Indicator: Vegetation clearing

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What the results tell us for Tumut

See also: | Landuse | Ecosystem diversity |

Up to 58% of Tumut Shire, or 227 492 hectares, were cleared or modified by the start of this reporting period in 1997. A further 15 hectares were removed under clearing applications during the 1997–2000 reporting period. However, from the data available, it is clear that the greatest changes have occurred prior to the reporting period.

Clearing from 1990–1995

There is some evidence from remotely sensed data that there was a net decrease of 2422 hectares of trees and shrubs from 1990 to 1995 (see Table 1 for more details). Much of the decrease was related to clearing for forestry activities, and it is likely that some of the replacement vegetation would have been new plantations, probably of Pinus radiata. The extent to which this represents an impact on native ecosystems cannot be determined without further information about what was cleared and replanted.

Clearly, forestry activities are an ongoing source of pressure on native ecosystems in Tumut Shire and the wider Region.

Clearing during 1997–2000

Applications to clear a total of 15 hectares² were approved during the reporting period from 1997 to 2000, almost all of which were approved in 1998–99. Some 12 hectares were under native vegetation, and the clearing application covered thinning as part of regular forestry activities. The remaining areas were to have exotic vegetation removed.

Areas with approved clearing applications were dispersed throughout the northern part of Tumut Shire (this map can be found on the CD-ROM that contains the report for the entire Australian Capital Region).

About the data

Estimates of the amount of vegetation cleared were made using three data sources.

1. The vegetation mapping project of the Eden and Southern Forest Regional Forest Agreements, which gave the estimated area cleared in 1997, at the start of the reporting period. More about this data source is described in the Ecosystem diversity results.
2. Clearing application data were derived from applications for clearing of any area over two hectares that were lodged with the Department of Land and Water Conservation. There is no requirement under the Native Vegetation Conservation Act to apply to clear areas of less than two hectares.
3. The estimates of change in native vegetation cover from 1990–95 were provided by the Bureau of Rural Sciences, from Landsat Thematic Mapper scenes for 1990 and 1995. These scenes were analysed as part of a national collaborative Bureau of Rural Sciences–State agencies to estimate changes in woody vegetation cover in that five year period. The report, and a full description of the methods, can be downloaded from their website at: http://www.brs.gov.au. The data used in this reported were provided from that database for each Government Area in the Australian Capital Region.

Description: What does 'vegetation clearing' measure?

Which data are collected?

• area and proportion of all vegetation types cleared each year in each biogeographic subregion and in specified catchments for each type of proposed landuse

Why do we report this indicator?

Clearing vegetation is one of the major pressures on terrestrial ecosystems - both native ecosystems and agricultural lands. For this reason it is a key indicator in State of the Environment reporting in the Region.

Removing native vegetation impacts on native ecosystems through the loss of habitat for native plant and animal species as well as direct removal of native plant species. It has also resulted in a decline in agricultural productivity in many areas due to changes in local hydrology (e.g. salinity), weather patterns (e.g. regional windspeed) and soil stability.

Loss of native vegetation reduces the size and connectedness of remnant native ecosystems, making them less able to withstand outside pressures such as fire and the introduction of pests, as well as restricting the movement of native animal species. Even where vegetation types appear identical to those in reserves, genetic stocks may be different, and remnants may be important sources of recolonisation if neighbouring areas lose species, such as by fire or by natural occurrence over time.