TY - JOUR A1 - Rikani, Albano A1 - Schewe, Jacob T1 - Global bilateral migration projections accounting for diasporas, transit and return flows, and poverty constraints JF - Demographic research N2 - BACKGROUND Anticipating changes in international migration patterns is useful for demographic studies and for designing policies that support the well-being of those involved. Existing forecasting methods do not account for a number of stylized facts that emerge from large-scale migration observations and theories: existing migrant communities - diasporas - act to lower migration costs and thereby provide a mechanism of self-amplification; return migration and transit migration are important components of global migration flows; and poverty constrains emigration. OBJECTIVE Here we present hindcasts and future projections of international migration that explicitly account for these nonlinear features. METHODS We develop a dynamic model that simulates migration flows by origin, destination, and place of birth. We calibrate the model using recently constructed global datasets of bilateral migration. RESULTS We show that the model reproduces past patterns and trends well based only on initial migrant stocks and changes in national incomes. We then project migration flows under future scenarios of global socioeconomic development. CONCLUSIONS Different assumptions about income levels and between-country inequality lead to markedly different migration trajectories, with migration flows either converging towards net zero if incomes in presently poor countries catch up with the rest of the world; or remaining high or even rising throughout the 21st century if economic development is slower and more unequal. Importantly, diasporas induce significant inertia and sizable return migration flows. KW - diaspora KW - international migration KW - migration transition KW - return migration KW - simulation model KW - transit migration Y1 - 2021 U6 - https://doi.org/10.4054/DemRes.2021.45.4 SN - 2363-7064 VL - 45 SP - 87 EP - 140 PB - Max Planck Inst. for Demographic Research CY - Rostock ER - TY - JOUR A1 - Geissler, Katja A1 - Fiedler, Sebastian A1 - Ni, Jian A1 - Herzschuh, Ulrike A1 - Jeltsch, Florian T1 - Combined effects of grazing and climate warming drive shrub dominance on the Tibetan Plateau JF - The Rangeland journal N2 - Encroachment of shrubs into the unique pastoral grassland ecosystems of the Tibetan Plateau has significant impact on ecosystem services, especially forage production. We developed a process-based ecohydrological model to identify the relative importance of the main drivers of shrub encroachment for the alpine meadows within the Qinghai province. Specifically, we explored the effects of summer livestock grazing (intensity and type of livestock) together with the effects of climate warming, including interactions between herbaceous and woody vegetation and feedback loops between soil, water and vegetation. Under current climatic conditions and a traditional herd composition, an increasing grazing intensity above a threshold value of 0.32 +/- 0.10 large stock units (LSU) ha(-1) day(-1) changes the vegetation composition from herbaceous towards a woody and bare soil dominated system. Very high grazing intensity (above 0.8 LSU ha(-1) day(-1)) leads to a complete loss of any vegetation. Under warmer conditions, the vegetation showed a higher resilience against livestock farming. This resilience is enhanced when the herd has a higher browser : grazer ratio. A cooler climate has a shrub encroaching effect, whereas warmer conditions increase the cover of the herbaceous vegetation. This effect was primarily due to season length and an accompanied competitive loss of slower growing shrubs, rather than evaporative water loss leading to less soil water in deeper soil layers for deeper rooting shrubs. If climate warming is driving current shrub encroachment, we conclude it is only indirectly so. It would be manifest by an advancing shrubline and could be regarded as a climatic escape of specific shrub species such as Potentilla fruticosa. Under the recent high intensity of grazing, only herding by more browsing animals can potentially prevent both shrub encroachment and the complete loss of herbaceous vegetation. KW - alpine grassland degradation KW - herd composition KW - rangeland management KW - shrub encroachment KW - shrubline KW - simulation model Y1 - 2019 U6 - https://doi.org/10.1071/RJ19027 SN - 1036-9872 SN - 1834-7541 VL - 41 IS - 5 SP - 425 EP - 439 PB - CSIRO Publishing CY - Collingwood ER -