Elsevier

Tectonophysics

Volume 806, 5 May 2021, 228796
Tectonophysics

Regional geology, extreme weather events and natural disasters: Environmentally-forced, involuntary settlement migrations of the indigenous people of southern Taiwan

https://doi.org/10.1016/j.tecto.2021.228796Get rights and content

Highlights

  • Indigenous people’s oral traditions and regional geology can be used to investigate effects of extreme weather.

  • Regional geology and site investigations of the ancient villages identify the possible causes of settlements migrations.

  • Extreme weather events and natural disasters may have important socio-economic impact on the indigenous peoples.

  • Indigenous peoples oral stories is a potential source as supporting data for variety studies as paleoenvironment reconstruction.

Abstract

Active mountain belts in monsoonal climates are characterized by rapid denudation due to erosion and mass wasting processes. In such areas, unstable topography caused by local geological conditions combined with extreme rainfall or earthquakes impact on indigenous people, especially through involuntary settlement migration. Anthropological surveys in southern Taiwan show that the oral traditions of indigenous people preserve records of natural disasters that took place several hundred years ago. When combined with geological data, these stories allow us to assess the triggers and underlying causes that led to settlement migrations. These settlements are located in the Central Range of southern Taiwan, a high-relief terrain comprised of Miocene formations characterized by well-developed slaty cleavage (S1) that forms dip slopes that are prone to landslides. Here, we investigate how extreme events coupled with the geological setting caused two relocations of a settlement of the Paiwan group within approximately 350 years. We also draw attention to the point that the oral traditions of indigenous groups can provide important data sets for reconstructing landslides in the recent past (less than 500 years) which other, more traditional methods (e.g. digital data archives) do not record. We conclude that extreme weather provides the trigger, and local geological conditions the underlying factors, for natural disasters that have had a significant impact on the indigenous people in southern Taiwan.

Introduction

Large-scale human migrations are typically associated with climatic, economic, political, cultural, or social changes (Cebula and Vedder, 1973; Hansen and Oliver-Smith, 1982; Greenwood, 1985; Oliver-Smith, 1999; Cullen et al., 2000; Oliver-Smith, 2002; Oliver-Smith, 2006; Black et al., 2011; Macklin and Lewin, 2015; Kathayat et al., 2017). At a local scale, however, human migrations are more often triggered by single-event natural disasters such as an earthquake, a tsunami, or a typhoon, and are generally caused by a conjunction of underlying factors (Button and Oliver-Smith, 2008; Levine, 2008; Wu and Chen, 2009; Tsou et al., 2011; Hsieh et al., 2012; Huang et al., 2016). These underlying factors can be broadly divided into three groups: 1) natural setting (e.g. flood plains, high-relief terrains, fractured rock formations), 2) natural processes (e.g. monsoons, earthquakes, glaciers, aeolian processes), and also 3), human activity (e.g. overloading or undercutting of hillslopes, groundwater utilization, deforestation). In addition, these can be further divided into: i) preparatory factors such as local geology, topography, long-term processes as progressive erosion or material removal; and ii) triggering factors such as extreme events, earthquakes, construction explosions) (Glade and Crozier, 2012). The interaction between them, in some cases, may lead to a natural disaster, which in anthropological terms is defined as an occurrence related to human social processes that take place within a structural and contextual frame of an affected group (Gilbert, 1995) that might result in a social consequence. One of these consequences is migration, either temporary or permanent (Oliver-Smith, 2006; Button and Oliver-Smith, 2008).

