Risk and vulnerability of Mongolian grasslands to climate change and grazing

Robust changes in climatic hazards, including droughts, heatwaves and dust storms, are evident in many parts of the world and they are expected to increase in magnitude and frequency in the future. At the same time, socio-ecological damage from climate-related disasters has increased worldwide, including the Eurasian steppes, notably Mongolian grasslands (MGs), which occur in arid and harsh cold climate and still support traditional nomadic livelihood and culture through the food supply, and agricultural and ecosystem services. In the 2000s, increasing climate disasters (droughts combined with anomalously harsh winters (dzuds in Mongolian), and dust storms) resulted in massive livestock deaths, causing socioeconomic stagnation. In this context, assessments of risk and vulnerability of MGs to climate change and grazing may support disaster risk management by helping to identify hazard risk hotspots, allowing herders in risky areas to be prepared for events, and to mitigate the future potential impacts. Here, we examine the risk and vulnerability of the MG ecosystem to droughts at the national-level during a 40-year (1976–2015) using simulations of a gridded process-based ecosystem model by contrasting the recent (1996–2015) and past (1976–1995) 20-years. In general, the model realistically simulates temporal and spatial variations of vegetation biomass and soil moisture that were captured by field and satellite observations during 2000–2015 over MGs. We apply a probabilistic risk analysis in which risk is the product of the probability of hazardous drought during June-August and ecosystem vulnerability. Results reveal that during 1976–2015, increases in droughts with rapid warming and slight drying occurred over MGs, particularly in the recent 20-year, accompanied by ever-increasing grazing intensity, which together resulted in declining trends in grassland productivity. During the recent 20-year, the risk of drought to productivity slightly increased over extended areas in MGs compared to the past 20-year. The increase in the risk to MGs predominantly caused by the climate change-induced increase in the probability of hazardous drought, and less by the vulnerability. Regionally, recent droughts modify the risk to grasslands particularly in northcentral and northeast Mongolia. Given the benefits of MGs for both ecosystem services and socio-economic consequences, recent increases in drought hazards and associated risk to MGs signal an urgent need to implement drought management policies that sustain MGs.