Climate

NASA-Led Study Finds Warming-Driven Megadroughts Jeopardizing Amazon Forest

An area of the Amazon rainforest twice the size of California continues to suffer from the effects of a megadrought that began in 2005, finds a new NASA-led study. These results, together with observed recurrences of droughts every few years and associated damage to the forests in southern and western Amazonia in the past decade, suggest these rainforests may be showing the first signs of potential large-scale degradation due to climate change.

At left, the extent of the 2005 megadrought in the western Amazon rainforests during the summer months of June, July and August as measured by NASA satellites. The most impacted areas are shown in shades of red and yellow. The circled area in the right panel shows the extent of the forests that experienced slow recovery from the 2005 drought, with areas in red and yellow shades experiencing the slowest recovery. Image credit: NASA/JPL-Caltech/GSFC

A NASA JPL news release

An international research team led by Sassan Saatchi of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., analyzed more than a decade of satellite microwave radar data collected between 2000 and 2009 over Amazonia. The observations included measurements of rainfall from NASA’s Tropical Rainfall Measuring Mission and measurements of the moisture content and structure of the forest canopy (top layer) from the Seawinds scatterometer on NASA’s QuikScat spacecraft.

The scientists found that during the summer of 2005, more than 270,000 square miles (700,000 square kilometers, or 70 million hectares) of pristine, old-growth forest in southwestern Amazonia experienced an extensive, severe drought. This megadrought caused widespread changes to the forest canopy that were detectable by satellite. The changes suggest dieback of branches and tree falls, especially among the older, larger, more vulnerable canopy trees that blanket the forest.

While rainfall levels gradually recovered in subsequent years, the damage to the forest canopy persisted all the way to the next major drought, which began in 2010. About half the forest affected by the 2005 drought – an area the size of California – did not recover by the time QuikScat stopped gathering global data in November 2009 and before the start of a more extensive drought in 2010.

“The biggest surprise for us was that the effects appeared to persist for years after the 2005 drought,” said study co-author Yadvinder Malhi of the University of Oxford, United Kingdom. “We had expected the forest canopy to bounce back after a year with a new flush of leaf growth, but the damage appeared to persist right up to the subsequent drought in 2010.”

Recent Amazonian droughts have drawn attention to the vulnerability of tropical forests to climate change. Satellite and ground data have shown an increase in wildfires during drought years and tree die-offs following severe droughts. Until now, there had been no satellite-based assessment of the multi-year impacts of these droughts across all of Amazonia. Large-scale droughts can lead to sustained releases of carbon dioxide from decaying wood, affecting ecosystems and Earth’s carbon cycle.

The researchers attribute the 2005 Amazonian drought to the long-term warming of tropical Atlantic sea surface temperatures. “In effect, the same climate phenomenon that helped form hurricanes Katrina and Rita along U.S. southern coasts in 2005 also likely caused the severe drought in southwest Amazonia,” Saatchi said. “An extreme climate event caused the drought, which subsequently damaged the Amazonian trees.”

Saatchi said such megadroughts can have long-lasting effects on rainforest ecosystems. “Our results suggest that if droughts continue at five- to 10-year intervals or increase in frequency due to climate change, large areas of the Amazon forest are likely to be exposed to persistent effects of droughts and corresponding slow forest recovery,” he said. “This may alter the structure and function of Amazonian rainforest ecosystems.”

The team found that the area affected by the 2005 drought was much larger than scientists had previously predicted. About 30 percent (656,370 square miles, or 1.7 million square kilometers) of the Amazon basin’s total current forest area was affected, with more than five percent of the forest experiencing severe drought conditions. The 2010 drought affected nearly half of the entire Amazon forest, with nearly a fifth of it experiencing severe drought. More than 231,660 square miles (600,000 square kilometers) of the area affected by the 2005 drought were also affected by the 2010 drought. This “double whammy” by successive droughts suggests a potentially long-lasting and widespread effect on forests in southern and western Amazonia.

