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Applied Geography 40 (2013) 212e221 Contents lists available at SciVerse ScienceDirect Applied Geography journal homepage: www.elsevier.com/locate/apgeog Altitude and adaptation: A study of geography and ethnic division Christopher Paik a, *, Tsering Wangyal Shawa b a b New York University Abu Dhabi, United Arab Emirates Map and Geospatial Information Center, Princeton University a b s t r a c t Keywords: Cohabitation China Tibet Diversity Ethnography Ethnic division Altitude Altitude illness In this paper we investigate the influence of geography on ethnic division by drawing evidence from Tibetan ethnic regions in China. Using a novel township name index that identifies the ethnolinguistic origin of each township name, our empirical findings first show that regions with Han Chinese settlement in the past also witness higher concentration of Han population today. We also show that townships located at higher altitudes have less Han concentration. This altitude effect can be both indirect and direct; we find that the indirect effect through historical settlement is small compared to the direct physiological effect through altitude illness. The challenging environment of the plateau region acts as a physiological hindrance only for Han Chinese, and the natural separation continues to persist between the two groups. Ó 2013 Elsevier Ltd. All rights reserved. Introduction Geography has long been instrumental in understanding various socioeconomic processes, including ethnic conflict and civil wars (Fearon & Laitin, 2003; Jha, 2009; Miguel, Satyanath & Sergenti. 2004; Wimmer, Cederman, & Min, 2009), as well as divergence in institutional performance and economic development (Acemoglu, Johnson, & Robinson, 2001; Acemoglu Johnson & Robinson 2002; Acemoglu, Johnson, & Robinson, 2005; Easterly, 2001; Easterly & Levine, 2002). While cultural and technological innovations have perhaps facilitated human adaptation to changes in nature over the years (Amaru & Chhetri, 2013; Eriksen & Selboe, 2012; Folke, Hahm, Olsson & Norberg 2005; Moser & Ekstrom, 2010; Nielson & Reenberg, 2010), socioeconomic divergence due to environmental barriers often persists in the long run, such that both historical processes and geography continue to influence the present. This persistence suggests that natural surroundings sometimes impose constraints especially on migrants who, despite efforts to put down their roots, may not overcome the changes they face in the new environment. The constraints that they face may even be physiological and different from cognitive-behavioral responses to adapting to new climate or places (Fresque-Baxter & Armitage, 2012). In this paper we specifically aim to identify the various causal mechanisms of geography on the familiar yet * Corresponding author. E-mail addresses: [email protected] (C. Paik), [email protected] (T.W. Shawa). 0143-6228/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.apgeog.2013.02.003 important outcome of ethnic division. In support of different works that have identified geographic variability as the foundation of ethnic diversity (Ahlerup & Olsson, 2012; Michalopoulos, 2012), we analyze the extent to which the effect of geography has persisted in the long run. Specifically, we first investigate both the origin of Han-Tibetan diversity and ethnic diversity today in Tibetan regions. We exploit the fact that the two groups continue to be separated by the regions’ high altitude. We then separate the impact of elevation on ethnic division, by exploring both its influence today and throughout history. In doing so we test whether the altitude effect is only indirect and temporary through historical settlements, or direct and persistent on the present population. We study Tibet as a unique case of how altitude can have a significant effect on ethnic diversity, as altitude illness predominantly affects Han Chinese but not Tibetans. China’s rising prominence in the world today, combined with the recent wave of protest movement and ongoing conflict between Han Chinese and Tibetans, has also sparked a renewed interest among both academics and policy makers. Altitude illness is a well-known medical condition that occurs when a person ascends to high mountainous slopes and suffers from lack of oxygen (known as hypoxia). Numerous studies have shown that Tibetans and Chinese have different genetic compositions, and that certain genes carried by Tibetans allow them to adapt better to the thin air surroundings than Chinese (Beall et al., 1998; Bigham et al., 2010; Groves et al., 1993; Gupta, Rao, Anad, Banerjee, & Boparai, 1992; MacInnis, Koehle, & Rupert, 2010; Moore, 1998; Simonson et al., 2010; Wu, Li, & Ward,, 2005). The Qinghai-Tibetan plateau, where Tibetans live, is bounded by the Himalayas in the south and the west, and the C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 Kunlun and Qilian mountains in the