Gregarious bamboo flowering in India

What is the Gregarious flowering of bamboo?

• Gregarious bamboo flowering refers to the phenomenon when all populations of a particular species flower roughly at the same time.
• The bamboo plants die after flowering and setting seeds.
• Such synchronised flowering, sometimes at intervals as long as 50 to 120 years, may bring in its wake a swarm of rats, subsequent famine and loss of lives and livelihoods.

Gregarious Flowering of Bamboo in Wayanad

• The “gregarious flowering of bamboo” inside the Wayanad Wildlife Sanctuary (WWS) and the nearby Mudumalai Tiger Reserve and Gudalur forest division in Tamil Nadu this year may pose a threat to wildlife in the Nilgiri biosphere, a major tiger and elephant habitat.
• The bamboo groves in the Wayanad forest are the mainstay of herbivores in the Nilgiri biosphere during summer.
• With the advent of the season, migration of wild animals starts from the adjacent sanctuaries in Karnataka and Tamil Nadu to Wayanad due to a shortage of fodder and water.
• “The gregarious flowering may adversely affect migration, especially by elephants, wild gaur, and other lower herbivores owing to the mass destruction of bamboo groves after the flowering.
• Bamboo groves, which grow in more than 500 hectares of the 344.44 sq km of the sanctuary, have fully bloomed, a phenomenon said to occur once in the life cycle of bamboo plants.
• Moreover, pointing to a threat to wildlife as well as the ecology of the Nilgiri biosphere, it is reported that over 25% of bamboo groves in the WWS and nearby sanctuaries have bloomed since 2010, and the phenomenon is continuing.
• Thorny bamboo (Bamboosa bambos) is a monocarpic (flowering only once) plant belonging to the Poaceae family (grass family), and its flowering cycle varies from 40 to 60 years.
• Profuse natural regeneration occurs from seeds after gregarious flowering. Seeds have no dormancy, and it helps germination under favourable conditions soon after seed fall, Mr. Babu said.
• But protection from fire and grazing is essential for proper establishment of seedlings, he observed.
• Fire incidents have been comparatively low in the sanctuary for the past five years owing to summer rain and conservation measures implemented by the Forest Department.

Gregarious Flowering of Bamboo in the Northeast

• Gregarious bamboo flowering is notorious for causing famine in Mizoram and Arunachal Pradesh. A saying goes in the northeast states, “when bamboo flowers, death and destruction will follow.”
• In Mizoram, which has about 31 percent of its geographical area under bamboo, the famine associated with the flowering of the bamboo species Melocanna baccifera (locally called ‘mautak’) is referred to as ‘mautam’ or ‘bamboo death’.
• Of the over twenty species of bamboo in the state, Melocanna baccifera is the dominant forest resource. It is a unique bamboo that produces the largest fruits among all bamboos. It flowers once every half a century, signalling death and destruction to the locals.
• The mautak bamboo grows naturally in northeast India, as also in Nepal, Myanmar and Bangladesh and is cultivated in several gardens world over.
• There are two major reasons for the fear surrounding mautam in Mizoram, observed Shyamal Biswas of the National Centre for Disease Control, Plague Surveillance Unit, Bengaluru.
• “The bamboo clumps die after flowering after every 48 years and it takes a few years before bamboo plants produce seeds again, leaving the soil bare and exposed which is disastrous in mountainous regions. This would lead to food scarcity, since several animals depend on this plant,” Biswas said.
• As the flowers bloom in synchronicity across vast swathes, hungry rats descend on them like a plague and feed on the flowers and seeds of the dying bamboo tree. Most outbreaks are usually due to rats (Rattus spp).
• “Because of the high nutritive value of bamboo fruits, there is a spontaneous increase in rat population. In addition, there is a drop in cannibalism [among rats] due to the availability of plenty of food during bamboo flowering.
• This leads to multiplication in rat numbers and they feed on agricultural crops in the fields and granaries, leading to famine,” Biswas told Mongabay-India.
• The rats not only devastate the naturally regenerating seeds and seedlings, they also reduce the regeneration rate of bamboo.