Smt. Kalpana Palkhiwala:India is endowed with a rich and diverse forest vegetation. The forests of the country vary. India is the second most populous and seventh largest country in the world having a population of over one billion with 1.8% of world’s forest cover. It is, however, important to differentiate between the forest cover and the tree cover, i.e., Trees Outside Forests (TOF).
There exists a significant tree cover wealth outside the conventional forest area, most of which is less than one hectare in extent. They include small patches of trees in plantations, and woodlands, or scattered trees on farms, homestead and urban areas or trees along linear features such as roads, canals, bunds etc. They constitute significant areas. Trees Outside Forests (TOF) are considered an alternative but significant source of fuel, fodder and timber. They give economic stability, support development and also provide environmental relief to the local people.
With the improvement in satellite data resolution and with adoption of digital image processing, it is possible to assess forest cover patches as small as one hectare that are termed as tree cover.
The tree cover estimate comprises tree patches outside the recorded forest area which are not captured by remote sensing satellites during forest cover assessment. This area is less than the minimum mappable area (1 ha) and comprises blocks and linear patches having areas up to 0.1 ha and scattered trees.
All areas more than 1 ha in extent and having a tree canopy density of 10% and above are included under forest cover. However, there are many small patches of trees less than 1.0 ha in extent, such as trees in small scale plantations, woodlots, or scattered trees on farms, homesteads and urban areas, or trees along linear features, such as roads, canals, bunds, etc. not being captured by satellite sensors under forest cover due to technological limitations.
The Forest Survey of India (FSI) started estimating the tree cover in the country in the year 2001 to have a complete picture of the forest and tree cover to compare it with the national goal of 33% forest and tree cover.
Methodology of Tree Cover Assessment
Trees outside forest areas are fragmented, scattered and there is no accurate knowledge of their geo-locations. They have a low density and their assessment by conventional methods becomes costly and time-consuming. In 2001, the FSI developed a methodology using high resolution satellite imageries (5.8m) for identification and classification of TOF resources. Appropriate sampling is then done and field inventory conducted for assessment of TOF which is used for estimation of tree cover. Based on this method, the first estimate of TOF and tree cover was published in ‘SFR 2003’, which was based on the inventory of 60 districts. There has been improvement in the present estimate because against the inventory data of 60 districts, the data of additional 60 districts inventory during 2003-2005, i.e. data of a total of 120 districts comprising 10,145 sample plots has been used to estimate the tree cover of the country.
The assessment of tree cover of a district has two components. One component consists of areas identified from satellite data under block and linear forms. The high resolution satellite imageries map tree blocks (patches between 1 and 0.1 ha) and linear plantations in the rural areas. The actual area covered by such patches is computed from the classified digital map using GIS methods. The second component is the computed area from scattered trees growing in rural and urban strata, which are not mapped/identified even with high-resolution satellite data (5.8m) currently used.
For computing area of tree cover from scattered trees, an exercise was conducted in 2001 to establish relationship between diameter (DBH) and tree crown of different species growing in different physiographic zones. This relation was used to derive the number of trees of a species in making 1 ha area with 70% density. To estimate the area of tree cover under scattered trees in rural and urban strata, adequate numbers of sample plots are laid and numbers of trees occurring in the sample plots are enumerated by diameter, class and species. This helps in estimating the number of trees per ha in scattered and urban strata. Using the number of trees by diameter and species constituting 1 ha area as published, the tree cover under scattered stratum is estimated. The entire Culturable Non-Forest (CNF) area of the district excluding block and linear patches already assessed is taken for estimating the tree cover under scattered stratum. The area under urban stratum is taken from Census data. The total tree cover for the selected district is obtained by aggregating the area of tree cover under block and linear strata, and computed area from scattered trees in rural and urban strata.
On the basis of the tree cover of sampled districts, the tree cover for the physiographic zone is estimated. Adding tree cover estimate for all the physiographic zones provides the estimated tree cover of the country.
Tree Cover in the Country
The total tree cover of the country has been estimated to be 91,663 km², which constitutes 2.79 per cent of the country’s geographic area.The tree cover constitutes the largest area in Maharashtra (8.978 km²) followed by Rajasthan (8,379 km²), Uttar Pradesh (8,203 km²) and Andhra Pradesh (7,640 km²). Considering the percentage of geographic area under tree cover, the highest rank goes to Lakshadweep (13.33%) followed by Pondicherry (8.66%), Daman & Diu (7.76%) , Goa (7.24%), Delhi (7.20%), Kerala (6.77%) and Dadra & Nagar Haveli (5.66%).
*Assistant Director ( M & C), PIB, New Delhi