New Study Examines Effects of Drought in the Amazon

From Woods Hole Research Institute:

Amazon Drought

Click on image for larger view. (Left) Average dry-season enchanced vegetation index (EVI) across central South America for the period 2000–2008. Overlaid circles represent average vapor pressure deficit (VPD), a measure of the drying power of air, at 280 meteorological stations across the region for the period 1996–2005. (Right) Coefficient of variation in annual EVI for the period 2000–2008.

Recent research surrounding the impact of drought in the Amazon has provided contradictory findings as to how tropical forests react to a drier and warmer climate. A new study published in the August 2 Early Edition of the Proceedings of the National Academy of Sciences (PNAS) examines the response of Amazon forests to variations in climate conditions, specifically considering how those changes may influence forest productivity. These findings provide possible context for why previous studies have offered varying conclusions. Scientists from the Instituto de Pesquisa Ambiental da Amazônia, the University of Florida-Gainesville, and the Woods Hole Research Center co-authored the paper.

According to Paulo Brando, the paper’s lead author, “Our study builds on field studies and remote sensing studies to demonstrate that relatively undisturbed Amazon forests are quite tolerant of seasonal drought, unlike other types of vegetation and severely disturbed forests. Our study also points to several potential mechanisms controlling seasonal and inter-annual oscillations in vegetation productivity across the Amazon Basin. To date, discussions of these mechanisms have been largely lacking in the scientific debate about how Amazon forests may respond to climate change.”

The study used a combination of remote sensing and field-based studies, including MODIS Enhanced Vegetation Index (EVI) data from the 2000-2008 dry seasons in the Amazon Basin. This was integrated with climate data from 1996-2005 recorded at 280 meteorological stations. Statistical relationships between EVI and several variables were also analyzed for both the entire Amazon Basin and for an intensively studied site (Tapajos).

Scott Goetz, a co-author, explains, “This analysis is unique in that it captures, in great detail, how forest productivity varies with meteorological measurements, particularly during drought years. Our findings build upon earlier work but take those several steps further by actually making the link with climate and examining how forests respond by flushing new leaves.”

In addition to contributing to the debate about vegetation vulnerability to drought, the authors report important patterns in climate across the Amazon Basin from 1996-2005. Precipitation decreased during the rainy season, while dry-season light availability increased. Given the importance of these changes to processes that permit forests to sequester carbon during drought conditions, the authors emphasize the need for better integration of field-based data and remote sensing studies.

This paper’s release coincides with calls within the scientific community for a better understanding of how Amazonian forests and other tropical forest formations may respond to climate- and land-use related drought.

According to Daniel Nepstad, also a co-author, “Our study further demonstrates that the response of forests to drought is complex. It is pre-mature to draw a big conclusion about the susceptibility of Amazon forests to drought from remote sensing data alone.”

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Dave F
August 11, 2010 6:01 pm
This was partially the result of drought also. And temperatures the authorities state were around 10C below normal.

James Sexton
August 11, 2010 6:15 pm

According to Daniel Nepstad, also a co-author, “Our study further demonstrates that the response of forests to drought is complex. It is pre-mature to draw a big conclusion about the susceptibility of Amazon forests to drought from remote sensing data alone.”
I guess that about sums it up. Perhaps we can apply the same summation to other jungles as well?

James Sexton
August 11, 2010 6:16 pm
James Sexton
August 11, 2010 6:17 pm
Gary Pearse
August 11, 2010 6:39 pm

There seems to be a wave of.real science breaking out now that the pal review blockage of non-supporting papers has largely broken down. I guess many of the pals are working on an exit strategy. Anyway, thanks for this interesting post. No deadly carbon to be found.

Charles Higley
August 11, 2010 7:30 pm

It’s fine know about all of the matter that passes through the ecosystems, but it scares me when they talk about carbon sequestration, as if it’s important for some unestablished, false reason.

