Human-mediated drivers of change — impacts on coastal ecosystems and marine biota of South Africa

  • A Mead
  • CL Griffiths
  • GM Branch
  • CD McQuaid
  • LK Blamey
  • JJ Bolton
  • RJ Anderson
  • F Dufois
  • M Rouault
  • PW Froneman
  • AK Whitfield
  • LR Harris
  • R Nel
  • D Pillay
  • JB Adams
DOI: 10.2989/1814232X.2013.830147

Abstract

Coastal ecosystems are highly vulnerable to human-mediated drivers of global change because they are located at the land–ocean interface and often host centres of urbanisation and development. The South African coastline comprises several distinct coastal ecoregions that support a wide range of coastal (inshore) ecosystems, including rocky, sandy and mixed shores, kelp beds, estuaries and seagrass communities. A growing body of evidence indicates that local air and sea temperatures, wind patterns, ocean current speed and upwelling regimes are all being affected by human-mediated climate change. In addition, anthropogenic activities, such as shipping (introducing coastal bioinvasives), exploitation of coastal marine resources, industry (releasing pollutants) and urban development, act synergistically with climate change to place pressure on coastal ecosystems and their biota. The aim of this review was primarily to synthesise and update research into causes of direct and indirect human-mediated global change and their effects on South African coastal systems. It incorporates both historic and the latest regional research on climate change and anthropogenic threats across the ecosystems listed above, much of which was supported by the South African Network for Coastal and Oceanic Research (SANCOR), specifically the SEAChange programme in recent years. It is evident that all these ecosystems are vulnerable to all the drivers considered, albeit to differing degrees, depending on their location on the coast. Whereas some bioinvasives have had a dramatic impact on rocky shore systems on the West Coast, their impact has been moderate on the South Coast and minimal on the East Coast; exploitation shows the reverse pattern. Furthermore, the impacts of human-mediated drivers on coastal ecosystems are synergistic. Of major interest is the fact that the West Coast and parts of the South Coast are exhibiting cooling trends in offshore sea surface temperatures, rather than warming. Correspondingly, a geographical spread of organisms associated with West and South-West Coast rocky shores and kelp beds has tended to be eastwards around Cape Point, rather than northwards along the West Coast as would have been expected with warming sea temperatures. Overall, significant progress has been made toward a better understanding of the combined pressures on each ecosystem and knowledge gaps have been identified, thus helping to direct future research themes.

Keywords: anthropogenic, bioinvasives, climate change, coastal development, exploitation, pollution

African Journal of Marine Science 2013, 35(3): 403–425

Author Biographies

A Mead
Centre for Invasion Biology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
CL Griffiths
Centre for Invasion Biology, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
GM Branch
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
CD McQuaid
Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
LK Blamey
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
JJ Bolton
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
RJ Anderson
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Branch Fisheries Management, Department of Agriculture, Forestry and Fisheries, Private Bag X2, Rogge Bay 8012, South Africa
F Dufois
Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Oceanography, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; CSIRO Marine and Atmospheric Research, Private Bag 5, Wembley WA 6913, Australia
M Rouault
Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Department of Oceanography, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Nansen Tutu Centre for Environmental Research, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
PW Froneman
Department of Zoology and Entomology, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
AK Whitfield
South African Institute for Aquatic Biodiversity, Private Bag 1015, Grahamstown 6140, South Africa
LR Harris
Department of Zoology, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa
R Nel
Department of Zoology, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa
D Pillay
Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa; Marine Research Institute, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa
JB Adams
Department of Botany, Nelson Mandela Metropolitan University, PO Box 77000, Port Elizabeth 6031, South Africa
Published
2013-10-24
Issue
Vol. 35 No. 3 (2013)
Section
Articles
Copyright for articles published in this journal is retained by the publisher.

Journal Identifiers


eISSN: 1814-2338
print ISSN: 1814-232X