t guess — but I question whether this can be called a simulation of a 100 percent deficit/complete drought. It may well be close enough, and certainly they demonstrate a dramatic difference.
This info is probably available, I just didn’t find it.
I realize it’s impossible to do a ‘perfect’ experiment — to tent the canopy and block all rainfall!
Doug Percival says
I’d point out that both the “good” and “not so good” articles that you linked to are reprints of articles that originally appeared together, in the same issue of The Independent.
With regard to comment #2, in which Jim Torson wonders “what the Woods Hole Research Center folks have to say about these articles discussing their research.”
The “good” article says that Dr. Dan Nepstead, the Woods Hole experimenter, “expects [emphasis added] ‘mega-fires’ rapidly to sweep across the drying jungle. With the trees gone, the soil will bake in the sun and the rainforest could become desert.”
It also quotes forest ecologist Dr Deborah Clark from the University of Missouri as saying “the research shows that ‘the lock has broken’ on the Amazon ecosystem” and that “the Amazon is ‘headed in a terrible direction'”.
And the “not so good” article notes:
I don’t really see any exaggeration or misrepresentation in either article. It appears to me that this situation is certainly a candidate for one of the most grave and imminent consequences of global warming (plus deforestation) that we can see actually happening today.
Almuth Ernsting says
Your article warns of a possible shift in the ITCZ, which could, in future, dry up parts of the Amazon. A separate concern, highighted in the media and by some NGOs, is that both clear-cutting and selective logging could be responsible for the present drought, and threaten a breakdown of the rainfall system. One report I saw suggested that 40% of the rainfall over Brazil is ‘recycled’ via evapotranspiration from the Amazon forest. The fear is that progressive logging itself will lead to a tipping point beyond which the forest is no longer dense and large enough to recycle enough rain to survive. This sounds pretty persuasive to me. Obviously, it’s not an either or question, since ever faster deforestationa and global warming are happening at the same time.
Is there any indication that the last 1-1.5 years of extreme drought in part of Amazonia may already be linked to forest and canopy loss, and not just to the recent movement of the ITCZ?
Lately I have been thinking about forests, having lived and worked decades in one on our land in the sometimes fog belt of CA, though our place has seen in some locations both forest type conversion, and outright clearing for various purposes related to anthropogenic pursuits of livelihood by means of livestock rearing, crop production, and domicile construction.
Having resided and worked intrinsically in this environ many years I notice looking out the valley, as it becomes populated by an augmentation factor of doubling every decade, that forest cover along these slopes actually seems to have various qualities: old stands harbor deep shadow; younger stands when one walks beneath their canopies, seem to have drier surface temperature, as if logging has induced some distant relative of desertification.
I have been looking on the web for more information about how logging and vegetation type conversion under anthropogenic management routines actually might affect future plant environments; needless to say, much information is available, such as that concerning erosion. But, having visited RealClimate.org a lot in the past few years, I have begun searching for a more macro view; a way to interpret best practices of land stewardship with an eye to climate change. I wonder if some visitors here have found websites with monographs on these kinds of impacts. I am looking for the factually and statistically dense scientific studies.
After reviewing recent occurrences in the Congo rainforest, it was quite a coincidence to find RealClimate.org is pondering similarly forested land in Amazon.
I appreciate the links in your article.
David Wilson says
I got interested in the drought last October and managed to put together a small collection of images which you can find on my blog if you want.
I am commenting here because of the hard time I had following the issue at the time armed only with Google. The best news source I found is http://www.amazonia.org.br but they tend not to carry photographs and it is almost entirely in Portuguese. If you are aware of any aggregated sites on the subject (in any language) I would appreciate hearing.
Thanks, be well.
Hank Roberts says
> Best practices
John, I’m an amateur working among other things on post fire restoration, in my copious spare time (Mendocino Nat’l Forest area, the dryer part of the Coast Range).
This is my current new good source, some technical, but some common sense and good ideas:
You probably know Island Press already but perhaps others don’t (one of their locations is Covelo). It’s the best I’ve found so far, looking for the same thing you are. I’d love to see a single forum somewhere, I don’t know of one.
“The overlap in climate and economic models might be more important than either acting alone.”
cat black has touched on a most fundamental principle. Climate change has and will have an inconceivable number of effects which extend outside the scope of purely climate models, but the effects of which are and will be real enough.
I think I’ve gleaned from this site that (without the professional hair splitting) climate is not “chaotic”, but is an immensely complicated system, difficult to model accurately.
Drop the worlds eco-system and humans (with everything that implies) into the mix and the system can only be quintessentially chaotic. This is what’s known as the real world. A nightmare for the computer modeller, but many normally functioning brains have managed to join up the dots and glimpse what the bottom line is….not a pretty sight!
