scholarly journals Overfishing and Climate Change Elevate Extinction Risk of Endemic Sharks and Rays in the Southwest Indian Ocean Hotspot

2021 ◽  
Author(s):  
Riley Pollom ◽  
Jessica Cheok ◽  
Nathan Pacoureau ◽  
Katie S. Gledhill ◽  
Peter M. Kyne ◽  
...  
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Indian Ocean ◽  
Extinction Risk ◽  
Critically Endangered ◽  
Southwest Indian Ocean ◽  
Bycatch Reduction ◽  
Level Data ◽  
Data Deficient ◽  
Distributional Shifts

Abstract The southwest Indian Ocean (SWIO) is a hotspot of endemic and evolutionarily distinct sharks and rays. We summarise the extinction risk of the sharks and rays endemic to coastal, shelf, and slope waters of the SWIO (Namibia to Kenya, including SWIO islands). Thirteen of 70 species (19%) are threatened: one is Critically Endangered, five are Endangered, and seven are Vulnerable. A further seven (10%) are Near Threatened, 33 (47.1%) are Least Concern, and 17 (24.2%) are Data Deficient. While the primary threat is overfishing, there are the first signs that climate change is contributing to elevated extinction risk through habitat reduction and inshore distributional shifts. By backcasting their status, few species were threatened in 1980, but this changed soon after the emergence of targeted shark and ray fisheries. South Africa has the highest national conservation responsibility, followed by Mozambique and Madagascar. Yet, while fisheries management and enforcement have improved in South Africa over recent decades, drastic improvements are urgently needed elsewhere. To avoid extinction and ensure robust populations and future food security, there is an urgent need for the strict protection of Critically Endangered and Endangered species and sustainable management of all species, underpinned by species-level data collection and bycatch reduction.

scholarly journals Circulation pattern controls of wet days and dry days in Free State, South Africa

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Southern Africa ◽  
Austral Summer ◽  
Free State ◽  
Austral Spring ◽  
Study Region ◽  
Southwest Indian Ocean ◽  
South Indian

AbstractAtmospheric circulation is a vital process in the transport of heat, moisture, and pollutants around the globe. The variability of rainfall depends to some extent on the atmospheric circulation. This paper investigates synoptic situations in southern Africa that can be associated with wet days and dry days in Free State, South Africa, in addition to the underlying dynamics. Principal component analysis was applied to the T-mode matrix (variable is time series and observation is grid points at which the field was observed) of daily mean sea level pressure field from 1979 to 2018 in classifying the circulation patterns in southern Africa. 18 circulation types (CTs) were classified in the study region. From the linkage of the CTs to the observed rainfall data, from 11 stations in Free State, it was found that dominant austral winter and late austral autumn CTs have a higher probability of being associated with dry days in Free State. Dominant austral summer and late austral spring CTs were found to have a higher probability of being associated with wet days in Free State. Cyclonic/anti-cyclonic activity over the southwest Indian Ocean, explained to a good extent, the inter-seasonal variability of rainfall in Free State. The synoptic state associated with a stronger anti-cyclonic circulation at the western branch of the South Indian Ocean high-pressure, during austral summer, leading to enhanced low-level moisture transport by southeast winds was found to have the highest probability of being associated with above-average rainfall in most regions in Free State. On the other hand, the synoptic state associated with enhanced transport of cold dry air, by the extratropical westerlies, was found to have the highest probability of being associated with (winter) dryness in Free State.

Circulation pattern control of wet days and dry days in Free State, South Africa

2021 ◽  
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Atmospheric Circulation ◽  
Southern Africa ◽  
Austral Summer ◽  
Free State ◽  
Study Region ◽  
Southwest Indian Ocean ◽  
South Indian ◽  
Circulation Patterns

