The bear that eats bamboo

Is the giant panda a conservation triumph, or a permanent obligation?

A The species is a reliable fixture of any discussion of extinction, and it has come to stand for a particular kind of argument about what conservation is worth. No animal is more frequently offered as evidence that evolution is not an optimising process than the giant panda. It is classified among the carnivores, possesses the short digestive tract of a meat-eater, and eats almost nothing but bamboo. It extracts a small fraction of the available nutrition from that diet, must therefore consume enormous quantities of it, and spends most of its waking hours doing so. The arrangement looks less like adaptation than like an animal that has painted itself into a corner and is coping.

B The physiological accommodations are nonetheless real and, examined closely, considerable. The animal's metabolic rate is exceptionally low for a mammal of its size, comparable to that of a sloth, which reduces the quantity of food the inadequate diet has to supply. It moves slowly and avoids climbing when it can. Its skull and jaw muscles are disproportionately developed for crushing stems, and its forepaw carries an enlarged wrist bone that works against the digits as a rough opposable thumb, allowing bamboo to be gripped and stripped. Its gut, though shaped like a carnivore's, contains bacteria that assist in breaking down plant fibre, if less efficiently than the specialised digestive systems of true herbivores.

C Nor is the diet quite the accident it appears. Bamboo is available in every season, does not run away, and requires no skill to catch, which suits an animal whose ancestors were opportunists rather than hunters; the genetic capacity to taste the savoury compounds that make meat attractive appears to have been lost, which suggests the switch is old and settled rather than recent and desperate. The animal is therefore not badly designed so much as narrowly designed, and the distinction matters for the argument that follows. A specialist thrives while its speciality is abundant. Bamboo is abundant, and being unpalatable to almost everything else, it is uncontested. What makes the strategy precarious is not the diet but the plant's peculiar habit of flowering: a bamboo species will bloom and then die across an entire region simultaneously, at intervals of decades, leaving nothing to eat until the seedlings mature. An animal that can walk to the next valley survives this. An animal whose valleys have been separated by farmland and roads may not.

D Habitat fragmentation, rather than any inherent feebleness, is what brought the species close to disappearance, and the conservation response has been correspondingly territorial. Logging, farming and roads reduced a continuous band of mountain forest to isolated patches, each holding a population too small to be secure and too separated to exchange animals with its neighbours; an isolated group that loses its bamboo has nowhere to go, and an isolated group that survives breeds only with itself. Reserves have been established across the mountain ranges of central China, connected in places by corridors of replanted forest, and the wild population has risen sufficiently for the species to be reclassified in 2016 from endangered to the less severe category of vulnerable. The reclassification was contested by those who considered it premature, on the grounds that climate projections suggest a substantial share of the remaining bamboo may become unsuitable within the century.

E Captive breeding, the effort most visible to the public, occupies an awkward position in this account, and it is the part of the enterprise that the public is most often asked to fund. Persuading the animals to breed in enclosures took decades of frustration and eventually succeeded, and the captive population is now self-sustaining. Yet very few of the animals bred in captivity have been released, fewer still have survived release, and the wild population's recovery is attributable overwhelmingly to habitat protection rather than to reintroduction. The programme's defenders argue that it has never been principally about numbers, and this is the point at which the disagreement becomes interesting.

F The case they make is that the species functions as an instrument rather than as an end in itself. Its expense is enormous — the loan of a pair to a foreign zoo costs a sum that would fund a great deal of ordinary fieldwork — but the attention it generates has protected mountains that no argument about invertebrates could have protected. The reserves created for it shelter thousands of other species, most of which nobody has heard of and none of which could have secured the land on their own. On this view the panda's cost is not diverted from conservation; it is what makes a certain kind of conservation politically possible.

G The objection is not that this reasoning is false but that it is difficult to check. Money spent on a charismatic animal is visible, and the alternative use to which it might have been put is not, so the comparison is always between a measured benefit and an imagined one. What can be said is that the species is now dependent on continuous human management: on maintained corridors, patrolled reserves and, increasingly, on decisions about which mountainsides will still support bamboo in fifty years. Whether that constitutes a success or a permanent obligation depends on what one believes conservation is ultimately for, and the argument over the panda has always been, at bottom, an argument about that.