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This indicator describes the percentage area of land cover class and land cover change using surrogate measure of woody vegetation change by bioregion (IBRA 5), the planning and management catchments and karst type. Land cover in Tasmania has been extensively modified as a result of land management decisions over the years. It is now widely accepted that the long-term maintenance of ecosystem health and, by implication, productive systems is dependent on the maintenance of native vegetation cover. In a recent publication, a figure of 30% cover has been nominated as the minimum lower limit of native vegetation cover (Williams 2000). Natural fluvial geomorphic landforms and processes are also highly dependent upon the maintenance of native vegetation cover. The classification of land cover used in this indicator is based on Landsat remotely sensed data. This source is useful in presenting a snapshot and overview of land cover and vegetation across different tenures and land uses. It is also able to assist in tracking changes in some land cover types, including some drier forests and woodlands outside the commercial forests that are the principal focus for the RFA vegetation mapping and State of the Forests reports. It is also useful for identifying some non-forest land cover such as pasture and grassland and, potentially, for tracking changes in other land uses such as urban areas. Background information on remote sensing is available from the CSIRO Division of Mathematical and Information Sciences and from the NASA Earth Observatory. However, remotely sensed data greatly simplifies vegetation and land cover types. It is also susceptible to misclassification with accuracy generally at about 80% for the classification presented in this indicator. TASVEG, the mapping of Tasmania's vegetation communities at 1:25,000 scale, is the authoritative source of information on the vegetation of Tasmania. Vegetation maps and other resources are available through the Parks and Wildlife Service. However, TASVEG does not presently allow trends in vegetation cover to be identified. The information contained within the indicator is generally not comparable with Forest Practices Board data on forest clearance, for the following reasons:
The following limitation is highlighted by the CSIRO (Division of Mathematical and Information Sciences 2002) in relation to remote sensing, and applies equally to the data contained within the indicator:
Land cover classification, ~2001 Landsat 7 data from 1999-02 were analysed and classified by the School of Geography and Environmental Studies at the University of Tasmania. Up to 30 land cover classes were identified (a description of the classes is contained in the downloadable file). Woody vegetation change, 1994-01 The analysis of woody vegetation change compares woody vegetation cover from Landsat satellite images from ~1994 with images from ~2001. The actual dates of the images vary around these years due, in large part, to the difficulties in finding cloud-free data. The dates of the base Landsat images are detailed in the table. The average change period for all Landsat scenes is seven years. For each pair of images to be compared, the extent of the woody vegetation was identified using a simplified classification. After combining the extent of the two woody areas, change detection was applied within this 'potentially woody' area, to identify more accurately on the raw data the areas that have actually changed to/from woody. 'Woody' includes (without identifying) all trees as well as, potentially, some scrub, blackberries, ferns, gorse and bracken. There are also some cases to be expected where a new forest is 'emerging'. That is, a cleared area has been replanted or is regenerating naturally, but it is so early in the regeneration phase that it also appears 'cleared'. This causes problems when it occurs in either the first image, or in the second. These situations were also identified in relation to the land cover classification with newly regenerating or plantation forest being placed in scrub or heath classes. On State Forest it is recognised that all harvested areas are reforested either by natural regeneration processes or plantation establishment. The output of the woody change analysis was four classes: (A) woody in both images. However, changes from non-woody to woody were insufficiently reliable to include and this class was aggregated with the 'woody in both images'. Both human and natural processes influence vegetation cover and it is often difficult to identify cause. Influences include clearing, fire, seasonal change and regrowth. It is important to maintain natural rates of change, as much as it is to protect existing levels and percentages of vegetation cover. There are four sections to the analysis of the data within this indicator, including (links are to the Data section): Land cover classification and woody vegetation change by bioregion Land cover classification and woody vegetation change by catchment Land cover classification by area of karst type Land cover classification by landscape type
Bioregion assessment
Woody vegetation decrease (ha), 1994-01 By major tenure classes Private property State Forest other totals total (ha) 76,007 35,374 14,135 125,515 annual (ha) 10,858 5,053 2,019 17,931 Source: Landsat 5 and 7 data , base images dated 1994 and 2001, processing by Ross Lincolne, Space Images Catchment assessment