Mark J. Fiore says
The news about the drying effect in the Amazon has been in the news for about 7 years now. Basically, as the eastern third of the Amazon drys there is less and less precipitation over the rest of the forest, culminating in extreme negative feedback cycles. Now the research has proven what was well known a long time ago, namely that the Amazon is drying and dying. Of course the Republican Congress and the executive branch are again failing to address the problem. Just another sad chapter in Steuart Brand’s “clock of the long now”.
Doug Percival says
This from the WHRC press release linked to in the RC article (emphasis added):
That’s pretty alarming, especially when considered in the context of other positive feedbacks including changes in albedo from melting icecaps and release of carbon and methane from thawing permafrost.
Over what time period might this savannization process release carbon “equivalent to several years of worldwide carbon emissions”, and how does that affect the assessment offered by Gore, Hansen and others that we have perhaps ten years in which to substantially reduce CO2 emissions to avoid irreversible catastrophic warming?
James Annan says
You call this commentary good??
I call it ridiculous – and I would be less polite, but you’d censor me :-)
You may not have realised that the first story was also in the Independent, that bastion of reasonable reporting that also brought us “before this century is over billions of us will die and the few breeding pairs of people that survive will be in the Arctic where the climate remains tolerable” Lovelock. The same Independent that was (rightly IMO) singled out as one of the worst “climate pron” offenders (mis-spelling to get round the spamblock!). There’s more discussion of that article here and subsequently.
BTW, I’d be interested to hear your view of the BBC “expert panel” (see here) that decided that Lovelock’s prediction of a 3-5C “likely” rise in temperature by 2100 was correct, and that a rise of 8C was merely “less likely”. When septics say equally silly stuff you are all over them like a rash.
[Response: Well I guess I meant better. The second article was definitely not-so-good and comparitively the first seemed reasonable, since it was actually reporting mostly what Nepstead actually said. However, I certainly agree with the paragraphs you highlighted are quite poor. I was aware that these were paired articles but the links to the paper are subscription only and so I used the mirror sites so that people could read them. You should however distinguish Lovelock’s op-ed piece from the reporting – there is a difference, even in the UK – gavin]
joel Hammer says
Of course the Republican Congress and the executive branch are again failing to address the problem.
Are you referring to the American govt? Last time I checked, Brazil was an independent country. I don’t think the US Congress dictates to Brazil.
Brazil has signed and ratified Kyoto.
Brazil is taking the lead in ethanol production, they say.
Brazil is a leader in the fight against climate change.
Statistically dense studies? May be too early in the game. You can look for modeling studies or start at the Stanford Jasper Ridge site, or maybe the LTER studies…
And, regionally, your local RCDs provide good how-tos.
wayne davidson says
There is some evidence of mega El-Nino’s causing some damage to Amazonia:
“n-14 dates establish their contemporaneity ca. 1500, 1000, 700, and 400 B.P.”
The most recent drought was 1926 during what is called an extreme El-nino year/
Combined with 1997 lack of hurricanes (coinciding with the most recent really big El-Nino). This drought may be a precursor to a major El-Nino, surely exacerbated by GW, since there was a drought last year without an El-Nino.
Re: 13 — “Are you referring to the American govt? Last time I checked, Brazil was an independent country. I don’t think the US Congress dictates to Brazil.”
The US accounts for a grossly disproportionate amount (per capita) of anthropogenic green house gas emisisons. Brazil has far less influence on a migration of the ITCZ than the US does. I think it is perfectly appropriate to chastize the US for its obstruction and obfuscation on AGW in a discussion of threats to the Amazon rainforest.
Chuck Booth says
Re #3 “Is there any way to estimate how much water the trees absorb from their leaves, since the leaves got full exposure to rainfall? (Maybe a radioactive tracer….)”
I’d be surprised if any water is absorbed across the leaves. Rain forest trees are famous for their adaptations for shedding water (e.g., waxy surface and drip tips), which probably reduces fungal infections. Bromeliads and other “tank” plants that trap water (and insects) do seem to absorb nutrients from the trapped water, so perhaps they also absorb some of the water itself. But, trees leaves – I suspect this is insignificant, if it occurs at all.
Hank Roberts says
I’d think it ought to be checked. I found this:
“Some trees … even have feeder roots on their canopy branches … to tap the nutrients trapped in epiphytes–a sort of rental on real estate used by the epiphyte! Some trees have deep tap or sinker roots but these are probably only to stabilise the tree and not to absorb water or nutrients.”
Not much else though, and I did find the mention of waxy leaves and drip tips. Six feet of rain seems around the minimum for a rain forest, but it’s been dry there. So — dunno.
Here’s an earlier article on the same study as it was being set up, with some satellite pictures as well as onsite pictures of the project:
Hank Roberts says
Visualize rainfall (among much other data, an amazing toolset)
Stephen Berg says
Re: #16, “I think it is perfectly appropriate to chastize the US for its obstruction and obfuscation on AGW in a discussion of threats to the Amazon rainforest.”
