Pub Date : 2023-05-04DOI: 10.1080/0035919X.2023.2205368
Onalenna Gwate, K. Canavan, G. Martin, David M. Richardson, V. Ralph Clark
Social-ecological systems in mountains are sensitive to the effects of climate change and are being affected at rates faster than other terrestrial habitats. We need to know which species are likely to be “winners” and which are likely to be “losers” in the context of climate change. This study evaluated the current and predicted future habitat suitability of selected range-expanding woody plant species (Acacia dealbata, Leucosidea sericea, Vernonanthura phosphorica) in African mountains under climate change. These species are representative of range-expanding plants, which have the potential to affect ecosystem services. Future average temperature is projected to decline in African mountains whereas global mean temperatures are projected to increase. Climate-change models may not be capturing dynamics in the climate of African mountains, possibly due to a lack of representative climate data used in calibrating these models. Although only climate variables were assessed, potential species distribution results were considered accurate according to model evaluation metrics, and some static factors thought to influence species distribution were strongly coupled to climate. Vernonanthura phosphorica and A. dealbata are likely to spread under climate change. The extent of habitat suitable for L. sericea is predicted to decline under climate change. An improved understanding of climate change in mountain systems through better representation of mountain climates in climate-change models could enhance the accuracy of species distribution models.
{"title":"Assessing habitat suitability for selected woody range-expanding plant species in African mountains under climate change","authors":"Onalenna Gwate, K. Canavan, G. Martin, David M. Richardson, V. Ralph Clark","doi":"10.1080/0035919X.2023.2205368","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2205368","url":null,"abstract":"Social-ecological systems in mountains are sensitive to the effects of climate change and are being affected at rates faster than other terrestrial habitats. We need to know which species are likely to be “winners” and which are likely to be “losers” in the context of climate change. This study evaluated the current and predicted future habitat suitability of selected range-expanding woody plant species (Acacia dealbata, Leucosidea sericea, Vernonanthura phosphorica) in African mountains under climate change. These species are representative of range-expanding plants, which have the potential to affect ecosystem services. Future average temperature is projected to decline in African mountains whereas global mean temperatures are projected to increase. Climate-change models may not be capturing dynamics in the climate of African mountains, possibly due to a lack of representative climate data used in calibrating these models. Although only climate variables were assessed, potential species distribution results were considered accurate according to model evaluation metrics, and some static factors thought to influence species distribution were strongly coupled to climate. Vernonanthura phosphorica and A. dealbata are likely to spread under climate change. The extent of habitat suitable for L. sericea is predicted to decline under climate change. An improved understanding of climate change in mountain systems through better representation of mountain climates in climate-change models could enhance the accuracy of species distribution models.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"87 - 101"},"PeriodicalIF":0.0,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41752937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-04DOI: 10.1080/0035919X.2023.2205373
R. Marchant, J. Thorn
THE CHALLENGE PRESENTED BY MOUNTAINS Mountains are among Africa’s most dramatic landscapes. Comprising 20% of the continental surface area (Nsemgiyumva, 2019; Platts et al., 2011), mountains are vital to the lives of the 1.1 billion people across Africa who depend either directly or indirectly on the many benefits that they provide. For the over 250 million people that live on mountains in Africa (FAO, 2015) this dependency is direct: montane environments are particularly attractive areas due to their high diversity of natural resources and biodiversity (Capitani et al., 2019b), high agricultural productivity, reliable water supply, cooler climate (Ashagre et al., 2018; CormierSalem et al., 2018), and supply of fuel. Mountains supply ecosystem services on which the continent relies, not least as all major rivers have headwaters in the highlands. Mountains largely determine Africa’s sustainable development potential by underpinning food production, energy security, biocultural diversity and tourism income, and they supply timber and non-timber forest products (Capitani et al., 2019b; Green et al., 2018; Cuni-Sanchez et al., 2021). Additionally, highland areas will be the focus of afforestation projects, important for current carbon emission targets (see Glasgow Leaders’ Declaration on Forests and Land Use 2021). As a result, highlands are the focus of many ecosystem “restoration” initiatives aiming to both sequester carbon and conserve biodiversity, and they are where historical degradation has been acute (Marchant 2021). Whilst recent studies of