SoE 2006 > Biodiversity > 6.1 Terrestrial ecosystems

6.1 Terrestrial ecosystems

Land clearing remains a major threat to the extent and condition of terrestrial ecosystems. However, new native vegetation legislation has been introduced to end broadscale clearing unless it improves or maintains environmental outcomes. In addition, $120 million has been allocated by State and federal governments for the management, conservation and protection of native vegetation through incentive programs that reward landholders for sound management practices. This investment is already having significant positive outcomes on the environment. As the legislation has only been in place for one year, it is too early to measure its effectiveness.

The extent of some vegetation classes, particularly woodlands and grasslands, has been substantially depleted since European arrival, mainly due to land clearing.

Approved clearing has been greatest in areas to the west of the Central Division for agriculture, and in coastal regions for urban development.

Even if all clearing were to cease now, the decline in vegetation condition is likely to continue for many years, because of the lag effects of vegetation fragmentation and growing pressure from climate change.

NSW indicators

Introduction

New South Wales has a great variety of native vegetation which closely reflects the diversity of species, habitats and ecosystems found across the State. Outstanding examples of rainforests, deserts, alpine habitats, wetlands, grasslands and eucalypt forests and woodlands all occur within NSW.

Native vegetation provides essential habitat for many plant and animal species, and is an integral component of healthy, functioning ecosystems. It is therefore an important indicator of ecosystem diversity (Saunders et al. 1998). However, it cannot indicate all components of biodiversity equally well, such as rare species and some fauna species.

Since European arrival, there has been extensive clearing of native vegetation for human settlement, industry and agriculture. Clearing is generally irreversible due to subsequent land uses. It displaces the majority of native biota and leads to ongoing habitat degradation through the effects of fragmentation. Clearing is therefore widely accepted to be the main driver of vegetation decline.

Clearing of native vegetation, with the associated destruction of habitat, has been identified as the process that represents the greatest single threat to biodiversity in NSW (Coutts-Smith & Downey 2006). It has been listed as a key threatening process under both the Threatened Species Conservation Act 1995 and the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth).

Current status and trends

Vegetation extent

Regional vegetation maps, based on species association data, are often used as a practical indicator of the status of ecosystems. More generalised mapping, based on vegetation structure and growth form, provides a useful statewide overview for reporting on vegetation extent but, as it is not based on species associations, it is less descriptive of ecosystems.

The current extent of native vegetation in NSW reflects the disproportionate impact of clearing across different habitat types. Map 6.1 depicts the remaining extent of 16 vegetation formations across the State in 2005, based on a broadscale information system describing native vegetation (Keith 2004). Generally, flat productive lands have been favoured for development, with particularly high rates of clearing in native grasslands, grassy woodlands and some types of wetlands and eucalypt forests.

Map 6.1: Existing native vegetation, 2005

Source: Modified from Keith 2004

Note: The data used to prepare this map only records losses in the extent of native vegetation cover through land clearing and does not indicate degradation or losses of vegetation or ecosystem diversity due to other processes, such as overgrazing and inappropriate fire regimes.

Much of the native grassland in NSW has been cleared or modified for pasture improvement by the application of fertilisers, ploughing and the sowing of introduced grasses and clovers. Only small fragments of native grasslands remain outside the semi-arid zone, although some grazing lands retain important remnants.

The grassy woodlands are one of the most threatened ecosystems in NSW. Only a small proportion of pre-European grassy woodlands still remains in NSW, with some classes of woodland depleted by more than 90% (Keith 2004).

Overall, wet and dry sclerophyll forests have suffered less clearing for agriculture, because of constraints imposed by steeper terrain and less fertile soils, although levels of depletion are still substantial in some classes.

Semi-arid woodlands have suffered low to moderate levels of clearing (10–60%), although activity in these ecosystems has increased in recent decades. The eastern fringe of the semi-arid zone continues to be transformed by the fastest rates of clearing in NSW (DLWC 2002), driven by an expansion in broadacre farming and the spread of irrigation.

The extent of rainforests has been substantially reduced – particularly littoral rainforests and sub-tropical and dry rainforests on fertile coastal lowlands – as a result of agriculture, sand mining and coastal development. Other rainforests and wet sclerophyll forests are less depleted, although there have been changes in structure and species composition in areas with a history of timber harvesting.

There has been comparatively little clearing in the alpine complex and in heathlands, due in part to the nature of the terrain and soils that are unsuitable for development. Arid shrublands are also unsuitable for intensive agriculture and have generally not been affected by significant clearing.

