«Giant Panda Conservation in the Wolong Nature Reserve: Examining the Effects of Bamboo Life History on Panda Populations in the Context of a Growing ...»
Giant Panda Conservation in the Wolong Nature Reserve:
Examining the Effects of Bamboo Life History on Panda Populations
in the Context of a Growing Rural Community
The giant panda (Ailuropoda melanoleuca) is a charismatic, large-bodied mammal in
the family Ursidae that has been the focus of numerous conservation efforts throughout the
world. This mammal is extremely rare because it exists at low densities and is found only in highly-specific habitats in the mountains of southwestern China. Aside from its highly-specific habitat, the diet of the giant panda consists almost entirely of a few species of bamboo.
Typically, numerous bamboo species are plentiful throughout giant panda habitats; however, they exhibit a semelparous life history pattern that involves synchronous flowering/ mast- seeding events and subsequent die-offs. This unique life history pattern results in a significant deficit of bamboo after each flowering event, which often leads to the starvation of giant pandas.
Several giant panda habitats have been designated as nature reserves in southwestern China with varied success. Although the objective of these reserves is to protect the giant panda, these ecosystems are hotspots of biodiversity and support many other rare and unique organisms. Because the giant panda serves as an umbrella species, its protection will ensure the preservation of many other species in its habitat.
The Wolong Nature Reserve in the Sichuan Province has been designated as a giant panda habitat reserve in the southwestern mountains of China. This reserve has been continually degraded by the rural population within the area. The utilization of resources, particularly through traditional fuelwood collection and timber harvesting within the reserve has led to the decrease and fragmentation of giant panda habitat. This loss of forest cover has also significantly decreased the amount of bamboo for the giant panda diet. These factors have contributed to the decline of giant panda populations in the reserve.
It is important to assess the ways in which bamboo life history and the growing rural population in the Wolong Nature Reserve affect giant panda populations. The inevitable combination of a bamboo mast-seeding event and the continued anthropogenic habitat degradation through fuelwood consumption and timber harvesting could potentially cause the local extinction of this giant panda population. During these mast-seeding events, giant pandas seek alternative patches of bamboo. However, as the use of resources grows because of the expanding rural population, these alternative patches are being depleted as a result of habitat destruction and fragmentation. It is imperative to manage the resource use by the rural population in order to devise a more effective conservation strategy for this nature reserve.
Once a reasonable management plan is devisedfor the Wolong Nature Reserve, it may be implemented in other giant panda nature reserves across southwestern China.
Giant Panda Habitat in the Wolong Nature Reserve:
The giant panda occupies a very specific niche in the mountains of southwestern China.
Before humans densely settled areas around the habitat of the giant panda, this species occupied lowlands that spanned across eastern and southern China, northern Myanmar, and northern Vietnam (Pan et al., 2001). Today the giant panda habitat has been reduced to an estimated 24 isolated populations in temperate deciduous and coniferous montane forests along six mountain ranges in southwestern China (China’s Ministry of Forestry & WWF, 1989).
Within this area, there are 40 nature reserves that support approximately 1,500 individuals in the wild (Xinhuanet, 2004).
preservation and contains approximately 10% of the current wild population (Zhang et al., 1997). In 1962, this area was established and was expanded to its current size in 1975. It encompasses a total area of 2,000 km2, and is located along the south side of Qionglai Mountain and the east side of the Hengduan Mountain Range (Zeng et al., 2005). The elevation of this area ranges from 1,200 to 6,250 m above sea level (Liu, 2001). Today, there are three subpopulations with 30-45 giant panda individuals in the Wolong Nature Reserve (Xu et al., 2006). In addition to the giant panda, there are approximately 4,000 plant species and 2,200 animal and insect species within the reserve (Wolong Administration, 1987). This area exhibits a high amount of species richness because it supports a mosaic of different habitats.