Karst type assessment
Landscape type assessment
Land cover classification and woody vegetation change by bioregion The following section reviews land cover and changes to vegetation cover for nine Tasmanian bioregions. The on-the-ground context in which changes are occurring is all important. For example, woody vegetation decreases in State forest (in forest-communities that are well represented in reserves) is associated with routine forest harvesting operations that is then regenerated with local seed or planted across all bioregions. This has significantly less impact than permanent forest clearance, particularly where this occurs in poorly-reserved forest-communities. Capturing land cover information using satellite remote sensing Caption: In principle, different land cover such as forests and built up areas can be identified from their spectral reflectance signature, provided the sensing system has sufficient spectral resolution to distinguish its spectrum. The land cover classes shown are some of those that have been identified in the classification of land cover from Landsat 7. The Ben Lomond Bioregion covers an area of 657,059 ha. It has a large area of its land cover identified as pasture, forest, scrub and heath. It has the second highest percentage of forest cover of any bioregion in Tasmania, with wet forest in particular covering about 30%. Pasture is also a significant land cover in this Bioregion (about 9%). The bare land class occupies a relatively small area of about 2% and includes both naturally bare areas such as exposed rock in alpine areas of the Ben Lomond Plateau and bare areas arising from human activity relating to such activities as agriculture and recent forest harvesting. Land cover statistics for the Bioregion are summarised in the table. Woody vegetation covered about 68% of the Bioregion in 2001. The woody vegetation decrease identified from Landsat data for the period 1994-01 is 17,782 ha, with approximately 32% occurring on private land and 65% on State Forest. A small percentage loss was attributed to other tenure classes. Minor changes in woody vegetation cover in reserves may be due to boundary changes or other processes such as fire. Woody change statistics for the period ~1994-01 are summarised in the accompanying table. The woody vegetation decrease was distributed across the following land cover classes: bare (18%); forest (37%); pasture (12%); and, regrowth (7%). The timing of clearance of woody vegetation during the change period from 1994-01 would account for some of the variations in the land cover classes in which it occurred. For example, woody vegetation cleared recently is more likely to be classed as 'bare' in a recent classification. Regeneration over a longer period is likely to be associated with the 'regrowth' or other forest cover classes. The Forest Practices Board approved a total of 18,992 ha for clearing on public and private land in the period 1997-02 (Forest Practices Board 2000). These figures are based on the older bioregional boundary (IBRA 4), although there is some similarity between IBRA 4 and IBRA 5 boundaries for the Ben Lomond Bioregion. A list of the vegetation communities in which a woody decrease is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Ben Lomond Bioregion are shown in the following maps.
Central Highlands The Central Highlands Bioregion has an area of 767,337 ha. According to the classification of land cover from Landsat data, the Central Highlands has the highest percentage of its area within alpine and alpine scrub classes (17.3%) and the second highest percentage of its area containing grassland vegetation (4.9%). Land cover statistics for the Bioregion are summarised in the table. A key land cover issue for the Central Plateau is the susceptibility of some parts to erosion: the Parks and Wildlife Service has mapped erosion at 1:25,000 scale. A summary erosion map for the Central Plateau is available from the Parks and Wildlife Service. The Bioregion includes intensive areas of plantation development in the Gunns Limited plantations at Surrey Hills near Hampshire, accounting for the relatively high proportion of this Bioregion identified in the 'forest activity' class (5.8%). The woody vegetation decrease identified from Landsat data for the period ~1994-01 is 14,963 ha, with approximately 73% occurring on private land and 10% on State Forest. A comparatively small percentage loss occurred on other tenure classes. As with the Ben Lomond Bioregion, post RFA changes in reserve may account for some of the changes identified in Conservation Areas and National Parks. The woody vegetation decrease of 14,963 ha was distributed mainly across the following land cover classes: bare (21%); forest (15%); regrowth (7%). The high proportion in the 'other' classes is due to difficulties in accurately identifying a unique spectral signature for young regrowth or plantation forest. Woody vegetation decrease information is summarised in the table. A list of the vegetation communities in which change is indicated is provided in the table. Woody vegetation decrease information by tenure and land cover is presented in the following graphs.