Rates of vegetation clearing

Since 1788, at least 61% of the original native vegetation of NSW has been cleared, thinned or significantly disturbed. This has primarily taken place to support agriculture, but more recently also for residential, commercial and industrial uses (DEH 1995). Map 6.2 shows the extent of clearing by biogeographic subregion since 1788.

Map 6.2: Clearing of native vegetation by subregions of the Interim Biogeographic Regionalisation of Australia, since 1788

Source: DEC data 2005

Note: The bioregions are defined under the Interim Biogeographic Regionalisation of Australia (Environment Australia 2000).

Clearing rates vary across the State with the highest levels in the wheatbelt of the Central West.

There are several methodologies for estimating clearing rates, including broadscale analyses of satellite images, fine-scale remote sensing, and analyses of clearing approval data. These approaches have different strengths and weaknesses, and produce a more reliable overview of clearing rates when considered together.

Since the early 1980s, broadscale analyses of moderate- to high-density woody vegetation have been conducted across NSW using coarse satellite images (AGO 2002; DLWC 2002). These suggest that around 25,000–33,000 hectares (ha) of the State's native vegetation was permanently removed each year in the early to mid-1990s, while in the late 1990s the removal rate fell to between 12,000 and 15,000 ha per year. Total clearing after 1988 appears to have continued at a similar rate until 2004 (Audit Office 2006).

The principal limitation of this methodology is that it only records removal of woody vegetation that is at least two metres tall with a canopy cover of 15% or more. These figures under-estimate the overall rate of clearing because they exclude changes in sparse open woodland and grasslands, which are extensive and among the most affected vegetation types in NSW.

Fine-scale remote-sensing studies allow a more accurate appraisal of clearing rates in woodlands, open woodlands and shrublands. However, their coverage is limited to particular regions of NSW. The most reliable and extensive analysis of this type has been carried out in the NSW wheatbelt, where woody vegetation with at least 5% canopy cover was mapped from aerial photographs and subsequently ground-truthed (Bedward et al. 2001; Cox et al. 2001; Metcalfe et al. 2003; Skully 2003).

Even though the authors of these studies employed conservative methods to identify clearing, their estimates indicate that clearing rates are substantially greater (8–10 times higher) than the estimates obtained from the coarse-scale analyses referred to above. However, being regional, they also provide an incomplete view of statewide clearing. Other estimates for all native vegetation cleared in NSW range from around 60,000 ha per year (Benson 2001) to 100,000 ha per year (ACF 2001).

A different perspective on clearing is provided by figures for vegetation clearing approvals under the Native Vegetation Conservation Act 1997 (NVC Act). The areas of vegetation subject to approvals for clearing decreased by 42% from 2000 to 2005 (Table 6.1). There was an increase to 64,000 ha in 2003 and 74,000 ha in 2004, and then a decrease to 44,902 ha in 2005.

At the end of 2005 the native vegetation reforms began operation under the Native Vegetation Act 2003 (NV Act) and supporting Regulations (see 'Response to the issue'). In the first six months of 2006, clearing approvals fell to 2207 ha, with the majority of land cleared under these approvals being issued for outstanding applications under the NVC Act.

Table 6.1: Applications for clearing in NSW

Source: DNR data 2006

Note: Estimates exclude vegetation cleared illegally and clearing that does not require approval. Clearing may not occur for some years after approval has been granted or may not occur at all.

^(a) Applications carried over from 2005.

^(b) Under the NV Act property vegetation planning process, formal applications are not required, but clearing approvals are based on negotiated agreements between landholders and catchment management authorities.

The clearing approval statistics are based on consistent methods of data compilation between 2000 and 2005. The data collection system was changed in 2006 with the introduction of the new Regulations. These estimates exclude the area of vegetation cleared illegally and clearing carried out legally under statutory exemptions. While the full extent of illegal clearing prior to 2005 is not known, in 2005 about 30,000 ha, or 40% of all clearing, was estimated to be illegal (Audit Office 2006). The extent of illegal clearing in 2006 is likely to be lower as a result of the native vegetation reforms because of a strengthened compliance regime.

The fringes of the Western Division have the greatest level of both legal and illegal clearing in NSW.

Revegetation

For the reporting period, there is not enough reliable data to report on the extent of active revegetation in NSW. The information that is available is highly variable from year to year and in most cases no attempt has been made to record the location or purpose of revegetation or to track its effectiveness over time. It is likely that most revegetation is for land or water management purposes or production, rather than habitat restoration. The information that is available, particularly for 2006, indicates a slow increase in the overall extent of revegetation.

Table 6.2 shows areas being conserved, restored or vegetated for native vegetation under a range of programs in the first half of 2006 (see also Biodiversity 6.2).

