Utilizing Multiple Lines of Evidence to Determine Landscape Degradation within Protected Area Landscapes: A Case Study of Chobe National Park, Botswana from 1982 to 2011

Abstract

Abstract:The savannas of Southern Africa are an important dryland ecosystem as they cover up to 54% of the landscape and support a rich variety of biodiversity. This paper evaluates landscape change in savanna vegetation along Chobe Riverfront within Chobe National Park Botswana, from 1982 to 2011 to understand what change may be occurring in land cover. Classifying land cover in savanna environments is challenging because the vegetation spectral signatures are similar across distinct vegetation covers. With vegetation species and even structural groups having similar signatures in multispectral imagery difficulties exist in making discrete classifications in such landscapes. To address this issue, a Random Forest classification algorithm was applied to predict land-cover classes. Additionally, time series vegetation indices were used to support the findings of the discrete land cover classification. Results indicate that a landscape level vegetation shift has occurred across the Chobe Riverfront, with results highlighting a shift in land cover towards more woody vegetation. This represents a degradation of vegetation cover within this savanna landscape environment, largely due to an increasing number of elephants and other herbivores utilizing the Riverfront. The forested area along roads at a further distance from the River has also had a loss of percent cover. The continuous analysis during 1982-2011, utilizing monthly AVHRR (Advanced Very High Resolution Radiometer) NDVI (Normalized Difference Vegetation Index) values, also verifies this change in amount of vegetation is a continuous and ongoing process in this region. This study provides land use planners and managers with a more reliable, efficient and relatively inexpensive tool for analyzing land-cover change across these highly sensitive regions, and highlights the usefulness of a Random Forest classification in conjunction with time series analysis for monitoring savanna landscapes.

A Healthy Park Needs Healthy Vegetation: The Story of Gorongosa National Park in the 21st Century

“…Jung et al (2010) [11] point to a global decline in precipitation leading to reduced soil moisture and evapotranspiration. This study found some decrease in precipitation in this region of southeastern Africa during the 21st century [10,44], linked to a decline in vegetation health [10][11][12], [52,53]. The observed decline in vegetation health (using NDVI as a proxy) further strengthens the link between vegetation biomass in savannas and its main driver, precipitation [5,[7][8][9]12,[20][21][22][23][24][25][26].…”

“…Therefore, this study provides a local exception to the literature on global greening [53][54][55][56][57][58][59][60]. de These results also highlight the importance of understanding specific vegetation types that make up the heterogeneous savannas [44], whose impacts may otherwise have been masked by contrasting trends. The various rates of decline of NDVI across differing vegetation types underline the importance of understanding the vegetation structural groups within LG and MG [31,[65][66][67][68].…”

“…Bush encroachment is a type of degradation that results in an increase in lower quality short woody plants [12,44,45]. Important drivers of savanna vegetation and therefore potential degradation include, decline in precipitation (already seen here), changes in herbivory (increases to a certain population level may mitigate degradation, but beyond that level, may actually exacerbate it), decreased fire frequency, and humans [4][5][6][7][42][43][44][45][46][47]. Under continued climate change and rewilding, these systems will need to be carefully monitored for further degradation [15,48].…”

Land Cover Change in Northern Botswana: The Influence of Climate, Fire, and Elephants on Semi-Arid Savanna Woodlands

“…In Southern Africa, land degradation is frequently associated with changes in vegetation structure, particularly the loss of mature trees and encroachment of low-growing shrub species into savannas [33][34][35][36][37]. While expansion of cropland, livestock grazing, and urbanizing land use are frequently cited as driving LCC in sub-Saharan Africa [38][39][40], in northern Botswana wildlife and fire disturbance, together with human encroachment and climate change, are identified as the primary threats to woodland resources [41].…”

Chobe district integrated land use plan

“…There is some evidence in woodlands not directly near the Chobe river front that, as in other parts of Africa, tree cover in part of the area may actually be increasing (Herrero et al 2016, Kalwij et al 2008. The generally held notion that tree cover has been decreasing is therefore mostly applicable to the vegetation close to the Chobe river front and along the Linyanti, and in some places where timber extraction has taken place in the 80's and 90's.…”