The average rise of mean annual temperature globally has substantially disturbed the seasonal winds in tropics resulting in an increase in annual monsoon precipitation and relative humidity in western Himalaya. The climatic variations often result in extreme rainfall events, such as observed in June 2013 in Uttarakhand western Himalaya. Lichen a symbiotic association of a dominant fungus and a green and/ or blue-green algae are known to be influenced by microclimatic variables. The lichen community of any habitat is shaped by the micro-climatic variables such as relative humidity, atmospheric temperature, and rainfall. The reported study was done at Birthi falls in Pithoragarh district of Kumaun, western Himalaya. The study area was sampled in July 2009 and Sept 2013 for quantitative assessment of macrolichen diversity. The study revealed presence of both green algae containing chlorolichens and blue-green algae containing cyanolichens. The quantitative diversity of cyanolichens increased from 2009 to 2013. The photosynthetic efficiency of macrolichens from both the collections was assessed by measuring photosynthetic absorption, photosystem II fluorescence (Fv/Fm) and pigment content. The photosynthetic efficiency assessment revealed that though there was an overall increase in photosynthetic parameters of macrolichens, the cyanolichens showed an abrupt increase in photosynthetic activity from 2009 to 2013. The quantitative increase in diversity and photosynthetic activity of cyanolichens was correlated with the overall increased rainfall and relative humidity in the region from 2009 to 2013. The study hereby concludes that macrolichens can be an appropriate indicator of climatic perturbations in western Himalaya.