The world over "sacred groves" are a means of conserving forests and biodiversity. These are today threatened with rapid degradation and modernisation.Urgent measures are needed to restore these groves, ranging from less than a hectare to a few square kms which may be the last vestiges of natural reservoirs in certain areas, says a new book.They denote a complex ecosystem on the one extreme or simply a small cluster of planted trees on the other, says, the book 'Conserving the Sacred -for Biodiversity Management', a compilation of articles by experts from home and abroad.