August 11, 2010 7:54 pm

I wish I could believe what Gary said (August 11, 2010 at 6:39 pm), but I don’t think that the wall is coming down, and that all of a sudden climate scientists might feel more inclined to say exactly what they think.
Instead, I think that Woods Hole, almost alone among science centers, is being straightforward about what they find.
Another, earlier example of this positive tendency on the part of Woods Hole is of the reaction of shelled creatures to VERY large increases in CO2 in the atmosphere, and thus to increasing CO2 in sea water, and thus to lowered pH (not acidic, but less alkaline).
I’m sure readers remember that according to the IPCC and Joe Romm and the other McCarthyites, with even slight increases in CO2, many sea creatures will lose their shells and die, to simplify only a little.
But the Woods Hole researchers discovered that only a few of the creatures with shells would even have a slower rate of growth of shell area at around 600 ppm volume CO2 (vs. 390 today, and the 450 “tipping point” beyond which humankind allegedly proceeds at their peril). They also discovered that many of the creatures would have substantially more shell at 600 ppm — and some, like blue crab, shrimp, and lobsters, would have more shell even at 2,800 ppm volume CO2 in the atmosphere! That is 7 times higher than today!
The biologists then discuss the mechanisms by which these creatures would add more shell, even thought the oceans would be “more acidic” (actually, just less alkaline). All the scare stories had neglected to actually do biology — they just said, if the oceans are acidic, shells will dissolve. Too bad they didn’t consult the crabs and shrimp and lobsters and others….but the Woods Hole people decided they would actually do the experiments that would reveal how actual creatures in a complex world would react. Kudos to them!
None of this should be a surprise. Most of these creatures were already here when CO2 was far higher than today. But the researchers told it like it is. Here is a link to the abstract:
If you google “”Marine calcifiers exhibit mixed responses to CO2-induced ocean Woods Hole”, the second link (a PDF) should be to the entire article. It is fascinating, and I urge everyone to read it carefully.

August 11, 2010 8:17 pm

1] Based on a site-specific study, we show that monthly EVI was relatively insensitive to leaf area index (LAI) but correlated positively with leaf flushing and PAR measured in the field.
-Brando et al, 2010
2] Here we report, from analysis of 5 years of recent satellite data, seasonal swings in green leaf area of 25% in a majority of the Amazon rainforests.
-Myneni et al, 2007
3] Similar to these previous studies (Huete et al., 2006; Myneni et al., 2007), our results suggest that EVI has a negative relationship with rainfall.
-Anderson et al, 2010
4] The combined effect of dead stems and leafless trees is very likely to reduce the heterogeneity of canopy reflectance and decrease the effect of shadows cast by the highest trees. It is likely that many other trees have also dropped their leaves during the drought period but did not die in the aftermath. Hence, the EVI response could be related to the structural change (i.e.decrease of shadows)
-also, Anderson et al, 2010
5] The observations of intact forest canopy “greenness” in the affection areas, however, are dominated by a significant increase (P < 0.0001) (3) not a decline
– Saleska et al, 2010
6] We find no evidence of large‐scale greening of intact Amazon forests during the 2005 drought ‐ approximately 11%–12% of these droughtstricken forests display greening, while, 28%–29% show browning or no‐change, and for the rest, the data are not of sufficient quality to characterize any changes.
-Samanta et al, 2010
7] MODIS Enhanced Vegetation Index (EVI, an index of canopy photosynthetic capacity) increased by 25% with sunlight during the dry season across Amazon forests, opposite to ecosystem model predictions that water limitation should cause dry season declines in forest canopy photosynthesis
-Huete et al, 2006
Number [4] is interesting. The authors claim, that the forest appear green to satellite because the trees shed their leaves.

August 11, 2010 8:18 pm

It’s almost as if the forests have been there awhile.

August 11, 2010 8:20 pm

Dear John
You’ve been had. You are talking about the Woods Hole Oceanographic Center.
This is the George Woodwell and John Holdren run Woods Hole Research Center. They do lots of ‘research’ here. 😉

August 11, 2010 8:52 pm

“We show that 10 of the 18 species studied exhibited reduced rates of net calcification and, in some cases, net dissolution under elevated pCO2. However, in seven species, net calcification increased under the intermediate and/or highest levels of pCO2, and one species showed no response at all.”
Marine calcifiers exhibit mixed responses to CO2-induced ocean acidification
The conclusion to the paper points out that :
“Even those organisms showing enhanced calcification under elevated pCO2 could be negatively impacted by the decline of less CO2-tolerant species within their ecosystems. We have only begun to generate the data needed to assess CO2-driven impacts on organisms and ecosystems in the geologic past, and to anticipate the effects of anthropogenic ocean acidification in the decades and centuries ahead.”
In other words even if your shell in doing fine, you could be in trouble if the critters you feed on decline.
It would be important to known how the eggs and larva of the species fare under reduced pH.

August 11, 2010 9:16 pm

My comment – still under moderation – should have begun with @John says: August 11, 2010 at 7:54 pm .

Martin Brumby
August 11, 2010 10:59 pm

According to Daniel Nepstad, also a co-author, “Our study further demonstrates that the response of forests to drought is complex. It is pre-mature to draw a big conclusion about the susceptibility of Amazon forests to drought from remote sensing data alone.”
But not premature for Nepstead to claim that the IPCC’s shameless use of a campaign group’s expired promotional website represents a peer reviewed scientific basis for purely political alarmist scare stories.
Tough, but Nepstead has blown it. He has no credibility left.

