ReviewRangeland degradation on the Qinghai-Tibetan plateau: A review of the evidence of its magnitude and causes
Introduction
Rangeland degradation is a global concern, affecting not only pastoralists who rely on healthy rangelands for their survival but others who suffer from resultant hydrological disturbances, dust storms, commodity scarcity, and social consequences of uprooted people. Rangeland health also affects biodiversity directly and indirectly because all native flora and fauna have adapted to the long-term evolutionary forces that have shaped these rangeland environments. Livestock grazing is the dominant form of land use in arid biomes worldwide, and grazing lands of the Qinghai-Tibetan plateau (QTP; Fig. 1) in the People's Republic of China are located in the source area for most of Asia's major rivers, upstream and upwind of upwards of 40% of the world's human population (Foggin, 2008). Pastoralism is also the dominant land-use in the other major biomes of western China (e.g., Mongolian Plateau, Tarim, and Dzungarian Basins), as well as in adjacent Mongolia, Kazakhstan, Kyrgyzstan, and Tajikistan, where land degradation is a similarly serious issue.
Awareness by Chinese scientists and policy-makers of the impacts of rangeland degradation on the QTP increased in the late 1990s as several disasters occurred, including Yangtze River floods that killed thousands of residents downstream and cost billions of dollars in economic losses, the Yellow River running dry increasingly often, and dust-storms and sand-storms originating in western rangelands that affected the health and economic wellbeing of millions of city-dwellers in China's east. Although lacking clear documentation and differing in specifics, Chinese scientific papers and government policy statements are unanimous in viewing the QTP as having become increasingly degraded in recent decades (Yan, 2001, Wang et al., 2005, Zhao and Zhou, 2005). A frequently repeated statistic is that 90% of China's grasslands are degraded to some extent, and that degradation is increasing at a rate of 200 km2/yr (State Council, 2002).
Causes for rangeland degradation are generally attributed to a combination of over-stocking of livestock, unscientific livestock management, historical-cultural impediments to adopting modern livestock management concepts, global climate change, and excessive herbivory and soil disturbance from small mammals (Li, 1994, Li and Huang, 1995, Chen, 1996, Wang and Zheng, 1999, Hou and Shi, 2002, Deng and Liang, 2003, Zhou et al., 2003, Shen et al., 2004, Zhang et al., 2004). In contrast, Western (and some Chinese) investigators have tended to question the assumption of wide-scale rangeland degradation on the QTP, and where they agree it has occurred, to cast their analysis in terms of rapid changes in socio-economic systems and alteration of land tenure arrangements (Goldstein et al., 1990, Miller et al., 1992, Miller, 1999, Miller, 2002, Miller, 2005, Williams, 1996, Williams, 1997, Williams, 2002, Ho, 1998, Ho, 2000; Foggin, 2000, Banks, 2001, Banks, 2003, Banks et al., 2003, Holzner and Kreichbaum, 2001). Because most pastoralists are Tibetan, Mongolian, or other non-Han ethnic minorities whereas political authority rests largely in the hands of Han Chinese, and because discussion of ethnic tension remains a sensitive issue in China, dispassionate analysis of rangeland degradation has been constrained by its close association with politically charged issues.
Chinese researchers (e.g., Luosan, 1996, Gu, 2000b, Ling, 2000) have emphasized technological solutions within the ecological domain. Suggested remedies for reducing overgrazing involve concentrating livestock in places where they can be protected from the elements and provided forage grown off-site, increased fencing to facilitate rotation of pastures, restructuring herds to increase the proportion of reproductive females, and manipulating herd size frequently to reflect seasonal rhythms of vegetation biomass and nutrient levels (Lobsang, 1998, Zhao et al., 2000). Suggested remedies for rehabilitating degraded rangelands invariably involve killing small mammals, temporary or permanent removal of livestock, fertilization, and/or re-seeding (Zhao and Zhou, 2005, Wang et al., 2006b).