Land cover and woody vegetation change for the Central Highlands Bioregion are shown in the following maps.
Flinders The Flinders Bioregion has an area of 487,556 ha. It contrasts with Ben Lomond and Central Highlands in having a relatively higher proportion of its land cover in the more intensive land cover classes, particularly agriculture and pasture which account for nearly 20% of its area. Suburbs and urban land cover account for some 8,809 ha of the Bioregion, but only about 2% of its area. Land cover statistics for the Bioregion are summarised in the table. Woody vegetation covers 35.6% of the Bioregion. The woody vegetation loss for the period ~1994-01 was 10,085 ha, with approximately 32% occurring on private land and 65% on State forest. A small percentage loss was attributed to other tenure classes. A significant proportion of the woody vegetation decrease (17%) occurred on non-allocated Crown Land, particularly in the Furneaux Group. This may highlight consequences of the extended drought on the islands together with land management impacts of grazing leases on Crown Land. A related measure of land cover stress is that the Flinders Bioregion also had the highest proportion of any bioregion in the 'bare' land cover class, with significant areas shown on Cape Barren Island and Clarke Island potentially related to fires or grazing. About 19% of the woody vegetation decrease in the Flinders Bioregion occurred in land that was classed as agriculture or pasture from the 2001 Landsat data A list of the vegetation communities in which woody vegetation decrease is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Central Highlands Bioregion are shown in the following maps.
Agriculture and pasture cover about 26% of the Bioregion's area of 426,091 ha. Scrub and heath are significant vegetation types, covering about 40% of the Bioregion, although this is likely to be an overestimate due to young plantations and regrowth giving a similar spectral signature to scrub, heath or buttongrass. About 55% of the Bioregion contains non-woody land cover. Land cover statistics for the Bioregion are summarised in the table. The King Bioregion overall has the highest proportion of forest communities and non-forest communities in need of conservation. The threatened species and ecological communities issue report notes, for example, that the King Island blue gum (Eucalyptus globulus) forest community is listed as endangered under the RFA (1997). The woody vegetation decrease identified from Landsat data for the period 1994-01 was 12,999 ha with the decrease occurring mostly on private property (53%) and State forest (28%). Woody change information for the Bioregion is summarised in the table. A list of the vegetation communities in which woody vegetation decrease is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the King Bioregion are shown in the following maps.
Northern Midlands The Northern Midlands Bioregion has an area of about 415,109 ha, with about 77% of this area containing non-woody vegetation cover. Northern Midlands has the highest percentage area of agriculture and pasture land cover of any bioregion. These two classes cover some 50% of the area of the Bioregion. Dry forest is the next most significant land cover, covering about 20% of the Bioregion. Northern Midlands has one of the highest percentage areas of native grassland vegetation, comprising some 9% of the area of the Bioregion according to the Landsat classfication. Land cover statistics for the Bioregion are summarised in the table. The threatened species and communities issue report notes how threats to plant species are greatest in the settled agricultural districts, especially in the Northern Midlands and eastern Tasmania, where clearing has diminished available habitat. Aside from the forested eastern and western margins of the Bioregion, two significant areas of woody vegetation are prominent in the classification showing remaining 'natural' vegetation cover. They are Epping Forest in the centre of the image and, to the south of Epping Forest, two patches of dry forest and woodland to the west of Campbell Town and the Macquarie River. Woody vegetation loss in the Northern Midlands Bioregion from 1994-01 was about 5,849 ha. About 96% of this loss occurred on private land, while the remaining loss occurred across a number of tenures. State forest, on the wetter forested fringes of the Bioregion, accounted for about 1% of the loss. Woody vegetation change information for the Bioregion is summarised in the table. The woody vegetation change map shows that Epping Forest, which is one of the last remaining areas of grassy woodland forest in the Northern Midlands, had relatively stable land cover in the period 1994-01. This is in part due to the Tom Gibson Nature Reserve (area 597 ha). A proposed 346 ha extension to the reserve is currently unproclaimed. Kirkpatrick and Mendel (unpublished report 2001) also note that in addition to conservation efforts, '…the returns from wool declined markedly during the nineties, giving less incentive and capability to clear the drier country, which is mainly used for grazing.' Vegetation loss is evident in patches of remaining native vegetation such as the northern end of the predominantly black peppermint (Eucalyptus amygdalina) forest to the west of Campbell Town and the Macquarie River. Other eucalypts supported in the drier areas of the State are silver peppermint (E.tenuiramis) and white peppermint (E. pulchella). A list of the vegetation communities in which woody vegetation decrease is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Northern Midlands Bioregion are shown in the following maps.