Martin Brumby
August 11, 2010 11:02 pm

Should be Nepstad, not Nepstead.
But it might as well be Bedstead for all the credibility he has left.

August 12, 2010 1:27 am

Looks as if Nepstad knows he’s being watched.
Now if this actually means his science sheds its armour-plated rubbish, and stays clean, fine. But does it? And is it actually helping to dismantle the core IPCC nonsense about catastrophic manmade global warming? or to rehabitate those scientists who have preferred truth to money?

allen mcmahon
August 12, 2010 4:24 am

According to Daniel Nepstad, also a co-author, “Our study further demonstrates that the response of forests to drought is complex. It is pre-mature to draw a big conclusion about the susceptibility of Amazon forests to drought from remote sensing data alone.”
As to what Nepstad really thinks:
An extract from : Nepstad et. al., Phil. Trans. R. Soc. B (2008) 363
“If sea surface temperature anomalies (such as El Nin˜o episodes) and associated Amazon droughts of the last decade continue into the future, approximately 55% of the forests of the Amazon will be cleared, logged, damaged by drought or burned over the next 20 years, emitting 15–26 Pg of carbon to the atmosphere.”
Wild speculation if far better than actual data if you are a CAGW advocate.

Paulo Arruda
August 12, 2010 6:29 am

The areas in blue on Brazil are not covered by forest. They were cleared for cattle ranches, or are cities.

August 12, 2010 7:46 am

The paper was recieved at PNAS in Aug 2009. You can bet it underwent significant surgery before being published – especially since Samanta et al 2010, whose remote sensing dataset becomes the latest. But at least the authors don’t try to push exotic explanations for forest green-up.
“At rates of land clearing seen before recent years, 40 percent of the Amazon could have been deforested by 2050.”
It seems Amazon researchers are addicted to the 40% figure. You know the number of times the same number pops up.
There is another reason why deforestation rates are down in the Amazon. Implementation of REDD+ requires ‘forest management’ to significantly demonstrate that they can control leakage -i.e., ‘loss of fixed carbon’ by inadvertent/intentional forest fires or logging which ‘leaks’ the ‘carbon’.

Theo Barker
August 12, 2010 11:57 am

Let me repeat, what Shub said so that it’s clear to everyone:
Woods Hole Research Center is NOT Woods Hole Oceanographic Institute.
WHRC is directed by John Holdren and did NOT produce the study on how CO2 concentrations affect the shells of marine animals. WHOI did the study.
More sneakiness on the part of CAGW crowd to name WHRC what they did…

August 12, 2010 2:58 pm

It makes sense that a forest which is 1000’s of years old has developed ways of adaptation to climate and its changes. In this case, during a 6 year drought, Amazon rainforest trees shed their large leaves associated with large volume transpiration and sprout new buds and increasing their chlorophyl concentration; quit growing taller and thicker and instead, send their tap roots deeper in the ground in search of water. If you have been around the block a couple of times as the global rainforests have, it is not surprising that adaptive mechanisms develop for the survival of the species. Hmm, where have I heard that before? What else do we have to learn?

August 12, 2010 4:45 pm

Managed to get as far as “Amazon” and “Woods Hole Research Institute” before I saw REDD and had to stop reading.
Mods – I think I may have become a climate cynic.

August 12, 2010 6:44 pm

You can’t get much more off-topic than this, but this is about how climate change is just as bad for the Arctic as it is for the Amazon. Apparently, the Eskimos are dreading the coming heatwave:

August 12, 2010 10:41 pm

Nepstad was also the lead author of a study that diverted about 50% of natural rainfall before it reached the soil at a large test site in the Amazon. It took more than three years of artificial drought before any clear signs of damage were observed. The first sentence of the discussion said: “The seasonally dry forest of the Tapajos is an extremely drought-tolerant ecosystem.” Tapajos, the study site, receives less rainfall than 95% of the Amazon and has a low water table.
Ecology. 88:2259-2269

August 13, 2010 6:34 am

Ref – Gary Pearse says:
August 11, 2010 at 6:39 pm
“There seems to be a wave of.real science breaking out now that the pal review blockage of non-supporting papers has largely broken down. I guess many of the pals are working on an exit strategy. Anyway, thanks for this interesting post. No deadly carbon to be found.”
Based on current site info at WHRI there is no change to their faith in AGW. They are still convinced that “the sky is falling” and GREAT changes are REQUIRED to save us all from certain destruction.

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