The drought rate in Amazonia during the past decade is unprecedented over the past century. In addition to the two major droughts in 2005 and 2010, the area has experienced several localized mini-droughts in recent years. Observations from ground stations show that rainfall over the southern Amazon rainforest declined by almost 3.2 percent per year in the period from 1970 to 1998. Climate analyses for the period from 1995 to 2005 show a steady decline in water availability for plants in the region. Together, these data suggest a decade of moderate water stress led up to the 2005 drought, helping trigger the large-scale forest damage seen following the 2005 drought.

Saatchi said the new study sheds new light on a major controversy that existed about how the Amazon forest responded following the 2005 megadrought. Previous studies using conventional optical satellite data produced contradictory results, likely due to the difficulty of correcting the optical data for interference by clouds and other atmospheric conditions.

In contrast, QuikScat’s scatterometer radar was able to see through the clouds and penetrate into the top few meters of vegetation, providing daily measurements of the forest canopy structure and estimates of how much water the forest contains. Areas of drought-damaged forest produced a lower radar signal than the signals collected over healthy forest areas, indicating either that the forest canopy is drier or it is less “rough” due to damage to or the death of canopy trees.

Results of the study were published recently in the Proceedings of the National Academy of Sciences. Other participating institutions included UCLA; University of Oxford, United Kingdom; University of Exeter, Devon, United Kingdom; National Institute for Space Research, Sao Jose dos Campos, Sao Paulo, Brazil; Boston University, Mass.; and NASA’s Ames Research Center, Moffett Field, Calif.

— A NASA Jet Propulsion Laboratory news release

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19 Responses to NASA-Led Study Finds Warming-Driven Megadroughts Jeopardizing Amazon Forest

  1. John McCormick says:

    and precipitation in the southeren belt of the US and eventually the world’s grain basket. The report might have looked into that prospect.

    We are watching the demise of the planet’s northern hemisphere weather engine as we measure the Amazon forest rain machine being liquidated. What, pray tell, is between the Arctic and the Amazon? Our food supply!!

    Just another thing to worry about. Oh, my.

  2. rollin says:

    My, the earth earth appears to have less eco-stability than previously thought. I wonder what the next surprise will be, rain in the central Sahara?

    All of these large-scale changes will add up to something in the near future. Well, I guess we were promised change.

  3. Mulga Mumblebrain says:

    Another sign that we have passed the point of no return to ecological catastrophe. How do you reverse something like this, in less than centuries?

  4. Merrelyn Emery says:

    Not sure how a ‘megadrought’ varies from a routine 5-10 year drought but trees are dying all over the world which should be enough to bring everyone to their senses, ME

  5. Paul Klinkman says:

    Sadly, yes. First comes the megadrought. Then comes the megadeath of trees in the forest. The trees soon turn into dry kindling. Then come the megafires which burn out the surviving trees. The megafires put even more black carbon and accumulated CO2 into the atmosphere, and then the ex-forests no longer absorb carbon dioxide. This is happening more or less to most forests on earth.

  6. Paul Klinkman says:

    An arduous how-to is better than none at all.

    First, remember that we’re a highly technological society. Our robot factories are able to mass-produce gadgets by the billions if necessary. Yes it takes energy to produce stuff, but not at all on the scale of what we’re already burning for traffic jams, coal exports to China and dirty little wars.

    So, for job one, we need (mold-free, radon-free heat at the application point) economical solar heat storage for hot water preheating, for heating of buildings at night and on cloudy days, for growing crops in winter. Not a problem, let’s do it now. We need to get the cost of algae biodiesel down to below about $5.00/gallon. We also need cheap solar-thermal electricity. Again, heat can be stored for nighttime generation. If we achieve all of this, most remaining oil/coal/gas/tar reserves become practically worthless to extract, forever. Our 395 ppm carbon dioxide level levels off.

