Natural and human dimensions of environmental change in the proximal reaches of Botswana's Okavango Delta

Abstract

Though wetlands are vital for the proper functioning of terrestrial ecosystems and provisioning of a wide range of goods and services, their sustainability is being threatened by inappropriate human resource use practices due to our limited understanding of how these systems operate and lack of appropriately informed interventions. We attempt to address these limitations by using historical CORONA photographs of 1967, Landsat imagery of 1989, 1994 and 2001 and information from the literature to investigate the role of natural and human factors in influencing the direction of environmental change in the proximal reaches of Botswana's Okavango Delta. Results of this investigation point to fragmentation of natural habitats, localised degradation of areas close to perennial water supplies, significant increase in woody cover, significant decrease in open grassland, increase in scrub and shrubs, deterioration in the quality of grazing and depletion of specific woody species. With the direction of change pointing to persistent decrease in the environment's supporting potentials, there is urgent need to adopt intervention strategies potentially capable of enhancing sustainable utilisation of natural resources in this sub‐region.

A nested hierarchical perspective to enhance interpretations and communication in fluvial geomorphology for use in water resources management: Lessons from the Okavango Delta, Botswana

“…In the Okavango catchment, for instance, there is a current, pressing need to understand the impacts of climate change, land use changes and water resource developments (e.g., dams, weirs, extensive extraction) in Angola, Namibia and Botswana on total annual flow volumes, seasonal flow variability, water quality, and sediment and nutrient loads in the Delta (Government of Denmark and Republic of Botswana, ; Kgathi et al., ; Pröpper & Gröngröft, ). These natural and human drivers, operating in large part at the catchment and landscape unit scales, influence the reach, site and geomorphic unit scale relationships between flow, sediment, vegetation and other biota that underpin the ecological diversity and other ecosystem services in the Delta (Hamandawana & Chanda, ; Jansen & Madzwamuse, ; Mendelsohn et al., ). Analyses by Andersson et al.…”

“…Indeed, detailed 3D hierarchies could be produced for each of the catchment, landscape unit, reach, site and geomorphic unit scales to visualise geomorphic changes over time, as well as the varying timeframes (millions of years to days) over which these changes occur. This approach could complement and extend previous approaches adopted by studies in and around the Delta that have investigated landscape and land cover dynamics but by necessity have had to rely on static imagery at a restricted range of spatial scales for temporal analysis (e.g., Hamandawana & Chanda, 2010).…”

“…In the Okavango catchment, for instance, there is a current, pressing need to understand the impacts of climate change, land use changes and water resource developments (e.g., dams, weirs, extensive extraction) in Angola, Namibia and Botswana on total annual flow volumes, seasonal flow variability, water quality, and sediment and nutrient loads in the Delta (Government of Denmark and Republic of Botswana, 2006;Kgathi et al, 2006;Pr€ opper & Gr€ ongr€ oft, 2015). These natural and human drivers, operating in large part at the catchment and landscape unit scales, influence the reach, site and geomorphic unit scale relationships between flow, sediment, vegetation and other biota that underpin the ecological diversity and other ecosystem services in the Delta (Hamandawana & Chanda, 2010;Jansen & Madzwamuse, 2003;Mendelsohn et al, 2010). Analyses by Andersson et al (2006) and Pr€ opper and Gr€ ongr€ oft (2015) of the impacts of climate change and development scenarios on the Okavango catchment indicate that in the long term, climate change will considerably reduce mean annual flow and increase flow variability, but in the short to medium term, the impacts of potential increases in irrigated agriculture, hydropower dam building and flow diversion are likely to be much more marked.…”

Australian forested wetlands under climate change: collapse or proliferation?

“…Tree cover expansion in large wetland complexes in Australia is consistent with trends in wetlands across the globe, covering a wide range of climatic, biogeographical and geomorphological settings. Tree cover expansion has been documented as replacing wetland grasslands in many of the world's most iconic wetlands, including the Pantanal (Barbosa da Silva et al 2016;Arieira et al 2018), the Florida Everglades (Martin et al 2009) and the Okavango Delta, where 27% of open grassland has been replaced by mixed woodland (Hamandawana and Chanda 2010). High-latitude and alpine sedgeland bogs and fens have also been subject to woody encroachment (Elmendorf et al 2012), including on the Qinghai-Tibet plateau (Brandt et al 2013) and in Alaska (Berg et al 2009), Canada (Favreau et al 2019), the US (Stine et al 2011), Europe (Middleton et al 2006) and Tasmania, Australia (Bowman et al 2008).…”

Southern African Geomorphology

“…The so-called Keyhole satellite series produced photographic data at a resolution of 7.5 to 1.8 m which is not only available to the public, but scanned and geocoded negatives can produce panchromatic high resolution data comparable to the latest sensors in orbit. The data are surprisingly global in extent and, for example, facilitated the production of a detailed image mosaic of the Okavango Delta and its channels (see Figure 14.9, Hamandawana et al, 2007) and high resolution monitoring of land use change and impacts in the region (Hamandawana and Chanda, 2010). For smaller, more site-specific change studies, aerial photography can be equally useful and extends considerably further back in time.…”