###### Abstract  
With uninterrupted space-based data collection since 1972, Landsat plays a key role in systematic monitoring of the Earth's surface, enabled by an extensive and free, radiometrically consistent, global archive of imagery. Governments and international organizations rely on Landsat time series for monitoring and deriving a systematic understanding of the dynamics of the Earth's surface at a spatial scale relevant to management, scientific inquiry, and policy development. In this study, we identify trends in Landsat-informed change detection studies by surveying 50 years of published applications, processing, and change detection methods. Specifically, a representative database was created resulting in 490 relevant journal articles derived from the Web of Science and Scopus. From these articles, we provide a review of recent developments, opportunities, and trends in Landsat change detection studies. The impact of the Landsat free and open data policy in 2008 is evident in the literature as a turning point in the number and nature of change detection studies. Based upon the search terms used and articles included, average number of Landsat images used in studies increased from 10 images before 2008 to 100,000 images in 2020. The 2008 opening of the Landsat archive resulted in a marked increase in the number of images used per study, typically providing the basis for the other trends in evidence. These key trends include an increase in automated processing, use of analysis-ready data (especially those with atmospheric correction), and use of cloud computing platforms, all over increasing large areas. The nature of change methods has evolved from representative bi-temporal pairs to time series of images capturing dynamics and trends, capable of revealing both gradual and abrupt changes. The result also revealed a greater use of nonparametric classifiers for Landsat change detection analysis. Landsat-9, to be launched in September 2021, in combination with the continued operation of Landsat-8 and integration with Sentinel-2, enhances opportunities for improved monitoring of change over increasingly larger areas with greater intra- and interannual frequency. L 2021 15 July 2021 22 July 2021 202  
deforestation, and agriculture has long-term impacts on the environment in different aspects, including climate, biodiversity, vegetation composition, energy balance, as well as the water and carbon cycle [6; 7]. For example, it has been estimated that approximately one-quarter of cumulative carbon emissions to the atmosphere are related to land use change [8]. To better understand the patterns and impacts of the ever-changing global landscape, information that captures anthropogenic alteration to the Earth's surface in a systematic and quantifiable fashion is of utmost importance [9]. Recent advances in remote sensing tools and techniques enable researchers to detect and monitor such changes. Landsat data has proven particularly useful, given its substantial historical record and continuous data gathering at national [10; 11; 12; 13; 14] and global scales [15; 16; 17]. These data are of value to policymakers and governments who increasingly apply Landsat change detection products in support of national reporting and policy development and to inform international programs [18; 19]. Landsat is currently nearing five decades of uninterrupted satellite imaging [9]. The initiation of the Landsat program was in 1972, providing for some locations an early baseline for change detection that is unique among satellite programs [20]. Later changes to the Landsat data policy in 2008 by the United States Geological Survey (USGS) resulted in free and open access to the global Landsat archive [21]. This policy change lead to a vast increase in global applications, particularly in terms of monitoring changes over large areas [22] and to the formalization of Landsat data in commercial and government programs [23].