    Job two is to grow algae in sealed evaporation-free bioreactors in arid settings. We don’t need to use prime corn and wheat belt land.

    Job three is to go all-electric on the roads with battery pack changing stations everywhere. The total cost of driving drops, and you can drive an electric to California and back. Old gas-guzzling Hummers are for deadbrains.

    Job 4 is to automate the transit system and put it above grade, hanging on a couple of cables for local transit. We remove 40,000 American traffic deaths a year with automation and take out traffic jams.

    Now, we tackle the 395 problem. Algae is 50% biodiesel and 50% cellulose (a stable carbohydrate) algae cell husks. Bury the cell husks in big lignite mountains in the arid areas. 394, 393, 392,… This is going to take many years even after we ramp up, but we have to do it.

    Job 6 is mitigating the damage of 395. Given the mantra that almost nothing is more expensive than catastrophic climate change, I recommend that all polar and temperate climates be covered with a light amount of snow as much as possible, whenever meteorological conditions allow. Every neighborhood (except near major roads) should have its own wind-powered snow-making equipment. In many cases, 33 degree well water can be pumped up to a good height and sprayed in fine particles into the wind whenever the air temperature is below freezing and the wind is whistling. If you make snow when the wind blows, the wind scatters the light snowflakes far and wide. Now there will be iconoclasts who say, “But I like Florida temperatures near my house in Manitoba in the winter.” We need to outvote these people. Let them go to the mall and walk around if they want to be warm. Manitoba should be naturally cold in the winter.

    We also need to transfer heat out of the planet’s polar oceans into the atmosphere in winter, so that the polar oceans develop an ice pack like they used to have. If we need a heat transfer gadget for every square mile of ice pack, then we’ll just have to ramp up and build that many. The value of reflecting sunlight back into space, of having seals, narwhals, polar bears and microflora in the Arctic Ocean, also the value of having the rest of the earth back to normal, far outweighs the cost.

    How’s that for a start? If you try to pick it apart, you’ll only have a better plan in the end. The only really bad climate change plan is no plan at all.

  7. Merrelyn Emery says:

    Great stuff! So what’s stopping us? ME

  8. Paul Magnus says:

    Were over the edge… its going to be a crazy ride….

  9. Spike says:

    Simon Lewis, an ecologist at the University of Leeds, and his team of researchers said that 2010′s crippling dry spell was worse than a “once-in-a-century” 2005 drought and may have caused more emissions than the United States does in a year.

    We see another feedback kicking in.

  10. Mulga Mumblebrain says:

    Lots of good ideas. I’m a techno-illiterate so I’d add biochar, massive reforestation (because I love trees)albedo tinkering with white roofs etc, vegetarian diets (encouraged, not made compulsory) criminalisation of belching (oops-fascist tendencies emerging)etc. As ME says below- ‘What is stopping us?’ We all know the answer, and part of it is our fear of being free, of breaking loose from the psychic bonds that make us obey buffoons.

  11. fj says:

    The developed world must start ramping up the production of large cadres of highly skilled scientists and tehnologists to deal with these very dangerous problems without delay.

  12. wili says:

    Solar thermal, yes. But we don’t have time to wait around for algae-based biodiesel.

    Just to point out a couple problems–locating production in arid regions is a problem because you need lots of water for algae bio-diesel. Also, those corn husks are needed by the soil. We use essentially a continuous Niagara Falls of liquid fuels. The likelihood that algae will ever be able to supply more than a tiny fraction of that is beyond remote.

    We don’t have time to wait for new or experimental technologies. Solar thermal is real had has been used for years. Some other forms of solar and wind are time tested and should be rapidly built out.

    But the things that are even more assured and cheaper are efficiency, conservation, insulation, and outright curtailment.