reforestation potential focus on ecological viability (Bastin et al., 2019; Brancalion et al., 2019), the feasibility of such projects under local and regional socio-economic settings and their impacts on local communities and biodiversity have yet to be adequately assessed. Understanding such socio-economic settings and impacts on communities is important for achieving the laudable aims of the “Bonn Challenge” of “restoring” 350 million ha of forest by 2030, while Africa100 aims to “restore” 100 million ha by 2030. Alongside this, in 2019 the United Nations (UN) launched the “Decade on Ecosystem Restoration” (2021–2030), aiming to massively scale up the restoration of degraded and destroyed ecosystems as a measure for communities to mitigate and adapt to the increasing frequency and magnitude of climate extremes (Platts et al., 2015; Lange et al., 2020; Adler et al., 2021), and to enhance food and water security and biodiversity (UN, 2021). Large parts of Africa nevertheless faces unique problems, with the highest rate of population growth globally (Molotoks et al., 2021) and the highest poverty gap index ( Molotoks et al., 2021), increasing pressure on both water supplies (Ashagre et al., 2018) and ecosystems (Marchant, 2021). This is combined with rapidly changing climates, transformation of models of socio-economic development, intensification of competing land uses, and often contradicting, ineffecti
{"title":"The value of researching the past for crafting sustainable African mountain futures","authors":"R. Marchant, J. Thorn","doi":"10.1080/0035919X.2023.2205373","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2205373","url":null,"abstract":"THE CHALLENGE PRESENTED BY MOUNTAINS Mountains are among Africa’s most dramatic landscapes. Comprising 20% of the continental surface area (Nsemgiyumva, 2019; Platts et al., 2011), mountains are vital to the lives of the 1.1 billion people across Africa who depend either directly or indirectly on the many benefits that they provide. For the over 250 million people that live on mountains in Africa (FAO, 2015) this dependency is direct: montane environments are particularly attractive areas due to their high diversity of natural resources and biodiversity (Capitani et al., 2019b), high agricultural productivity, reliable water supply, cooler climate (Ashagre et al., 2018; CormierSalem et al., 2018), and supply of fuel. Mountains supply ecosystem services on which the continent relies, not least as all major rivers have headwaters in the highlands. Mountains largely determine Africa’s sustainable development potential by underpinning food production, energy security, biocultural diversity and tourism income, and they supply timber and non-timber forest products (Capitani et al., 2019b; Green et al., 2018; Cuni-Sanchez et al., 2021). Additionally, highland areas will be the focus of afforestation projects, important for current carbon emission targets (see Glasgow Leaders’ Declaration on Forests and Land Use 2021). As a result, highlands are the focus of many ecosystem “restoration” initiatives aiming to both sequester carbon and conserve biodiversity, and they are where historical degradation has been acute (Marchant 2021). Whilst recent studies of reforestation potential focus on ecological viability (Bastin et al., 2019; Brancalion et al., 2019), the feasibility of such projects under local and regional socio-economic settings and their impacts on local communities and biodiversity have yet to be adequately assessed. Understanding such socio-economic settings and impacts on communities is important for achieving the laudable aims of the “Bonn Challenge” of “restoring” 350 million ha of forest by 2030, while Africa100 aims to “restore” 100 million ha by 2030. Alongside this, in 2019 the United Nations (UN) launched the “Decade on Ecosystem Restoration” (2021–2030), aiming to massively scale up the restoration of degraded and destroyed ecosystems as a measure for communities to mitigate and adapt to the increasing frequency and magnitude of climate extremes (Platts et al., 2015; Lange et al., 2020; Adler et al., 2021), and to enhance food and water security and biodiversity (UN, 2021). Large parts of Africa nevertheless faces unique problems, with the highest rate of population growth globally (Molotoks et al., 2021) and the highest poverty gap index ( Molotoks et al., 2021), increasing pressure on both water supplies (Ashagre et al., 2018) and ecosystems (Marchant, 2021). This is combined with rapidly changing climates, transformation of models of socio-economic development, intensification of competing land uses, and often contradicting, ineffecti","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"103 - 107"},"PeriodicalIF":0.0,"publicationDate":"2023-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48036986","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-03-17DOI: 10.1080/0035919x.2023.2190179
Dzunani A. Ngobeni, J. Knight
{"title":"Evaluation of river mouth dynamics along the Eastern Cape coastline, South Africa","authors":"Dzunani A. Ngobeni, J. Knight","doi":"10.1080/0035919x.2023.2190179","DOIUrl":"https://doi.org/10.1080/0035919x.2023.2190179","url":null,"abstract":"","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48349478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-21DOI: 10.1080/0035919X.2023.2177361
C. Curtis, N. Rose, Tahir Khanzada, Handong Yang, M. Humphries