Abstract Atmospheric circulation is a vital process in the transport of heat, moisture, and pollutants around the globe. The variability of rainfall depends to some extent on the mechanisms of atmospheric circulation. This paper uses the concept of classifying the recurrent large-scale atmospheric circulation patterns in southern Africa, and the linkage of the classified patterns to wet days and dry days in Free State, South Africa, for the analysis of how the probability of wet and dry events in Free State can be associated with specific synoptic situations, in addition to the underlying dynamics. Principal component analysis was applied to the T-mode matrix (column/variable is time series and row is grid points at which the field was observed) of daily mean sea level pressure field from 1979 to 2018 in classifying the recurrent circulation patterns in southern Africa. 18 circulation types (CTs) were classified in the study region. From the linkage of the CTs to the observed rainfall data, from 11 stations in Free State, it was found that dominant austral winter and late austral autumn CTs have a higher probability of bringing dry days to Free State. Dominant austral summer and late austral spring CTs were found to have a higher probability of bringing wet days to Free State. Cyclonic/anti-cyclonic activity over the southwest Indian Ocean, explained to a good extent, the inter-seasonal variability of rainfall in Free State. The synoptic state associated with a stronger anti-cyclonic circulation at the western branch of the South Indian Ocean high-pressure, during austral summer, leading to enhanced moisture transport by southeast winds was found to have the highest probability to bring above-average rainfall in most regions in Free State; while the synoptic state associated with enhanced transport of cold dry air, from the Benguela current, by the extratropical westerlies was found to be associated with the highest probability of (winter) dryness in Free State.

scholarly journals A decadal climate shift in the southwest Indian Ocean linked to recent malaria downturn in South Africa

2019 ◽  
Author(s):  
Swadhin Behera ◽  
Takayoshi Ikeda ◽  
Yushi Morioka ◽  
Venkata Ratnam Jayanthi ◽  
Takeshi Doi ◽  
...  
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Southwest Indian Ocean ◽  
Climate Shift ◽  
Decadal Climate

scholarly journals Potential range shifts and climatic refugia of rupicolous reptiles in a biodiversity hotspot of South Africa

2021 ◽  
Vol 48 (4) ◽  
pp. 264-273
Author(s):  
Melissa Anne Petford ◽  
Graham John Alexander
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Extinction Risk ◽  
Future Research ◽  
Potential Range ◽  
Suitable Habitat ◽  
Ecological Niche Models ◽  
Reptile Species ◽  
Limited Dispersal ◽  
High Conservation

SummaryClimate change is causing the geographical ranges of some species to track suitable conditions. Habitat specialists, range-restricted species and species with limited dispersal abilities may be unable to track changing conditions, increasing their extinction risk. In response to changing conditions and species movement patterns, there is a need to account for the effects of climate change when designing protected areas and identifying potential climate refugia. We used ecological niche models projected into future climates to identify potential impacts of climate change on the distribution of 11 rupicolous reptile species in the Soutpansberg Mountains, South Africa. Lygodactylus incognitus, Lygodactylus soutpansbergensis, Platysaurus relictus and Vhembelacerta rupicola were identified as being vulnerable to climate change due to substantial reductions in suitable habitat and low spatial overlap between current and future niche envelopes. We identified areas of high conservation importance for the persistence of these species under present-day and projected future conditions. The western Soutpansberg was identified as an area of high conservation priority as it is a potential refuge under future projections. Projecting distributions of vulnerable species into future climate predictions can guide future research and identify potential refugia that will best conserve species with restricted ranges in a world with climate change.

scholarly journals On Sverdrup Discontinuities and Vortices in the Southwest Indian Ocean

2007 ◽  
Vol 37 (12) ◽  
pp. 2940-2950 ◽  
Author(s):  
J. H. LaCasce ◽  
P. E. Isachsen
Keyword(s):  
South Africa ◽  
Indian Ocean ◽  
Equation Model ◽  
The West ◽  
Primitive Equation ◽  
Flat Bottom ◽  
Southwest Indian Ocean ◽  
Barotropic Model ◽  
Numerical Studies ◽  
The Indian Ocean

