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Open and analysis-ready data, as well as methodological and technical advancements have resulted in an unprecedented capability for observing the Earth’s land surfaces. Over 10 years ago, Landsat time series analyses were inevitably limited to a few expensive images from carefully selected acquisition dates. Yet, such a static selection may have introduced uncertainties when spatial or inter-annual variability in seasonal vegetation growth were large. As seminal pre-open-data-era papers are still heavily cited, variations of their workflows are still widely used, too. Thus, here we quantitatively assessed the level of agreement between an approach using carefully selected images and a state-of-the-art analysis that uses all available images. We reproduced a representative case study from the year 2003 that for the first time used annual Landsat time series to assess long-term vegetation dynamics in a semi-arid Mediterranean ecosystem in Crete, Greece. We replicated this assessment using all available data paired with a time series method based on land surface phenology metrics. Results differed fundamentally because the volatile timing of statically selected images relative to the phenological cycle introduced systematic uncertainty. We further applied lessons learned to arrive at a more nuanced and information-enriched vegetation dynamics description by decomposing vegetation cover into woody and herbaceous components, followed by a syndrome-based classification of change and trend parameters. This allowed for a more reliable interpretation of vegetation changes and even permitted us to disentangle certain land-use change processes with opposite trajectories in the vegetation components that were not observable when solely analyzing total vegetation cover. The long-term budget of net cover change revealed that vegetation cover of both components has increased at large and that this process was mainly driven by gradual processes. We conclude that study designs based on static image selection strategies should be critically evaluated in the light of current data availability, analytical capabilities, and with regards to the ecosystem under investigation. We recommend using all available data and taking advantage of phenology-based approaches that remove the selection bias and hence reduce uncertainties in results.
All-embracing human activities have transformed one-third to one-half of the Earth’s land surface. There is a strong correlation of human well-being with ecosystem function, including poverty alleviation programs as well as enhancements of the health sector. To assess and evaluate the progress and outcome of initiatives stringent periodic observation is necessary. The presented approach combines the strengths of remote sensing and GIS analysis with social research applications. The Bach Ma National Park as an area under investigation was designated as protected area in 1991 and extended in 2008. The national park is uninhabited, but in the surrounding buffer zones approximately 62000 to 79000 people live in rural areas and in mostly impoverished conditions. The comprehensive nature conservation efforts of the Vietnamese Government during the last two decades has led to growing forest coverage of both plantation and natural forests. Nevertheless, the decreasing biodiversity and ongoing illegal logging and hunting activities in the national park are seen as major threats to conservation initiatives in the future. The remote sensing component consists of an analysis of a time series of Landsat images with seven steps ranging from 1973 to 2010. The resulting land cover analysis had 13 different classes. The accuracy assessment revealed an overall accuracy ranging from 84 to 90%. The basis for the second monitoring component was the Landsat images. A total of 25 different landscape metrics on the landscape, class, and patch level were calculated by FRAGSTATS. The third monitoring component is itself divided into two parts. This part consists of a qualitative social research study with 26 expert interviews. The second part consists of 61 standardized questionnaires and an evaluation by SPSS. The assessment reveals a more or less stable forest cover, but with a considerable degradation process during the last four decades. Urban areas outside of the national park have increased in size considerably. For dense and medium forest patches an increasing fragmentation and isolation of patches was observed. Patches of natural forests and habitats of thousands of species have declined dramatically, a trend that is related to a decreasing core area characterised by its undisturbed conditions. The Landsat images and landscape metrics reveal the major differences between the national park and surrounding areas. Despite extensive alterations near the border, remaining forest patches in the national park are still bigger and less fragmented. Nevertheless, the third monitoring component revealed undiscovered changes in the forest beyond the possibilities of used images and metrics. It includes illegal logging and hunting activities. Non-timber forest products are similar to faunistic species collected for both the subsistence of the local residents and associated markets as important sources of income. Based on this bisection, local residents as well as certain strangers are responsible for the activities in the forest. The plan of national park management is to intensify existing monitoring and patrolling in the forest to limit the exploitation and impact in relevant zones. Furthermore, the importance of a network of protected areas has attracted increasing attention. The assessment of the questionnaires reveals that deforestation and also reforestation were the key aspects of historical land cover change. Additionally, for the local residents the conversion of forests into arable land as income alternative is of major importance. Capacity development is not only one priority of the Bach Ma management but also of the international community for all of Vietnam. The tourism industry, one of the most promising opportunities of recent years, stands to support both national park management as well as the local residents. For local residents the extraction of non-timber forest products is an essential portion of the income. The current pilot policy 126/QD-TTg in the extension zone of the national park and research on an appropriate sharing mechanism is of the utmost importance. The established and presented monitoring components are cost-effective and can be used to regularly assess the land cover change of a protected area. They can be implemented together or individually into existing monitoring schemes. A smart combination of pre-existing datasets is necessary to overcome the inconsequential amount of money for monitoring procedures. Supplemented by socio-economic monitoring and the demands as well as impacts of human activity need to be integrated. These extensive requirements for prospective monitoring are only feasible with comprehensive and reliable collaborations.