Taiwan is an actively growing mountain belt that is characterized throughout much of the island by rapidly evolving, high-relief topography due to collision between the Eurasian passive margin and the Luzon volcanic arc on the Philippine Plate (Fig. 1). Consequently, the Taiwan is often affected by earthquakes and monsoons as well as extreme weather in the form of typhoons, and natural disasters are common (Chang et al., 2007; Tsou et al., 2011; Hsieh et al., 2012; Lee, 2014). For example, in August of 2009, typhoon Morakot passed over the island, triggering over 22,000 landslides (Lin et al., 2011a) (Fig. 2). Many of them had a direct impact on settlements, especially in mountainous areas. In particular, the village of Xiaolin in southern Taiwan was buried beneath a landslide, leaving more than 400 dead. While typhoon Morakot was the trigger for this disaster, the underlying determining factor was provided by the local geology in the form of bedding, joints, fractures, and faults (Tsou et al., 2011; Giletycz et al., 2012; Hsieh et al., 2012). Numerous single-event natural disasters in the recent history of Taiwan have been well studied and their underlying triggers with contributing factors are understood (Chang, 1996; Teng et al., 2006; Tso and McEntire, 2011; Saunders et al., 2015; Marc et al., 2018; Steer et al., 2020). We define ‘recent history’ as being since the beginning of the Japanese occupation in 1895, when the first systematic documentation of such events started. Distantly past events (before 1895) that affected the indigenous people in the mountains of Taiwan are, however, less well understood because documented information about them is mostly lacking (Russell, 2009; Balcom and Balcom, 2005). Although these distantly past natural disasters occurred in the sparsely populated mountainous areas of Taiwan, they had such an important socio-economic impact on the indigenous peoples that information about them is still preserved in their oral traditions. The aim of this paper is to combine the oral traditions of the Paiwan people of southern Taiwan with forensic geological site investigations to examine how extreme weather events combined with local geological conditions resulted in natural disasters in past centuries. In our survey we focus on one indigenous group and the sequence of their involuntary migrations that were provoked by natural disasters. These migrations began with the abandonment of the village of Tjuvung, located in a high-relief terrain, the subsequent settling and leaving of Paridrayan and, finally, settling in the current village of Linali in a low-relief terrain (Fig. 1b).

Section snippets

Geology, topography, and landslides

Our study area (Fig. 1) is comprised entirely of low-grade metamorphic rocks of the Miocene-aged Chan-Shan Formation, which is characterized by rocks that are strongly folded and sheared (Conand et al., 2020). Throughout much of the study area bedding (S0) is only rarely preserved (Fig. 3a). The Chan-Shan Formation is made up by very fine-grain slates with, locally, thin (c. 1 to 10 cm thick) beds of sandstone (Fig. 3a). The dominant planar fabric found in these rocks is a penetrative salty

Paiwan oral traditions

Anthropological primary data were collected between 2012 and 2017 during ‘semi-structured’ interviews. These semi-structured interviews consisted of open-ending questions that were designed to prompt discussion among the interviewees. Each 1-to-2-h interview was carried out with seven members of the Paiwan group between the ages of 35 to 80 (see supplementary Data Set 1). The interviewees, all of whom are recorders of the oral traditions of the Paiwan people, now live in the villages of

Site investigation

Site investigations were carried out in the areas of Tjuvung and Paridrayan (Fig. 1, Fig. 4) to determine the local geological and geomorphological features and their relation, if any, to the possible events that caused the settlement migrations recorded in the Paiwan oral traditions.

The abandoned village of Tjuvung is located on c. 300 m-wide bedrock terrace on the southern bank of Dashe River, about 40 m above the deeply incised river bed (Fig. 6). The northern bank of the river is

Discussion

In southern Taiwan, Paiwan indigenous villages are distributed in high-relief terrains in an underlying bedrock made up of slates with a penetrative cleavage (S1) that makes them a factor in rain-induced landslides (e.g. Lacerda et al., 2004; Evans et al., 2006; Chang et al., 2015; Huang et al., 2016). According to the Central Geological Survey of Taiwan, nearly 95% of the landslides that take place in the Chan-Shan Formation occur in areas where the hillslope has an orientation parallel or

Conclusions

Our study demonstrates that the oral stories of the indigenous Paiwan people of south Taiwan can, when combined with site-specific geological investigations, be used to gain insight into both the triggers and the causes of natural disasters that have had an historical, long-term effect on the socio-cultural and economic dynamics and wellbeing of the community. For example, we show that the story about “a big wave” that resulted in the involuntary relocation of the village of Tjuvung about

Authors contribution

Dr Slawomir Jack Giletycz, was the concept main initiator and contributor. He covered geological data, visualized general image of the story presented in the manuscript and the message that is addressed, discussed and concluded. His several fieldtrips to the study area between 2012 and 1018 included sites investigation, geological mapping (geological formations as well as landslides), structure geological measurements (bedding- S0; and foliation- slaty cleavage- S1), and UAV surveys (eventually

Declaration of Competing Interest

None.

Acknowledgments

Brown acknowledges funding from the Spanish Ministry of Science, Innovation, and Universities through grant number PGC2018-094227-B-I00, as well as a Chaired Professor stipend from the Department of Earth Sciences, National Central University, Taiwan. J. Alvarez-Marron, E. Bingaman, R. Carbonell, and J. Schmitt are thanked for comments on the text. Journal reviewers T. Byrne and L. Siame are thanked for their constructive comments. We would like also to thank Odin Marc for the landslide data

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