Agreed. If the US chemical companies (i.e. Monsanto) would stop trying to get American farmers to continue to grow GMO soybeans and grow organic, non-GMO soybeans, Brazil wouldn’t have the deforestation problems they have.
Europeans import non-GMO soybeans from Brazil in great quantities since they have a GMO ban in place. Perhaps this is a way American farmers could get ahead of the game, by growing organically and with non-GMO seeds. They’d have an open market and would maybe even deserve the subsidies they’re getting.
Pavel Chichikov says
Re: the Amazon and climate change, there are, potentially, a billion people in the Catholic and Orthodox Churches who could be allies: See:
pete best says
I have also heard that some 3 billion people directly or indirectly rely on the Asian monsoons and that AGW could disrupt this to. Couple that with the potenital drying out of the Amazon by 2040 (as predicted by some climate models I believe), the melting of permafrost exposing siberian and other bogs to methane release on a large scale, asian rainforest and bogs drying out to and there is a potential for more warming that seems to be currently predicted by the climate models alone.
But of course I am probably being alarmist because there simply is not enough Science in these areas to know what will happen at the present time to these carbon sinks and sources and hence any speculation is simply that, pure speculation with no scientific basis.
Eric (skeptic) says
Stephen, the Kyoto Protocol allowed GMO trees to mitigate climate change, although not without controversy. The climate effects of GMO undoubtedly deserve more study, but Europeans might want to reconsider their opposition in light of the problems in Brazil.
Eric (skeptic) says
Stephen, I should not be so quick to recommend anything to Europe. They have studied this http://ec.europa.eu/agriculture/publi/gmo/ch3.htm#22.214.171.124 and saw no increase in GM soybean crop yields.
We read all these frightening things about the Amazon but how can we help.Is there an organisation we can join?
I live in Africa and watch the same sort of thing going on here.
John L. McCormick says
Peter, being an alarmist is a responsible role for any who see, experience, suffer from, research or educate themselves about the direct impacts of a warming world.
One would not be an alarmist if he shouted to skaters that the ice is cracking. He’d be a hero.
In this climate, the alarmist is a skunk at the party.
Add to your check list of reality the fact that Himalayan glaciers are melting at an alarming rate (see RC threads on tropical glacier melt); enough so that flash flooding, from overflowing glacier-melt lakes, is a serious and life-threatening concern of downstream populations. Then, add to that reality the fact that nearly 400 million people rely, to some degree, on Himalayan snowpack and glacier melt to feed the Ganges and Brahmaputra Rivers which provide irrigation and drinking water for the heavily populated lands surrounding northern India.
Eventually the scientific basis becomes as irrelevant as are Pat Michaels and Senator Inhofe.
Imagine India and Pakistan fighting over water resoures! Or, imagine the U.S. cutting its carbon emissions by 80 percent in the next 30 years.
Alarmism is fast becoming passe. Desparation will eventually dictate how we discuss the scientific basis for global warming. And, unless we are total fools, the developed nations will soon begin to shift some attention (also)towards measures to adapt (regardless of the mind-numbing refusal of environmental groups to utter the word) so that our children will have a fighting chance to survive the chaos we have brought to them.
Dan Hughes says
Stephen, GM soybeans are grown in Brazil and other countries in SA. A part of the increase in converting forest to farmland in Brazil is the demand for soybeans in the production of biodiesel. The demand for soybeans for this application will only experience continued growth. It has long been known for certain that biomass-for-energy is not ‘Green’. For example, growing organically will certainly be very much less efficient than growing non-organically.
Simply do some Googles to find out all kinds of true facts about GM and non-GM soybeans, biodiesel, Brazil, South America, and the rain forest.
Blair Dowden says
I have not been able to find any connection between what is happening in the Amazon rainforest and global warming. The RealClimate article you referenced says rainfall amounts are influenced by the sea surface temperature gradient between the north and south Atlantic ocean, rather than the absolute temperature. Is there a connection between greenhouse warming and these temperature gradients?
I do know that in the cooler climate of the ice age the tropical rainforests almost disappeared in both South America and Africa. In general, a warmer climate should mean larger rainforest area, although of course local conditions may vary. There may be a reason that the Amazon is an exception to that rule, but I do not know what it is.
Hi all. I live in the Peruvian Amazon and have an interest in this so have catalogued some reports and papers that might be of interest to you.
First one above is “drought stress and carbon uptake using space borne imaging spectroscopy”
Second link, “Globally significant changes in Biological Processes of the Amazon Basin: Large Scale Biosphere-Athmosphere Experiment”
Third Link above. “Rainfall variability at the end of the dry season”.
Fourth Link: ENSO effects on monthly river flows during the 20th century.
Fifth above: Satellite observations of El Nino effects on Amazon forest phenology and productivity.