north and the east. On the northern side of the Himalayan watershed, Tibet, now divided among the Tibetan Autonomous Region of the Peoples’ Republic of China and several other Chinese provinces, has an average elevation of 4380 meters. Covering more than 2.5 million kilometerssquared, the Qinghai-Tibetan plateau is the highest and largest plateau in the world. Wu (2001) reports that in 1990 about 4,594,188 Tibetans lived on the plateau, with 53 percent living at an altitude over 3500 meters. Furthermore, about 600,000 live at an altitude exceeding 4500 meters in the Chantong-Qingnan area. Tibetans are lifelong high-altitude residents and do not easily move to higher or lower elevation.1 The fact that a majority of Tibetans live at the altitude comparable to the Andeans in South America suggests that Tibetan’s ability to adapt to their landscape is unique to the people. Taking advantage of the native background of one of the authors in this paper, we introduce a novel data set containing the names of all townships in Tibetan regions. With this data, we use the ethnic origin of the town name to infer any historical Chinese presence in the area. While a small number of these township names are recent outcomes of the central government’s effort to establish Handominated towns in Tibet, most go back in history at least to the 13th Century. This was the period when the first formal contact took place between the Yuan Dynasty and Tibet, a kingdom then only known by pilgrims and surrounded by almost insurmountable natural barriers restricting access for foreigners. We argue that, given the lack of historical data on the ethnic composition of each township population, the township name is a good proxy for historical Chinese presence in the region.2 For comparison between the past and the present population, we match these names with the National Bureau of Statistics of China’s Historical China Township Population Census Data with GIS Maps for the year 2000 (the year for which the most recent census data at the township level are available). Our main findings suggest that both historical settlement and altitude effect are significant determinants of current ethnic division. First, townships with at least some evidence of Chinese presence in the past see a 0.12 point increase in the fraction of population identified as Han Chinese in 2000. Second, on average a higher elevation by 1000 meters means a 0.18 point decrease in the Han fraction of township population. This altitude effect can be further separated into indirect and direct effects. Once migrants settle down, they put down their roots so that both the descendants and kin group become easily adapted to the land in subsequent generations. The altitude effect would have influenced both the population groups in the past, and also in the present. The indirect altitude effect through historical presence, while significant, has only limited impact (0.03) on the current population today. Its magnitude is only one fourth of the direct effect (0.12) on the level of Han concentration. These findings show that altitude not only influenced the historical legacies of ethnic diversity, but continues to have much stronger and direct impact on the current population. They also suggest that any policies aimed at changing the ethnic demography in Tibetan regions will likely face difficulties in surmounting the lasting effect of elevation. This paper follows closely the social sciences literature on ethnic demography and genetic divergence of groups (Fearon, 1 Wu (2001) reports that over 90 percent of the population are engaged in farming and herding; in farming the altitude limit of crops is around 4500 meters, while the nomads reside between 4800 and 5500 meters. Even the recent shift of some livelihood into mining has not changed the permanent residence of Tibetans at altitudes between 3700 and 6000 meters. 2 Here the term Chinese predominantly refers to the Han people but is inclusive of Manchus who founded the Qing Dynasty, since Manchus and their language have been assimilated into the Han population. 213 2003; Montalvo & Reynal-Querol, 2005; Spolaore & Wacziarg, 2009). It also complements seminal works by Goldstein (1997) and Barnett (2009) on Tibet, by employing quantitative methods to study a region that has hitherto lacked such analysis. In regard to the cultural, institutional and technological innovations that facilitate adaptation (Chhetri, Chaudhary, Tiwari, & Yadaw, 2012, Chhetri & Easterling, 2010; Moser & Ekstrom, 2010), this research provides a rare case study for which these adaptation advances may prove yet ineffective in the face of certain natural barriers. Finally, the research adds to the highly interdisciplinary field of mountain geography by bringing together studies from the medical, anthropology, linguistics, political science and economics literature. The rest of the paper proceeds as follows: in Section 2 we first discuss altitude