Abstract Very little is known about the impacts of Anthropocene environmental change on aquatic systems in the mountains of southern Africa. The Maloti-Drakensberg region forming the border between South Africa and Lesotho is not generally associated with natural, permanent lakes, but there are dammed wetland lakes with evidence that natural water bodies were present before lake levels were raised, including Mountain Lake in the Eastern Cape in South Africa. In order to address a regional lack of long-term monitoring data, here we present evidence from lake sediment records spanning over 50 years from Mountain Lake that industrial signals of contamination associated with distant coal fired power stations are transported across the region, including trace metals, mercury (reaching 95 ng·g−1) and spheroidal carbonaceous particles. In addition, high concentrations of the organochlorine pesticides DDT (ΣDDT = 166.3 ng·g−1) and methoxychlor (39.3 ng·g−1), most likely from catchment sources, are recorded in recent sediments. Finally, the diatom record indicates shifts in assemblages within the last 20 years indicative of possible nutrient enrichment, which is consistent with known intensification of agricultural and other human activity within the catchment, shown by increasing sediment enrichment of P, Mn, Fe, As and Co. Hence there are multiple lines of evidence for increasing environmental pressures on the ecosystems of Mountain Lake and its catchment over the period of the proposed Anthropocene. Further studies are required to assess the magnitude of threats to the unique but largely unstudied biodiversity associated with lakes in the region, including those in protected areas.
{"title":"Anthropocene environmental change in an overlooked South African lake: Mountain Lake, Matatiele, Eastern Cape","authors":"C. Curtis, N. Rose, Tahir Khanzada, Handong Yang, M. Humphries","doi":"10.1080/0035919X.2023.2177361","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2177361","url":null,"abstract":"Abstract Very little is known about the impacts of Anthropocene environmental change on aquatic systems in the mountains of southern Africa. The Maloti-Drakensberg region forming the border between South Africa and Lesotho is not generally associated with natural, permanent lakes, but there are dammed wetland lakes with evidence that natural water bodies were present before lake levels were raised, including Mountain Lake in the Eastern Cape in South Africa. In order to address a regional lack of long-term monitoring data, here we present evidence from lake sediment records spanning over 50 years from Mountain Lake that industrial signals of contamination associated with distant coal fired power stations are transported across the region, including trace metals, mercury (reaching 95 ng·g−1) and spheroidal carbonaceous particles. In addition, high concentrations of the organochlorine pesticides DDT (ΣDDT = 166.3 ng·g−1) and methoxychlor (39.3 ng·g−1), most likely from catchment sources, are recorded in recent sediments. Finally, the diatom record indicates shifts in assemblages within the last 20 years indicative of possible nutrient enrichment, which is consistent with known intensification of agricultural and other human activity within the catchment, shown by increasing sediment enrichment of P, Mn, Fe, As and Co. Hence there are multiple lines of evidence for increasing environmental pressures on the ecosystems of Mountain Lake and its catchment over the period of the proposed Anthropocene. Further studies are required to assess the magnitude of threats to the unique but largely unstudied biodiversity associated with lakes in the region, including those in protected areas.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"45 - 66"},"PeriodicalIF":0.0,"publicationDate":"2023-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"59098061","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-16DOI: 10.1080/0035919X.2023.2175077
S. Grab
Globally, mountain environments have undergone substantial climate warming and associated environmental and socio-economic changes. Although past studies have alluded to recent climate change in the Lesotho Highlands, these have largely lacked scientifically based evidence for assessing actual climate change. This paper thus aims to establish (a) instrumental-based changes in rainfall and temperature; and (b) people’s views about the contemporary and past weather, and memories of past extreme weather events, in Lesotho. This was achieved through undertaking 60 interviews across 42 villages in 2008, and then comparing outcomes with (a) instrumental climate records from Mohale’s Hoek and Mokhotlong; and (b) documentary-based evidence of past severe snowfalls. While there is good agreement between people’s views and instrumental records for recent trends in summer temperature and spring rainfall, there is disagreement in winter temperature and annual rainfall trends. Interviewees demonstrate remarkably accurate remembrance of prominent snowfalls since 1930. A key outcome is that the “lived climatic experience” and thus views about “the weather” are determined not only by actual climate patterns and trends in Lesotho, but also by personal frames of reference, prominent weather-related experiences and changes in personal circumstances that impact on weather-related coping capacity and comfort levels.