Table 6.2: Area of NSW conserved, restored, revegetated or managed to enhance or maintain native vegetation outcomes from 1 January to 30 June 2006

Source: DNR 2006

Note: ^(a)Area under a PVP to treat invasive native scrub (INS). INS is the term used to describe native plant species that have spread rapidly within their natural range.

Vegetation condition

The condition of vegetation ranges from pristine to total replacement. Between these two extremes, native vegetation may be modified to varying degrees by land management practices and unplanned threats and disturbances. The impacts include changes to the structure, function and species composition of vegetation, reduced regeneration, and a lowering of habitat values and integrity.

Decline in vegetation condition is generally less visible than clearing and occurs over a longer time frame. It is therefore more difficult to detect and assess. As broadscale information about vegetation condition is not available, the following discussion addresses the pressures that drive changes in condition.

Table 6.3 summarises the principal pressures on vegetation condition, together with an estimate of gross changes to the levels of pressures experienced in NSW over the past decade. The pressures are generalised by vegetation classes (Keith 2004) and the figures represent the total number of classes affected (to a maximum of 99 classes). They are not, however, indicative of the intensity or the significance of each pressure, or necessarily the areas that are affected. For instance, the most severe pressure – land clearing – affects only 61 classes, whereas climate change (99), soil degradation (86), fire regimes (84) and invasive species (74) all affect more classes.

Table 6.3 demonstrates that most pressures are ongoing with little sign of abatement. Some pressures are intensifying, particularly those associated with climate change, while a relatively small number are abating. As the instances where pressures are easing are relatively few, the overall expectation is for the condition of most vegetation classes to continue to decline over time.

Table 6.3: Changes to pressures on native vegetation in NSW over the past decade

Source: DEC data 2006

Note: ^(a) Severity refers to the intensity of the pressure and is not related to the number of classes affected.

The impacts of clearing continue, or even intensify, after clearing has ceased, due to the ongoing effects of habitat fragmentation on the remaining biota.

While most arid shrublands and grasslands are not subject to extensive clearing, they are affected by overgrazing. Total grazing pressure has increased, leading to a reduction in perennial plant cover and an increase in erosion in sensitive landscapes. Further effects of overgrazing include lack of regeneration, habitat simplification and an over-abundance of less palatable species.

Climate change is pervasive and affects all classes of vegetation throughout the State. However, some vegetation classes could be expected to be especially sensitive – notably alpine vegetation, wetlands and rainforest. In alpine habitats, for example, there has been a significant decline in snow cover over the past decade, which will have an impact on both the area and suitability of habitat for a range of specialist alpine species.

Other pervasive pressures affecting vegetation condition include those attributable to invasive species (see Biodiversity 6.4), fire (see Biodiversity 6.5) and soil degradation (see Land 4.2, Land 4.3 and Land 4.4).

Table 6.3 represents a view of pressures on native vegetation generalised by vegetation classes. An alternative perspective is provided by considering the pressures imposed on native vegetation by land use and land management regimes. Map 6.3 shows the pressures on native vegetation due to land management related activities in NSW.

Map 6.3: Relative vegetation pressure – land-use index

Source: DEC data 2005

The land-use index incorporates the present vegetation extent and spatial configuration (fragmentation), present land use, land capability and population pressure, all interpreted as a single score. It broadly depicts the relative strength of pressures leading to vegetation disturbance and deterioration that are directly attributable to human land use and management practices, including land clearing and fragmentation.

These pressures are considered to be important determinants of vegetation condition. In the absence of active management to counter these pressures, the index is broadly indicative of current condition and future trends, especially at State and larger regional scales. It is expected that the rate of decline in vegetation condition over time will be related to the intensity of the pressures. Even areas with the lowest values, essentially in reserves, will be affected eventually if appropriate management is not in place.

However, the land-use index has not been calibrated against actual pressures and is indicative only of the relative strength of pressures between different areas. No prediction is possible about the rate of decline in condition in different areas. The index does not consider all pressures on vegetation, particularly those that are less predictable, such as fire, invasive species and climate change. As it lacks some historical context (such as changes that have occurred in land use over time), in some areas it may be less predictive of current condition than future trends.

Response to the issue

Reservation system

From the perspective of conserving biodiversity, the most effective response to clearing and degradation of natural ecosystems is their protection within the reserve system (see Biodiversity 6.2). A landscape management approach across all tenures will maximise outcomes in maintaining vegetation condition (see 'Native vegetation reforms' below).

Clearing approvals and controls

Until December 2005, the NVC Act provided the means for approving and controlling the clearing of vegetation in NSW. Under this Act a register of clearing approvals was maintained (Table 6.1), and breaches of the Act investigated.

