[1] This paper provides a review of stratosphere-troposphere exchange (STE), with a focus on processes in the extratropics. It also addresses the relevance of STE for tropospheric chemistry, particularly its influence on the oxidative capacity of the troposphere. After summarizing the current state of knowledge, the objectives of the project Influence of Stratosphere-Troposphere Exchange in a Changing Climate on Atmospheric Transport and Oxidation Capacity (STACCATO), recently funded by the European Union, are outlined. Several papers in this Journal of Geophysical ResearchAtmospheres special section present the results of this project, of which this paper gives an overview. STACCATO developed a new concept of STE in the extratropics, explored the capacities of different types of methods and models to diagnose STE, and identified their various strengths and shortcomings. Extensive measurements were made in central Europe, including the first monitoring over an extended period of time of beryllium-10 ( 10 Be), to provide a suitable database for case studies of stratospheric intrusions and for model validation. Photochemical models were used to examine the impact of STE on tropospheric ozone and the oxidizing capacity of the troposphere. Studies of the present interannual variability of STE and projections into the future were made using reanalysis data and climate models.

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Violence in the Rakhine State of Myanmar has led to a humanitarian crisis as Rohingya people flee across the border to Bangladesh (1). With the rapid influx of nearly 700,000 arrivals between August 2017 and the beginning of 2018, the Bangladeshi city of Cox's Bazar is now under severe strain from a Rohingya population of almost 1 million, one of the largest concentrations of refugees in the world (2). The crisis seized global attention, and the international response was rapidly escalated to a Level 3 emergency (3). In addition to the humanitarian challenges, the mass influx of Rohingya refugees has resulted in environmental degradation both within the refugee camps and in the surrounding areas (2). The expansion of existing campsites has led to more than 2000 ha of forest loss in the Cox's Bazar region (4). Expansion of the old Kutupalong camp blocked the only corridor used by the globally endangered Asian elephant as a migration route and trapped about 45 elephants in the western side of the camp (5). The latest Rohingya settlement has also amplified humanelephant conflict in the area, with 13 human casualties so far (6). The remaining elephant habitat is under severe pressure from uncontrolled fuelwood collection in the forest (7). The pressure on forests has caused tensions with local

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