Remote sensing is a tool for estimating forage biomass on plots using satellite images.

The Normalized Difference Vegetation Index (NDVI) is calculated from the "red" and "near-infrared" (PIR) spectral bands of a multispectral satellite image. The PIR reacts to the chlorophyll contained in plants. It thus allows us to estimate the forage biomass present on plots. It is a non-destructive method that allows us to obtain data over large areas and at a distance. For this, a field survey phase is necessary beforehand in order to link the quantity of biomass in the field to the calculated NDVI. This work was carried out during the first phase of the ARChE_Net project.

Initially, the objective of the studies conducted via NDVI is to validate one or more dependent soil-climate models adapted to each country in the Indian Ocean zone. Satellite images will be used to measure the evolution of plant activity during the different seasons and the data acquired by the satellites in the visible and near-infrared regions will be used to calculate NDVI indices; these indices are highly correlated with the density of the plant cover and the capacity of plants to absorb sunlight and convert it into biomass.

The biomass monitoring tool thus interrelates soil-climate-dependent grass growth patterns and geo-referenced information (NDVI indices, meteorological data, ground measurements) to map (Geographic Information System) the availability and nutritional value of a territory's forage resources. The tool can thus provide information, in real time, that enables livestock farmers to better manage their animal numbers and/or the mobility of their herds in relation to the expected availability of fodder resources.

A vegetation index used in the ECLIPSE project is the NDVI (Normalized Difference Vegetation Index). It highlights the difference between the visible red band and the near-infrared band to show the amount of vegetation. It results in values ranging from -1 (see photo - light green: very low density of vegetation) to +1 (see photo - dark green: high density of vegetation).

Photo : ECLIPSE project, all rights reserved