Effects of climate change on vulnerabilities of rangeland ecosystems over permafrost regions of Mongolia
Mongolia is a country vulnerable to climate change because a significant part of the country’s population depends on climate-dependent sectors for livelihood, particularly on pastoral livestock husbandry. Historical records show that the annual mean air temperature in Mongolia has increased by 2.1°C since 1940. Several IPCC AR5 related models predicted that further warming will continue if emissions of greenhouse gases continue. Previous studies focused on the effects of climate changes on permafrost, water resources and grassland production separately, rare of them on the interactional mechanisms on aboveground and belowground feedbacks in the terrestrial ecosystems. In this study, we have established an aboveground and belowground observation system to investigate the mechanism among the permafrost degradation, surface water stress or drought, and grassland productivities and developed an ecosystem model to evaluate both environmental carrying capacities and vulnerabilities over permafrost regions in Mongolia, approximately 60% of total territory.
It was found that: (1) the rise in air temperature is predicted to cause increased rates of evapotranspiration, which will further contribute to an increase in the drought intensity. (b) The climate warming might cause an increase in active layer thickness and the degradation of permafrost both in its thickness and distribution area. (c) The increase of evapotranspiration and the degradation of permafrost will further make effects on surface water deficit and soil water condition, and finally cause the decrease in environmental carrying capacities of rangeland ecosystems. (d) The water loss from the bottom of active layer due to drought might accelerate the degradation of permafrost, and grassland degradation caused by overgrazing could facilitate permafrost degradation. Finally, we come to a conclusion that with climate warming, rangeland ecosystems in the permafrost region of Mongolia would become more vulnerable if drought and overgrazing occurred simultaneously, and an insufficient water supply from the soil due to permafrost degradation is believed to be associated with poor carrying capacities and is highly likely to increase the damage to livestock when natural disaster, i.e. a zud occurs.
This study is supported by a policy contribution-oriented research project (No. 2E-1203: Vulnerability Assessment and Adaptation Strategies for Permafrost Regions in Mongolia) of the Environment Research and Technology Development Fund, Ministry of the Environment, Government of Japan.