The 86-year-old environmentalist was admitted at the hospital this morning when he had trouble in breathing, doctors at the hospital said.
Though his condition is improving he has lost a lot of weight which is a cause for concern and will have to be kept at the hospital under the observation of doctors for some more time, they said.
Bahuguna's name is closely associated with the Chipko movement of the 1970s and the anti-Tehri dam movement.