Northern Slopes The Northern Slopes Bioregion has a total area of 623,104 ha. Woody vegetation covers about 55% of the Bioregion. Agriculture and pasture covers about 22% of the Bioregion and 'forestry activity' accounts for about 13% of the Bioregion according to the classification. Land cover statistics are summarised in the accompanying table. As indicated on the map of woody change, patterns of forest clearance are evident particularly in the Surrey Hills plantations east of Waratah. A belt of relatively recent forest harvesting extends across the Great Western Tiers towards Lake Cethana. The largest percentage of woody vegetation decrease occurred on private land (77%), followed by State Forest (21%). Woody change statistics for the Bioregion are summarised in the table. Approximately, 25% of the woody vegetation decrease occurred in land that was classed as agriculture and pasture in 2001. A further 25% occurred in land that was classed as 'bare'. Land in the 'bare' class may end up as, for example, regenerated forest, plantation or agriculture and pasture. The forest and forest activity classes contained nearly 60% of the woody vegetation increase whilst, probably due to younger forest or plantation age classes, nearly 20% of the increases occurred in classes identified as scrub or heath. A list of the vegetation communities in which change is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Northern Slopes Bioregion are shown in the following maps.
South-east The South-east Bioregion covers an area of 1,373,676 ha. It has a higher percentage of its area in the classes of dry forest (27%), pasture (18%) and woodland (17%). Scrub and heath, and grassland are other significant vegetation in the region. This Bioregion includes Hobart and suburbs, and urban and suburban areas account for about 19,304 ha or about 2% of the total area of the Bioregion. The major proportion of the area of bare land in the Bioregion is located in the southern half, predominantly in the catchment of the River Derwent. Although bare land occurs naturally in locations such as on the rocky outcrops of Mt Wellington, it is also an indication of land cover change or land use activity such as the harvesting of agricultural products and timber, although it is a very transient marker of such land cover. Land cover statistics for the Bioregion are summarised in the accompanying table. 'Modified' land cover classes identified from Landsat data include agriculture, pasture, urban and forest activity. These cover about 27% of the Bioregion. In total, woody vegetation covers about 55% of the Bioregion. Woody vegetation loss was 11,237 ha with 86% of this loss occurring on private land. Harvesting on State Forest represented some 9% of the identified vegetation loss. Woody change statistics for the Bioregion are summarised in the accompanying table. A list of the vegetation communities in which change is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Northern Slopes Bioregion are shown in the following maps.
Southern Ranges The Southern Ranges Bioregion has an area of 752,771 ha. It has a high percentage of its area containing forest (72% woody vegetation cover), although in contrast to the south-east, the most common vegetation communities are wet forests, which account for about 37% of the area and a further 9% identified as rainforest. Eucalyptus coccifera and E. delegatensis are relatively common forest types identified in the vegetation classification, accounting for 5% and 9.1% respectively of the area of the Bioregion. Pasture and agriculture occupy only a comparatively small proportion of about 4% of the Bioregion. Land cover statistics for the Bioregion are summarised in the accompanying table. Woody vegetation loss from the Landsat change analysis was 15,164 ha in the period 1994-01. Harvesting on State Forest represented about 54% of the identified vegetation loss while 33% occurred on private land. A further 7% of loss occurred in State forest on Hydro-Electric Corporation land. The woody vegetation decreases occurred across the following main land cover types: bare (28%); forest and regrowth (35%); agriculture and pasture (8%) and other (23%). Woody change statistics for the Bioregion are summarised in the accompanying table. A list of the RFA vegetation communities in which woody change is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the Southern Ranges Bioregion are shown in the following maps.