Recent Chinese policy has followed 3 sometime conflicting approaches: (1) small mammal (usually termed “rodents”) eradication; (2) subsidizing transition from semi-nomadic herding over large spatial scales to household-level ranching on much smaller spatial scales; and (3) subsidizing (or even coercing) pastoralists to sell their herds and abandon livestock raising entirely. Begun as early as the mid 1950s, efforts to poison small mammals such as the plateau pika (Ochotona curzoniae, not a rodent at all, but rather a member of the rabbit family, Lagomorpha) have ebbed and flowed with funding and interest and achieved variable results. By 1990, a cumulative total of 208,000 km2 had been subject to such poisoning, usually carried out by county level agricultural, grazing, or forestry bureaus (Fan et al., 1999). Despite conclusions of most scientists that high densities of pikas were more likely a result than a cause of grassland degradation (Smith and Foggin, 1999, Smith et al., 2006), poisoning campaigns have continued, most recently in late 2006 and early 2007, when extensive efforts were expended to spread Botulinin C toxin over ∼320,000 km2 of the QTP.
Although given differing names, a number of programs share the goals of sedentarizing pastoralists and encouraging responsible rangeland husbandry by clarifying tenure of pasture land tenure on a family basis, subsidizing construction of permanent winter homes, fences and livestock shelters, and providing plots for growing supplemental winter fodder. Government outlays for these programs (often termed the “set of four” (Wu and Yan, 2002)) have been substantial; during 2003–2006, the central government reported investing some ¥7.1 billion (∼$1 billion) for fencing alone (SEPA, 2007). Despite the enthusiasm with which they have been promoted by government sources, the long-term ecological and economic viability of these programs remains uncertain (Miller, 2002, Wu and Yan, 2002, Yan et al., 2005, Richard et al., 2006, Davidson et al., 2008).
In contrast, newer initiatives (“retire livestock, restore pastures”) make no attempt to encourage responsible husbandry through a tighter linking of families with specific tracts of land; instead, they strive to break that linkage entirely. Under the theory that only complete elimination of livestock (for periods of 5, 10, or an undefined number of years) can restore rangeland productivity (but see Gao et al., 2007a, Gao et al., 2007b for a contrary view), pastoralists have been provided free housing in township and county seats and modest 10-year living subsidies in exchange for selling their herds and ceasing pastoralism (Qinghai Province, 2003, Li, 2004, Yeh, 2005, Perrement, 2006). No training or alternative livelihoods have been reported being provided to such displaced pastoralists. In 2005 alone, the central government invested some ¥1.8 billion (∼$226 billion) in this program (SEPA, 2006). However, even if the “retire livestock, restore pastures” program succeeds in reducing rangeland degradation (which itself is open to question, given that most rangeland species are adapted to some level of herbivory), it is likely to carry enormous financial burdens and create considerable social and cultural dislocation. Although implementation may encounter obstacles (Levine, 1995, Clarke, 1995, Nyima, 2003, Yan et al., 2000, Yeh, 2003), its high costs in monetary, social, and cultural terms may disqualify it from constituting a sustainable social-economic system (sensu Walker et al., 2006).
Section snippets
Extent and magnitude of degradation on the QTP
Estimates of the area variously categorized as degraded throughout China generally and on the QTP specifically have been published (Wang, 1993, Gu, 2000a, Berry, 2003, Hu and Zhang, 2003, Wang et al., 2004, Han et al., 2008), but rarely subjected to scrutiny or scientific peer review. The State Environmental Protection Agency (SEPA) estimated that one-third of China's grasslands were degraded in 1999 (SEPA, 1999), yet shortly afterward, the figure that 90% of China's grasslands were degraded
Hypotheses of rangeland degradation on QTP
Before assessing the wisdom of strategies to safeguard or rehabilitate existing rangelands one must first understand the causes of rangeland degradation. Many analyses of this question rely on logical shortcuts, selective inclusion of existing data, and/or underlying prejudices. Although it is likely that there is no single cause, the presence of multiple, interacting factors does not preclude dispassionate and skeptical analysis of each. Simply listing a number of possible (or even probable)
Summary and research needs
I have identified 12 non-exclusive hypotheses to explain range degradation on the QTP, and attempted to examine the basis and evidence available for each (Table 1). Some appear to fail the most basic tests of logic and should be abandoned. Others seem to lack supporting evidence, and thus should be viewed skeptically. Yet others are logically plausible and can claim some support from data (or at least from anecdotal evidence). In my view however, none has been explored sufficiently rigorously
Acknowledgements
Major support for my work on the QTP came from the Robert M. Lee Foundation. I thank J. M. Andereis, D. Bedunah, D. J. Miller, A. Smith, E. Yeh, and an anonymous reviewer for ideas and improvements to the manuscript.
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