Bamboo Bloom in India

On January 27th, 2011 the India Times ran the story of fears of famine in Wayanad Wildlife Sanctuary in Tamil Nadu in Southern India. The cause of the possible famine is the mass flowering or gregarious flowering of vast stretches of bamboo groves in the Sanctuary.

Why would flowering bamboo cause such trouble? The reason is that flowering bamboo produces an overwhelming abundance of seeds (between 50 to 100 kg per grove). This causes a sudden invasion of rodents to feed on the seeds. This invasion of rodents then enters nearby human settlements and eats crops causing widespread famine amongst tribal communities living in the area. At the same time 1,400 migrating Asiatic elephants are soon expected to arrive in the Sanctuary to feed on the bamboo shoots and leaves. When they find all the bamboo dead (bamboo dies after flowering) they will raid human crops for food. The results are havoc, food shortages and the spread of diseases such as typhus, typhoid and bubonic plague from the rat infestation.

The bamboo in Wayanad is thorny bamboo (Bambusa bamboos) which like all bamboo plants is classified as monocarpic. This means it flowers only once at the end of its life. The length of time between gregarious flowerings differs for different species of bamboo. In Wayanad the last two recorded flowerings were in 1913 and 1991.

The incredible thing about bamboo flowering is that it is spontaneous. All bamboo groves, even those separated geographically and those living under different climatic conditions suddenly ‘know’ when it is time to flower. This has prompted scientists to suggest that each cell of bamboo has some type of alarm clock that alerts the plant to flower en masse.

It is a mystery as to why bamboo has these mass flowering events. There are two hypotheses as to why bamboo flowers at the same time (young and old culms alike). One hypothesis is called the predator satiation hypothesis. This hypothesis suggests that by mass flowering predators fill up on seeds and there remain plenty of seeds left over to grow into more bamboo. Also by stretching out mass flowering events beyond the lifespan of rodents, bamboo reduces the number of rodents and thus increases the potential yield from the seeds. Critics of this hypothesis point out that the gregarious flowering events are much more widely spaced than the lifespan of rodents and that it would make more sense if the bamboo flowered just a few months or years after the expected lifespan of the rodents.

The other hypothesis is called the fire cycle hypothesis. This hypothesis claims that the bamboo creates a huge mass of dry fuel to encourage fires that will clear the area to provide space and nutrients for the new seedlings to flourish. The problem with the fire cycle hypothesis is that India doesn’t have a history of natural fires caused by lightning or other causes. And furthermore, such a tactic has no precedent in nature.

The only silver lining for the human population living in and near the Wayanad Wildlife Sanctuary in Tamil Nadu is that the park managers allow them to collect the bamboo seeds. These seeds are used in the preparation of many delicacies and are used as a rice substitute to stave off starvation. That doesn’t help the elephants and wild gaurs of the area who feed on the bamboo. And it doesn’t help solve the rodent problem.

1) India Times

2) Bamboo entry in Wikipedia