West This Bioregion has an area of 1,550,715 ha, the largest in Tasmania. As would be expected in a region with a large proportion of its area contained within the World Heritage Area, the West has the highest percentage of any bioregion in 'natural' land cover classes (89.8%). The classification identifies rainforest (23.9%), scrub/heath (17.5%), buttongrass moorland (16.2%) and wet forest (14.6%) as among the most common vegetation communities. The Bioregion also has the highest percentage of any in the 'water' class, in large part due to the significant area of hydro-electricity impoundment in Lake Pedder and Lake Gordon. Land cover statistics for the Bioregion are summarised in the accompanying table. This Bioregion has a relatively high percentage of woody vegetation cover and this cover has changed little in extent over the period 1994-01. This highlights the role of reserves and national parks in providing areas where land cover is relatively protected from disturbance allowing natural cycles and rates of change to occur. Yet, even in reserves, management intervention is evident: around Bathurst Harbour in the south-west the woody change image shows evidence of efforts by the Parks and Wildlife service to create a mosaic of different vegetation age classes for the Orange Bellied Parrot (Neophema chrysogaster). The birds feed on plants in moorlands that have been burnt 5 to 12 years previously, and also on other plants that are more common in moorlands burnt three to five years previously. Woody change statistics for the Bioregion are summarised in the table. A list of the RFA vegetation communities in which woody change is indicated is provided in the table. Woody vegetation change statistics by tenure and land cover are presented in the following graphs.
Land cover and woody vegetation change for the West Bioregion are shown in the following maps.
Land cover classification and woody vegetation change by catchment Area of land cover class by catchment Catchments may also be assessed in terms of land cover and the percentage of catchment area under modified land cover classes. The modified land cover classes include more intensive land cover classes identified through the 2001 land cover classification of Tasmania: pasture, agriculture, urban, suburban, bare land, and forest activity. The following table ranks planning and management catchments according to percentage area under these land cover classes and codes catchments with greater than 30% 'modified' land cover, 20-30% modified land cover, and less than 20% 'modified' land cover. The results generally accord with the woody vegetation decrease. Catchments in the south-west and west of the State indicate a relatively pristine condition demonstrated by less of their catchment areas being under 'modified' land cover classes. These catchments include Port Davey, Wanderer-Giblin, and Gordon-Franklin. A number of east coast catchments have maintained relatively high percentage catchment areas under 'natural' land cover (less than 20% modified): George, Swan-Apsley and Prosser. In the south-east, the Huon catchment also maintains a relatively high percentage of natural land cover. Great Lake is indicated as having a high ranking with a small percentage of its area under 'modified' land cover classes. However, it is a substantially modified catchment. It was Australia's largest natural body of persistent fresh water, and had extensive marshes around the fringe (Kirkpatrick & Tyler 1988). These have not recovered since the water level was first raised by a hydro-electric scheme in 1916. Subsequent dramatic expansions to the lake after dam construction in 1922, 1967 and 1982, and the frequent fluctuations in water level from power station operations, have continued to place pressure on this area. The Lagoon of Islands has been subject to a series of ecological stresses as a result of the damming of Great Lake, and subsequent management regimes. Other catchments were ranked highly as having experienced little woody vegetation increase or decrease. In a number of cases, this was due to catchments having already been substantially converted to agriculture, pasture or urban uses. These catchments include the Meander, Lower Derwent, Jordan, Macquarie, Clyde and the Tamar Estuary. A number of catchments ranked poorly both in terms of containing a high percentage of their areas experiencing woody vegetation change and a high percentage of their areas under modified land cover classes. These catchments were the Cam, Inglis, Blythe, Rubicon, Leven, Montagu and King Island. Twenty catchments in Tasmania exceed the minimum level of native vegetation retention of 30% suggested by Williams (2000) A further six catchments are approaching this figure of 30%: Little Swanport; Black-Detention; Derwent Estuary-Bruny; Pipers; Furneaux; and Great Forester-Brid. The second table ranks catchments in terms of their percentage area under urban and suburban land cover. Urban and suburban uses represent a substantial modification of land cover with significant flow-on impacts for catchment condition. The five catchments with the highest percentage area under urban and suburban land uses are Lower Derwent, Derwent Estuary-Bruny, Cam, Tamar Estuary, and North Esk.
