Forest survey is the act of making measurements and assessments of various forest related physical parameters, such as forest area, forest cover, growing stock, distribution of tree species, extent of forest fire damage, etc. The information generated may be spatial (presentable on maps) or non-spatial (shown through statistical tables). This information provided by forest survey is essential for judicious planning, development and management of forest resources. Forest, a renewable natural resource, occupies a unique position due to its role in maintaining ecological balance and environmental stability and in sustaining economic development.
Under the pressure of demands from ever-increasing population, the forests, which initially seemed inexhaustible, are struggling for survival leading to over all deterioration in the environment, threatening the very existence of civilization. Over the last two decades, concern about the world's forests has risen dramatically on the global political agenda. Large areas of the world's forests, which served in subsistence and advancement of human kind, have been converted to other uses or severely degraded. There is a need to use all possible tools and information to manage and utilize forest resources wisely and scientifically in a sustainable manner. Application of forest survey techniques generates such information that can be used for sound management of forest resources.
Forest Cover Assessment
Space borne Remote Sensing technology has proved to be an important tool in rapid assessment and mapping of natural resources over a large area with reasonable accuracy. Application of satellite data in assessment of forest cover in India was first demonstrated by the National Remote Sensing Agency (NRSA), Department of Space, Hyderabad in 1985, when it came out with the first ever estimate of country's forest cover based on interpretation of Landsat (an American Satellite ) data. Almost simultaneously Forest Survey of India (FSI) started interpreting satellite data for assessment of forest cover of the country and published the country's forest cover in 1987 using Landsat (MSS) data.
Thereafter, FSI was mandated to assess and map the forest cover of the country on a two-year cycle and monitor the changes in forest cover of the country during the intervening period. Since then FSI is assessing and mapping forest cover of the country using satellite data on a two-year cycle. Results of these assessments are published in the form of a biennial report – State of Forest Report (SFR). So far FSI has completed ten biennial assessments, the latest being the State of Forest Report, 2005. During this period, there has been a rapid development in satellite-based technology and also in related high-end hardware and software for digital image processing of satellite data.
FSI kept pace with these developments by continuously updating its methodology to suit the new developments. Each assessments had improvement over the previous one with the addition of unique features. The technological improvement in the quality of data as well as the imaging software has led to improvement in the accuracy of the assessment of the forest cover.
The scale of forest cover maps increased to the present 1:50,000 scale. The minimum mappable area (cartographic limit) of the assessment was improved from 400ha in the 1987 assessment to 1ha in the eighth and ninth assessment.
Forest Cover in Hill Districts
Forest cover in hills is essential to maintain ecological balance and environmental stability as it prevents soil erosion and land degradation. The National Forest Policy (1988) aims at maintaining two thirds of the geographical area in hills of the country under forest and tree cover.
Forests Survey of India(FSI) has been assessing forest cover in the hill districts of the country since 1997. The hill districts identified for the forest cover analysis are the same as other identified by the Planning Commission for Hill Areas and Western Ghats Development Programme. As per the Planning Commission's criterion, a hill taluka is the one with altitude more than 500m from the mean sea level. A hill district is the one whose total area of hill talukas is more than half of the geographic area of the district. Based on this criterion, there are 124 hill districts spread over 16 States and UTs.
The forest cover in the hill districts is 274,932 sq.km., which is 38.85% of the total geographic area of these districts. Out of 124 hill districts, 55 have over two thirds of geographic area under forest cover; 36 have been between one third and two third; and 33 have less than one third. Moreover, forest cover is less than ten percent of geographic area in ten hill districts.
Compared to the 2003 assessment of forest cover, there has been a loss of forest cover of 255 sq. km in the above hill districts mainly due to the practice of shifting cultivation.
Forest Cover in Tribal Districts
Forests have traditionally played a central role in the economy of tribal people who are also known to protect forests and to live in harmony with nature. Since, 1997, FSI has been assessing forest cover in the district identified as tribal district by the Government in the Integrated Tribal Development Programme. This includes all the districts of the State of Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Nagaland, Sikkim, Tripura. The UTs of Dadra & Nagar Haveli and Lakshadweep have also been considered as tribal districts.
Although all tribal districts constitute only 33.57% geographic area of the country, the forest cover in these districts is 60.11 % of the total. All the North-Eastern States have over 75% geographic area under forest cover, except Assam (23.89% in 16 tribal districts) and Sikkim (45.97%). Overall, these figures indicate the richness of forest resources in the tribal districts in general, and in North-East region in particular.
The country is endowed with rich and diverse forest vegetation. The forests vary from alpine to coastal forests and from rain forests to arid forests. The recorded forest area of the country is 769,626 sq.km. (23.41% of the country's geographic area) and the forest cover of the country as per the 2005 assessment is 677,088 sq.km. (20.60% of country's geographic area). The volume of growing stock in the forest is estimated to be about 4,602 million cu.m. Being the second most populous and seventh largest country in the world having a population of over 1 billion with 1.8 per cent of world's Forest Cover. It is sustaining the needs of 17% of human and 18% of the livestock population of the world.