Signs of Climate Warming Through the Eyes of Yak Herders in Northern Bhutan

A questionnaire survey was conducted to understand how a mountain ecosystem in northern Bhutan is perceived by local yak herders to be changing under climate warming. One hundred elderly herders were selected using a 2-stage sampling. The questionnaire sought information on herders' awareness and perceptions of weather patterns, climate changes, and their impact on vegetation, herding practices, and livelihoods. Most study participants were aware of global warming. They perceived that global warming has led to warmer and longer vegetation growing periods, increased rainfall, decreased water availability, more frequent droughts, the ascent of snow lines, and an increase in flash floods and landslides. Many herders also perceived that vegetation is growing faster, new vegetation is gradually becoming established in formerly barren lands, and meadows have been encroached on by rhododendrons, which has reduced grassland size and caused a decline in forage availability and quality. Warming was perceived to have caused difficulties in herding and transhumant migration. It was also perceived to have caused a decrease in milk production and increase in livestock predation, which affected the livelihoods of herders who rely on yak. The study concluded that yak herders' perceptions provide critical signs of warming and their vulnerability to changing climatic conditions in the alpine environment.


Introduction
Mountain ecosystems, which play an important role in sustaining the livelihoods of mountain pastoralists, are under increasing pressure from stressors stemming from climate change. Climate change has added stress to the agriculture sector (IPCC 2007). Developing countries dependent on natural resources and with low capacity to fight the adversities of climate change will be affected; the poorest countries will be the most vulnerable (McCarthy et al 2001). Scientific communities have acknowledged that climate extremes threaten rural livelihoods. Yet the development strategies of least developed countries mostly overlook the risks of climate change, and this makes them more vulnerable.
In the Himalaya, millions of people living both upstream and downstream will face the burden of changing climate (Immerzeel et al 2010). The significance of the Himalaya in relation to global climate change and the likely impact of warming on the Himalaya and its ecosystems were discussed by Singh et al (2010). Academic debates on the changing climate in the Himalaya focus primarily on glacier melt Liu et al 2006) and the consequent negative impact on water resources IUCN 2011). However, until recently and with few exceptions, most climate change studies have ignored local knowledge (Byg and Salick 2009). Perceptions of climate change in the Himalayan environment have been studied recently (Vedwan and Rhoades 2001;Byg and Salick 2009;Salick and Ross 2009;Sharma et al 2009;Tse-ring et al 2010;Chaudhary and Bawa 2011;Islam et al 2014). A study of people's perceptions of climate change could improve understanding of how humans respond to climate change (Vedwan and Rhoades 2001).
Indigenous peoples are keen observers and have creative ways of interpreting and reacting to the impacts of climate change (Salick and Ross 2009). Traditional knowledge gained over many years is used to cope with changes in climate and environment. Thus, indigenous people have the ability to monitor the changing climate, adapt to it, and mitigate its effects. They provide innovative perspectives to strengthen climate change efforts and enhance ecosystem resilience. Indigenous knowledge also reinforces the available empirical evidence and increases our understanding of how shifts in climate may affect ecosystems and trigger cascading effects on livelihoods. Consequently, indigenous knowledge has benefited climate science (Cruikshank 1981;Reidlinger and Berkes 2001;Moller et al 2004). Such indigenous knowledge needs to be better understood, which could help scientific communities to design sound interventions aimed at alleviating the adverse effects of climate change.
Climate studies in the Himalaya have been confined to only a few countries (Chaudhary and Bawa 2011), which are not representative of the overall Himalayan scenario. The Himalaya's diverse topography offers a variety of climatic conditions, leading to large differences in farming practices. Perceptions of climate change and its effects have been found to differ significantly between sites in the Himalaya (Byg and Salick 2009). These geographic complexities suggest that local perceptions in one region may be of less value for another. To help address this gap in knowledge, we conducted a questionnaire survey with the main aim to investigate yak herders' perceptions on the effects of climate warming in the alpine environment of Bhutan.

Questionnaire design
Survey questions were framed as closed-ended with 3 possible answers: ''agree,'' ''disagree,'' and ''neither.'' The questionnaire was pretested to ensure that the questions were easy to understand and did not influence participants' responses.
The survey questionnaire, which used a 3-point Likert scale (Likert 1932), gathered information on informants' perceptions of changes in the environment, weather patterns, herding practices, and livelihoods. It was divided into 6 sections. The first section consisted of questions on the herders' general awareness of changes in the climate and environment over the last 15 years. The second section sought information on their perceptions of specific signs of climate change, such as changes to the tree line, seasons, and soil conditions. The third section focused on weather patterns, the fourth on water and vegetation, and the fifth and sixth on the impacts of warming on herding practices and herders' livelihoods, especially in regard to transhumant migration and animal health.