illness, the main exogenous variation we exploit to explain the natural separation between Tibetans and Han Chinese. We then present arguments for how the township name may be an appropriate indicator of the region’s ethnic history in Section 3. In Section 4 we discuss the empirical strategy and describe the data in Section 5. Finally we provide the empirical findings in Section 6, and conclude in Section 7. Natural separation and altitude illness Ancient records indicate that the human difficulty with rarefied air at high altitudes has existed for a long time. Writings attributed to Aristotle (384e322 BC) for example describe travel on Mount Olympus in Macedonia: “Also, because the rarity of the air which was there did not fill them with breath, they were not able to survive there unless they applied moist sponges to their noses” (West, 1998). Ward (1990) documents the first recorded case of altitude illness coming from the Karakorums, with Chinese sources dating to 37e32 BCE describing the route from Yarkand to Afghanistan as passing the aptly named ‘Great Headache’ and ‘Little Headache’ mountains. McKay (2007) also presents an account of the well known Chinese Buddhist traveler Fa-Hsien, who took the western route to India in 399e414 CE. He describes a death from what was probably high-altitude pulmonary edema, or swelling of lungs. In contrast, Tibetan sources are mainly reticent about their landscape and the difficult journeys undertaken through it; furthermore, accounts of Tibetans suffering altitude sickness are extremely uncommon (McKay 2007). The psychological impact of la-drak, or “The Poison of the Pass,” or the “exhalations of mischievous Gods” (West, 1998) would have been even greater on Chinese in the ancient times, when the scientific cause of altitude illness was not known.3 Altitude illness is a collective term that encompasses major conditions caused directly by hypobaric hypoxia, or lack of oxygen due to falling in partial pressure oxygen in high altitudes (Murdoch, Pollard & Gibbas 2006, chap. 15). It is the only condition in which traditional technology is incapable of mediating its effects among the various environmental stresses that modern humans have encountered and succeeded in overcoming (Peng et al., 2011). Deprivation of adequate oxygen supply leads to severe physiological stress, leading to a number of symptoms including headache, loss of appetite, nausea, vomiting, fatigue, weakness, dizziness, light-headedness or sleep disturbance. Left untreated, severe forms of altitude illness may result; Acute Mountain Sickness (AMS) might progress to fatal high altitude cerebral edema (HACE), or 3 Paik (2013) provides a detailed summary and literature review on this topic, showing that an increase in elevation is directly correlated with less presence of Han population in the region. The paper also shows that the impact of elevation on Han population is through altitude illness, and not through other contemporaneous factors, such as urbanization and education attainment levels. 214 C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 swelling of extremities and face, that leads to brainstem herniation, or high altitude pulmonary edema (HAPE), or swelling of lungs that lead to difficulty in breathing. A comparison between Tibetans and Han Chinese shows that there is a much lower frequency of acute mountain sickness among the highlanders owing to genetic adaptation (Wu et al., 2005). Chronic mountain sickness, a disease that tends to occur later in life among natives or long-life high-altitude residents, is also less common in Tibetans than in similarly exposed Andeans (Moore, 1998). A number of highly selected genes play a role in maintaining hematocrit levels (the ratio of red blood cells to the total volume of blood), which may contribute to this apparent resistance (Bigham et al., 2010). The overall number of people impacted by either AMS or CMS is relatively few (León-Velarde et al. (2005) reports that about 5e10 percent of population in highlands are affected), but the number naturally increases past different stages of high altitudes, and affects Chinese much more than Tibetans. Town names and heritage We use the names given to each town as artifacts reflecting historical Chinese influence in Tibet. The assertion that place names, or toponyms, are outcomes of the past cultural and political landscape finds much support from the linguistics and geography literature. For example, Radding and Western (2010) shows that names are given intentionally to impart a certain meaning, and that they have layers of meanings that people do not want to see erased; toponyms are deeply entrenched in culture, and their substitutions come with consequences. The authors in Radding and Western (2010) go on to argue that even literal or phonetic translation is one type of name change that can be construed as a political act, since the meaning of names is embedded in cultures, and