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Carnegie scientists unveil initial data on Amazon drought

Carnegie Airborne Observatory

Scientists were still debating the satellite signal of the megadrought that struck the Amazon Basin in 2005 when another megadrought hit in 2010. That work continues, but this time around, the Carnegie Institution for Science in Stanford, California, was ready with a new tool that goes beyond blurry pixels and provides a detailed view of individual trees — and indeed large branches.

Early results provide a new window into the Amazon’s response to drought, which some scientists fear is a harbinger of a warmer world (see ‘The Amazon basin in transition‘). After using satellite data to gauge the severity and extent of the drought, Carnegie’s Greg Asner flew a new aerial observing system over some 500,000 hectares of the Peruvian Amazon in July 2011 (see ‘A new eye on biodiversity‘). The team ran transects into areas hardest hit by the drought in eastern Peru along the border with Brazil, and then compared the results against data collected using an earlier version of the system in 2009.

Speaking at the American Geophysical Union’s fall meeting in San Francisco, California, on Friday, Asner provided an initial analysis of the damage, from broken branches to partial crown loss to downed trees. Limb loss increased as much as fourfold as the team flew into the epicentre of the drought, and the rate of downed trees increased by about 50%. But trees are big and take time to come down, which means that the rate of downed trees will increase in the coming years.

To get a sense of what the data look like and how the team is able to make these assessments, take a look at the animated tour (embedded below) through a digitally reconstructed swath of the Amazon. The imagery is based on ‘hyperspectral’ data collected across more than 400 frequencies of light, which are then overlaid onto a three-dimensional map constructed using a separate laser-based instrument (details here).

https://youtu.be/-KKgr686lqc

The technology is being put to other uses as well. The Carnegie team presented its latest biodiversity research, showing that the system can be used to analyse landscapes and identify individual tree species with an average of nearly 80% accuracy. Meanwhile, the National Ecological Observatory Network, based in Boulder, Colorado, has been conducting flights to test and validate systems as well as collect initial data with its airborne observation platform, modelled on the Carnegie system (see NEON’s poster at AGU).

Asner and his crew are still working to quantify the overall impact, but upwards of 60% of the trees were leafless in the hardest-hit areas, “as far as the eye can see, as far as the plane can fly,” Asner says. Differentiating between dead and deciduous trees is difficult, but Asner says that deciduous trees typically make up just 1–5% of the total, depending on the area. Extending this view across the Amazon remains a challenge, but the team is looking for ways to leverage the high-resolution ground data to better interpret the signals satellites pick up from space.

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