An Evaluation of Vegetation Health in and around Southern African National Parks during the 21st Century (2000–2016)

Abstract

Roughly 65% of the African continent is classified as savanna. Such regions are of critical importance given their high levels of biological productivity, role in the carbon cycle, structural differences, and support of large human populations. Across southern Africa there are 79 national parks within savanna landscapes. Understanding trends and factors of vegetation health in these parks is critical for proper management and sustainability. This research strives to understand factors and trends in vegetation health from 2000 to 2016 in and around the 79 national parks across southern Africa. A backward stepwise regression was used to understand the factors (e.g., precipitation, population density, and presence of transfrontier conservation areas) affecting the normalized difference vegetation index (NDVI) during the 21st century. There was a statistically significant positive (p < 0.05) relationship between mean annual precipitation and NDVI, and a significant negative relationship between population density and NDVI. To monitor vegetation trends in and around the parks, directional persistence, a seasonal NDVI time series-based trend analysis, was used. Directional persistence is the net accumulation of directional change in NDVI over time in a given period relative to a fixed benchmarked period. Parks and buffer zones across size classes were compared to examine differences in vegetation health. There was an overwhelmingly positive trend throughout. Additionally, national parks, overall, had higher amounts of positive persistence and lower amounts of negative persistence than the surrounding buffer zones. Having higher positive persistence inside of parks indicates that they are functioning favorably relative to the buffer zones in terms of vegetation resilience. This is an important finding for park managers and conservation overall in Southern Africa.

Vegetation Dynamics and Climatological Drivers in Ethiopia at the Turn of the Century

“…With a sample size of 12 years being compared to the baseline, the critical value of +/−8 is used to distinguish pixels with statistically significant DP, using a two-tailed test and α level of 0.05. That means a pixel must observe ten or more years where NDVI is higher (lower) than the baseline to be considered significant cumulative greening (browning) [57]. This methodology enables spatial and temporal specificity by using values at a pixel level and can detect nonlinear trends, which have been noted as an important factor when examining long-term NDVI [13,58].…”

Precipitation, vegetation productivity, and human impacts control home range size of elephants in dryland systems in northern Namibia

“…There was especially high fidelity to Etosha and Khaudum by elephants, which points to the success of these parks in meeting elephants' needs. Vegetation productivity and persistence are higher in national parks compared with buffer areas throughout Southern Africa (Herrero et al, 2016 ). The persistence of vegetation, related to restricted human use, may in part explain why elephants remain within national parks as elephants are known to respond strongly to long‐term patterns in productivity (Tsalyuk et al, 2019 ).…”

Spatio-Temporal Mixed Pixel Analysis of Savanna Ecosystems: A Review

“…Because of their large spatial extend and since they are a prime target for conversion from their natural states to agriculture, the provision of rangelands for livestock and subsistence for native populations, majority of the studies have been conducted in the African and South American savannas (Figure 3) [3,5,14,28,30,32,36,38,39,46,47,52,86,95,106,112,114,[116][117][118]129,130,. The African and Southern American savannas have a significant role in vegetation trends as a result of interactions by climate change and increasing carbon dioxide [15].…”

“…About 20% of the world's population live in savannas. Savannas are pivotal and play a crucial role in the global carbon cycle; they store about 15% of the global carbon stock and contribute about 30% to the global terrestrial net primary productivity [2,3]. At continental level, such as in Africa, savannas are critical to wildlife biodiversity and contribute immensely to environmental conservation, economic, and livelihood gains in form of nature-based tourism, food supply, livestock grazing, and firewood for populations who live within these ecosystems [3][4][5].…”