Modified land cover (including agriculture and urban) area by catchment, ~2001 Name catchment area (ha) modified area (ha) % area modified Port Davey 284,321 11,412 4.0 Gordon-Franklin 589,357 25,276 4.3 Wanderer-Giblin 175,638 8,634 4.9 Great Lake 39,637 2,050 5.2 Pieman 414,893 33,607 8.1 Nelson Bay 86,755 8,284 9.5 King-Henty 179,271 20,901 11.7 George 61,500 8,383 13.6 Arthur 250,542 35,141 14.0 Huon 380,790 54,410 14.3 Ouse 148,238 24,363 16.4 Upper Derwent 354,134 60,389 17.1 Swan-Aspley 136,032 23,845 17.5 North Esk 106,550 19,432 18.2 Ringarooma 98,284 18,312 18.6 Prosser 114,850 22,223 19.3 Scamander-Douglas 68,656 13,874 20.2 Tasman 92,706 20,155 21.7 South Esk 334,951 75,485 22.5 Musselroe-Ansons 97,209 22,128 22.8 Little Forester 35,356 8,108 22.9 Forth-Wilmot 117,961 29,942 25.4 Little Swanport 87,892 24,494 27.9 Black-Detention 64,616 18,298 28.3 Derwent Estuary-Bruny 109,149 31,010 28.4 Pipers 75,370 21,605 28.7 Furneaux 188,791 54,656 29.0 Great Forester-Brid 78,301 23,004 29.4 Clyde 111,752 37,939 33.9 Pitt Water-Coal 91,977 31,356 34.1 Boobyalla-Tomahawk 65,219 22,718 34.8 Macquarie 273,244 95,434 34.9 Mersey 190,891 67,777 35.5 Brumbys-Lake 150,855 53,805 35.7 Tamar Estuary 107,439 39,425 36.7 Jordan 125,325 48,284 38.5 King Island 109,400 42,166 38.5 Lower Derwent 160,374 63,173 39.4 Montagu 47,607 19,018 39.9 Welcome 67,480 27,243 40.4 Leven 72,740 31,065 42.7 Emu 25,462 11,036 43.3 Rubicon 71,755 31,558 44.0 Blythe 37,718 18,330 48.6 Meander 156,863 76,471 48.8 Inglis 61,570 34,436 55.9 Cam 28,859 16,353 56.7 Duck 55,242 32,954 59.7 Source: Landsat 7 satellite data, base images dated ~2001, processing by School of Geography and Environmental Studies, University of Tasmania; Catchment boundaries are the 48 planning and management catchments developed by the Water Division of DPIWE. Urban and suburban land cover area by catchment, ~2001 Name catchment area
Urban and suburban
% catchment
Great Lake 39,637 0 0.0 Port Davey 284,321 121 0.0 Upper Derwent 354,134 161 0.0 Pieman 414,893 392 0.1 Wanderer-Giblin 175,638 198 0.1 Gordon-Franklin 589,357 666 0.1 Arthur 250,542 430 0.2 Nelson Bay 86,755 237 0.3 Furneaux 188,791 575 0.3 Ouse 148,238 466 0.3 Huon 380,790 1,361 0.4 Forth-Wilmot 117,961 547 0.5 King-Henty 179,271 1,041 0.6 Prosser 114,850 735 0.6 George 61,500 426 0.7 Macquarie 273,244 2,029 0.7 King Island 109,400 842 0.8 Scamander-Douglas 68,656 587 0.9 Little Swanport 87,892 761 0.9 South Esk 334,951 2,965 0.9 Clyde 111,752 990 0.9 Tasman 92,706 861 0.9 Montagu 47,607 450 0.9 Ringarooma 98,284 1,009 1.0 Little Forester 35,356 371 1.1 Musselroe-Ansons 97,209 1,025 1.1 Jordan 125,325 1,452 1.2 Swan-Aspley 136,032 1,619 1.2 Black-Detention 64,616 808 1.3 Welcome 67,480 895 1.3 Mersey 190,891 2,581 1.4 Leven 72,740 1,003 1.4 Duck 55,242 805 1.5 Brumbys-Lake 150,855 2,336 1.5 Rubicon 71,755 1,151 1.6 Meander 156,863 2,533 1.6 Great Forester-Brid 78,301 1,277 1.6 Blythe 37,718 672 1.8 Pipers 75,370 1,359 1.8 Boobyalla-Tomahawk 65,219 1,284 2.0 Pitt Water-Coal 91,977 1,883 2.0 Emu 25,462 548 2.2 Inglis 61,570 1,334 2.2 North Esk 106,550 2,783 2.6 Tamar Estuary 107,439 4,029 3.7 Cam 28,859 1,086 3.8 Derwent Estuary-Bruny 109,149 8,154 7.5 Lower Derwent 160,374 24,477 15.3 Remotely sensed data greatly simplifies land use types. It is also susceptible to misclassification with accuracy generally at about 80% for the classification presented in this indicator. Misclassification of urban and suburban areas is known to have occurred. For example, some quarries were classed as urban or suburban. Source: Landsat 7 satellite data, base images dated ~2001, processing by School of Geography and Environmental Studies, University of Tasmania. Woody