translating a name runs the risk of destroying its meaning. Place names are therefore “one of the most conservative elements in a language. surviving even repeated language shift” (Burenhult & Levinson, 2008). Their resilience is reflected often in cases when both internal societal changes and external threats from another language or society supplant the existing one, and yet the place name may well remain (Herman, 1999). When a political regime takes over another, multiple place names may be created, each used by different groups. Even more dramatic shifts in political regimes are reflected in the complete loss of original toponyms. The name changes can therefore be interpreted as outcomes of political shifts, often imposed by colonial authorities who use name changes as means to aid in the establishment and legitimation of a state (Radding & Western, 2010). Horsman (2006) similarly argues that bestowing a name on a physical entity is an act of appropriation, and with each change in political regime comes new names for a given geographical location. Kangding, the prefectural capital of Ganzi in Tibet Autonomous Prefecture (TAP), Sichuan Province, is a good example of how a township name represents the region’s history. The city has historically been known among Tibetans as Dartsedo. In an old Qing map published by Christian missionaries in 1717 (d’Anville, 1737), Dartsedo is labeled as Tachienlu, apparently the phonetic translation of Dartsedo. Since the Qing Dynasty, the Chinese kept a garrisoned office in this important trading mart for both Tibetan and Chinese merchants. The name Kanding reflects the historic Chinese presence in the region; in 1725 the Qing military occupied Dartsedo area and a place called Kata near Dartsedo, which was made the military headquarters for the Chinese Troops. The capital was subsequently renamed Kangding by the Chinese. Xihai City is another example; the city is the prefectural capital of Haibei TAP, Qinghai Province with no Tibetan heritage. Xihai, also known as Two Two One Factor (Er Er Yao Chang), is a former site of China’s top-secret nuclear weapons research. Xihai means the western sea, the name of the first and only Chinese administrative unit established in the immediate locale before the 20th century. The name therefore reflects a carefully-chosen historical parallel for the Chinese, and takes after the original “Xihai Commandery,” a military settlement whose ruins lie little more than ten kilometers away. (Marshall & Cooke, 1997; Pg. 1724). Empirical strategy Our empirical approach is to use town names as indicators of historical Chinese presence in the region. We first assume that when Han Chinese moved to the west toward Tibet, they made their marks in the land close to the border and attractive for trade and military purposes. That is, whether or not to settle in a region was a function of how much one could gain from trade or territorial takeover, as well as how close it was to the Chinese-dominant regions. This assumption will be violated if regions differed in important ways in their initial conditions that may also have had an effect on these areas, for example, through variations in the type of biogeography suitable for Chinese. The more attractive for agriculture a region was, for example, the more likely it would have been settled by the migrants. One may also argue that the due to lifestyle differences, Tibetan agriculturalists may have had different cultural ties to Han Chinese than Tibetan herders, which in turn affected the level of Chinese settlement.4 In order to control for these alternative mechanisms, we introduce a set of location as well as biogeographic control variables, in addition to the altitude variable. Elevation is directly correlated with the likelihood that the Chinese would have become ill due to high altitudes. It identifies variations in “Tibetanness” due to altitude mountain illness. The historical Chinese presence in certain Tibetan towns may have been influenced by the group’s inability to adapt to new altitudes, and this physiological hindrance to living in certain places led to different levels of Chinese presence across Tibet and its surrounding regions. We assess the impact of altitude on population, whether through the past settlement or through its physiological impact today. In order to do this we first run reduced-form equations of the following simple form: Hi ¼ a0 þ a1 Ai þ a2 Xi þ εi1 (1) where Hi is the fraction of population identified as Han Chinese in township i in our sample, Ai is the altitude variable, Xi is a vector of control variables, and ε is a normally distributed error term. The parameter of interest in this setting is a1, showing the reducedform impact of altitude on current Han concentration. Our hypothesis is that a1 is negative, i.e. an adverse average impact of elevation on Han population. Since we recognize a key role of historical presence as an intermediate variable, we