Nieuws - 25 juni 2009


After many years of working as a ranger in the Chinese Qinling Mountains, Tiejun Wang decided to devote his career to science. In his PhD he examined the remaining panda habitat. An examination from space. ‘Our high-tech approach enabled us to acquire a better understanding of the panda’s habitat, making panda conservation more effective.’

Giant pandas are picky eaters: they will eat nothing but bamboo, and that in vast quantities. ‘In spring, adult pandas consume half their body weight, about fifty kilograms, of bamboo daily.’ states Tiejun Wang. But the fibrous vegetable is hard to digest and contains few nutrients, hence the panda’s enormous appetite. Unfortunately, its reliance on bamboo as its only food makes the panda vulnerable. Wang realized early on that bamboo forests of sufficient quality are the main prerequisite for the panda’s survival.

In a collaboration between the International Institute for Geo-Information Science and Earth Observation (ITC) in Enschede and the Department of Resource Ecology of Wageningen University Wang embarked on his PhD research on the quality of panda habitat. At the start of his research, only inaccurate bamboo maps were available. ‘Many of our mountains are inaccessible and we had no clue where the bamboo was.’ Wang explains. ‘We desperately needed new methods of assessing panda habitat quality.’ Remote sensing, where satellites measure the understory of bamboo, proved to be an almost perfect technical solution. Wang: ‘Bamboo is an evergreen. During winter, when most trees have shed their leaves, remote sensing was very effective in measuring bamboo coverage.’

With detailed bamboo maps available, Wang now focused on the pandas themselves. ‘During winter, pandas spend their time at lower elevations, but during spring they migrate to higher altitudes.’ he says. ‘In fall they migrate down again.’ Wang wondered if this migration was associated with bamboo. He radio-collared a number of pandas to track their movements and followed vegetation development from space. The scientist also deployed radio collars on golden takins. These goat-like antelopes use a similar habitat to the pandas, but are much less picky about what they eat. ‘We were curious to what degree they use the same habitat as pandas’, Wang explains. ‘Besides panda protection, we also want to protect biodiversity in the panda territories.’

Only during the summer do pandas and golden takins utilize similar areas, Wang found. Wang: ‘Pandas start their upward spring migration later than golden takins.’ They spend little time in the middle elevations. Golden takins stay about twice as long in these regions.’ Similarly, in fall, when the animals return, pandas move down much faster than the antelopes. Wang convincingly linked the migration patterns of both species to vegetation developments. ‘Pandas time their migration perfectly to coincide with the occurrence of bamboo shoots, and spend most of their time in large, dense bamboo forests.’ Wang explains his findings: ‘They spend more time at lower elevations to benefit from the early bamboo shoots.’ Pandas clearly follow their stomachs. Bamboo shoots are highly nutritious and easily digestible and pandas specifically select this nutritious part. During their upward migration they lose little time on the steep slopes with their open, less attractive, bamboo forests.

Lessons learned from Wang’s research have important consequences for panda conservation. Since pandas select dense bamboo forest patches, habitat fragmentation is the death blow for the species. Logging has been banned in panda territory since 2000, but it is essential that the habitat fragmentation is reversed. In order to reconnect fragmented pieces of panda habitat, there are plans to construct corridors. ‘In the Qinling Mountains several big highways cut through panda habitat.’ the scientist says. ‘Thanks to satellite imagery we can choose the optimal locations, places with sufficiently large patches of bamboo forest, to build those corridors.’ / Hans Wolkers

Tiejun Wang will defend his PhD thesis on 25 June in the presence of his supervisors, Professor Dr. A.K. Skidmore of the International Institute for Geo-Information Science and Earth Observation (ITC) in Enschede and Professor Dr. H.H.T. Prins of the Department of Resource Ecology in Wageningen.