MATERIALS AND METHODS
4.3. LAND USE CLASSIFICATION
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As there are many different kinds of land and possible land uses, it is necessary to identify and classify land according to its characteristics and use potentials (Rhind 1993). Land use and land cover maps typically enumerate the types of land usages and vegetation covering the earth. For the purpose of this research, detailed observations of land use had to be classified into set defined groups or categories in order to characterise the land use features with some level of consistency and accuracy over time and space.
Classification as defined by Di Gregorio (1996, 3), "is an abstract representation of the situation in the field using well-defined diagnostic criteria". Classification schemes are a means of organising spatial information in an orderly and logical way and are fundamental to any mapping project as they create order out of chaos and---reduce the total number of classes (Congalton and Green, 1999).
To determine a set of land use classes to map land use at different time periods in the study area, a standardised classification scheme had to be defined and reviewed.
To achieve this scheme the following had to be reviewed:
• the anticipated use of the land use map;
• the relationships between features in the study area; and
• the level of detail required by the user.
4.3.1. Standardised Classification
Classification Standards provide a consistent model for classifying land uses based on their characteristics (Ducca and McDuffie, 2001). That many land use classifications exist, according to Rhind and Hudson (1980), should not come as a surprise, especially when the succinct summary is considered:
There is no one ideal classification of land use, land uses and land cover, and it is unlikely that one could ever be developed. There are
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different perspectives in the classification process, and the process itself tends to be subjective, even when an objective numerical approach is used. There is, in fact no logical reason to expect that one detailed inventory should be adequate for more than a short time, since land use and land cover patterns change in keeping with demands for natural resources. Each classification is made to suit the needs of the user, and few users will be satisfied with an inventory that does not meet most of their needs (Andersonet.al., 1976,4).
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In trying to define a standard a priod classification scheme that would be appropriate in achieving the objectives of this research, the following desiderata were taken into consideration:
• the classes must be mutually exclusive;
• the classes must be totally exhaustive;
• should be hierarchical in nature;
• it has to meet the needs of the user;
• it has to be easily understood and applied;
• it has to be sufficiently stable for surveys carried out at different moments in time to be compared;
• a clear distinction must exist between the type of classifiers used;
• it should be suitable for mapping and monitoring purposes;
• it must be scientifically sound and practically oriented.
(Congalton and Green, 1999; Di Gregorio, 1996; Rhind and Hudson, 1980).
4.3.2. Proposed Land Use Classes
The classification scheme proposed in this research was prepared after an in- depth evaluation of RBM's needs, the land cover and land use within the study area, the level of detail required to meet the research objective and other exrsting standardised classification schemes (see appendix 1). Bearing in mind the criteria of land classification discussed above, the land use and land cover classes highlighted in table 4.1 below were selected and utilised.
1classes defined before actual data collection takes place
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Table 4.1 Hierarchical land cover and land use classification scheme.
Natural environment Natural vegetation Natural
Wetlands Wetlands
Agriculture Commercial Plantation Plantation
Subsistence Cultivation Cultivation
Developed land Legal commercial Formal
Illegal Rural residential Homesteads
Transportation Roads Roads
Disturbed Land Disturbed
4.3.3. Description of classes
A classification scheme has two critical components:
• a set of labels, and
• a set of rules or definitions.
Without a clear set of rules, the assignment of labels to land use types can be arbitrary and lack consistency (Congalton and Green, 1999). If a rigorous set of rules and labels are not developed prior to mapping, the accuracy of the mapping is compromised, as difficulty will be found allocating geographic individuals to classes.
The following are a description of the different classes and rules selected for the research.
• Natural - this category incorporates all land that is covered by a minimum of 60% natural vegetation indigenous to the study area.
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•
•
•
•
•
•
•
Wetlands -this class includes all wetlands and areas covered by natural inland freshwater lakes or ponds, the open water body or the aquatic vegetation within it defines these areas.
Plantation - all areas of land covered by a minimum of 60% commercial forests being either Eucalyptus or Pine are labelled as plantation.
Cultivation - while this class may be used to cover a broad range of agricultural practices it is included here to account for areas of land that are under subsistence agriculture within the lease. All land that is under cultivation, has recently been harvested or planted are included within this class.
Formal - this category incorporates all legal commercial land use or services within the lease area. This includes two forestry stations, the Esikhaweni sewage plant and the Port-Durnford lighthouse.
Homestead - all rural residential dwellings and houses that occupy land illegally in the lease area define this class. This class includes storage sheds, outhouses and yards within its definition.
Roads - the land used for the purpose of transportation, dirt roads and major footpaths were incorporated under the category of ROADS, this includes the verge directly disturbed by road use and users.
Disturbed - in general this category includes all areas were significant vegetation cover has been removed in excess of 40%, land that is fallow, bare land, land that is in transition to another class, land that has been slashed and burnt or land that has an exotic vegetation cover greater than 40% (that do not fall into the plantation or cultivation class).
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