will also employ the standard estimation of mediation effects (MacKinnon, 2008). Mediation analysis is based on the following set of linear equations: Mi ¼ b0 þ b1 Ai þ b2 Xi þ εi2 (2) Hi ¼ q0 þ q1 Ai þ q2 Mi þ q3 Xi þ εi3 (3) 4 Michalopoulos (2012) for example argues that the origin of different ethnic groups may come from variations in biogeography of the land, which determines different lifestyles and occupations of the people. It is not clear however whether Tibetan agriculturalists associated themselves as closer to Han migrants, who were predominantly agricultural, or to their Tibetan neighbors herding animals at higher altitudes. C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 where Ai represents the mean altitude for township i, Mi represents the mediating variable, in this case the indicator variable for whether there was any historical Han Chinese presence, and Hi is the current Han population as the fraction of total township population. Xi represents a set of observed exogenous geographic covariates. The product of coefficients b1q2 estimates the average causal mechanism effect (ACME), where b1 and q2 are obtained by separately fitting least squares regressions based on the above equations. a1 and q1 measure the average and the direct effect of altitude on Han concentration, respectively. A significant q1 will indicate that the altitude itself had an impact on current Han presence independent of historical settlement. As with a1, we hypothesize that q1 is negative. Finally, a significant and positive q2 will suggest that a history of Han settlement explains a higher current level of Han Chinese population, controlling for elevation and other geographic variables. Data We use the township-level Han population data from China’s National Bureau of Statistic’s Historical China Township Population Census Data with GIS Maps for the year 2000. In order to assess the extent to which a homogenous Tibetan region historically witnessed Han Chinese influence, we introduce a novel index of town name classifications, and argue that these names are indicators of the past history. We use Tsering W. Shawa’s Tibet Township Map and Place Name Index Database based on the 2000 Chinese census township level administrative units. This index includes Tibetan, Chinese and English script township names in Tibet Autonomous Region (TAR), as well as Tibet Autonomous Prefectures (TAP) and Counties (TAC) in the surrounding provinces of Gansu, Qinghai, Sichuan and Yunnan. The year 2000 was the first time the Chinese township level census data became available to the public. The township is a fourth-level of census geography unit. It includes Jiedao (the urban street location which is part of a larger urban area), Zhen (township with an urban population), and Xiang (township with no urban population). In addition, the township classification includes virtual townships such as sheep breeding areas, special farming areas, etc. The township names are written in three scripts: Tibetan, Chinese, and English. Pinyin is the romanization standard for Chinese script, and Wylie is a standard transliteration of Tibetan script in scholarly literature in the English world. The romanization is provided for a general reader to sound out Tibetan town names. The Wylie transliteration is created from Tibetan script using Universal Tibetan Font Converter. The program was developed by Tashi Tsering at the China Tibetology Research Center in Beijing. The main motivation for creating the index was to record traces of remaining Tibetan place names in traditionally Tibetan towns. Some of these towns have increasingly seen changes in the composition of population groups. Recording each town’s existing name in various scripts required finding information from various sources, including the official toponym lists published by the Chinese government in these areas, the Tibet map in Tibetan language published by Tibetan-Government-Exile and by Amnye Machen Institute, and toponym database from the Tibetan and Himalayan Library. In the few case that there were only Chinese toponyms on official records but the authors recognized the existence of Tibetan counterparts for the towns through Shawa’s own heritage and personal interviews with townspeople, these Tibetan names were recorded as well. For the purpose of the following empirical analysis, this paper introduces another classification of these toponyms. Each town is first categorized as having only a Chinese name (C), both Chinese 215 and Tibetan names (CT), or only a Tibetan name (T). Since all towns have their official names written in Chinese characters and in Pinyin, the extent to which the original town name has been preserved is determined by how phonetically or literally it is similar to the Tibetan counterpart (if the Tibetan name does exist). A town in the C-category means that it has a name instantly recognizable as Chinese with no counterpart in the Tibetan