Interviews
An official approval was sought for the sampling and selection of villages and questionnaire survey of participants. Yak herders were selected because their heavy dependence on natural resources makes them sensitive to environmental changes and thus the best informants on the effects of warming in the alpine environment. A questionnaire survey was administered in the 5 study villages.
Villages and respondents were selected in 2 stages. In the first stage, researchers, development workers, and local government bodies were consulted and villages were selected for surveying. In the second stage, village leaders were consulted and households and elderly herders were identified as potential respondents. Interviews were conducted with 100 elderly herders. Elderly herders were interviewed because they had witnessed the past climate and environmental changes over several years.

Data analysis
Yak herders' perceptions on the effects of warming were identified through their responses to different questions. These responses were categorized and codified for statistical analysis and are displayed as percentages. Differences in responses were tested with nonparametric chi-square tests. The software SPSS 23 (Landau and Everitt 2004) was used to analyze the dataset.

Perceptions of changes to weather and climate
Herders' perceptions of climate change are presented in Table 1. The majority of respondents were aware of the changing climate. When asked to compare the current climate to that of 15 years ago, the vast majority of respondents agreed that temperatures have risen and the climate is warmer at present. According to a large majority of respondents, this has led to a gradual change in the environment over the last 15 years. Most respondents perceived that weather patterns are changing; the vast majority agreed that the weather was worsening and becoming more unpredictable and was likely to worsen further in the future.
Regarding the signs of changing climate, most respondents agreed that snow and glaciers are melting faster, causing the snow line to ascend. The majority of respondents said that the frequency of landslides and flash floods has increased and the warm period has become longer. Many also said that water sources are drying gradually and water availability has declined. Despite agreeing that the amount of rainfall has increased, the vast majority of respondents said there is increasing water scarcity due to warming and soil fertility has declined. Over half of the respondents said that the changing climate and warming have led to more droughts and desertification; less than half perceived that the tree line has ascended. Respondents were divided on whether warming has led to changes in the amount of soil moisture content and number of lake outbursts. Respondents felt that the frequency of hailstorms has not increased. According to less than half of the respondents (statistically not significant), the size of rivers is perceived to have decreased.

Perceived impact of warming on vegetation
Yak herders' perceptions of the impacts of warming on vegetation are presented in Table 2. Many agreed that the barren lands are gradually being colonized by plants. Grassland size and fodder availability were perceived to have decreased. According to over half of the respondents, rhododendrons are encroaching on alpine meadows at a faster rate and forage quality has declined. Just under half reported that vegetation has started to grow faster, yet no new plant species have been found in the meadows.
Perceived impact of warming on herding practices and livelihoods Table 3 shows respondents' perceptions of the impact of warming on herding. According to most respondents, climate warming has made herding difficult. Yaks were reported to feel discomfort during transhumant migration and livestock health is declining. Most respondents said that unlike in the past, transhumant migration has become difficult and the timing of migration has changed over the recent years. However, respondents were evenly divided on whether the prevalence of gid disease (Coenurus multiceps multiceps) in yak is increasing. The majority felt that warming has not contributed to rural-urban migration of yak herders. Only a smaller proportion said that the transhumant migration route itself has changed or become longer. Table 4 presents the perceived impact of warming on herders' livelihoods. The majority agreed that milk production has declined and that their livelihoods have been affected by warming. Many have lost animals to

Perceptions of changes to weather and climate
Yak herders' responses provide important insights into their local knowledge on the changing climate in the alpine region of northern Bhutan. The widespread awareness and perceptions of herders not only demonstrate their ability to view the changing climate holistically through various indicators but also reflect their fears and concerns. The herders' ability to assess the changing climate probably arises from the long and dynamic human-environment relationship that structures perceptions of climate change (Vedwan and Rhoades 2001). The findings of our survey reinforce the empirical evidence of several studies that warming in the alpine environment causes erratic weather patterns, increasing glacial melt, and reducing snow cover ( The perceived drying up of water sources is consistent with the findings of Chaudhary and Bawa (2011). Yak herders associate declining water availability with drying up of water sources due to increasing frequency of drought. This conforms with the projection by Bhutan's Gross National Happiness Commission (2011) that temperature change will influence overall rainfall patterns and increase droughts. Perceived decline in water availability likely indicates drinking water shortages, which are a prominent effect of global warming (Sudmeier-Rieux et al 2012). Decline in water availability could also be due to changes in seasonality and increases in variability, increases in demand, and increases in temperature and evapotranspiration.

