Cumulative pressure mapping is used to evaluate ecosystem degradation, and to determine the state of marine ecosystems.

Sink KJ, Van der Bank MG, Majiedt PA, Harris LR, Atkinson LJ, Kirkman SP, Karenyi N (eds). 2019. South African National Biodiversity Assessment 2018 Technical Report Volume 4: Marine Realm. South African National Biodiversity Institute, Pretoria. South Africa. http://hdl.handle.net/20.500.12143/6372

This layer was developed as part of the 2018 National Biodiversity Assessment.

This data may not be reproduced by any means, nor redistributed via web site or ftp site, without prior permission. Whilst every effort has been made to ensure the accuracy of data, users are advised to use the data and conclusions drawn from its use with caution. Users noting errors and omissions are requested to notify the data custodian (A.Skowno@sanbi.org.za) to improve data accuracy. These data are not for resale or replicating. This digital version is in the public domain requiring only the conventional acknowledgement of source in publications and reports. A.Skowno@sanbi.org This data may not be reproduced by any means, nor redistributed via web site or ftp site, without prior permission. Whilst every effort has been made to ensure the accuracy of data, users are advised to use the data and conclusions drawn from its use with caution. Users noting errors and omissions are requested to notify the data custodian (A.Skowno@sanbi.org.za) to improve data accuracy. These data are not for resale or replicating. This digital version is in the public domain requiring only the conventional acknowledgement of source in publications and reports.

APPROPRIATE USE OF THIS DATASET: There are limitations associated with this dataset. For more information on the limitations please consult the National Biodiversity Assessment 2018 – Technical Report Vol 4, Marine Environment.

PROJCS["AEA_RSA_WGS84",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Albers"],PARAMETER["False_Easting",0.0],PARAMETER["False_Northing",0.0],

PARAMETER["Central_Meridian",25.0],

PARAMETER["Standard_Parallel_1",-24.0],

PARAMETER["Standard_Parallel_2",-33.0],

PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]

The following 31 datasets were used to create the NBA2018 Marine Cumulative Pressures layer:

- Demersal Inshore and Offshore Trawling

- Crustacean Trawling

- Midwater Trawling

- Linefishing (commercial and recreational boat-based fishing)

- Recreational Shore-based Fishing

- Demersal Longline Fishing

- Pelagic Longline Fishing

- Tuna Pole Fishing

- Small Pelagic Fishery

- Netfishing: Gillnet Fishing

- Netfishing: Beach-seine Fishing

- West Coast Rock Lobster Harvesting

- South Coast Rock Lobster Harvesting

- Squid Harvesting

- Abalone Harvesting

- Oyster Harvesting

- Kelp Harvesting

- Subsistence Fishing

- Shark Control

- Sea-based Aquaculture

- Coastal Development

- Coastal Disturbance

- Mining

- Petroleum Activities

- Invasive Species

- Port and Harbour Activities

- Shipping

- Wastewater

- Ammunition Dumping

- Dumping of Dredge Material

- Freshwater Flow Reduction

Data on the each of the pressures were summarised to 30m grid to facilitate data processing during the spatial assessment. Note that this grid size does not imply that the data should be interpreted or displayed at this scale. For most pressures, pressure values were converted to a 0-100 range using formulas such as p=100*d1/d80, where d1 is the raw pressure value at a site, d80 is the 80th percentile of the pressure values for that entire data set, with resultant values over 100 being assigned a value of 100. This method was required as some of the datasets are extremely skewed and contained some very high values which would have masked the potential impact of what would have become “moderate” levels of pressure without the adjustment for the skewed upper tail of values. The compilation of the individual pressure layers into this consistent format and range was necessary to allow spatial patterns of intensity of different pressures to be compared and cumulative pressures to be calculated.

For a detailed description of the processing methodology applied to each pressure dataset, please refer to the NBA 2018 Technical Report Volume 4: Marine Realm.

SANS 1878

FGDC-STD-001-1998