language; that is, the town name has no literal or phonetic connection to any Tibetan word. This implies no Tibetan population and only Chinese presence in history, or recent foundation of the town under the government initiative to relocate Han Chinese to the town. In either case, historical Tibetan presence is essentially non-existent in the area. A town in CT category on the other hand has two distinct names, one in Chinese and one in Tibetan. Furthermore, the Chinese name is not a phonetic or literal translation of the Tibetan name, such that each name has its own origin. The categories C and CT are therefore labeled as those that witnessed at least some Chinese settlement in the past. A town in the T category has a Chinese name that is the direct phonetic translation of the town’s Tibetan name. In a small number of cases, Chinese town names are literal translations of the Tibetan counterparts and are also coded as T. As an example, the town of Yeniugou (Donglung in Tibetan) in Qinghai Province is classified as having only a Tibetan town name, despite the pronounced difference in the two town names. Both Yeniugou and Donglung in fact mean the same thing; they are translated as the wild yak country. There are 1960 townships in the 141 counties of the five provinces included in the dataset. 50 towns were dropped due to ambiguity of name origins. Appendix A presents a set of examples from Tibet Township Map and Place Name Index Database. The 22 towns in Kangding County, Sichuan Province, show both Chinese and Tibetan origins. Geographically the region has had close contact with Chinese as it lies close to the eastern edge of the traditional Tibetan region of Kham, a main gateway region of Tibet to China. We see that in a few cases the town’s ethnic name origin is not representative of the current level of Tibetan population. For example, Liuba (Lugpa in Tibetan) is a town with the total population of 2660 in the year 2000. 98 percent of the population is Tibetan, and the Chinese name is a phonetic translation of the Tibetan name. The town name is hence classified as having only a Tibetan originated name (T). Pusharong (Phouharrong in Tibetan), on the other hand, is a town with a Chinese name that has no recognizable Tibetan counterpart, despite its dominant Tibetan population (97 percent). Another example is the town of Jiju (Kyikyi) with 99 percent Tibetan population. It has both Tibetan and Chinese names distinct from each other, despite the dominant presence of Tibetan population in 2000. The Chinese town names therefore do not always indicate current Chinese population dominance in the town, but rather suggest Chinese presence in history. The following analysis controls for a number of geographic variables. Each county’s ecological surroundings are defined by a set of fractions of the land occupied by different biomes from ESRI 2008 Data. These biomes are identified as climatically and geographically different from each other. Temperate Broadleaf and Mixed Forests, and Temperate Conifer Forests are grouped together as Temperate Forest (Mixed Forests include Coniferous forests). Other types of biomes include Shrublands (Deserts and Xeric Shrublands, and Montane Grasslands and Shrublands), Rock and Ice, and Tropical and Subtropical Moist Broadleaf Forests. The set of ecological variables, together with the mean elevation, provide information on the type of plant structures, climate and vegetation occupying each county. They proxy for the different habitat types which likely influenced the initial settlement patterns of people in history. Here we use the contemporary biogeographic data to 216 C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 Table 1 Summary statistics. Variables Fraction of population identified as Han in 2000 ¼1 if historically settled by Han Mean elevation in km Area in 100 km-squared Longitude Latitude Fraction covered by rock and ice Fraction covered by shrublands Fraction covered by tropical forest Fraction covered by temperate forest ¼1 If township in Gansu ¼1 If township in Qinghai ¼1 If township in Sichuan ¼1 If township in Xizang ¼1 If township in Yunnan (1) (2) (3) (4) (5) N Mean sd min max 1709 1910 1960 1960 1960 1960 1960 1960 1960 1960 1960 1960 1960 1960 1960 0.191 0.229 3.813 0.110 97.49 32.17 0.007 0.738 0 0.254 0.068 0.255 0.294 0.369 0.015 0.296 0.421 0.812 0.378 5.610 2.802 0.045 0.383 0.014 0.383 0.252 0.436 0.456 0.483 0.121 0 0 1.265 0.490 78.96 27.08 0 0 0 0 0 0 0 0 0 1 1 5.762 7.939 104.6 38.91 0.560 1 0.577 1 1 1 1 1 1 proxy for historical vegetation spread prior to human settlement. This approach presents potential pitfalls, since vegetation types may have changed regionally over a long time. The measurement error may also be systematic, in that both the settlement decision and vegetation may be affected by the same factor, thereby producing a spurious result. In order to address these issues we conduct our analysis by including provincial