Emergy evaluation of semi-arid watersheds under different management strategies.

摘要

Due to the environmental impacts generated by economic activities faced with the challenge of producing food for an increasing population, the sustainability of production methods should be analyzed to determine those with the highest relative yield and the least degradation of the environment. Seeking alternatives for sustainable use of the caatinga biome, this research tested two types of management strategies in watersheds of the semi-arid region in Iguatu, Ceara, Brazil, and compared them to a preserved area of caatinga. To evaluate the performance of the systems an emergetic methodology, suggested by Odum, was used. The thinned-out area showed the best emergy results, with a transformity of 12,975 seJ S while the preserved area B2 and that planted with grass B3, presented transformities of 14,477 and 22,062 seJ S respectively. Through the activity of thinning, where the energy produced was 45% higher, the transformity was lower than the unchanged caatinga, showing that the investment in labour for thinning was offset by an increase in energy production.The high transformity of the untouched caatinga indicates that there could be better use made of available resources. This system could be used in beekeeping, or ecological tourism, or in anyother activity which, as with thinning, would not alter the system beyond its capacity for tolerance but that would allow a more efficient use of the natural resources by users.