{"title":"“The sun has become intolerably hot”: local views and memories about Lesotho’s weather – present and past","authors":"S. Grab","doi":"10.1080/0035919X.2023.2175077","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2175077","url":null,"abstract":"Globally, mountain environments have undergone substantial climate warming and associated environmental and socio-economic changes. Although past studies have alluded to recent climate change in the Lesotho Highlands, these have largely lacked scientifically based evidence for assessing actual climate change. This paper thus aims to establish (a) instrumental-based changes in rainfall and temperature; and (b) people’s views about the contemporary and past weather, and memories of past extreme weather events, in Lesotho. This was achieved through undertaking 60 interviews across 42 villages in 2008, and then comparing outcomes with (a) instrumental climate records from Mohale’s Hoek and Mokhotlong; and (b) documentary-based evidence of past severe snowfalls. While there is good agreement between people’s views and instrumental records for recent trends in summer temperature and spring rainfall, there is disagreement in winter temperature and annual rainfall trends. Interviewees demonstrate remarkably accurate remembrance of prominent snowfalls since 1930. A key outcome is that the “lived climatic experience” and thus views about “the weather” are determined not only by actual climate patterns and trends in Lesotho, but also by personal frames of reference, prominent weather-related experiences and changes in personal circumstances that impact on weather-related coping capacity and comfort levels.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"29 - 43"},"PeriodicalIF":0.0,"publicationDate":"2023-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43194775","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-13DOI: 10.1080/0035919X.2023.2175076
P. Gordijn, T. O’Connor
The phenomenal level of biodiversity in the Drakensberg mountains was shaped by and depends on the disturbance regimes which prevailed before the intensification of human settlement in the region. Global change has, however, changed these disturbance regimes leaving an uncertain future for biodiversity. In order to reduce uncertainty around the influence of human society on biodiversity, we propose the Socio-Ecological Disturbance Regime (S-EDR) construct, which implicitly considers the effects of interactions between society, ecosystems, and associated disturbance regimes. We aimed to provide insight into how disturbance regimes have deviated from their “natural” range of variation, and developed into novel S-EDRs that are increasing uncertainty around the fate of plant diversity in the region. Drakensberg grasslands house high levels of indigenous grassland-plant species, many of which only occur in this mountain range. To achieve this we present findings from palaeoecological, through to more recent history, to establish the context of disturbance regimes in this landscape. Over the last 150–200 years there have been rapid and large changes in disturbance regimes, and these novel S-EDRs are demonstrated to have been shaped by interactions between the dominant “social systems” in the study area, that is, communal, private, and protected areas, and the nature of the ecosystems they inhabit. Owing to their prevalence in the landscape the disturbance regime components, fire and herbivory, and land transformation, are focused on. Understanding the nature of developed S-EDRs will be important for understanding contemporary research, guiding future investigations, and the maintenance of plant diversity in Drakensberg grasslands.