fixed effects, accounting for any provincial-level unobserved factors that may have affected both the Han Chinese presence and vegetation spread. This approach controls for any bias induced by within-province unobserved heterogeneity. Finally, the following empirical analysis also includes geographic coordinates and the area of each township.5 Findings Map 1 shows the boundaries surrounding Tibetan Autonomous Prefectures (TAP), inclusive of Tibetan Autonomous Region (TAR) and Tibetan-dominated parts of other provinces. Table 1 presents summary statistics, first showing the fraction of township population identified as Han Chinese in the year 2000. The average township had about 19 percent of the population identified as Han. For comparison, on average 23 percent of all townships experienced at least some historical Chinese influence, according to the town names. The average township elevation is 3813 meters, and out of 1960 townships 1500 of them are located at altitudes lower than 4500 meters, which approximates the mean elevation of the plateau region. Figs. 1 and 2 show in detail the elevation spread of township locations. In Fig. 1, townships with Chinese names have a unimodal distribution that peaks around 2700 meters. Among these towns, those with both Tibetan and Chinese names tend to be located at higher altitudes, with the peak of the distribution at around 5 The current county boundaries of east and south regions of Tibetan Autonomous Region (TAR), and the broader Tibetan Autonomous Prefectures (TAP) are primarily based on previous tribal borders, while those in the west are mainly drawn from historical administrative borders of the central Lhasa government before the Qing Dynasty. Historically, each county centered around a Dzong (fort), and had a monk and Dzong-pon (civilian- Lhasa delegate administrator) to collect taxes. Since a GIS map illustrating administrative boundaries of Chinese townships was unavailable, the following approach was taken to calculate the area of each township. The land area of each town was obtained by using Thiessen Polygon feature in ArcGIS on township centroids. The features creates a border between two adjacent towns by first calculating the map distance between two towns’ centroids, and drawing a line through the point that is equidistant from both centroids. Fig. 1. Number of towns with Chinese names. 3800 meters. No town with a Chinese name is located above 4600 meters, as shown clearly in Fig. 2. While most towns with Chinese names are located in the lowlands at around 2700 meters in altitude, towns with Tibetan names are generally located much Fig. 2. Number of towns with Chinese names vs. Tibetan names. C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 Fig. 3. Fraction covered by shrubs. 217 Fig. 4. Fraction covered by temperate forest. higher up in altitude. In fact the highest number of Tibetan towns found is at 4500 meters, and the distribution of Tibetan towns shows a sharp decline only past 5200 meters. The bimodal spread of these town locations suggests that there is a decreasing level of Chinese presence in Tibetan ethnic regions as the elevation increases. For comparison, Maps 2 and 3 show the Tibetan plateau and plot townships based on their geographic location coordinates. In addition, Map 2 presents information on the ethnolinguistic origin of township names, while Map 3 shows the fraction of Han Chinese population in each township. While we see a clear indication that the settlement pattern diverged around 4500 meters, this divergence may also be a sign of how the initial biogeographic setting (prior to first human settlement) changed around this altitude. If there was a dramatic change in biogeography over the same threshold to separate agriculturalists from herders, the historical claim attributing the source of ethnic division to altitude illness may not be the only mechanism explaining the current settlement pattern. To illustrate whether this is the case, Map 4 first shows the vegetation spread in Tibet. Fig. 3 shows that out of 1500 townships which have the mean elevation below 4500 meters, 767 of them are completely covered by shrubs. Furthermore, the majority of these (1029 out of 1500) have more than half of the land covered with shrubs. Shrubs continue to be the dominant vegetation type above 4500 meters; 323 townships that are above 4500 meters are completely covered by it, and the majority (428 out of 460) have more than 50 percent of the land covered with shrubs. Fig. 4 clearly shows that most townships above 4500 meters have less than half the land covered by temperate forest. However, the majority of counties below 4500 meters also have less than half the land covered by temperate forest as well. 384 counties above and 773 counties below 4500 meters all have zero temperate forest coverage. These figures suggest that the fraction of shrubs and temperate forests, which together occupy 99 percent of the