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 devised for 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).
The Wolong Nature Reserve is one of the largest areas dedicated to giant panda 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 in bamboo combined with the inefficiency of the giant panda digestive tract, this organism 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.
Because the giant panda is a specialized feeder, it has a short searching time (s), and a 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 mast-seeding 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 (Schaller, 1987). After the 1983 episode, pandas were observed foraging beyond their usual elevation limit of 3,200m (Reid et al., 1989), and also foraged on the dense bamboo in human-induced 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 al., 2006). Aside from fuelwood collection, their primary activities include timber and 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).
Predictions of resource and habitat depletion within the Wolong Reserve have been 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).
Most of this habitat depletion will be in specific areas of the reserve. Valleys and lower elevation areas below 2,600 m will be the most affected, causing a concentrated spatial distribution of these impacts (Linderman et al., 2006). These areas, which comprise less than 1/10 of the total reserve, are more accessible to households, and will incur 95% of the total human disturbance in the area (Linderman et al., 2006). Higher elevations have also been impacted by road building (Zeng et al., 2005). Within the lower elevation area, 17% of habitat and 15% of highly-suitable giant panda habitat will be disturbed if 1997 consumption levels continue; moreover, double fuelwood consumption and a 50% increase in household would yield a 30% reduction in forested habitat (Linderman et al., 2006).
Logging activities within the Wolong Nature Reserve have lead to the increase of fragmentation and decrease in available habitat for the giant panda. From 1965 to 1975, large-scale timber extraction impacted the area until the reserve was established and commercial logging was prohibited (Zeng et al., 2005). In 1998, a moratorium on commercial logging was implemented throughout the area (Zeng et al., 2005). Small-scale logging has not been adequately regulated, and continues to occur in the reserve (Zeng et al., 2005).
The result of household activities in the Wolong Nature Reserve has significantly changed the landscape and reduced the total area of giant panda habitat. The encroachment of humans upon the giant panda habitat through various activities is illustrated by two major outcomes, which include the shrinking of forest areas located next to non-forested areas, and the division of larger areas of forest into smaller areas of fragmented forest (Liu et al., 2001). These kind of human disturbances cause a compounding effect on the giant panda population through reducing the availability of food and space.
Implications of Human Activities on the Giant Panda Habitat in the Wolong Nature Reserve:
Habitat destruction caused by human activities within the Wolong Nature Reserve has rendered serious consequences on the giant panda population. As human activity within the reserve increases because of the expanding rural community, giant panda populations continue to decline. Today, only approximately 41% of habitat within the reserve is considered highly or marginally suitable for giant pandas mostly due to human-induced degradation (Liu et al., 1999). The long-term survival of the giant panda is at risk because of the increasing amount of fragmentation that continually occurs within the Wolong Nature Reserve. Habitat destruction may divide larger populations of giant pandas into smaller populations that are very susceptible to inbreeding depression which may eventually lead to extinction (Xu et al., 2006). In the Wolong Reserve, the continued separation of the three subpopulations of giant pandas increases their propensity towards extinction by a factor of 10 in 2100 if they remain isolated (Xu et al., 2006).
There is a considerable recovery time for vegetation in the Wolong Nature Reserve after it has been affected by timber and fuelwood consumption. After this type of harvesting, vegetation in the area takes approximately 80 years to recover (Liu et al., 1999). Strong effects on the vegetation occur for 20 years, moderate effects occur between 20 and 50 years, and weak effects occur between 50 and 80 years (Liu et al., 1999). As long as these practices continue, the size and quality of giant panda habitat will decline as bamboo biomass is depleted. The long regeneration time of vegetation is especially threatening to giant panda populations because bamboo is less likely to grow in deforested areas.
Inadequate bamboo and lack of vegetation cover are two of the most important factors that limit giant panda populations (Xu et al., 2006). Because the giant panda is a large-bodied organism, it requires a large amount of space so that it can forage a sufficient amount of bamboo to sustain a viable population. The giant panda is an extreme K-strategist, and lives well below its carrying capacity in the Wolong Nature Reserve, where it is usually situated in concentrated areas of high-quality bamboo habitat (Linderman et al., 2005). Because the giant panda is a K-strategist, maintaining a population is difficult, especially within the context of changing environmental conditions caused by human activity. It is believed that loss of forest cover, in addition to mast-seeding of bamboo was responsible for the giant panda population decline at Wolong Reserve from 145 animals in 1974, to 72 animals in 1986 (Liu et al., 2001). The loss of forested area through clearcutting also leads to decreased giant panda food availability because remaining bamboo is often less palatable in these areas (Linderman et al., 2006). Therefore, human activities have directly affected the giant panda population size.