Perceived impact of warming on vegetation
Alpine vegetation is perceived to have undergone considerable changes, including growing faster than the normal pace because of warming. Study participants stated that the impacts of climate change have included new vegetation growth on formerly barren land and rapid encroachment on meadows by rhododendron shrubs. The perceived changes in vegetation growth conform to reports that warming stimulates the growth of herbaceous and woody plant species (Bazzaz 1996). The perception of encroachment on meadows by rhododendrons indicates both horizontal and vertical movement by this species. It explains the decline in grassland size, availability, and quality, as perceived by yak herders. It is widely accepted that, with rising temperature, alpine plant species shift their elevational ranges to stay within the most favorable climatic zones and habitats. Aryal et al (2014) found a decrease in the size of agricultural fields, grassland, and forest due to shrub encroachment in the alpine region of Nepal. Studies conducted elsewhere have also highlighted denser and higher shrub infestation due to climate warming (Tape et al 2006;Hudson and Henry 2009;Brandt et al 2013). In northeastern Yunnan in Himalayan China, about 39% of alpine meadows are reported to have been encroached on by shrubs from 1990 to 2009 (Brandt et al 2013). In Bhutan, an estimated 22% of the grazing area has been lost to shrub encroachment from 1998 to 2008 (Chophyel 2009).
Increased growth of alpine vegetation could reduce soil erosion, improve water storage and quality, and provide hydrological benefits to the hydropower industry. However, in terms of herders' livelihoods and conservation, shrub encroachment appears less desirable. Alpine meadows sustain yak farming, and the expansion of shrubby vegetation would reduce meadows' size and carrying capacity, which would exacerbate the existing forage shortage. Thus, shrub encroachment may pose a major threat to herders' livelihoods, as well as to the many endemic plants and animal species living in alpine meadows. Bush encroachment is reported to alter habitat structure and decrease herbaceous production and may threaten livestock production and natural resource conservation (O'Connor and Crow 1999).

Perceived impact of warming on herding practices and livelihoods
Because of changes in the alpine environment caused by warming, herding is becoming increasingly difficult. This is reflected by the decline in animal health, increasing difficulty of transhumant migration, and increasing discomfort of migrating yaks. It is also reflected in changes to the time of year at which migration takes place. According to study participants, such changes show the sensitivity of yak to high temperatures. Nardone et al (2010) reported that livestock experience physical discomfort at high temperatures. Decline in overall livestock health is probably explained by the fact that the rise in temperature causes physiological stress in yak and leads to reduced feed intake and altered physiological functions and impaired health (Beede and Collier 1986). However, herders were divided on the increased prevalence of gid disease, which causes high mortality in yaks. Although the rangeland ecology in northern Bhutan seems to be undergoing a change unfavorable to yak farming, warming has not contributed to rural outmigration of yak herders.
Most yak herders have been affected by warming, but few have lost their animals to flash floods and landslides. Although a detailed assessment of yak mortality due to predation was not covered by this study, respondents revealed during informal discussions that predators have increased in number and that they have sighted new species of wild animals. Survey respondents mentioned a recent increase in predation by snow leopards near village settlements. The ascent of the tree line has most likely reduced the size of the alpine area and thus the habitat of snow leopards (Lovari et al 2013), which has probably increased their presence near grazing fields and thus their encounters with and predation of livestock. The ascent of the tree line may also have increased the habitat of other predators that previously remained at lower elevations. Another possible explanation is that, because of shrub encroachment, grasses are less abundant, and livestock might have moved in search of forage to more distant places where they are more vulnerable to predators. Livestock predation adversely impacts local livelihoods (Aryal et al 2014).
Warming is also perceived to have resulted in a decline in milk production, which is explained by the reduced size, productivity, and quality of grasslands. Declining milk production and predation pose major challenges to yak farming. However, warming has not resulted in a decline in annual income for the majority of herders. Alternative income sources-in particular, the collection and sale of Cordyceps (caterpillar fungus) (Wangchuk and Wangdi 2015)-appear to have made up for the losses from yak farming.

Conclusions
This study investigated the perceptions of yak herders in the alpine region of northern Bhutan. These perceptions provide critical signs of rising temperature and herders' vulnerability to climate change. The yak herders' perceptions are consistent with the findings of empirical studies, except on the issue of water availability. Warming is expected to cause discomfort to yaks and make migration and herding more difficult, and might reduce grasslands through shrub encroachment. As an adaptation strategy, herders may have to reduce herd size, which might affect their livelihoods. Herders are likely to confront increasing difficulties in coping with the changing climate and sustaining their livelihoods, which will compel them to seek alternative economic opportunities. Challenges lie ahead in designing interventions to make yak farming sustainable and attractive under changing environmental conditions.