{"title":"The “eco-story” of a mountain range: the development of Socio-Ecological Disturbance Regimes in the northern Drakensberg and consequences for grassland-plant diversity","authors":"P. Gordijn, T. O’Connor","doi":"10.1080/0035919X.2023.2175076","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2175076","url":null,"abstract":"The phenomenal level of biodiversity in the Drakensberg mountains was shaped by and depends on the disturbance regimes which prevailed before the intensification of human settlement in the region. Global change has, however, changed these disturbance regimes leaving an uncertain future for biodiversity. In order to reduce uncertainty around the influence of human society on biodiversity, we propose the Socio-Ecological Disturbance Regime (S-EDR) construct, which implicitly considers the effects of interactions between society, ecosystems, and associated disturbance regimes. We aimed to provide insight into how disturbance regimes have deviated from their “natural” range of variation, and developed into novel S-EDRs that are increasing uncertainty around the fate of plant diversity in the region. Drakensberg grasslands house high levels of indigenous grassland-plant species, many of which only occur in this mountain range. To achieve this we present findings from palaeoecological, through to more recent history, to establish the context of disturbance regimes in this landscape. Over the last 150–200 years there have been rapid and large changes in disturbance regimes, and these novel S-EDRs are demonstrated to have been shaped by interactions between the dominant “social systems” in the study area, that is, communal, private, and protected areas, and the nature of the ecosystems they inhabit. Owing to their prevalence in the landscape the disturbance regime components, fire and herbivory, and land transformation, are focused on. Understanding the nature of developed S-EDRs will be important for understanding contemporary research, guiding future investigations, and the maintenance of plant diversity in Drakensberg grasslands.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"17 - 28"},"PeriodicalIF":0.0,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43257242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-02-13DOI: 10.1080/0035919X.2023.2175075
A. J. van der Walt, J. A. Kruger, S. J. Roffe
Consistent with global patterns, heatwaves have increased in frequency, duration and intensity across southern Africa; under enhanced global warming this is projected to worsen. Heatwaves have many adverse impacts, but in biologically unique mountainous regions, like the Maloti-Drakensberg region, impacts on ecological processes and hydrological cycles are particularly dire given their highly sensitive nature. Despite this, extreme temperature changes and interannual variability patterns remain understudied in mountainous regions, owing largely to remoteness and inaccessibility. This is especially true for the Maloti-Drakensberg region. Hence, using heatwave indices developed by the World Meteorological Organization (WMO) Expert Team on Sector-Specific Climate Indices (ET-SCI), we explored spatiotemporal patterns for the seasonal average number, length and magnitude of summer (November-March) heatwaves for 1979/80–2020/21 using the AgERA5 reanalysis. Although higher elevation regions typically experienced more frequent, longer-lasting heatwave events with higher interannual variability levels, on average the Maloti-Drakensberg region experienced 1.4 heatwave events, lasting for 6.5 days with a magnitude of 3.5°C2. Interannually, the El Niño-Southern Oscillation influenced variability of heatwave characteristics, with positive (negative) heatwave number and length anomalies predominantly detected during El Niño (La Niña) phases, while for heatwave magnitudes no clear pattern was evident. These heatwave aspects were predominantly characterised by increasing trends, however, few regions exhibited statistically significant trends. Overall, trends averaged 0.003 events/year, 0.03 days/year and 0.02°C2/year for the mean number, length and magnitude of heatwaves, respectively. These results highlight that the Drakensberg-Maloti region is vulnerable to an increasing frequency, duration and magnitude of heatwaves, however, implications thereof require further study.
{"title":"Fine-resolution analysis of the spatiotemporal characteristics of heatwaves in the Maloti-Drakensberg region, southern Africa: 1979–2021","authors":"A. J. van der Walt, J. A. Kruger, S. J. Roffe","doi":"10.1080/0035919X.2023.2175075","DOIUrl":"https://doi.org/10.1080/0035919X.2023.2175075","url":null,"abstract":"Consistent with global patterns, heatwaves have increased in frequency, duration and intensity across southern Africa; under enhanced global warming this is projected to worsen. Heatwaves have many adverse impacts, but in biologically unique mountainous regions, like the Maloti-Drakensberg region, impacts on ecological processes and hydrological cycles are particularly dire given their highly sensitive nature. Despite this, extreme temperature changes and interannual variability patterns remain understudied in mountainous regions, owing largely to remoteness and inaccessibility. This is especially true for the Maloti-Drakensberg region. Hence, using heatwave indices developed by the World Meteorological Organization (WMO) Expert Team on Sector-Specific Climate Indices (ET-SCI), we explored spatiotemporal patterns for the seasonal average number, length and magnitude of summer (November-March) heatwaves for 1979/80–2020/21 using the AgERA5 reanalysis. Although higher elevation regions typically experienced more