Dietary habits of pastoralists on the Tibetan plateau are influenced by remoteness and economic status

Abstract

In general, dietary habits of pastoralists are livestock-derived, but are also influenced by external food sources under globalization. We hypothesized that dietary habits of pastoralists would be influenced by their remoteness, and that changes from the traditional diet would result in deviations in the local ecological chain. To test this hypothesis, we determined the δ¹³C and δ¹⁵N values of soil, plants, and hair of animals and pastoralists (n = 885). The δ¹³C value in human hair reflects the proportions of protein originating from C₃ and C₄ plants; whereas, the δ¹⁵N value reflects the proportions of protein derived from plants and animals, with higher values indicating a greater consumption of meat. The isotopic signatures enabled us to estimate the variation in dietary habits of pastoralists across a socio-economic gradient of easily accessible to remote areas on the Tibetan plateau, and to determine the trophic transfer of the isotopes along an ecological chain. The trophic magnification factor (TMF) evaluated the trophic transfer of δ¹⁵N in the soil-plants-animals-pastoralists ecological chain. The high δ¹⁵N values in soil and plants were not recovered in animals and pastoralists in easily accessible and developed areas, indicating the use of external feed and food resources, and that they deviated from the ecological chain. The mean δ¹³C (-22.0 ‰) and δ¹⁵N values (6.9 ‰) of pastoralists indicated diets consisting mainly of local C₃ plants and animal products. However, pastoralists in remote areas relied more on meat protein and on the local ecological chain than pastoralists in easily accessible areas, as their δ¹⁵N values and trophic magnification factor of δ¹⁵N in the ecological chain were greater. In addition to remoteness, per capita GDP influenced dietary changes in pastoralists, with richer pastoralists consuming more external food. We concluded that dietary changes of pastoralists in the easily accessible areas were due to external food resources and alterations in the local ecological chain of animals and plant-based foods available to the pastoralists.

Keywords: Carbon isotope; Ecological chain; Geographical divergence; Nitrogen isotope.