Sixth: More globally, climate driven increases in global NPP ’82 to ’99
“Reconstruction of Amazon Basin effective moisture availability over the past 14,000 years”
NUMERICAL SIMULATION OF BIOMASS BURNING EMISSIONS AND
TRANSPORTATION DURING 1998 RORAIMA FIRES
FOREST FIRE, DEFORESTATION AND LANDCOVER CHANGE IN THE
Hope these are of some use. I’d add more but the solar panel here is flashing red. I will add that the rainy season was not very rainy to say the least. Anyway, hope to have a page up and running soon.
One more link i might ad is an extensive bibliography of publications that have come from this area.
Alastair McDonald says
Re 21 Where A. Wright (no pun intended) wrote “We read all these frightening things about the Amazon but how can we help.Is there an organisation we can join?”
There is nothing you can do until the scientist like Gavin and James Annan face up to the fact that they have failed to predict the disaster that is upon us, and order all national governments to take action. Even subscribing to Greenpeace is useless, as I have found.
Re 28 Where Blair wrote “I have not been able to find any connection between what is happening in the Amazon rainforest and global warming.”
The connection is the movement of the ITCZ, which determines the gradient. But it is easier to view the situation as a movement of the climate zones north due to the melting of the Arctic sea ice. (I looks as though in late August both the North West and North East Passages will be open for the first time in recorded history.)
Not only is the ITCZ moving north but so are the great desert regions, with the Sahara trying to jump the Mediterranean, the Kalahari bringing drought to Malawi, and the Australian Red Centre moving north into Queensland. A. Wright also wrote “I live in Africa and watch the same sort of thing going on here.”
Gavin and James are shooting the messengers. The Independent reporters are only repeating what the scientists on the ground are seeing – two years of drought, which if followed by two more could lead to the death of the Brazilian jungle. Do we act now, or wait till those scientists have been proved right?
[Response: No. This is just the point. The scientists are not saying that the jungle will die in two years: this is a conclusion that the journalists have jumped to from erroneously connecting two similar things. But I guarantee that if you asked the scientists involved they would not make the same leap. -gavin]
Almuth Ernsting says
Re 25: A Wright asks whether there is an organisation to join. You might like to look at the Climateark website, to which Realclimate provide a link. This is part of Ecological Internet, with specific sites looking at climate change, rainforests, forests worldwide, etc, and contains both action alerts and information about all the different websites, including those by different campaigns groups worldwide.
Gene Hawkridge says
Sometimes it is appropriate to raise an alarm. However, we should be very careful in doing so that we do not provide more propaganda fodder for the US Republican Party, and right-wing talk show hosts.
I think of the Northern Spotted Owl controvesy that raged a few years ago in the northwestern US. This concern was used as a reason to restrict logging activities in the old growth forests of Washington and Oregon – something which has benefitted the logging industry in neighboring British Columbia, I note. But worse were the revelations that the “Northern Spotted Owl” wasn’t really quite as unique as biologists wanted us to believe, and that some populations were doing just find in new growth forests. This goes to credibility: the public stops listening to alarmists when they find out that what they’ve been told isn’t quite true.
Spreading alarmist tales of forests in the Amazon dying off in a year or two does more to help head-in-the-sand pro-Corporate interest Republicans than it does to protect the environment of the Amazon. Someone should put a gag on these morons. Or maybe they work for the oil companies after all…
Pete Best says
re #26 John
The press and press journalists who write books say much but maybe do not say much at all. The books I have read on climate change for the interested lay person are (to my mind at least) laden with alarmist and “we’re all doomed prohecy” based on far out notions of the new climate science ie the non linear type II climate change that seems to have become the norm in recent years.
Real climate and the IPCC are still fighting the skeptics and hence they will only error on the side of extreme caution regarding what will happen to the world by 2100. All they will say is that with a business as usual attitude of the world emissions will be around 2 ppm per annum now and 4 ppm by 2050 and hence around 550 ppm by the end of century. What that translates into in terms of disaster and doom is anyones guess but scientific bodies only speak of what they know.
Interestingly enough both Stephen Hawking and Martin Rees (astronomer royale here in the UK) have recently professed to being in fear of human kinds continued existance beyong the 21 st century. It would seem that alternatives to fossil fuels are the issue and nothing at the present time can replace them and be rolled out in time to stop climate change from being serious.
Almuth Ernsting says
There is actually a very strong argument that the next 15 months could be ‘make or break’ for the Amazon, albeit one slightly different from what the Independent articles say:
It is clear that large-scale forest fires are
1) very rare in recent centuries until recently and now becoming much more frequent
2) linked to droughts
3) always in the vicinity of human activity, ie selective logging, roads, agriculture.