vegetation change by catchment Using the woody vegetation change information, Tasmania's 48 planning and management catchments are ranked in relation to woody vegetation change in the period since the last SoE report (~1994-01). The catchment boundaries are aggregations for planning and management purposes only and, in reality, there are thousands of surface water catchments in Tasmania. Additional resolution on catchments is needed for natural resource management decisions at local and regional scales. The first table shows woody decrease by total area and percentage catchment area. The second table shows woody vegetation increase by total area and percentage of catchment area for the period (~1994-01). The tables and maps provide an indication of land cover activity by catchment, representing a measure of catchment condition for the inland waters and wetlands chapter and the pressure on estuaries from land use activities for the coastal, estuarine and marine chapter. The information does not imply that all woody vegetation decrease is bad for catchment condition and woody vegetation increase is necessarily good. The on-the-ground context in which changes are occurring is all-important. For example, a woody vegetation loss of native riparian vegetation in catchments which have already significantly depleted vegetation cover or in areas with a high salinity hazard presents a greater catchment threat than, for example, regeneration of native vegetation with local species where riparian vegetation is protected by streamside buffers. Woody vegetation increases resulting in large areas of plantation cover per catchment have potential consequences for water availability and environmental flows.
Catchments in the south-west and west of the State indicate a relative pristine condition evidenced by little woody vegetation change over the period ~1994-01. These catchments include: Port Davey, Wanderer-Giblin, and Gordon-Franklin. The estuaries that receive the water from these catchments are also ranked as near pristine under the Naturalness Index (NI) (Edgar et. al. 1999). The exception is the King-Henty catchment where woody vegetation change is a poor measure of the severely degraded catchment and estuary condition as a consequence of mining impacts. Other catchments have experienced little woody vegetation loss because their land cover has already has been substantially altered to pasture, agriculture or urban. These catchments are identified using the land cover ranking. Examples of substantially modified catchments that have not changed significantly in their woody vegetation cover include the Jordan and Clyde. However, the relatively high rankings for the Swan-Apsley and Little Swanport catchments has greater justification due to a larger percentage of their catchment areas in reserves. Catchments with the highest percentage of their areas subject to woody vegetation decrease are in the north-west of the State. These decreases are due to forest harvesting in upper catchments and agricultural activity in middle and lower sections. These catchments are the Emu, Cam, Leven, Blythe, Mersey and Forth Wilmot. The Arthur catchment has a significant area of its head-waters in the Gunns Limited private forest estate. King Island is ranked as having a high woody vegetation loss over this period in part due to a fire in heath in the north-west, which was recorded as woody vegetation loss. Nevertheless, there is also evidence of forest clearance on the island through analysis of Landsat data for the period. Bushcare undertook a detailed study of vegetation loss on King Island for the King Island Council and | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