frequent, longer-lasting heatwave events with higher interannual variability levels, on average the Maloti-Drakensberg region experienced 1.4 heatwave events, lasting for 6.5 days with a magnitude of 3.5°C2. Interannually, the El Niño-Southern Oscillation influenced variability of heatwave characteristics, with positive (negative) heatwave number and length anomalies predominantly detected during El Niño (La Niña) phases, while for heatwave magnitudes no clear pattern was evident. These heatwave aspects were predominantly characterised by increasing trends, however, few regions exhibited statistically significant trends. Overall, trends averaged 0.003 events/year, 0.03 days/year and 0.02°C2/year for the mean number, length and magnitude of heatwaves, respectively. These results highlight that the Drakensberg-Maloti region is vulnerable to an increasing frequency, duration and magnitude of heatwaves, however, implications thereof require further study.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"78 1","pages":"5 - 15"},"PeriodicalIF":0.0,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46231708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-12-14DOI: 10.1080/0035919x.2022.2152507
P. Mataruse, K. Nyikahadzoi, A. Fallot
{"title":"Smallholder farmers' perceptions of the natural and anthropogenic drivers of deforestation and forest degradation: a case study of Murehwa, Zimbabwe","authors":"P. Mataruse, K. Nyikahadzoi, A. Fallot","doi":"10.1080/0035919x.2022.2152507","DOIUrl":"https://doi.org/10.1080/0035919x.2022.2152507","url":null,"abstract":"","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2022-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45325505","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-02DOI: 10.1080/0035919X.2022.2144538
D. Matarira, O. Mutanga, M. Naidu
The diversity of informal settlement morphologies across locales makes their mapping inherently challenging in heterogeneous urban landscapes. The aim of this study was to evaluate the potential of pansharpening techniques on Sentinel 2A data, and textural features, in enhancing informal settlement identification accuracy in a fragmented urban environment. Brovey transform, intensity, hue and saturation transform, Environmental Systems Research Institute (ESRI), simple mean, and Gram–Schmidt techniques were employed to pansharpen multispectral bands of Sentinel 2A, bands 5, 6, and 7 in the first group, and bands 8A, 11 and 12 in another, using an average of bands 4 and 8 as the panchromatic band. The main objective was to investigate the efficacy of pansharpening Sentinel 2A imagery and texture analysis in automated mapping of morphologically varied informal settlements. An evaluation of the quality of fused images was undertaken through computation of the correlation between the spectral values of the original multispectral and pansharpened image. Grey-level-co-occurrence matrix texture features were extracted from the pansharpened images, and subsequently incorporated in the classification process, using a support vector machine classifier. Our results confirm that the Gram–Schmidt fusion technique yielded the highest informal settlement identification accuracy (F-score 95.2%; overall accuracy 91.8%). The experimental results demonstrated the potential of pansharpening Sentinel 2A, and the added value of image texture for a more nuanced characterisation of informal settlements.
{"title":"Performance evaluation of pansharpening Sentinel 2A imagery for informal settlement identification by spectral-textural features","authors":"D. Matarira, O. Mutanga, M. Naidu","doi":"10.1080/0035919X.2022.2144538","DOIUrl":"https://doi.org/10.1080/0035919X.2022.2144538","url":null,"abstract":"The diversity of informal settlement morphologies across locales makes their mapping inherently challenging in heterogeneous urban landscapes. The aim of this study was to evaluate the potential of pansharpening techniques on Sentinel 2A data, and textural features, in enhancing informal settlement identification accuracy in a fragmented urban environment. Brovey transform, intensity, hue and saturation transform, Environmental Systems Research Institute (ESRI), simple mean, and Gram–Schmidt techniques were employed to pansharpen multispectral bands of Sentinel 2A, bands 5, 6, and 7 in the first group, and bands 8A, 11 and 12 in another, using an average of bands 4 and 8 as the panchromatic band. The main objective was to investigate the efficacy of pansharpening Sentinel 2A imagery and texture analysis in automated mapping of morphologically varied informal settlements. An evaluation of the quality of fused images was undertaken through computation of the correlation between the spectral values of the original multispectral and pansharpened image. Grey-level-co-occurrence matrix texture features were extracted from the pansharpened images, and subsequently incorporated in the classification process, using a support vector machine classifier. Our results confirm that the Gram–Schmidt fusion technique yielded the highest informal settlement identification accuracy (F-score 95.2%; overall accuracy 91.8%). The experimental results demonstrated the potential of pansharpening Sentinel 2A, and the added value of image texture for a more nuanced characterisation of informal settlements.","PeriodicalId":23255,"journal":{"name":"Transactions of The Royal Society of South Africa","volume":"77 1","pages":"181 - 194"},"PeriodicalIF":0.0,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49516179","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-09-02DOI: 10.1080/0035919X.2022.2160548
W. Bond
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