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Summary It has been shown in recent surveys, that in India there is an upward trend in the area of open forest, which has grown from 10.06 million ha to 26.32 million ha in a few years. But the closed forests of India have registered a fall from 36.02 million ha to around 33 million ha. The latter fact is both significant and disturbing. It proves that in spite of the Forest Conservation Act, 1980, the process of degeneration of forests, in India, constantly continues. It is obvious that a part of the open forests must have come from closed forests due to the reckless denudation of forests, carried out in the name of development. A massive afforestation/reforestation programme is desired to achieve the target of one third of the geographical area of the country to be under forest cover for proper ecological balance. India has to develop a sound National Forest Policy to meet the requirements of the country, to produce industrial wood, for forest based industries, defence, communication and other public purposes, and small timbers fuel wood and fodder for the rural community. In this context the decision taken by the Control Board of Forestry in December, 1987, is quite encouraging. It was resolved that the extraction of wood from the forests would be stopped and the country's need for timber and fuelwood would be met by importing wood and by means of farm forestry. The reconstitution of the National Wasteland Development Board and the planting target of 5 million ha p.a. are other positive steps in this direction. Extensive research is needed for a better and new approach to social and commercial forestry.Dr Om Prasad, the senior author, is a biologist in the Department of Zoology, University of Allahabad. He is responsible for developing a number of Environmental Biology Courses at graduate and post-graduate level. Besides being actively engaged in research on the adverse toxilogical effects of a number of commonly used food additives, he supports environmental protection activities including the provision of guidance to the Students Nature Club which is affiliated to WWF-India.Dr Pawan Kumar, after teaching for seven years in the Department of Forestry at Birsa Agricultural University, Ranchi, Bihar, recently joined the Department of Environment of the Government of India where he is in charge of a number of environmental projects. Dr O.N. Pandey is a specialist in Forestry teaching at Birsa Agricultural University, India.  相似文献   
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The present work presents the results of 137Cs concentration in seawater, fish and sediments samples collect in 11 sampling points, crossing the Brazilian Southeastern coastal region, from Vitória (ES) to Santos (SP), on a routine basis from 1997 to 2002. This monitoring program was carried out by the Instituto de Radioproteção e Dosimetria (IRD/CNEN/MCT), in cooperation with the Instituto de Estudos do Mar Almirante Paulo Moreira (IEAPM/Brazilian Navy), aiming at determining artificial radionuclides in marine samples. Additionally to the 137Cs results, 90Sr concentrations in fish samples from 1998 to 2002 are also reported.The 137Cs in seawater follows a lognormal distribution, with a geometric mean of 1.8 Bq m-3 and a geometric standard deviation of 1.4 (n=54), decay corrected to June/2002. For 137Cs levels in fish samples a geometric mean of 0.19 Bq kg−1 and a geometric standard deviation of 2.9 (n=39), decay corrected to June/2002, with a range of 0.03 to 1.7 Bq kg−1, were obtained. Based on the 137Cs mean concentration in fish as well as in seawater, a transfer factor of 1 × 102 was calculated, which is quite in agreement with the recommended value found in the Safety Report Serie 19.  相似文献   
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Twenty ropes with 400 Perna perna mussels seeds (3 cm shell size) were set-up on floating structures at Cabo Frio Island, Arraial do Cabo, approximately 100 km northeast of Rio de Janeiro city. A rope was taken out on a monthly basis, and the shell sizes of 100 seeds were measured. The haemolymph of 10 male and 10 female individuals was taken, and the same individuals were separated for 210Po/210Pb determination. After one year of monthly sampling, no clear correlation was observed between the 210Po concentration, mussel's age and weight. A mean 210Po concentration of 155 Bq kg(-1) wet weight basis, was obtained, which is comparable with data reported in the literature. The radiation dose did not have any observable effect on the micronuclei frequency and DNA breaks in the mussels. This was probably due to the low dose rate, 0.02 mGy d(-1), in comparison with the suggested potential dose limit of 10 mGy d(-1).  相似文献   
4.
Abstract:  On Pacific islands non-native rats and mongooses threaten many native species. In Fiji we compared visitation rates of rats and mongooses at bait stations and measured biomass of leaf-litter invertebrates to assess the relative predation pressure from these species in forest areas at different distances from the forest edge. Forest areas over 5 km from the forest edge had significantly fewer baits encountered by rats or mongooses than did natural forest areas nearer agricultural and urban habitats. Remote forest areas may function as a last refuge for island species threatened by predation from non-native rats and mongooses. The biomass of leaf-litter invertebrates in remote forest areas was higher, indicating a refuge effect for some taxa targeted by rats and mongooses. Protection of the few remaining large blocks of natural forests on Pacific islands may be the most cost-effective approach for conserving many island endemics threatened by rats and mongooses. Logging roads can compromise this refuge effect by acting as dispersal routes for rats into natural forests.  相似文献   
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