    We’re talking about the future of the freakin’ planet. Can’t we look over what activities are not benefiting us very much and desist from at least some of those. Do we have to light up the night sky with endless lights left on all night every night turning what should be the dark side of our planet into a glowing star. What an idiotic use of the energy that we should see as extremely scarce and precious, if we understood the full costs our children will bear for it.

    And that is just one of a myriad of uses that are mostly or completely frivolous, unnecessary or even directly harmful that could be curtailed without much threat or harm to anyone.

  13. wili says:

    And don’t forget the termites whose numbers then explode to take advantage of the new food sources and turn much of this newly available carbon into that very powerful greenhouse gas, methane.

  14. wili says:

    True, but it is more than a technical problem.

    It is ultimately a question of our very self-definition.

    We have by our actions defined ourselves as planet destroyers.

    It is now likely too late to redefine ourselves as “planet savers,” appealing as such a fantasy would be.

    At best we can redefine ourselves as ‘planet destruction minimizers’–though I’m afraid that doesn’t come across as a very inspiring sound bite in a political speech.

    Perhaps the inspiring image remains that of the anonymous (as far as I know) Chinese man who stood in front of the line of tanks, knowing that they may well ride over him, knowing that his act would almost surely not avert that Tien An Min Square massacre that was about to ensue, but knowing that he had to put his body between the forces of destruction before him and the horror that was to come–that there was no other human choice left to him.

    Our inspiration cannot be motivated by baseless panglossian dreams that we can utterly stop the unraveling that is already manifesting itself around us.

    True inspiration must come from the image of those who stand against annihilating madness because it must be opposed, even at risk to our lives and bodies, even if it can no longer ultimately be stopped.

  15. wili says:

    Thanks for the reminder that this is ow just a tragic symptom of the unfolding maelstrom, but also part of a dynamic that is forcing us ever further into a death spiral of ever worsening climate change–one of many feedbacks that are beginning to kick in, most of which also re-enforce each other.
    The complexity of such multiple, interacting feedbacks is, not surprisingly, beyond the ability of our models to accurately capture. But knowledge that they are there should help remind us that nearly all estimations of future warming are likely underestimations, perhaps by a long shot.

    We have thrown a spanner into the gears of a mechanism we did not make and don’t fully understand. The breakdown that will ensue will similarly be beyond our full understanding. To paraphrase an old Jackson Brown song, we are sure to be amazed by the magnitude of the fury in the final hours.

  16. Paul Klinkman says:

    There are two answers for algae in arid areas. First, a sealed bioreactor has no evaporation at all. Second, some species of algae grow in seawater.

  17. Solar Jim says:

    Direct and indirect ecologic impacts of man-made carbonic acid gas, and resulting liquid carbonic acid, are now destroying forest and phytoplankton ecosystems. These are our planet’s primary sources for the maintenance of oxygen in both ocean and air. Without sufficient levels of oxygen respiration eventually becomes impossible, leading to suffocation.

    We might therefore expect forthcoming scientific papers on our planet’s decreasing oceanic and atmospheric concentration of oxygen.

  18. wili says:

    And what is the energy input necessary to have a sealed bioreactor large enough to produce a continuous Niagara Falls of bio-diesel??

    If you are taking carbon-hydrogen chains out, you have to have continuous more-than-Niagara-Falls levels of input of stocks that have those. Presumably most of the C is coming from the air, but that still means most of the H has to come from water. So you need continuous new sources of water, again at continuous Niagara levels.

    Even if you are planing on getting that from the sea, it is not an energy free process to pump a Niagara of water continuously out of the ocean up to wherever your bioreactor is, then to pipe the resulting diesel to market. And presumably that is going to leave a lot of salty residue–how do you deal with that?

    Sorry. I’m not against continuing some research on it, but this tech is a long, long way from prime time.

  19. Merrelyn Emery says:

    Hole in one! (following Fromm) Dependency is so acceptable so let’s all go on waiting for our ‘leaders’ to do something and whinge like hell when it doesn’t suit us, ME