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Posts tagged NDVI

Vegetation Index of Amazon Rainforest, Brazil

4.2S 66.7W

March 27th, 2013 Category: Climate Change, Vegetation Index

Brazil – March 26th, 2013

This image shows the Normalized Difference Vegetation Index (NDVI) of the Amazon Rainforest, mostly in the Brazilian state of Amazonas. Dark green areas indicate a high index, while yellow and brown areas indicate a low index. Scientists have reported that climate change is leading to substitution of rainforest with savanna-like and semiarid vegetation, a phenomenon known as the Amazon forests’ “dieback”, particularly around the edges of the forest. Monitoring the NDVI in images such as this one allows researchers to see how fast and how much rainforest is being replaced with drier vegetation.

Comparative Vegetation Index East and West of the Andes

26.6S 68.9W

March 21st, 2013 Category: Vegetation Index

Argentina – March 21st, 2013

The Normalized Difference Vegetation Index (NDVI) is a simple graphical indicator that can be used to analyze satellite data, and assess whether the target being observed contains live green vegetation or not.

Live green plants absorb solar radiation in the photosynthetically active radiation (PAR) spectral region, which they use as a source of energy in the process of photosynthesis. Leaf cells have also evolved to scatter (i.e., reflect and transmit) solar radiation in the near-infrared spectral region. Hence, live green plants appear relatively dark in the PAR and relatively bright in the near-infrared.

The pigment in plant leaves, chlorophyll, strongly absorbs visible light (from 0.4 to 0.7 µm) for use in photosynthesis. The cell structure of the leaves, on the other hand, strongly reflects near-infrared light (from 0.7 to 1.1 µm). The more leaves a plant has, the more these wavelengths of light are affected, respectively.

Since early instruments of Earth Observation acquired data in visible and near-infrared, it was natural to exploit the strong differences in plant reflectance to determine their spatial distribution in these satellite images. Here, the color contrast shows a stark difference in the vegetation index between arid Chile and western Bolivia, which appear brown to yellow (low vegetation index), and more fertile Argentina, which appears green (high vegetation index).

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