Land Tenure Security

Find further information on the Conservation of Freshwater Ecosystem Values (CFEV) Program and its data at www.dpipwe.tas.gov.au/cfev.

Spatial data

TitleLand Tenure Security (LTS)

CustodianWater and Marine Resources Division, Department of Primary Industries, Parks, Water and Environment

CreatorRod Knight, GIS Services

DescriptionThe degree to which land tenure may be considered to have the potential for protecting Tasmania’s freshwater-dependent ecosystem values.

Input data

1. Land Information System Tasmania (LIST) 1:25 000 Cadastral Parcels (version February 2005), Department of Primary Industries and Water (DPIW)
2. LIST Land Tenure (version April 2005), DPIW
3. Non-forest Vegetation Conservation Program CAR (Comprehensive, Adequate and Representative) Reserves data layer (version January 2005), DPIW
4. Private Forest Reserves Program (PFRP) private forest reserves data layer (version February 2005), DPIW
5. Regional Forest Agreement (RFA) land tenure (version 2002), DPIW

Lineage

The LTS data layer was developed to provide a classification of the land tenure of Tasmania in terms of the security of land tenure for conservation management. The categories high, medium and low were used, although the CFEV Project’s Technical Management Group (TMG) noted there is a substantial gap between the high and medium security categories.

The input data layers were examined for their suitability for the task. The data sets were examined for computability of classification and also for consistency of polygon boundaries (i.e. the same boundary matched in all layers reporting it). It was determined that there was some inconsistency and logical rules would therefore be required to interpret the data. Where possible, conformity with the Information and Land Services Division cadastre was enforced.

The data were combined by converting each layer (accounting for known overlaps e.g. strata titles) to a 10 m grid on the basis of their tenure classes. Each grid was then combined using a mathematical calculation (see below) to preserve each class in the resultant combination layer. The calculation below produces a numeric value of 19082315, which is then converted to a string of the same characters and each of the contributing classes extracted and attribute values reattached to the attribute table. The resulting layer was then reconverted to a polygon layer.

1. Cadastre layer - class 15; plus
2. CAR reserves - class 23 * 100; plus
3. RFA Review - class 08 * 10000; plus
4. Tenure - class 9 * 100000; plus
5. PFRP - class 1 * 1000000

Each unique combination of tenure classes was examined for logical consistency and, where possible, assigned to a land tenure class. In some instances, a single determination could not be made, so the class options were examined to determine which of the tenure security categories they would be placed in. Table 1 shows the land tenure classes and the security assigned to them for the CFEV Project.

Table 1. CFEV land tenure classes and tenure security.

LTS categories were assigned to estuary, karst, saltmarsh, river, waterbody and wetland spatial units using rules which generally assigned the lowest LTS type according to agreed thresholds (by the TMG) for what constitutes a potential impact to the protection of freshwater values (see below).

Data limitations

The assigning of LTS categories to each land tenure class (shown in Table 1) assumes knowledge of the way a particular area is managed. A range of land and vegetation management may occur across individual Land Tenure Security types.

Date createdMarch 2005

Scale and coverage1: 25 000; Statewide

Attribute data

TitleLand Tenure Security (LTS)

Column headingES_LTENSEC, KT_LTENSEC, SM_LTENSEC, RS_LTENSEC, WB_LTENSEC, WL_LTENSEC, ES_LTSMAP, KT_LTSMAP, SM_LTSMAP, RS_LTSMAP, WB_LTSMAP, WL_LTSMAP

Input data

1. CFEV Land Tenure Security spatial data (described above)

Type of dataCategorical

Number of classes3

Assigning values to ecosystem spatial units

A LTS category (Low, Medium or High) was assigned to each of the estuary, karst, saltmarsh, river, waterbody and wetland spatial units as **_LTENSEC (where ** is the prefix for each ecosystem theme i.e. ES = estuaries, KT = karst, RS = rivers, SM = saltmarshes, WB = waterbodies and WL = wetlands) using the following rules:

1. Calculate the proportion of the spatial unit’s local catchment that is made up of each of the LTS categories (i.e. Low, Medium and High).
2. Accumulate the proportional values (weighted by River Section Catchment area) for each LTS category (i.e. Low, Medium and High) for all the upstream RSCs (including the local catchment) and assign value to each spatial unit as **_LTS_L, **_LTS_M and **_LTS_H, respectively.
3. Using the accumulated values of L, M and H (e.g. ES_LTS_L, ES_LTS_M and ES_LTS_H, assign a **_LTENSEC category to the spatial unit according to the following thresholds:
1. If the value for Low (**_LTS_L) >0.2, then assign as Low.
2. Else, if the value for Medium (**_LTS_M) >0.2, then assign as Medium.
3. Else, if the value for High (**_LTS_H) >0.8, then assign as High.
4. Otherwise, assign as Medium.

A category was also assigned to each of the spatial units (as **_LTSMAP) to depict if the LTS within the catchment was all of one type (e.g. whole catchment has High LTS) or was of mixed tenure (e.g. part High and part Medium). This was done by applying the following rules:

1. Using the accumulated values of L, M and H (e.g. ES_LTS_L, ES_LTS_M and ES_LTS_H, assign a **_LTSMAP category to the spatial unit:
1. If the value for Low (**_LTS_L) <1, then assign as Mixed.
2. If the value for Medium (**_LTS_M) <1, then assign as Mixed.
3. If the value for High (**_LTS_H) <1, then assign as Mixed.
4. If the value for Low (**_LTS_L) =1, then assign as Low.
5. If the value for Medium (**_LTS_M) =1, then assign as Medium.
6. If the value for High (**_LTS_H) =1, then assign as High.

Certain limitations of this process should be noted.

1. The threshold set is not smooth, consequently there can potentially be a large jump in LTS type with just a small change in catchment coverage.
2. The assigning of LTS data does not take into account the position of the land tenure types within the catchment.
3. The assigning of LTS data does not take into account the variation of potential land use impacts within each category.

CFEV assessment framework hierarchy

1. Estuaries>Conservation evaluation>Conservation Management Priority
2. Karst>Conservation evaluation>Conservation Management Priority
3. Rivers>Conservation evaluation>Conservation Management Priority
4. Saltmarshes>Conservation evaluation>Conservation Management Priority
5. Waterbodies>Conservation evaluation>Conservation Management Priority
6. Wetlands>Conservation evaluation>Conservation Management Priority