For a detailed discussion, see here: http://www.environmentaldefense.org/documents/4930_TropicalDeforestation_and_ClimateChange.pdf
It also seems pretty clear that massive die-back of the Amazon can only be prevented by strong action against logging, as well as action against global warming. And, as far as logging goes, the next 15 months could indeed be decisive:
The Kyoto Agreement completely fails to tackle tropical deforestation, despite its signigicance for global carbon emissions. Indeed, some people argue that it may even make it worse, by including the carbon sinks of the rich nations (the Annex 1 states) only, and not allowing rainforests to benefit for carbon trading. This year, the Coalition of Rainforest Nations will be pushing for an amendment, called ‘compensated reduction in deforestation’. Couuntries like Brazil would voluntarily opt in, and by doing so agree to binding commitments under the Kyoto Agreement. Billions of dollars would be made available, through the carbon market, to effectively reduce deforestation rates, as monitored by satellites. For details, see here: http://www.rainforestcoalition.org/eng/ . Such an amendment would be quite possible and could go to a vote this November (a vote by the Kyoto ratifying nations, that is). Once the First Commitment Period starts in 2008, there is very little scope for improvement until it ends in 2012. And I have heard of no meaningful international proposal to reduce rainforest destruction otherwise. Without such action, deforestation rates could well accelerate for another six years – by which time it will certainly be too late for many millions of hectares of Amazon forest – and there will be considerably less rain evapotranspiration to sustain the rest.
In this sense, the ‘one year to save the Amazon’ may yet be true!
Elizabeth Braun says
Posted on behalf of Daniel Nepstad, senior scientist at the Woods Hole Research Center, and lead investigator on the forest drought experiment. (Via Elizabeth Braun, Director of Communications at the Center.) –
On July 23, The Independent report on the recent findings of our forest drought experiment in the Amazon, in which we reduced rainfall inputs to a hectare of forest over a five-year period. This alarmist article involved no interview, and it contains many statements that I do not support.
To clarify, our results do not show that the rainforest ‘could become a desert’. In the third paragraph, the piece implies that I support the position that drought in the Amazon will lead to drought that would spread to Britain, with the world spinning out of control, becoming uninhabitable. That is simply not true.
What our work does show is that the drought we imposed caused big trees to die more than small trees, which was a surprise. We also know that the amounts of carbon that may be going to the atmosphere following Amazon droughts are probably big enough to accelerate global warming. Currently trends suggest that a big chunk of the Amazon forest will probably be displaced by fire-prone scrub vegetation; global warming will probably exacerbate this trend.
The challenges we are confronting and those that we will be faced with in the future are significant. The world’s tropical rainforests will be changed in important ways by global warming. But public understanding of these processes is not served by evoking apocalyptic images. What is needed now is credible reporting and sound journalism so that the global community can act wisely.
[Response: Thank you very much for the clarification. – gavin]
Don Baccus says
Knowing a thing or two about the population ecology of the northern spotted owl, I’d like to offer a few facts.
Yes, NSO do reaonsably well in younger redwood forests. The timber industry has worked very hard to extrapolate this fact to the mixed-conifer old-growth forests to the north, in OR/CA/BC.
Sad thing here is we KNOW why NSO do well in younger redwood forests, and those reasons don’t apply to the mixed-conifer forests to the north. You never hear that from the timber industry, of course.
For starters, redwoods (unlike doug fir, spruce, etc found to the north) sprout from the stump after being logged. This causes regeneration to occur much more rapidly. Also the warmer and wetter climate (which is why the redwood stands are there in the first place) leads to rapid growth. Stumps that are a few years old tend to have a “crown”-like circle of sprouts encircling them, and wood rats (also known as packrats) find these ideal for their nests. In such forests, NSO are known to dine largely on wood rats. The more northern forests don’t provide good wood rat habitat, and NSO dine largely on red-backed vole, itself old-growth dependent to a large degree.
And, something that’s also overlooked by timber industry propagandists, even in redwood forests productivity is significantly higher for NSO nesting in old-growth than in yonger redwood forests.
Of course, to the north of the redwoods we do find NSO nesting in younger forests. Almost invariably, these are young pairs pushed to less-than-ideal habitat and almost invariably, the nesting attemps fail, and even when they don’t, the average level of productivity falls below the average level of mortality.
And people often find single juveniles in the oddest of places (something true of most bird species), and assume this means that they can thrive in such places.
In reality, in nearly all cases such lost little birdies just die.
Given that NSO populations continue to fall and that most western ornithologists are pessimistic about their continued survival, exactly what was “alarmist” about concerns raised by scientists in the 1980s?
The ONLY sigificant surprise here has been the rapid invasion of the related barred owl, an invasion which further threatens NSO and which is entirely due to logging and agricultural practices.
The USF&W recently commissioned a study of the status of the northern spotted owl, after the timber industry (believing their own propaganda) urged the Bush administration to do so. Since the timber industry is convinced that the USF&W and the academics it works with are lying about the population ecology of the species (sounds like Exxon v. climate science, eh?), it was farmed out to a private biological consultancy firm.
