Plight of the Panda: a bamboo story

There are few creatures more iconic than the giant panda. These bears are the poster children for conservation movements around the world. Unlike their ursine relatives, pandas have abandoned carnivory for a diet that consists almost entirely of bamboo. In the light of human destruction, specialist lifestyles like the pandas are a risky strategy. It doesn't take much to upset such obligate relationships and humans are quite proficient at doing just that. However, the plight of the giant panda has just as much to do with the ecology of its food source as it does man-made destruction of its habitat.

Essentially giant grasses, the bamboo tribe consists of over 1,400 species worldwide. Not only are bamboo some of the tallest grasses in the world, they are also some of the fastest growing plants. Some have been known to grow 250 cm (90 in) in only 24 hours! As typical with grasses, bamboo can reproduce via underground rhizomes, forming dense stands of clones. Entire forests can be made up of the clones of only a few individuals.

The strangest part of bamboo ecology is that they rarely flower. A typical bamboo will live for 20 to 60 years before flowering, with some species taking well over 100 years. As such, bamboo experiences mast flowering events, with entire bamboo forests flowering all at once. After flowering and setting seed, the bamboo dies. Entire bamboo forests are lost in only a matter of weeks.

There have been many hypotheses put forth to explain this and while each has likely played a role in the evolution of this strategy, these mast flowering and subsequent death of bamboo forests probably serve to ensure the survival of the next generation. If the adults were to live through flowering and seed set, it is likely that the thick canopy of the parents would be too much for young seedlings to overcome. What's more, mass die offs create a significant fuel load for fires to sweep through. However catastrophic a fire may be, it reduces competition for bamboo seedlings.

Before humans fragmented their habitat, giant pandas had no trouble dealing with mass bamboo die offs. They simply migrated to a new bamboo forest. Anymore today, they cannot do that. When a bamboo forest flowers and dies, pandas in that area have nowhere to go. They simply starve to death. Because of this, pandas now occupy a mere fraction of their former range. What intact bamboo forests remain are restricted to the highlands of the Sichuan, Shaanxi, and Gansu provinces.

Despite considerable success in the captive breeding of pandas, there is simply not enough habitat to support their recovery in the wild. Because of this, captive breeding programs have come under harsh criticism. It has been argued that the massive amounts of money spent on captive breeding of pandas could be spent on habitat conservation projects elsewhere. No matter where you stand on the subject, there is no denying that pandas fall under the charismatic megafauna syndrome. They captivate the hearts and minds of people all over the globe. They also encourage the masses to open up their wallets. Sadly, it is probably too late giant pandas in the wild. If anything else, they certainly serve as a stark reminder of the importance of habitat conservation on a large scale.

Photo Credit: Abby Wood, Smithsonian's National Zoo (http://bit.ly/1qDX21K) and Daniel J. Layton (Wikimedia Commons)

Further Reading:

http://www.jstor.org/stable/10.1086/303243?seq=1#page_scan_tab_contents

http://www.completebamboo.com/bamboo_behaviors.html