## 4 Discussion and Conclusions
Our research found that the overwhelmingly strong trend in significant directional persistence was positive for much of the region, i.e., that by using NDVI as a measure of vegetation greenness, the years 2005-2016 were greener or had higher NDVI relative to the benchmark years in the earlier part of the 21 st century. This greening is not necessarily a positive change biologically. It is also possible that this could be a type of shrub encroachment (correlated local factors, such as increased herbivory, or global factors, such as increased carbon dioxide) or this greening could be from invasive species [55]. This is why it is important for local scale, fieldwork-basedstudies, in conjunction with these national and macro-scale analyses, to better understand the local landscape dynamics. The advantage of using the metric of directional persistence is that it provides a robust and statistically driven foundation for more in-depth analysis. Unlike more traditional approaches, this does not just describe the conversion of the system, but gives us more information on vegetation trends over time that could be further broken down into monthly time steps if desired. Directional persistence can be used to understand vegetation dynamics and, from this, we can highlight areas of vulnerability based on patterns of positive and negative persistence over time. Another major advantage of this technique is that each pixel has a statistical significance that the user can specify. This rigorous and innovative approach is an important contribution to the study of vegetated systems globally, as it can be used for any vegetation system. One limitation of this metric is that it quantifies the amount of vegetation rather than type of vegetation. In these savanna systems, determining the grass-shrub-tree components is important for further quantifying degradation. Therefore, these products may be more difficult for local managers to utilize, and more in-depth localized field-based studies should be carried out. In conclusion, from this study we can determine that, of the variables we included, precipitation, human population, and transfrontier conservation areas are the most important factors of vegetation health in these savanna parks and buffers. For the future, refining rainfall data and including burn area index data as a proxy for fire occurrence may improve these models further. Another variable that is much more difficult to quantify, but may improve models in the future, is that of herbivory on the landscape. Future research will work to incorporate these additional factors of savanna park vegetation. Across different park sizes and seasons, but especially during rainy seasons, positive persistence is the dominant trend. Positive persistence is higher inside of parks than buffers, and negative persistence tends to be higher inside the buffer zones than in the parks. This suggests that parks are functioning as designed from the perspective that they are important stable features in an increasingly dynamic world. These protected areas are important for conserving biodiversity, which helps to promote tourism and increase the socio-economic activity in this region, which is particularly important to communities who have been largely dependent on subsistence agriculture [56]. While these findings are a regionally important tool, managers should also continue to monitor vegetation at the more localized scale, and their expertise and field-based, site-specific knowledge is of paramount importance. The use of both types of data in concert will provide park managers and conservationists with a very powerful set of analysis tools, both now and in the future. Conceptualization, H.H., J.S., and B.C. ; methodology, J.S. and H.H. ; software, R.K. and E.B. ; formal analysis, H.H., R.K., C.M. and E.B. ; data curation, R.K., H.H., and E.B. ; writing--original draft preparation, H.H. J.S. and C.M; writing--review and editing, J.S., R.K., H.H., E.B., C.M., and B.C. All authors have read and agreed to the published version of the manuscript.