Browsing by Author "Archibald, Sally"

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    An analysis of the recent fire regimes in the Angolan catchment of the Okavango Delta, Central Africa
    (SpringerOpen [Commercial Publisher], 2022-07) Van Wilgen, Brian W.; De Klerk, Helen M.; Stellmes, Marion; Archibald, Sally
    Background: This paper presents an analysis of fire regimes in the poorly studied Angolan catchment of the Okavango Delta in Botswana. We used MODIS data to examine the frequency and seasonality of fires over 20 years (from 2000 to 2020) in three dominant vegetation types (miombo woodlands, open woodlands and grasslands, and short closed to open bushlands), and in areas where people were present, and where they were absent. Results: The median fire return intervals for both open woodlands and grasslands and short bushlands were relatively short (1.9 and 2.2 years respectively). In miombo woodlands, fires were less frequent (median return periods of 4.5 years). Human population density had no discernible effect on the fire return intervals, but about 14% of the miombo woodlands experienced no fires over 20 years. Ongoing shifting cultivation within miombo woodlands has led to structural changes and the introduction of fire into this vegetation type where fires were rare or absent in the past. About 12% of the miombo did not burn during the period examined where people were present, whereas close to 20% of the sites remained unburnt where people were absent. This suggests that people did not change the fire return interval in any of the vegetation types studied, but that they altered the amount of the landscape that is flammable in miombo vegetation. Fires occurred between June and September, with a peak in the late dry season (August and September). Conclusions: Historical research indicates that late dry-season fires are detrimental to miombo woodlands, and our analysis suggests that degradation in parts of the catchment has led to the introduction of fire to this previously firefree and fire-sensitive vegetation type. Deforestation of miombo woodlands, and the consequent introduction of fire, is a cause for concern with respect to the ecological stability of the Okavango Delta. Managers should therefore aim to protect the remaining closed-canopy miombo stands from further clearing and to attempt to shift the timing of burns to the early dry season to reduce their intensity.
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    Natural hazards in a changing world : a case for ecosystem-based management
    (PLoS, 2014) Nel, Jeanne L.; Le Maitre, David C.; Nel, Deon C.; Reyers, Belinda; Archibald, Sally; Van Wilgen, Brian W.; Forsyth, Greg G.; Theron, Andre K.; O’Farrell, Patrick J.; Kahinda, Jean-Marc Mwenge; Engelbrecht, Francois A.; Kapangaziwiri, Evison; Van Niekerk, Lara; Barwell, Laurie
    Communities worldwide are increasingly affected by natural hazards such as floods, droughts, wildfires and storm-waves. However, the causes of these increases remain underexplored, often attributed to climate changes or changes in the patterns of human exposure. This paper aims to quantify the effect of climate change, as well as land cover change, on a suite of natural hazards. Changes to four natural hazards (floods, droughts, wildfires and storm-waves) were investigated through scenario-based models using land cover and climate change drivers as inputs. Findings showed that human-induced land cover changes are likely to increase natural hazards, in some cases quite substantially. Of the drivers explored, the uncontrolled spread of invasive alien trees was estimated to halve the monthly flows experienced during extremely dry periods, and also to double fire intensities. Changes to plantation forestry management shifted the 1∶100 year flood event to a 1∶80 year return period in the most extreme scenario. Severe 1∶100 year storm-waves were estimated to occur on an annual basis with only modest human-induced coastal hardening, predominantly from removal of coastal foredunes and infrastructure development. This study suggests that through appropriate land use management (e.g. clearing invasive alien trees, re-vegetating clear-felled forests, and restoring coastal foredunes), it would be possible to reduce the impacts of natural hazards to a large degree. It also highlights the value of intact and well-managed landscapes and their role in reducing the probabilities and impacts of extreme climate events.
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    Strategies for managing complex social-ecological systems in the face of uncertainty : examples from South Africa and beyond
    (Resilience Alliance, 2015) Biggs, Reinette, 1979-; Rhode, Clint; Archibald, Sally; Kunene, Lucky Makhosini; Mutanga, Shingirirai S.; Nkuna, Nghamula; Ocholla, Peter Omondi; Phadima, Lehlohonolo Joe
    Improving our ability to manage complex, rapidly changing social-ecological systems is one of the defining challenges of the 21st century. This is particularly crucial if large-scale poverty alleviation is to be secured without undermining the capacity of the environment to support future generations. To address this challenge, strategies that enable judicious management of socialecological systems in the face of substantive uncertainty are needed. Several such strategies are emerging from the developing body of work on complexity and resilience. We identify and discuss four strategies, providing practical examples of how each strategy has been applied in innovative ways to manage turbulent social-ecological change in South Africa and the broader region: (1) employ adaptive management or comanagement, (2) engage and integrate different perspectives, (3) facilitate self-organization, and (4) set safe boundaries to avoid system thresholds. Through these examples we aim to contribute a basis for further theoretical development, new teaching examples, and inspiration for developing innovative new management strategies in other regions that can help address the considerable sustainability challenges facing society globally.