Soil erosionl



 Satellite–derived NDVI variations to assess agricultural vulnerability to climate change

Variations in satellite based vegetation index were analyzed to assess agricultural vulnerability in India. Time-series NDVI data composites from NOAA-AVHRR and MODIS-TERRA satellites (1982 - 2012) were analyzed for variations in Max. NDVI and in length of crop growing period (LGP) in various agro-eco-sub-regions (AESRs) in order to develop typology of agricultural vulnerability essential to formulate adaptation and mitigation strategies in the country. This facilitated the drawing of typologies of agricultural vulnerability based on extent of agriculture hazarded by climate change, bioclimate determined by Thorthwaite’s Moisture Index, normal LGP based on water-balance model, LGP derived from vegetation index and prevalent cropping systems. This information is essential for prioritizing adaptation and mitigation measures in vulnerable districts.

Results indicated that agriculture was vulnerable to climate change in 122 districts in 12 states in the country. Of the 74 million ha under agriculture in these districts, MODIS dataset with 250 m resolution indicated that over 47 million ha of net sown area (NSA) was vulnerable. Coarser AVHRR dataset with 8 km resolution indicated that over 29 million ha of NSA was vulnerable. It is indeed noteworthy that nearly 1/5th to 1/3th of NSA in the country out of a total NSA of 142 million ha was vulnerable to climate change.

To analyze drivers of agricultural vulnerability, a methodology was developed to estimate length-of-crop-growing-period (LGP) using vegetation index. Variations in LGP derived from AVHRR and MODIS datasets were compared with normal LGP estimated through water-balance model. Typology of agricultural vulnerability was drawn based on variations in LGP compared to normal. LGP trends in districts with > 50% area under agriculture were analyzed. It was seen that in 80 districts there was a decrease in LGP of which 6 were located in arid region, 70 in semi-arid and 4 in sub-humid region. Thirty-one districts were experiencing an increase in LGP - 23 in arid and 8 in semi-arid tracts where pearl millet, pulses and groundnut are grown. Eleven districts did not experience any change in LGP - 1 in arid, 2 in semi-arid and 8 in sub-humid regions in India.






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