Though well-positioned geographically to benefit from China's Silk Road Economic Belt initiative, Central Asia nevertheless suffers from a fragile ecological environment. Therefore, it is crucially important for the five Central Asian countries of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan to achieve sustainable development of their respective social economies and ecological environments through the evaluation of their ecological security. This paper applies the modified emergy ecological footprint (EEF) model to optimize the traditional ecological footprint model by analyzing and evaluating the ecological security of Central Asia during the time frame of 1992-2014. The paper will also use the autoregressive integrated moving average (ARIMA) model to forecast changes which might occur during 2020-2025. The results indicate that the EEF mainly decreased from 1992 to 1998 but then gradually increased from 1999 onwards, with Kazakhstan and Turkmenistan showing the largest change rates of 3.93% and 2.77%, respectively, from 1999 to 2014. The highest EEF occurred in Turkmenistan (20.27 hm(2)/cap), followed by Kazakhstan (19.19 hm(2)/cap), with Tajikistan registering the lowest (2.96 hm(2)/cap). In Kazakhstan, Turkmenistan and Uzbekistan, fossil energy consumption footprints contributed the most to total EEFs, at 38.34%, 57.06% and 46.52%, respectively, while grassland (51.52%) and building land (50.49%) contributed the most to Kyrgyzstan's and Tajikistan's total EEFs, respectively. The emergy ecological carrying capacity (EEC) largely decreased in all five Central Asian countries, with the largest decrease occurring in Turkmenistan at annual average change rates of -1.93%. The highest EEC was in Kazakhstan (30.36 hm(2)/cap), followed by Turkmenistan (15.85 hm(2)/cap), while the lowest occurred in Uzbekistan (2.86 hm(2)/cap). Additionally, during the period under study, the ecological surpluses and deficits in Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan were 11.18, 2.21, 2.04, -4.42 and -7.57 hm(2)/cap, respectively, with the largest ecological deficit occurring in Uzbekistan. There was also a persistent rise in ecological pressure in all five countries, especially in Turkmenistan and Uzbekistan. Furthermore, the ARIMA model forecasts that Kazakhstan, Kyrgyzstan and Tajikistan will change from ecological surpluses to ecological deficits from 2020 onwards, and that the ecological pressure grades for these countries will rise to level 3 (relatively unsafe). Turkmenistan and Uzbekistan are forecast to be at level 1 (at risk). The significance of this research is optimizing the ecological footprint model and applying it in Central Asia for the first time. The work also quantitatively investigates Central Asia's ecological footprint and ecological carrying capacity on both a national and regional basis and evaluates the ecological security of each country. Overall, this research not only provides guidance for decision-makers to develop sustainable strategies in Central Asia, but also serves as a scientific reference for other arid regions to pursue ecological security and sustainable development. (C) 2019 Elsevier Ltd. All rights reserved.