Rather than supporting the timber industry’s lies, they concluded that the status of the northern spotted owl is MUCH WORSE than stated by the USF&W.
Get your climate science from climatologists, not Exxon. Get your population ecology from scientists, not the timber industry. Gain understanding of the history of life on earth from evolutionary biologists, not bible-thumpers.
See a pattern here?
Alastair McDonald says
Re Gavin’s response to #30 “But I guarantee that if you asked the scientists involved they would not make the same leap.”
I gone over the two article to see what the scientists did say, and extracted mostly direct speech. The first article is:
Dying Forest: One year to save the Amazon
Just the day before, top scientists had been delivering much the same message â�¦ that global warming and deforestation were rapidly pushing the entire enormous area towards a “tipping point”, where it would irreversibly start to die.
This year, says Otavio Luz Castello [a young naturalist], the water is draining away even faster than the last one – and there are still more than three months of the dry season to go. He adds: “I am very concerned.”
Dr Antonio Nobre, of Brazil’s National Institute of Amazonian Research, told the floating symposium â�¦ of unpublished research which suggests that the felling is both drying up the entire forest and helping to cause the hurricanes that have been battering the United States and the Caribbean.
“We believe there is a vicious cycle” says Dr Nobre.
â�¦ And if you add these two figures together, the total is growing perilously close to 50 per cent, which computer models predict as the “tipping point” that marks the death of the Amazon. The models did not expect this to happen until 2050. But, says Dr Nobre, “what was predicted for 2050, may have begun to happen in 2005.
One of Dr Nobre’s colleagues, Dr Philip Fearnside, puts it this way: “With every tree that falls we increase the probability that the tipping point will arrive.”
“If we do not act now”, says Dr Fearnside, “we will lose the Amazon forest that helps sustain living conditions throughout the world.”
The second artilce was:
Amazon rainforest ‘could become a desert’
Dr Nepstead expects “mega-fires” rapidly to sweep across the drying jungle. With the trees gone, the soil will bake in the sun and the rainforest could become desert.
Dr Deborah Clark from the University of Missouri, one of the world’s top forest ecologists, says the research shows that “the lock has broken” on the Amazon ecosystem. She adds: the Amazon is “headed in a terrible direction”.
As I have already explained to James, if you cannot bring yourself to believe catastrophe could strike, then it is easy to dismiss these and other similar reports as being produced by Chicken Littles. If, however, you take the rational view that there is no logical reason why catastrophe should not strike, then you will quickly realise that it may in fact be imminent :-(
In other words, your computer models may say that this generation is safe ‘But, says Dr Nobre, “what was predicted for 2050, may have begun to happen in 2005.’
Thomas Lee Elifritz says
Perhaps they will save the Amazon with ethanol.
wayne davidson says
#33, To be quite blunt, the “world” has been mostly cold and uncaring about the the earths environment, most non-Brazilians will not jump off the nearest bridge hearing news about the potential demise of the Amazon forest. But the real issue is predicting the future accurately, many stake their reputations, including newspapers, that a certain future will happen. It becomes a gross mistake, when certain predictions don’t happen, and therefore poor projections feedback negatively to the source, which becomes less credible. It is survival of the fittest when it comes to predictions, and freedom of expression should be allowed fully, the one who is right might get the credit, but sadly predicting climate or ecological mega-events is so marred with failures that correct predictions, are forgotten amongst a sea of failures. I fault not the Independent on reporting dire predictions on the Amazon, but I fault most media on not encouraging those who have predicted the future accurately, one example: Hansen et al. at NASA with correct GT projection from the 80’s, it is rare that one reads this success story, in popular press Hansen’s voting preferences are better known. In the case of the Amazon, who is Hansen’s equivalent? Would like to hear his or her opinion,
and what’s missing, is Amazon forest aboriginal opinions, I haven’t heard them say anything yet, may be the media has forgotten that they are just as much in sync with the Amazon, as any top expert.
Hank Roberts says
>37 and any other followups on the article
See #35, from the researcher directly.
Barton Paul Levenson says
Aaaaarrgh! My JGR paper was shot down out of the sky and plummeted in flames to the rocks of rejection below. I am reduced once again to non-scientist status. Alas.
Alastair McDonald says
Re #40 which says “See #35, from the researcher directly.”
Post #35 is not from the researcher directly. It is from the communications director Elizabeth Braun not Dr Nepstadt. How much did she help in its drafting?
On the WHRC web site, where the results of the experiment are presented, http://www.whrc.org/southamerica/drought_sim/results.htm it states the following which I do not regard very different from what appeared in the article as Dr Nepstadt’s attitude.