The habitat of the giant panda is defined by very specific biotic and abiotic factors. It is a function of forest cover, slope, altitude, and bamboo availability (Liu, 2001). The forest cover is an important aspect of the giant panda’s habitat because it provides shelter and cover (An et al., 2002). Typically, pandas prefer gently sloping or flat areas so that they can move more easily within their habitat (Schaller et al., 1985). They cannot exist in low temperatures or high elevations that maintain a low food abundance and little vegetative cover (Liu et al., 1999). The elevation range of the giant panda occurs mostly between 2700 and 3200 m, but occasionally extends up to 3,500 m and down to 2,000 m (Schaller et al., 1985).
Giant Panda Diet and the Life History of Bamboo:
Wild giant pandas feed almost exclusively on bamboo species. Although giant pandas belong to the order Carnivora, they are highly-specialized bamboo feeders. Approximately 99% of the panda diet consists of bamboo, and because of the low energy and nutrient content
must spend up to 14 hours per day foraging (Schaller et al., 1989).
There are two dominant bamboo species within the Wolong Nature Reserve. Bashania fangiana (arrow bamboo) is the preferred food for giant pandas while Fargesia robusta (umbrella bamboo) is eaten in different seasons and during B. fangiana mast-seeding episodes (Schaller et al., 1985). Together they comprise 80% of the total bamboo in the Wolong Nature Reserve (Linderman et al., 2006). Depending on aspect, B. fangiana grows at elevations between 2,700-3,440m, whereas, F. robusta grows between 2,600-2,800m (Reid et al., 1991).
The giant panda maintains a very specific diet breadth and foraging strategy. The bamboo upon which the giant panda feeds typically occurs in the understory of mixed deciduous and coniferous evergreen montane and sub-alpine forests in monospecific patches (Reid et al., 1991). Depending on the season and availability, giant pandas prefer different parts of bamboo to maximize the ingestion of energy (Schaller et al., 1985). During the winter, giant pandas feed mostly on tall and thick B. fangiana culms less than 1 year old found in mixed deciduous-evergreen forests, whereas, in the summer, they feed on the leaves of B.
fangiana (Schaller et al., 1985). In general, leaves are typically preferred over branches and culms because they are more digestible and nutritious (Dierenfeld et al., 1982). This preference is important for the dietary selectivity of the giant panda because it has an inability to digest a significant amount of the bamboo that is eaten (Tarou et al., 2005). The giant panda has a short and simple digestive tract similar to other organisms in the order Carnivora, which does not involve microbial breakdown of plant material typical of herbivores (Dierenfeld et al., 1982). Because of this disadvantage, giant pandas must consume large quantities of bamboo as efficiently as possible (Reid & Hu, 1991). When considering net energy intake, it is important for the giant panda to be selective of bamboo parts with the highest nutritional value.
long handling time (h). This strategy is an example of optimal foraging theory, which maximizes energy intake (E), determined by the sum of searching (s) and handling (h) times, expressed by E=(h+s). It is apparent that the force of natural selection has led the giant panda to prefer certain species and plant parts of bamboo through the selective pressures that improve the fitness of this organism.
Most bamboo species in China are semelparous and exhibit a synchronized mastseeding event every 3-120 years (Janzen, 1976). After these die-off periods, the bamboo species is typically dormant for a brief time before it regenerates (Linderman et al., 2006). In the Wolong Nature Reserve, a mast-seeding and subsequent die-off of the monocarpic B.
fangiana occurred in 1983 over 80-90% of its range (Schaller et al., 1985). The inter-mast period for B. fangiana is 45 years, whereas, the inter-mast period for F. robusta is an estimated 60-80 years (Schaller et al., 1985). Both B. fangiana and F. robusta are predicted to flower in the next 30 years at the Wolong Nature Reserve (Linderman et al., 2006). It has been observed that bamboo species that have recently experienced mast-seeding and die-off events are less likely to regenerate when there are significant environmental stresses (Taylor & Qin, 1993).
Under normal conditions, B. fangiana regenerates to its full size between 15-20 years after a die-off (Taylor et al., 2004). The regeneration time for F. robusta is currently unknown.