regions, show very small changes in spread patterns around the altitude at which there is a dramatic shift in town names. The threshold seems therefore related to settlement choices due to altitude illness, but not biogeography. In Table 2, we introduce the indicator for historical Han presence as an intermediate variable, in line with our hypotheses. The main purpose of this table is to check whether elevation mainly affects current levels of prosperity through its impact on historical Han presence, or if there is also a direct impact through the altitude illness argument as presented above. From Columns 1 and 2, we see that the mean township elevation has a very strong negative impact on the past Han presence, both with and without the controls. For example, the coefficient value under Column 2 Table 2 Historical settlement and current Han population. Variables (1) (2) OLS (DV: historical presence) Mean elevation ¼1 If historically settled by Han Controls Constant Observations R-squared 0.273*** (0.015) No 1.240*** (0.068) 1910 0.362 (3) (4) 0.256*** (0.016) Yes 1.110*** (0.334) 1910 0.389 (5) (6) OLS (DV: Han presence in 2000) 0.245*** (0.019) No 0.026*** (0.003) 1660 0.364 0.207*** (0.019) Yes 1.497*** (0.201) 1660 0.394 0.215*** (0.012) No 0.933*** (0.053) 1709 0.416 Yes 0.606*** (0.214) 1709 0.447 Robust standard errors in parentheses. ***p < 0.01, **p < 0.05, *p < 0.1. Controls include the township area, longitude and latitude, and a set of vegetation variables occupying the township. All regressions include provincial dummies. (8) SUR 0.205*** (0.012) Average causal mechanism effect via historical Han presence (7) 0.161*** (0.015) 0.142*** (0.015) No 0.737*** (0.046) 1709 0.447 0.178*** (0.015) 0.124*** (0.011) Yes 0.422 (0.441) 1709 0.447 0.041*** (0.006) 0.032*** (0.004) 218 C. Paik, T.W. Shawa / Applied Geography 40 (2013) 212e221 suggests that the likelihood of witnessing historical Han settlement in history decreases by roughly 26 percent as elevation increases by 1000 meters. Furthermore, when run alone, historical Han presence has a strong negative impact on the current Han concentration, as shown in Columns 3 and 4. The result indicates that a township with Han heritage has 20 to 25 percent more Han concentration today, depending on the regression specification. Finally, the average effect of altitude on the level of current Han presence is shown in columns 5 and 6, where we see that an increase in the township mean elevation by 1000 meters leads to a 20 point drop in the fraction of population identified as Han Chinese. However, when we do a mediation analysis as in columns 7 and 8, our results show that the mean elevation variable mainly has a direct effect on Han presence that is independent of its impact on historical settlement. The direct effect is in the magnitude of 0.16 and 0.18 under Column 8 respectively. This effect is greater by 4e6 times the magnitude of the average causal mechanism effect. As the regression results show, the altitude effect is robust to matching towns by location and biogeography. These findings confirm that the historical settlement of Han Chinese leads to more Han presence today, and that the channel through which the elevation influences the population mainly runs through altitude illness, rather than through its influence on the historical settlement. Conclusion In this paper, we aim to show that both geography and historical settlement have long term impact on current population. In particular, we discuss the various channels through which altitude can influence the level of ethnic division today, and present empirical evidence from Tibet’s unique landscape and township name index. We find that the region’s high altitude has determined the level of Han Chinese concentration both through historical settlement and hypoxia. Even after controlling for historical settlement, nature’s influence on physiology continues to be heavily influential. The high altitude has proven to be a daunting challenge for Han Chinese when trying to settle in the region. In addition to influencing the local population’s culture and lifestyle, Tibet’s formidable terrain appears to have essentially confined inter-ethnic relations mostly to the region’s geographically defined borders. Today, the altitude influence on the population is increasingly challenged as the Beijing administration encourages more Han Chinese migration to these regions. This is evident from the Great Development of the West initiative beginning in the year 2000, when the central administration started providing more infrastructure and other economic incentives for the westward migration of Han Chinese. The 2005 completion of the Qinghai-Tibetan Railway also connected Tibetan regions to the rest of the country. Our results in this paper nevertheless indicate that ethnic integration in the face of natural barriers is never an easy process. 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