The combination of the delicate bamboo life cycle and ecologically-damaging household activities within the Wolong Reserve will have compounding effects on the native giant panda population far into the future as the rural population expands. After a simultaneous die-off of both the B. fangiana and F. robusta species, a scenario of a doubled fuelwood consumption and 50% increased in households would further reduce the already 49% of naturally-lost bamboo habitat an additional 14% of habitat and 25% of highly suitable habitat (Linderman et al., 2006). In a low elevation scenario below 2,600 m, simultaneous die-offs would reduce bamboo availability between 13-29% (Linderman et al., 2006). In this area, household activities would further reduce bamboo habitat an additional 4-25% (Linderman et al., 2006). These scenarios are based on models that predict the effects of future resource consumption by the rural community on giant panda habitat in the reserve. It is clear that the implications of human activities within the Wolong Reserve are especially pronounced during bamboo die-off periods.
In addition to having an adequate habitat space, it is important for giant pandas to be able to migrate to different areas within a reserve when bamboo becomes scarce during its semelparous flowering episodes. If a population is unable to migrate to an area that supports an alternative bamboo species, the pandas will most likely starve. The ability of a population to migrate will determine the survivorship of the population. This influence on giant panda migrations, combined with habitat loss, fragmentation, and the regeneration dynamics, is clearly impacting the population in a vigorous and unprecedented manner. The overall effect of human disturbance of these habitats will result in altered species composition, vegetation dynamics, and wildlife habitat (Linderman et al., 2006).
The Wolong Nature Reserve is designed to preserve the giant panda population; however, the impact of the rural community has degraded the habitat for these animals, especially through decreasing bamboo availability. Studies performed in this area have clearly shown that the rural community is contributing to the decrease of giant panda populations in the Wolong Nature Reserve. The evidence gathered by these studies presents a strong case for limiting the amount of anthropogenic influence in the area to preserve the giant panda habitat, especially during periodic bamboo die-offs. Unfortunately, successful management of the giant panda population in the context of a growing rural community has proven to be a difficult endeavor.
In addition to the preservation of the giant panda habitat, it is important to consider the livelihood of the rural population in the Wolong Nature Reserve. Their traditional lifestyle, which includes fuelwood collection and small-scale timber harvesting must be respected and preserved. However, the increasing expansion of this community must be limited. If the number of households continues to increase, more forest resources will be depleted, and the rural community will likely collapse from a resource deficit. Although it is important for the rural community to continue their traditional lifestyle, it must be done in a sustainable manner.
Alternative livelihoods for individuals within the rural community of Wolong Nature Reserve should be explored. The implementation of ecotourism in the area would bring income to rural families in a sustainable manner. Ecotourism would also be a valuable educational tool that would alert the public on the importance of giant panda habitat conservation. With this income, each household may be able to pay for electricity. The widespread use of electricity would decrease the need for fuelwood collection and timber extraction. With this reduction in resource use, the giant panda habitat would be less impacted, and bamboo would be more readily available.
Ecological restoration projects involving the rural community should be implemented in the Wolong Nature Reserve. A system of replanting deforested areas, including the sowing of bamboo seeds, will help regenerate areas of giant panda habitat that have been disturbed. Corridors must be maintained between giant panda habitats so that they will be able to migrate to other areas, especially in times of food shortages. These corridors may be crucial for repopulating a locally extinct subpopulation. During periods of bamboo die-offs, fuelwood collection and timber harvesting should be prohibited so that additional bamboo biomass is not lost. If such strategies were implemented in the reserve, the giant panda population would have more success in survivorship, especially during the periods of bamboo die-offs.
Finally, the expanding rural population within the Wolong Nature Reserve must be limited. A restriction on the growing rural community should be implemented to prevent further habitat loss. New construction of households should be prohibited within the reserve. Individuals within the remaining households must be subject to strict environmental regulations concerning any kind of habitat destruction. Enforcing a new management strategy within the Wolong Nature Reserve will require attractive incentives for the rural community along with government intervention. Although there are laws designed to protect the giant panda population in nature reserves such as the one in Wolong, these laws are weakly enforced. These laws may be more easily enforced if the rural community is educated on the importance of preserving the giant panda population.
In order to prevent the starvation and subsequent extinction of the giant panda population in the Wolong Nature Reserve, the current system of mismanagement must be reevaluated. The continued loss of habitat and bamboo availability is indicative of a failing strategy at the Wolong Reserve. Once the resource consumption of the rural community is properly managed, the giant panda population should eventually rebound to its previous population numbers during the time when the reserve was established. Otherwise, the increased loss of habitat and bamboo will lead to the demise of the local giant panda population. The rural community must recognize the importance of the giant panda, its habitat, and its primary food source, bamboo, so that the unique ecosystem within the Wolong Nature Reserve can be protected and preserved.
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