The assessment of landcover disturbance for the ELZ was based entirely on expert interpretation of the satellite image data. As such, it was far more subjective and far less quantitative in its result than the assessment for clearing.
Accepting these limitations, what were the findings for this type of landcover within the ELZ?
This question is answered in three parts: how much?; where?; and which landcover type was most affected?
The relative distribution of disturbance classes across all landcover types aggregated indicates the largest area of the ELZ (62%) to be only slightly or not disturbed, approximately 15% to be substantially disturbed, and some 26% to be significantly disturbed. The latter class was allocated only to landcover types within tenure types 1 (Freehold) and 2 (Pastoral). This was not an entirely surprising result given the large proportion of the ELZ that is subject to little or no grazing landuse.
Table 8: The distribution of the area of the ELZ among the four landcover disturbance classes. Where no valid interpretation could be made, the indeterminate class was assigned.
Disturbance Slight Substantial Significant Indeterminate Total ________________________________________________________________________ Area (km2) 2773596 655700 1152127 6189 4708092 ELZ (%) 58.9 13.9 24.5 0.1 100.0 Continent (%) 36.1 8.5 15.0 0.1 61.2
Translating these figures from just the ELZ to the entire continent we have: 37% was slightly or not disturbed, 9% was substantially disturbed, and 15% was significantly disturbed.
The area of significantly disturbed landcover was approximately the same as the area cleared (See Table 5).
In terms of the management of biotic erosion, the figures are not as daunting as those for clearing because clearing represents a far more severe and permanent impact than do the landcover impacts of grazing
Where is the landcover disturbance?
The spatial patterns are displayed in this ELZ disturbance image.
The pattern of assessed disturbance for all landcover types within the ELZ. The colour code is: slight (dark green); substantial (brown); significant (white); indeterminate (blue). The indeterminate class was allocated where no valid assessment could be made.
These patterns are the result of the interaction of irregular landcover boundaries with the geometric tenure boundaries. Recall that the assessment of landcover disturbance was based on landcover type within tenure types.
Which landcover types are most disturbed?
The distribution of disturbance between landcover types varied greatly.
Table 9: The proportion of each landcover type within the ELZ allocated to each of the four disturbance classes.
Code Indeterminate Slight Substantial Significant _______________________________________________________________________ xTML4 0 100 0 0 eTML3 0 75 25 0 wTML3 0 100 0 0 xTML3 0 100 0 0 eM2 0 100 0 0 xM2 0 100 0 0 eL2 0 100 0 0 wL2 0 100 0 0 xL2 0 44 56 0 eM1 35 65 0 0 eL1 0 100 0 0 wL1 0 24 0 76 xL1 0 58 42 0 wS3 34 66 0 0 xS3 3 97 0 0 eS2 0 100 0 0 wS2 0 37 0 63 xS2 0 12 0 88 eS1 0 65 35 0 wS1 0 68 0 32 xS1 0 25 0 75 xZ3 56 44 0 0 xZ2 0 34 66 0 wZ1 0 3 0 97 xH2 0 100 0 0 xG4 0 81 19 0 xG3 0 5 95 0 xG2 0 3 0 97 Littoral 0 100 0 0 xG1 0 21 79 0 xF1 0 16 0 84
These differences in condition reflect both their relative distribution within tenure types, and their resilience under grazing.
Most landcover types were only slightly disturbed. The significantly disturbed landcover types were the open grasslands (xG2), and the open and sparse Acacia forests and shrublands. The disturbance status of many of these landcover types is presented in greater detail in Case Studies.