Different bamboo species exhibit growth patterns and morphological variations depending on environmental conditions, which likely affect giant panda habitat selection (Reid & Hu, 1991). After mast-seeding episodes, giant pandas either seek out any remaining patches of the preferred bamboo or choose less preferable species of bamboo to feed on (Linderman et al., 2006). Subsequently, because of the 1983 mast-seeding of B. fangiana, pandas were forced to migrate in the winter of 1986 to lower elevations where F. robusta is more dominant
elevation limit of 3,200m (Reid et al., 1989), and also foraged on the dense bamboo in humaninduced clearcuts during the summer (Reid & Hu, 1991). Pandas moved to adjacent areas to pursue alternative bamboo resources when the preferred B. fangiana was scarcely available in order to maximize foraging efficiency.
Because giant pandas are so reliant on bamboo availability, it often dictates the location of their habitat. These animals store little or no fat and require constant and dependable food resources and environmental conditions (Schaller et al., 1989). The fecundity and survivorship of giant pandas are density dependent on bamboo biomass, and reductions in carrying capacity are often the result of the synchronous semelparity of preferred bamboo species, which is considered the major non-human threat to this species (Carter et al., 1999). Therefore, the synchronization of the life history of a bamboo species will determine the long-term survival of giant panda populations as much as the available bamboo biomass (Carter et al., 1999). The ability for a population to migrate across a region to find additional bamboo will also significantly influence the population’s carrying capacity (Carter et al., 1999).
Household Growth and Habitat Destruction in the Wolong Nature Reserve:
Although the Wolong Nature Reserve is a protected area, the considerable unrestricted growth of the local rural population has degraded this ecosystem. Many families live within the Wolong Nature Reserve and derive resources directly from the area. Resource extraction in the form of fuelwood and timber harvesting, along with other anthropogenic influences has further endangered the giant panda population in this area.
Today, the Wolong Nature Reserve supports over 1,000 households of primarily subsistence farmers who frequently collect fuelwood for cooking and heating (Linderman et
traditional medicine harvesting, agriculture, road construction, and tourism (Lu et al., 2003).
There are also approximately 10 hydropower stations that supply a limited amount of electricity for the rural population (Zeng et al., 2005). The area has experienced a significant population increase in recent decades. In 1995, 4,260 residents lived in 904 households across the reserve; whereas, 2,560 residents lived in 421 household in 1975 (Zeng et al., 2005). The one child policy does not apply to many of these rural inhabitants because they are part of minority ethnic groups including the Tibetan, Chang, and Hui people (Liu et al., 1999).
Household activities have increasingly fragmented and depleted areas of giant panda habitat within the reserve. Fuelwood collection and logging by the rural inhabitants of the Wolong Nature Reserve have increased substantially over the past 30 years, resulting in the depletion of forested area (Liu et al., 2001). In fact, annual fuelwood consumption increased from 4,000 m3 to 10,000 m3 between 1979 and 1999, reducing giant panda habitat by 20,000 ha (Liu et al., 1999). The effect on bamboo regeneration is most apparent in F. robusta, because it is found at elevations near household activity (Linderman et al., 2006).
Although the rugged terrain and decreasing amount of forest area makes fuelwood collection more difficult for the rural inhabitants, most households still prefer to use fuelwood for cooking and heating instead of electricity (An et al., 2001). As increasingly larger areas are exhausted of fuelwood, rural inhabitants are seeking areas of higher elevation for collection, which increases giant panda habitat destruction (Liu et al., 2001). Cultural traditions, along with the price of electricity, deter most of the rural population from abandoning fuelwood collection (An, et al., 2002). Higher income households are more likely to use electricity (An et al., 2002). Therefore, there is a clear correlation between habitat destruction and socioeconomic status (Liu et al., 2001).
estimated through several studies. Considering different scenarios that may occur by 2030, the creation of new households along with fuelwood collection will likely reduce the amount of forested area by 2.7-14% (Linderman et al., 2006). Optimistic scenarios predict a 2.7-3.5% decrease in forested habitat, while a doubling of fuelwood consumption and 50% increase in household would result in a 14% reduction with 23% reduction of highly suitable giant panda habitat (Linderman et al., 2006). Currently, 30% of the landscape within the reserve has been impacted by human activities (Zeng et al., 2005).