“Another surprise was that the observed sensitivity of large canopy trees to drought is greater than expected. Once the moisture that is stored in deep soil is depleted, the largest trees – towering 130 to 150 feet above the ground and basking in full sunlight – begin to falter and die. The death of such large trees that may take centuries to reach the top of the forest canopy, increased from about one percent per year to nine percent in the fourth year of the experiment, when soil water was depleted. This sensitivity of large trees to drought means that a decline in rainfall would likely cause a gradual transition from tall, green, lush rainforest towards a shorter, more stunted forest where a great deal more sunlight penetrates to the forest floor.
As the forest becomes shorter and its canopy more open, compromising its remarkable resistance to fire, it is clear that drought in tandem with fire could swiftly push the tall, dense rainforests of the region towards savanna scrub. The amount of carbon that could be released to the atmosphere by this savannization process is significantâ��equivalent to several years of worldwide carbon emissions â��and could accelerate climate change processes already in place.
In addition to these global effects, drought and fire, a tool of choice among the Amazonâ��s farmers and ranchers, pose a serious threat to a forest that is home to more plant and animal species, and more indigenous cultures, than any other forest in the world. ”
It seems to me that the Independent took two years of drought and the WHRC results and warned that the trees would start dying in the fourth year. In other words the took two plus two and got four. It is all very well Dr Nepstadt implying he never got to four. Is he denying that the drought has lasted two years?
Finally, Braun/Nepstadt conclude “What is needed now is credible reporting and sound journalism so that the global community can act wisely.” What they seem to be asking for is that the facts should be played down to avoid public panic. Let’s be quite clear – the global cummunity has not acted wisely. It has not acted at all! Fifteen years of quietly, quietly by the IPCC has produced nothing. It is time that the public were told the truth, and less of this sanitised rubbish in the name of scientific uncertainty.
Blair Dowden says
Re #30: I am still trying to connect drying in the Amazon with global warming. I understand that a northward shift of the ITCZ will move the zone with the most rainfall to the north. If part of that zone moves from land to ocean, then the region that can support rainforest will be reduced.
The connection with global warming seems to be that the northern hemisphere warms faster than the southern hemisphere, because of the presence of Antarctica. However, I was unable to find any support for that in the RealClimate article previously cited or in any of its references. Instead, the location of the ITCZ depends on a complex set of other factors.
From my reading of paleoclimate data, the area of tropical rainforest was at a minimum during the ice age, and has been increasing as temperatures have risen. Is there any reason this process will stop or reverse itself as greenhouse warming starts to take effect?
I think that many of the problems with the Amazon rainforest are human caused, but most of it is due to logging and human settlement. In this case, I think global warming is a minor factor.
re: 41. I realize this is little consolation after your paper was rejected but the one bright spot is that the fact that it was rejected shows the skeptics/denialists here that there is no collusion in the climate research world as some claim there is.
Alastair McDonald says
Re #43 Ignore what I wrote in #30. I will to answer your problem regarding the tropics, rather than flannel my way around with references to the movement of the subtropics.
The key is in this section of the Independent article that Gavin described as “not so good”. http://www.ecoearth.info/articles/reader.asp?linkid=58636
In it “Dr Antonio Nobre, of Brazil’s National Institute of Amazonian Research, told the floating symposium – whose delegates ranged from politicians and environmentalists, to Amazonian Indian shamans and Roman Catholic cardinals – of unpublished research which suggests that the felling is both drying up the entire forest and helping to cause the hurricanes that have been battering the United States and the Caribbean.
The hot, wet Amazon, he explained, normally evaporates vast amounts of water, which rise high into the air as if in an invisible chimney. This draws in the wet north-East trade winds, which have picked up moisture from the Atlantic. This in turn controls the temperature of the ocean; as the trade winds pick up the moisture, the warm water that is left gets saltier and sinks.
Deforestation disrupts the cycle by weakening the Amazonian evaporation which drives the whole process. One result is that the hot water in the Atlantic stays on the surface and fuels the hurricanes. Another is that less moisture arrives on the trade winds, intensifying drought in the forest. “We believe there is a vicious cycle” says Dr Nobre.”
There are a couple of points that are not explained and which I have worked out for myself. First, the jungle behaves like a lake providing a wet surface. The wetness is produced by transpiration from the top of the canopy. The water is taken there from the jungle floor by the trees using capiliary action. The evaporation from the tree tops creates clouds, and rain which replenishes the water on the jungle floor. Thus the jungle acts like a resevoir of water. Without the shade from the trees, the surface would dry out in the hot tropical sun.
The next point to realise is that the convection in the tropics is not caused by hot air rising, but by light air rising. It is light because it contains a lot of water vapour which as a lower molecular weight than air. The subropics (eg the Sahara) are hotter than the tropics, but it is in the tropics where the convection occurs because the air has gained water vapour travelling over the ocean from the sub tropics. If it had to travel over dry land it would not convect because it could not gain water vapour. The Amazon jungle, because it is a water resevoir, provides this water vapour, and so the covection, clouds and rain can happen. Remove the high trees and you lose the resevoir.
