Estimating Plantation Survival in Himachal Pradesh Using Remote Sensing Based forest Cover Assessments: Possibilities and Limitations

Abstract

The biennial forest assessment reports of the Forest Survey of India (FSI) are eagerly awaited by all stake holders particularly the forest managers to satisfy their curiosity about the impact of various forestry interventions, specifically afforestation. Positive changes in forest cover are attributed mainly to successful plantations, though change in forest cover is outcome of several factors. In this paper, an attempt is made to explore the possibility of delineating contribution of plantations on the basis of the forest cover assessed by FSI using Multi-date Satellite Remote Sensing taking Himachal Pradesh as a case. First hurdle in this attempt was posed by the incompatibility of forest cover data arising from significant changes in technology over these years which, however, had been overcome to some extent by FSI by normalizing the time series in 2009. Second hurdle was the lack of collateral data on survival and referenced maps of plantations. Third constraint was near impossibility of segregating real and interpretational changes from the forest cover already assessed. Notwithstanding these constraints, the paper attempts to provide a notional estimate of survival of plantations making certain assumptions. The estimates are made in relation to change in overall forest cover, forest cover coupled with scrub and change in forest cover vis a vis plantation raised during the intervening period. Assuming that 4-6 year old plantations would, normally, get captured in the satellite imageries and further assuming that the entire increase in forest cover (2216 km²) was due to plantations, the estimated over all possible survival of plantations raised from 1976-77 to 2008-09 worked out in the range of 7.25% to 26.8%. The survival of plantations raised during 1994-95 to 2008-09 could possibly be in the range of 38.9% to 46.58%. However, very low survival (1.75%) was revealed in respect to plantations raised from 2000-01 to 2008-09. The survival so estimated provided theoretical perspective (based on assumptions) which might or might not hold good on the ground but the increase in the forest cover over the last 30 years (1981-83 to 2013-14 corresponding to the period of satellite imageries used in assessment) reflects actual improvement @ 7386.67ha annually which is quite encouraging for the State. The factors responsible for influencing capture of plantation in the satellite imageries and the correct perspective of the usability of forest cover data in such an estimation have been elaborated.