Abstract The southwest Indian Ocean is distinguished by discontinuities in the wind-driven Sverdrup circulation. These connect the northern and southern tips of Madagascar with Africa and the southern tip of Africa with South America. In an analytical barotropic model with a flat bottom, the discontinuities produce intense westward jets. Those off the northern tip of Madagascar and the southern tip of Africa are always present, while the strength of that off southern Madagascar depends on the position of the zero curl line in the Indian Ocean (the jet is strong if the line intersects Madagascar but weak if the line is north of the island). All three jets are barotropically unstable by the Rayleigh–Kuo criterion. The authors studied the development of the instability using a primitive equation model, with a flat bottom and realistic coastlines. The model produced westward jets at the three sites and these became unstable after several weeks, generating 200–300-km scale eddies. The eddies generated west of Madagascar are in accord with observations and with previous numerical studies. The model’s Agulhas eddies are similar in size to the observed eddies, both the anticyclonic rings and the cyclones that form to the west of the tip of South Africa. However, the model’s Agulhas does not retroflect, most likely because of its lack of stratification and topography, and so cannot capture pinching-off events. It is noteworthy nevertheless that a retroflection is not required to produce eddies here.

scholarly journals Revisiting the 1992 severe drought episode in South Africa: the role of El Niño in the anomalies of atmospheric circulation types in Africa south of the equator

2021 ◽  
Vol 146 (1-2) ◽  
pp. 723-740
Author(s):  
Chibuike Chiedozie Ibebuchi
Keyword(s):  
South Africa ◽  
High Pressure ◽  
Indian Ocean ◽  
El Niño ◽  
El Nino ◽  
Severe Drought ◽  
The South ◽  
Southwest Indian Ocean ◽  
Drought Episode ◽  
South Indian

AbstractDuring strong El Niño events, below-average rainfall is expected in large parts of southern Africa. The 1992 El Niño season was associated with one of the worst drought episodes in large parts of South Africa. Using reanalysis data set from NCEP-NCAR, this study examined circulation types (CTs) in Africa south of the equator that are statistically related to the El Niño signal in the southwest Indian Ocean and the implication of this relationship during the 1992 drought episode in South Africa. A statistically significant correlation was found between the above-average Nino 3.4 index and a CT that features widespread cyclonic activity in the tropical southwest Indian Ocean, coupled with a weaker state of the south Indian Ocean high-pressure. During the analysis period, it was found that the El Niño signal enhanced the amplitude of the aforementioned CT. The impacts of the El Niño signal on CTs in southern Africa, which could have contributed to the 1992 severe drought episode in South Africa, were reflected in (i) robust decrease in the frequency of occurrence of the austral summer climatology pattern of atmospheric circulation that favors southeasterly moisture fluxes, advected by the South Indian Ocean high-pressure; (ii) modulation of easterly moisture fluxes, advected by the South Atlantic Ocean high-pressure, ridging south of South Africa; (iii) and enhancement of the amplitude of CTs that both enhances subsidence over South Africa, and associated with the dominance of westerlies across the Agulhas current. Under the ssp585 scenario, the analyzed climate models suggested that the impact of radiative heating on the CT significantly related to El Niño might result in an anomalous increase in surface pressure at the eastern parts of South Africa.

The World Economic Forum Principles on "Climate Governance on Corporate Boards": can soft law help to face climate change around the world?

2020 ◽  
pp. 37-55
Author(s):  
Sabrina Bruno
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Comparative Analysis ◽  
Boards Of Directors ◽  
Soft Law ◽  
Corporate Boards ◽  
World Economic Forum ◽  
Financial Factor ◽  
The World ◽  
World Economic

Climate change is a financial factor that carries with it risks and opportunities for companies. To support boards of directors of companies belonging to all jurisdictions, the World Economic Forum issued in January 2019 eight Principlescontaining both theoretical and practical provisions on: climate accountability, competence, governance, management, disclosure and dialogue. The paper analyses each Principle to understand scope and managerial consequences for boards and to evaluate whether the legal distinctions, among the various jurisdictions, may undermine the application of the Principles or, by contrast, despite the differences the Principles may be a useful and effective guidance to drive boards' of directors' conduct around the world in handling climate change challenges. Five jurisdictions are taken into consideration for this comparative analysis: Europe (and UK), US, Australia, South Africa and Canada. The conclusion is that the WEF Principles, as soft law, is the best possible instrument to address boards of directors of worldwide companies, harmonise their conduct and effectively help facing such global emergency.

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