Tag Archives: Amazon

Mapping ecological impact of 2010 Amazonian drought

From NASA EOS Image of the Day:

Between July and September 2010, severe drought gripped the Amazon Basin. The Negro River, a tributary of the Amazon, reached its lowest level in 109 years of record-keeping, and uncontrolled fires spread a pall of smoke over the drying basin. But how did the drought affect the trees?

This image shows a possible answer. Made with vegetation “greenness” measurements from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, the image shows vegetation conditions between July and September 2010 compared to average conditions for the same period between 2000 and 2009 (except for 2005, another drought year). The vegetation indices are measurements of the how much photosynthesis could be happening based on how much leafy vegetation the satellite sees. In 2010, the vegetation index recorded lower values than in previous years, an indication that trees under drought stress either produced fewer leaves or the chlorophyll content of leaves was lower, or both.

Ecological memory of Amazonian agriculture

I just wrote this note on Faculty of 1000 on the paper (doi:10.1073/pnas.0908925107) I mentioned the other day:

Pre-Columbian agricultural landscapes, ecosystem engineers, and self-organized patchiness in Amazonia
McKey D, Rostain S, Iriarte J, Glaser B, Birk JJ, Holst I, Renard D
Proc Natl Acad Sci U S A 2010 Apr 12  [related articles]

This fascinating study describes how ecological engineers (such as ants, termites, and earthworms) maintained a newly described pre-Columbian agricultural landscape. The authors describe sites along the Guianan coastal plain (in Guyana, Suriname, and French Guiana) where pre-Columbian farmers constructed raised fields in flat, marshy locations.

The paper is particularly interesting because it combines new archaeological evidence in favour of the relatively new, and somewhat controversial, idea of a fairly densely settled pre-Columbian Amazonia with an ecological analysis of i) how spatial self-organization of ecosystems was likely used by pre-Columbian agriculturalists to enhance the yield and resilience of their agriculture system and ii) how these same processes have preserved aspects of the agricultural system during about five centuries of abandonment. This study is also interesting for its demonstration of how ecological memory can maintain patterns produced by past disturbance (whether natural or human), and in its hints of how different types of agriculture that work with biodiversity could possibly be reinvented today.

Some photos from the supplementary info of the paper:

Pre-Columbian raised fields in the Guianas. (A–D) Pre-Columbian raised fields in coastal French Guiana are located in flooded depressions, in flat savannas, along sandy ridges, or in talwegs. (A) Piliwa, on the left bank of the Mana River in extreme western French Guiana. (B) Corossony, on the left bank of the Sinnamary River. (C) K-VIII, west of the city of Kourou, near the Bois Diable site. (D) Maillard, between the town of Macouria and Cayenne Island.

(E) Map of raised-field complexes along coastal Amazonia from eastern Guyana to near Cayenne in French Guiana.

Short Links: Networks, Amazonian historical ecology, and development data

Two recent papers and comments + a new data site:

1) Tom Fiddaman on a new Nature paper (doi:10.1038/nature08932) from Eugene Stanley‘s lab on cascading failure in connected networks, that shows that feedbacks between connected networks can destabilize two stable networks.

2) Wired news article Lost Tribes Used Clever Tricks to Turn Amazon Wasteland to Farms by Brandon Keim, who is writing a book on ecological tipping points,describes recent research on  newly discovered remains on novel agricultural systems in the coastal Amazon.  Its based on a paper by  Doyle McKey and others in PNAS -  Pre-Columbian agricultural landscapes, ecosystem engineers, and self-organized patchiness in Amazonia (doi:10.1073/pnas.0908925107.  The paper is really cool, combing an exploration of ecological memory with historical ecology. From  the abstract:

… we show that pre-Columbian farmers of the Guianas coast constructed large raised-field complexes, growing on them crops including maize, manioc, and squash. Farmers created physical and biogeochemical heterogeneity in flat, marshy environments by constructing raised fields. When these fields were later abandoned, the mosaic of well-drained islands in the flooded matrix set in motion self-organizing processes driven by ecosystem engineers (ants, termites, earthworms, and woody plants) that occur preferentially on abandoned raised fields. Today, feedbacks generated by these ecosystem engineers maintain the human-initiated concentration of resources in these structures. Engineer organisms transport materials to abandoned raised fields and modify the structure and composition of their soils, reducing erodibility. The profound alteration of ecosystem functioning in these landscapes coconstructed by humans and nature has important implications for understanding Amazonian history and biodiversity. Furthermore, these landscapes show how sustainability of food-production systems can be enhanced by engineering into them fallows that maintain ecosystem services and biodiversity. Like anthropogenic dark earths in forested Amazonia, these self-organizing ecosystems illustrate the ecological complexity of the legacy of pre-Columbian land use.

3) The World Bank has launched a new web site: data.worldbank.org to provide free access to development data. Their data catalog provides access to over 2,000 indicators from World Bank data.