Thomas Lee Elifritz says
Here is something Elizabeth Braun is also bragging about :
Controlled burns in a drought striken Amazon rainforest.
Doesn’t seem like a particularly bright idea to me.
Hank Roberts says
Controlled burns are the only way I know of to do this sort of study. Have you an alternative to suggest?
I’m working on post-fire restoration (everyone needs a hobby that will outlive them). The info from controlled burns is very helpful here.
When you know an area is, eventually, going to burn, you want to know (1) what was there, (2) exactly how it burned, and (3) what grew afterwards, among much else. Only (3) is available in studying accidental or agricultural fire sites.
There are a number of factors associated with rising temperatures and plant and vegetation responses. One example of this is the role of isoprenoids and other VOC’s which are released in greater quantities by plants during periods of intense heat and/or drought. These VOC’s (though not all), act as a positive feedback for nocturnal emissions, by their role in ozone formation and as cloud condensation nuclei, though they do aid plant survival during hot days. In all reality they are an uncertainty in calculating the effect of increased temperatures on the Amazon, because they are highly species dependent, and as such depend on local factors. Heres what the authors of the LBA experiment have to say
“Canopy emissions of VOCs amount to only a few percent of gross primary productivity (Guenther, 2002; Kesselmeier et al., 2002), but their effects on atmospheric chemical processes and physical climate processes far exceed their modest contribution to the C
cycle. Biogenic hydrocarbons are critically important in the regulation of ozone, hydroxyl radical, and other important trace gases and radicals in tropical atmospheric chemistry. Terpenes also make aerosol particles that affect the radiation budget and that also act as
cloud condensation nuclei in Amazonia. Hence, part of the precipitation formation mechanism could be controlled by the vegetation itself through terpene emission (Artaxo et al., 2001). Hence, links between the biosphere and the atmosphere may be extremely
complex, with climate affecting VOC emissions and vice versa. Moreover, the new results published in this issue beg the question of how species composition and their strategies to produce VOCs in response to physiological stresses might be related to variation in
climate, soil fertility, and C allocation”
further they speak about the role of wetlands in CH4 emissions.
“Emissions from Amazonian wetlands alone appear to contribute about 4% of the global annual emissions of CH4 from all natural and anthropogenic sources. As shown later in
this paper, the global warming potential of the annual emissions of CH4 from Amazonian wetlands is equivalent to about 30â40% of the estimated annual accumulation of C in woody biomass of mature Amazonian forests.”
Whilst this may not answer your point about the ITCZ, not something i feel competent to talk about, it shows the extent to which the climate has an impact on the forest and visa versa. The forest doesn’t necessarily have to die back to scrubland for it to become a net contributor to the GHG problem.
By the way, last year we had spontaneous fires in palm swamps at the end of oxbow lakes. The leaf litter normally falling into stagnant water was so dry it just went up like a light.
RE: Blair Dowden, #43
“From my reading of paleoclimate data, the area of tropical rainforest was at a minimum during the ice age, and has been increasing as temperatures have risen. Is there any reason this process will stop or reverse itself as greenhouse warming starts to take effect?”
If you look only at temperature, the answer is no. If you’re studying ancient climate trends then you should be aware of the many intricacies of our planets ecosystem, making this question narrow in scope.
Lastly, global warming has already started and its effects can be seen and measured today.
Never in the history of our planet has any animal mechanically altered the chemical composition of our atmosphere. Except for humans in the last 300 years.
RE: Thomas Lee Elifritz, #45
Thanks for the link. If current science shows the Amazon is in fact at risk of extinction, then a controlled burn may produce data that ultimately helps save it. Given the role the rainforest plays in our ecosystem, I believe the risk is justified.
I found some discerning statements in the WHRC bio at the end of this article. Here’s the bio:
“The Woods Hole Research Center is dedicated to science, education and public policy for a habitable Earth, seeking to conserve and sustain forests, soils, water, and energy by demonstrating their value to human health and economic prosperity. The Center sponsors initiatives in the Amazon, the Arctic, Africa, Russia, Boreal North America, the Mid-Atlantic, New England and Cape Cod. Center programs focus on the global carbon cycle, forest function, landcover/land use, water cycles and chemicals in the environment, science in public affairs, and education, providing primary data and enabling better appraisals of the trends in forests that influence their role in the global carbon budget.”
There are two things I don’t like.
1. From a business perspective, there is no ‘economic’ prosperity in conservation.
2. The phrase ‘global carbon budget’ bugs me. So we have a CO2 budget, do we? I tend to think nature already created the atmospheric rulebook and we humans haven’t finished deciphering it. Knowing only some of the rules we’ve decided we can indiscriminately spend CO2. I’m not certain it’s been determined we can spend CO2 at all.
Never in the history of our planet has any animal mechanically altered the chemical composition of our atmosphere. Except for humans in the last 300 years.