Reports by the NSW Audit Office (Audit Office 2002; Audit Office 2006) have described the regulatory system that existed under the NVC Act as ineffective in preventing illegal clearing. The reports identified difficulties in meeting the requirements of the Act to launch successful prosecutions for illegal clearing, and an inability until 2005 to detect and measure where it was occurring. Between 2001 and 2005, a total of 1988 reported breaches of the Act were investigated, of which about half have been substantiated or are still being investigated (DNR data 2006). However, the Audit Office found there had been very low levels of prosecution since 1998, including just 12 cases since 2002 (Audit Office 2006).

In response, the Government has passed new legislation – the NV Act – which came into effect in December 2005. In its latest report on the regulation of clearing, the Audit Office found that 'a new regulatory system has been established that is capable of ending illegal clearing' and that progress in establishing a more effective control regime has been made. They also noted that a record of successful prosecution will still be needed to serve as an effective deterrent (Audit Office 2006). The Department of Natural Resources has also implemented a compliance policy to complement the Act.

Native vegetation reforms

The NV Act has the stated intention of putting an end to broadscale land clearing in NSW. Clearing will no longer be permitted unless it improves or maintains environmental outcomes.

Regulations supporting the NV Act came into effect on 1 December 2005. The regulations define 'routine agricultural management activities' that are exempt from the Act and provide a framework for determining whether clearing proposals maintain or improve environmental outcomes through the Environmental Outcomes Assessment Methodology. This methodology is implemented through a system of voluntary, negotiated agreements between individual landholders and their local catchment management authority (CMA), known as property vegetation plans (PVPs). Landholders must demonstrate that any proposed clearing (and agreed offset or mitigating action) will maintain or improve environmental outcomes at the property scale for each of four criteria: biodiversity, soils, water quality and salinity.

A system of 'offsets' has also been introduced which will allow farmers to clear an area of native vegetation, provided they agree to plant, improve, or better manage other vegetation on their own property or elsewhere.

The Act gives special protection to vegetation classes that have been cleared below 30% of their original extent, and encourages revegetation and rehabilitation of land with native vegetation. It rewards farmers for effective land management and encourages investment in voluntary conservation through the development of PVPs.

The new legislation is accompanied by public funding to assist landholders repair degraded landscapes. The NSW and Australian governments have committed $436 million through the NSW Sustainability Trust and the National Action Plan for Salinity and Water Quality from 2003–04 to 2006–07, with $120 million of this dedicated to assisting landholders to practise sound native vegetation management. The money will be allocated by CMAs to landholders according to priorities identified in their catchment action plans and investment strategies.

The NSW Government has also committed $37 million to a structural adjustment package for landholders who experience financial hardship as a result of the new laws.

Information and monitoring

While much information is collected on vegetation from a variety of perspectives, it is seldom adequate to present a complete statewide picture. New remote-sensing technologies have been proposed to overcome these limitations, and though promising, it has yet to be clearly demonstrated that they offer an adequate solution. Reliable data on the location, extent, purpose and effectiveness of on-ground revegetation works is also badly needed.

The statewide natural resource management (NRM) target relevant to this theme is 'By 2015 there is an increase in native vegetation extent and an improvement in native vegetation condition'. There is a need for further data on a statewide basis to provide a full picture of progress towards the target.

Future directions

New legislation and administrative changes have been introduced to halt, and then reverse, the harmful effects of over-clearing in NSW.

The condition of native vegetation is likely to continue to decline, even after clearing has ceased, due to the ongoing effects of habitat fragmentation and the growing impact of climate change. Some early signs of climate change are emerging and its impacts are likely to become more tangible, bringing greater pressures on vegetation condition.

Scientific evidence indicates that practices that enhance habitat value and vegetation condition should continue to be supported and promoted. Maintaining or improving the condition of existing vegetation is likely to be more productive than trying to restore land that has been substantially altered.

Nonetheless, revegetation and restoration of native vegetation may reverse some of the historical effects of clearing. This should be encouraged and managed strategically to maximise ecological benefits by improving habitat connectivity and creating buffer zones around high-quality remnants.

While significant revegetation activity is already occurring, its effects have not been monitored. A framework to support better collection of information on revegetation works is needed so that the effectiveness of the revegetation effort can be assessed and programs better targeted.

The greatest information need (and the one that will be most important in the longer term) is agreed methodologies for assessing vegetation condition that will facilitate its monitoring and reporting.

There is an ongoing need for finer scale regional mapping of vegetation communities that is consistent across the State, including a definitive description of the vegetation communities of NSW. This is needed to support adaptive management within regions, allow effective comparison between regions (CMAs), and provide a connection between regional and statewide monitoring and reporting for SoE and NRM purposes.